Gold Nanoflowers Sensitivity and Selectivity Improvement by Thiolation to Detect Breast Cancer Volatile Organic Compound Biomarkers
Sravani M., Yadav A.B., Checker R.
Article, IEEE Transactions on Biomedical Engineering, 2026, DOI Link
View abstract ⏷
Breast cancer is a malignant disease, and patient prognosis significantly improves when detected at an early stage. Therefore, various advanced chemiresistive sensors have been adopted to detect Volatile Organic Compounds (VOCs), which are byproducts of cellular metabolism exhaled in breath, for early breast cancer detection. In this work, gold nanoflowers (AuNFs) with a high surface area to volume ratio and a face centered cubic (FCC) crystalline structure of 203 nm were synthesized, as confirmed by X-ray diffraction (XRD) and High resolution scanning electron microscopy (HRSEM). After dispersion in deionized (DI) water, the AuNFs were drop coated onto interdigital elliptical aluminum electrodes patterned on glass substrates, forming a continuous film (neighboring AuNFs closely packed) with an initial resistance of up to 2 KΩ. The AuNFs films were then functionalized with phenylethyl mercaptan and 2-methyl-1-propanethiol using a simple and controllable drop coating method offering an advantage over conventional ligand ion exchange techniques. The large electrode spacing significantly reduces noise compared to traditional low spacing gold electrodes, which require costly photolithography. Furthermore, thiolation enhances both sensitivity and selectivity. The sensors exhibited very high sensitivity, attributed to the high conductivity of the AuNFs films and the sharp petal like active sites promoting strong VOC interactions. To the best of the authors' knowledge, this is the first report demonstrating high sensitivity for breast cancer related VOCs using aluminum electrodes on a glass substrate.
Density functionality theory based study of phenol sensing by gold functionalized CNT
Conference paper, AIP Conference Proceedings, 2025, DOI Link
View abstract ⏷
The ongoing quest for novel materials has paved the way for discovering materials with exceptional applications, primarily due to their distinctive properties. This study delves into the electrical properties of one such remarkable material: Carbon Nanotubes (CNTs). Renowned for their extraordinary material qualities, including exceptional physical strength and superior electrical conduction, CNTs stand out as a pinnacle of material science innovation. In particular, Single-Walled Carbon Nanotubes (SWCNTs) with specific orientation and functionalization were meticulously analyzed using advanced computational tools such as Quantum Espresso (QE) [2]. The study is based on DFT, which is run QE platform to simulate and understand the intricate electronic structures and properties of the functionalized SWCNTs. Following the computational analysis, these CNTs were evaluated for their potential applications in gas i.e. VOCs (Volatile Organic Compounds) sensing, a field that benefits immensely from materials with high sensitivity and specificity to various gases. The results highlight the promising capabilities of SWCNTs in enhancing gas sensor technology, thereby opening new avenues for their application in environmental monitoring, industrial safety, and healthcare diagnostics. This research not only underscores the versatility of CNTs but also contributes to the broader understanding of their functionalized forms in practical applications.
Negative barrier height in sol-gel drop-coated ZnO thin film-based MSM structure for cancer biomarker detection
Article, Ceramics International, 2025, DOI Link
View abstract ⏷
The high surface-to-volume ratio of ZnO thin films nanostructure makes them an attractive solution for various gas and Volatile Organic Compounds (VOCs) sensing applications. In the present study, a low-cost, simple sol–gel drop-coating method has been developed to deposit uniform ZnO thin films of two different thicknesses aimed at fabricating a negative barrier height MSM structure for detecting cancer-associated VOCs at levels up to 800 ppb. Core electron elastic scattering was considered to determine the energy band gap of the ZnO thin films through XPS analysis, and the results are consistent with the UV-visible findings. The room-temperature sensing of biomarkers makes these films suitable for point-of-care applications in cancer screening based on VOC signatures. The sensitivity of the ZnO film to these analytes is determined by factors such as surface-adsorbed oxygen, film thickness, analyte molecular weight, and the bonding between analyte atoms and surface hydroxyl groups. In conclusion, the room-temperature detection of cancer biomarker VOCs at the parts-per-billion (ppb) level using a very thin layer of drop-coated ZnO, coupled with the negative barrier variation with film thickness, represents a novel finding.
Gold nanoflower-functionalized ZnO thin film-based elliptical interdigital MSM structure for the detection of volatile organic compounds associated with breast cancer
Yadav A.B., Mishra S.P., G.V. S.R., Checker R.
Article, Journal of Alloys and Compounds, 2025, DOI Link
View abstract ⏷
Gold nanoflowers were synthesized in an aqueous solution and incorporated into the sol–gel derived zinc acetate salt precursor based colloidal solution. Five microliters of the colloidal solution, which contains a pure zinc acetate precursor solution and gold nanoflowers, was dropped onto a glass substrate to create a transparent functionalized and pristine ZnO thin film. XPS, XRD, scanning electron microscope and transmission electron microscope analysis revealed a successful functionalization of gold nanoflowers on ZnO. The functionalized ZnO films decorated with gold nanoflowers, when used in an MSM structure, showed excellent sensitivity to isopropyl myristate, a crucial biomarker of breast cancer. UV light was used to improve the sensing properties of the device. In addition to improving the sensing properties, the gold nanoflowers lower the specific contact resistance at the Al/gold nanoflower-functionalized ZnO interface.
Sol–gel drop coated ZnO/SnO2 nanostructure thin film heterojunction on glass substrate for ethanol sensing
Vanga S.R., Sarada V., Yadav A.B.
Article, Applied Physics A: Materials Science and Processing, 2025, DOI Link
View abstract ⏷
Here we report the fabrication of a ZnO/SnO2 heterojunction on glass substrate using environment-friendly low cost-effective sol–gel drop coating method for UV assisted ethanol sensing. Surface, structural and elemental properties of the ZnO, SnO2 and ZnO/SnO2 thin film heterojunction was analysed by using Scanning electron microscope, EDX and X-ray diffraction (XRD) method that were confirming the polycrystalline nature of SnO2, ZnO, and their nanostructure thin film heterojunction. The electrical and gas sensing properties of SnO2, ZnO, and ZnO/SnO2 nanostructure thin film heterojunction was studied by fabricating metal (Ti/Al)-semiconductor (ZnO/SnO2)-metal (Ti/Al) structure exposed with different low concentration of the ethanol. An UV light exposure was carried out to improve the sensitivity towards ethanol of this heterojunction. Finally, density functional theory with Hubbard correction is employed to explore the band gap of the individual semiconductor monolayer and nanostructured ZnO thin film. The sensing properties of the heterojunction are revealed by density functional theory by exposing the ethanol molecule on the surface of the ZnO/SnO2.
Highly Sensitive Chemiresistive Sensor Based on Hydrothermally Synthesized ZnO Nanorods for Detection of Volatile Organic Compounds Associated With Breast Cancer
Kakarla V., Yadav A.B., Checker R.
Article, IEEE Sensors Letters, 2025, DOI Link
View abstract ⏷
In this study, zinc oxide (ZnO) nanorods were synthesized using a hydrothermal method and precisely drop-coated onto an interdigitated electrode as sensing material for detecting breast cancer associated volatile organic compounds, such as heptanal and 2-propanol. The synthesized ZnO nanorods were characterized using X-ray diffraction, scanning electron micro- scopy (SEM), UV–visible spectroscopy, and energy-dispersive X-ray spectroscopy to analyze their structural properties, surface morphology, optical behavior, and elemental composition. The sensor demonstrated excellent sensitivity, strong linearity, and reliable repeatability in its detection performance. To the best of the authors' knowledge, this is the first report on the use of ZnO nanorods for the detection of breast cancer-associated volatile organic compounds, such as heptanal and 2-propanol.
Thiolated Gold Nanoflowers for Breast Cancer Volatile Organic Compound Biomarker Sensing
Sravani M., Yadav A.B., Mishra S.P., Reddy G.V.S., Checker R.
Article, IEEE Sensors Journal, 2025, DOI Link
View abstract ⏷
Breast cancer is a malignant disease, and patient prognosis significantly improves when it is detected at an early stage. Consequently, various advanced techniques have been adopted to enable early stage detection. One promising approach involves the classification of volatile organic compounds (VOCs) byproducts of cellular metabolism that are exhaled in breath, using chemiresistors based on thiolated gold nanoparticles. These sensors can selectively detect a range of VOCs, with tunability achieved by selecting thiols of specific molecular shapes. In this work, we synthesized gold nanoflowers (AuNFs) with a high surface-area-to-volume ratio, a face-centered cubic (FCC) crystalline structure, and an average size of 203 nm, as confirmed by energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The AuNFs were dispersed in deionized (DI) water, pipetted, and drop coated onto interdigital gold electrodes patterned on SiO2/p-Si (100) substrates to form a continuous film with an initial resistance of up to 5 kΩ. Subsequently, the AuNF films were functionalized with 2-ethyl-1-hexanethiol, 2-methyl-1-propanethiol, and phenylethyl mercaptan using a simple and controllable drop coating method; this technique offers advantages over the ligand ion exchange method. Thiolation increased the film resistance to approximately 10 kΩ. The resulting chemiresistor sensors demonstrated excellent sensitivity to breast cancer VOC biomarkers, including 2-ethyl-1-hexanol, 2-propanol, and heptaldehyde. Notably, 2-methyl-1-propanethiol functionalized AuNFs exhibited the highest sensitivity (21.07%) toward heptaldehyde, outperforming other thiol-modified sensors and previously reported values in literature. The sensors also demonstrated ultrafast response and recovery times of 5 and 6 s, respectively. To the best of the author's knowledge, neither this novel sensor design nor this approach has been previously reported.
Fabrication and Characterization of ZnO/Graphene Thin Film Alcohol Sensor
Santosh R., Yadav A.B., Tripathi B.M.M., Checker R., Kumar P.
Article, IEEE Transactions on Nanobioscience, 2025, DOI Link
View abstract ⏷
The experimental and theoretical realization of 10% graphene doped ZnO/Graphene thin film alcohol sensor has been reported. The alcohol sensor has been fabricated by sol-gel method and theoretically verified by DFT-based first principle calculations. The quality of the fabricated device has been studied using SEM and UV measurements. To determine its figures-of-merit, the conductivity, transfer characteristics, and response measurements have been analyzed. In addition, the device has undergone three different exposures of alcohol concentrations such as Brandy, Whiskey, and Rum with varying exposure times.
Performance Investigation of Bottom Gate ZnO Based TFT for High-Speed Digital Display Circuit Applications
Kumar B.B., Kumar S., Tiwari P.K., Yadav A.B., Dubey S., Singh K.
Article, Transactions on Electrical and Electronic Materials, 2024, DOI Link
View abstract ⏷
This paper explores possibility of device as well as circuit performance enhancement in the bottom gate ZnO based TFT via Mg and Cd material doping. DC, Analog & RF performance, Energy efficiency and Noise analysis were performed for both doped (i.e., MgyZn1-yO and CdxZn1-xO) and undoped ZnO channel TFT structures. Further, successful circuit implementation of these devices was done in resistive inverter and AMLCD pixel display circuits. Performance wise both MgyZn1-yO and CdxZn1-xO channel TFTs were found to be superior against its undoped variant. ~ 376%, ~ 105% and ~ 162% are the percentage improvement in (ION/IOFF) ratio, field effect mobility (μFE) and effective mobility (μeff) for CdxZn1-xO based TFT with respect to ZnO based TFT, same parameters show ~ 194%, ~ 103% and ~ 133% percentage improvement for the case of MgyZn1-yO TFT. Also, ~ 23% is percentage decrease in subthreshold swing (SS) for CdxZn1-xO based TFT with respect to ZnO based, whereas ~ 11% is percentage decrement for MgyZn1-yO. Intrinsic gate delay, the percentage decrement is ~ 54.15 and ~ 59.95% for MgyZn1-yO and CdxZn1-xO respectively w.r.t ZnO. Both the CdxZn1-xO and MgyZn1-yO TFT shows unanimous decrease in delay for the resistive inverter as well as AMLCD pixel display circuits. The reported results shows that bottom gate CdxZn1-xO TFT has better performance for above-mentioned performance parameters. The numerical simulations are performed on Silvaco ATLAS TCAD simulator.Please confirm if the author names are presented accurately and in the correct sequence (given name, middle name/initial, family name). Author 1 Given name: [Binay Binod] Last name [Kumar], Author 3 Given name: [Pramod Kumar] Last name [Tiwari], Author 4 Given name: [Aniruddh Bahadur] Last name [Yadav]. Also, kindly confirm the details in the metadata are correctYes, the sequence of authors is correct and the details in the metadata is also accurate. Journal instruction requires a city and country for affiliations; however, these are missing in affiliation [1, 2, 4]. Please verify if the provided city is correct and amend if necessary.We apologize for the misunderstanding. However, the city and country names are already correctly mentioned in Affiliation [1, 2 and 4].
Study of Electrical Characteristics with different Channel lengths of Bottom gate oxide Semiconductor based Thin Film Transistor
Sannakashappanavar B.S., Rao A.S., Yadav A.B., Khatri S., Garg R., Prabhat K.
Conference paper, 2024 IEEE Silchar Subsection Conference, SILCON 2024, 2024, DOI Link
View abstract ⏷
This research work focuses on studying ZnO bottom gate thin-film transistors by investigating their electrical characteristics and performance. The simulation of thin-film transistors (TFTs) was performed by using COMSOL Multiphysics 5.6. ZnO is a most promising material for TFTs due to its desirable properties like higher electron mobility and transparency. The design of TFTs involves creating a structural model of the device structure which includes ZnO as active layer, (gate, source, drain) contacts and silicon dioxide as insulating layers. The designed structure is evaluated by studying its electrical behavior by solving Poisson's equation and continuity equation to determine the electron mobility. Various parameters like material properties, dimensions and applied voltages are varied to evaluate the TFTs performance. Important device characteristics like Drain current (Id), Gate voltage and Drain voltage characteristics are studied. The effect of gate voltage on the carrier concentration across source, gate and drain terminals have been evaluated. It was observed that as the gate voltage increases, the electron concentration shifts from drain terminal to source terminal. In addition, the effect of channel length on the drain current has also been evaluated. It is observed that the drain current (Id) of the transistors decreases as the channel length of the transistor increases. This is attributed to the fact that the channel will increase with increase in its length. The comparative study of different channel lengths of 9μm, 10μm and 11μm is analyzed. This work allows the researchers for a practical exploration of ZnO based thin film transistors at lesser dimensions using a powerful simulation tool like COMSOL Multiphysics.
Effect of high k dielectric layer on the performance of Silicon based Nanoscale MOSFET
Sannakashappanavar B.S., Meghashree M., Bhat M., Rao A.S., Guruprasad B., Yadav A.B.
Conference paper, 2024 Control Instrumentation System Conference: Guiding Tomorrow: Emerging Trends in Control, Instrumentation, and Systems Engineering, CISCON 2024, 2024, DOI Link
View abstract ⏷
In this paper, the effect of High K dielectric layer on Silicon based Metal-oxide-semiconductor field-effect transistors (MOSFETs) was studied. As we know MOSFET place a very important role in modern electronics, this work investigates the relationship between drain current and gate voltage in MOSFETs with different High K dielectric materials. The dielectric layer in MOSFETs separates the gate electrode from the semiconductor channel, controlling the flow of current through the device. Silicon dioxide (SiO2) has historically been the dielectric of choice due to its excellent insulating properties and compatibility with silicon technology. However, as transistor dimensions shrink and performance demands increase, alternative dielectrics with higher permittivity (high-k dielectrics) have gained more prominence. Consequently, MOSFETs employing high-k dielectrics exhibit enhanced performance characteristics, including lower threshold voltages and higher drain currents at equivalent gate voltages compared to SiO2 based MOSFETs. To understand the dielectric properties of different High-k materials, gate voltage, and drain current is essential for optimizing the MOSFET performance. In this work Al2O3, HfSiO4, and HfO2 which has high dielectric constant than SiO2 were used to study the MOSFET performance. The HfO2 dielectric layer shows more current then the remaining dielectric layers.
Investigation of Gold Nanoparticles Functionalized Silicon for Sensing Biomarkers of Lung Cancer Using Density Functional Theory
Mekala B.C.S., Yadav A.B., Jaseem S., Sulthana S.S.
Conference paper, 2024 IEEE Students Conference on Engineering and Systems: Interdisciplinary Technologies for Sustainable Future, SCES 2024, 2024, DOI Link
View abstract ⏷
This study investigates the potential of Silicon functionalized with gold nanoparticles in sensing major lung cancer biomarkers like Acetone, Toluene and Propanol by utilizing DFT (Density Functional Theory). Silicon functionalized with gold nanoparticles (AuNPs) combines the advantageous properties of both materials, making it highly suitable for sensing applications. Computational tools like VESTA and Quantum Espresso are used to analyze the electronic behavior, bonding characteristics of Si, Si-Au, Si-Au-Acetone, Si-Au-Toluene and Si-Au-Propanol by performing DOS and Band Structure calculations. We observe the Band gap for Si, Si-Au, Si-Au-Acetone, Si-Au-Toluene and Si-Au-Propanol are 0.716eV, 0.19eV, 0.16eV, 0.16eV, 0.17eV. Our study contributes to the understanding of utilizing silicon functionalized gold nanoparticles for sensing application and paving the way for a promising new approach to lung cancer detection.
Scan and Automated Test Pattern Generation in VLSI
Conference paper, Proceedings - 2024 5th International Conference on Image Processing and Capsule Networks, ICIPCN 2024, 2024, DOI Link
View abstract ⏷
Integrated circuits (ICs) are becoming more and more complicated, which makes it difficult to guarantee their functioning and dependability. Automated testing techniques are crucial for identifying and resolving this issue by identifying and diagnosing IC problems. Among these approaches, test pattern generation and scan-based testing are essential for quickly locating and analyzing flaws. The creation of an automated system for test pattern generation and scan-based testing in the context of ICs is the main goal of this study. The suggested solution makes use of cutting-edge algorithms and methodologies to improve the efficacy and efficiency of the testing procedure. The system's initial component entails incorporating scan chains into the IC design. Scan chains offer observable and adjustable places in the circuit, making it possible to apply test patterns and track responses. This integration makes it possible to isolate and analyze particular IC portions, which enables thorough testing. The system's second part deals with the automatic creation of test patterns. Given the complexity of current ICs, traditional approaches for generating test patterns may be both time-consuming and not the best. The suggested method creates test patterns intelligently by utilizing sophisticated algorithms, including machine learning and artificial intelligence. These algorithms create effective and high-coverage test patterns by examining the circuit's architecture, functioning, and past test data. Moreover, the system integrates self-learning techniques to adjust to changing fault models and integrated circuit designs. Because of its flexibility, testing can continue to be efficient even with increasingly complex IC architectures. The suggested system's efficacy in terms of fault coverage, test time reduction, and adaptation to different IC designs is demonstrated by the experimental evaluation. The outcomes show a notable improvement over conventional testing methods, underscoring the automated scan and test pattern generation system's potential to raise the effectiveness and dependability of IC testing.
Effect of deposition temperature on growth of Zinc oxide Nanorods on Zinc oxide thin film for Optoelectronics and Sensing Applications
Sannakashappanavar B.S., Pattanashetti N.A., Yadav A.B.
Article, Interactions, 2024, DOI Link
View abstract ⏷
In the present research work, Zinc oxide (ZnO) thin film was depos-ited on the Silicondioxide(SiO2)(~ 200 nm)/Silicon substrate by using Radio Frequency (RF) sputtering at 4000C to study the effect of deposition temperature on growth of ZnO Nanorods on ZnO thin films. The thin-film surface morphology was examined using X-ray diffraction and Atomic Force Microscopy. Hydrothermal method was used for the growth of ZnO nanorods on ZnO thin films. The ZnO nanorods’ structural properties were determined using Field Emission Scanning Electron Microscopy and X-ray diffraction.To investigate the effect of temperature variation onZnO Nanorod growth and orientation was studied. The Metal Semiconductor Metal(MSM) based device structure was fabricated by depositing Ti/Au contact using thermal evaporator and shadow mask technique. Further, the electrical characteristics were carried out by using semi-conductor parameter analyzer. Later the device was exposed to UV light of frequency 365 nm and 380 nm to study the photodetection capability.And finally the sensing propertiesof the device was measured by exposing it to ethanol. The obtained results support positively for their wide applications in the area of optoelectronic and sensing based electronic devices.
Metal-Semiconductor – Metal structure on Graphene Doped ZnO Thin Film
Kalyanapu H.S., Vemuri N.G., Rayapati V.P.S.H., Yadav A.B., Yella G.P.
Conference paper, 2023 2nd International Conference for Innovation in Technology, INOCON 2023, 2023, DOI Link
View abstract ⏷
A unique combination of its extraordinary qualities has made graphene one of the most promising nanomaterials, it is not only the thinnest material, but also one of the strongest materials. It is a superb electrical conductor and does so better than any other material. Instead of using polymers, polymer composites are employed in numerous applications. Due to its uses, stable graphene dispersions with high graphene concentrations have received a lot of attention recently. To enhance the dispersion of graphene and create a stable graphene solution with a high concentration, 1-vinyl 2pyrrolidone was used. To create ZnO/graphene composites, this stable graphene solution was combined with ZnO. A sol-gel method was used to deposit a thin coating of Graphene doped ZnO composite. With the addition of graphene, ZnO's electrical conductivity was significantly increased.
Nanoelectronics Devices: Design, Materials, and Applications (Part II)
Book, Nanoelectronics Devices: Design, Materials, and Applications (Part II), 2023, DOI Link
View abstract ⏷
Nanoelectronics Devices: Design, Materials, and Applications provides information about the progress of nanomaterial and nanoelectronic devices and their applications in diverse fields (including semiconductor electronics, biomedical engineering, energy production and agriculture). The book is divided into two parts. The editors have included a blend of basic and advanced information with references to current research. The book is intended as an update for researchers and industry professionals in the field of electronics and nanotechnology. It can also serve as a reference book for students taking advanced courses in electronics and technology. The editors have included MCQs for evaluating the readers’ understanding of the topics covered in the book. Topics Covered in Part 2 include applications of nanoelectronics for different devices and materials. - Photonic crystal waveguide geometry - 8kW to 80kW power grids with simple energy storage systems - Two-dimensional material and based heterojunctions like MoS2 /graphene, MoS2 /CNT, and MoS2 /WS2, - 5G communication material - Wearable devices like electronic skin, intelligent wound bandages, tattoo-based electrochemical sensors - PEDOT: PSS-based EEG - New materials for medicine Audience: Researchers and industry professionals in the field of electronics and nanotechnology; students taking advanced courses in electronics and technology.
PREFACE
Editorial, Nanoelectronics Devices: Design, Materials, and Applications (Part II), 2023,
Density Functionality Theory Study of Gold Functionalized CNT for Acetone Sensing
Conference paper, 2023 14th International Conference on Computing Communication and Networking Technologies, ICCCNT 2023, 2023, DOI Link
View abstract ⏷
The electrical properties of a (5,0) zigzag single-walled carbon nanotube (SWCNT) functionalized with gold and its potential for acetone sensing are investigated in this study utilizing density functional theory (DFT) calculations. We choose the well-known Perdew-Burke-Ernzerhof (PBE) functional due to its accuracy and computational effectiveness. The choice of exchange-correlation function is crucial in DFT calculations. We perform both band structure and density of states (DOS) calculations using Visualization of Electronic and STructural Analysis (VESTA) and Quantum ESPRESSO (QE). We observe the band gap for CNT, Au-CNT, C3H6O-CNT, and Au-CNT-C3H6O are 0eV, 0.54eV, 1.12eV, and 0.35eV. Our research enhances knowledge of functionalized carbon nanotubes for use in gas sensing applications and emphasizes the use of the PBE functional, as well as the software suites VESTA and QE.
PREFACE
Editorial, Nanoelectronics Devices: Design, Materials, and Applications (Part I), 2023,
Density Functional Theory-Based Study of Ag/ZnO Schottky Diode
Yadav A.B., Narasimha Murty N.V.L., Lasya B., Mamilla S., Sannakashappanavar B.S.
Article, Journal of Electronic Materials, 2023, DOI Link
View abstract ⏷
Here, a ZnO thin film was deposited on a silicon substrate. The hexagonal structure of this deposited film was measured by x-ray diffraction and atomic force microscopy (AFM) without further processing, specifically annealing. Density functional theory (DFT) and DFT+U calculations were conducted on ideal ZnO bulk crystal with crystal size a=3.249Å and c=5.207Å, and an experimental unit cell estimated by x-ray and AFM analysis a=3.069Å and c=5.3156Å. A vertical Schottky diode with the structure Ag/ZnO/Ti/Al/n-Si(100) was fabricated on the aforementioned deposited film with optimized parameters. The structure showed Schottky behavior without annealing, indicating oxide layer formation at the Ag/ZnO interface. We obtained contradictory results to the experimental Schottky nature for Ag/ZnO when calculating the structure by DFT+U. When the silver oxide work function was used, we found that the current–voltage characteristics of the device simulated using COMSOL Multiphysics were closer to the experimental results, strengthening the hypothesis of dielectric formation at the interface. Finally, we introduced a vertical power diode structure that is not known to date.
Fabrication and characterization of ultra-thin ZnO based bottom gate thin film transistor for UV detection
Sannakashappanavar B.S., Yadav A.B., Singh K., Sai T.A.
Article, Micro and Nanostructures, 2023, DOI Link
View abstract ⏷
An RF sputtered ZnO thin film was utilized in a thin film transistor (TFT) fabrication. The film was fabricated on SiO2 gate oxide that was thermally grown on Si Substrate. Few lithography steps were used to fabricate the device and device structure was proved to be a bottom gate TFT. The grown film was ultra thin of 25 nm thickness and the Si wafer was n-type. The structural and optical properties of ZnO films were investigated by Field Emission Scanning Electron Microscopy (FESEM), X-Ray Diffraction (XRD) and Photo luminance (PL) spectroscopy. The photo luminance study confirmed a high-quality absorbance in UV spectra and relatively good transmittance in the visible region. The electrical performance of the transistor was studied using Proxima B1500 and the on/off current ratio was measured to be ∼107. The ZnO bottom gate TFT is simulated using the commercial TCAD tool Silvaco ATLAS™. Later the simulated I–V characteristic of the device is compared with the experimental one and both are in fairly good agreement. Further the UV detection capability of the fabricated device was studied by using UV LED light of 365 nm wavelength. The measured value of threshold voltage was found to be 9V under dark light and 10V under UV light.
Nanoelectronics Devices: Design, Materials, and Applications (Part I)
Book, Nanoelectronics Devices: Design, Materials, and Applications (Part I), 2023, DOI Link
View abstract ⏷
Nanoelectronics Devices: Design, Materials, and Applications provides information about the progress of nanomaterial and nanoelectronic devices and their applications in diverse fields (including semiconductor electronics, biomedical engineering, energy production and agriculture). The book is divided into two parts. The editors have included a blend of basic and advanced information with references to current research. The book is intended as an update for researchers and industry professionals in the field of electronics and nanotechnology. It can also serve as a reference book for students taking advanced courses in electronics and technology. The editors have included MCQs for evaluating the readers’ understanding of the topics covered in the book. Topics covered in Part 1 include basic knowledge on nanoelectronics with examples of testing different device parameters - The present, past, and future of nanoelectronics, - An introduction to Nanoelectronics and applicability of Moore’s law - Transport of charge carrier, electrode, and measurement of device parameters - Fermi level adjustment in junction less transistor, - Non-polar devices and their simulation - The negative capacitance in MOSFET devices - Effect of electrode in the device operation - Second and Sixth group semiconductors, - FinFET principal and future, Electronics and optics integration for fast processing and data communication - Batteryless photo detectors - Solar cell fabrication and applications - Van der Waals assembled nanomaterials Audience: Researchers and industry professionals in the field of electronics and nanotechnology; students taking advanced courses in electronics and technology.
A low cost Sn doped ZnO thin film based Schottky diode for UV detection
Yadav A.B., Rawat G., Sannakashappanavar B.S.
Article, Materials Today Communications, 2022, DOI Link
View abstract ⏷
In this paper thin films of Sn doped ZnO was prepared via low-cost chemical sol-gel spin coating process. The Ohmic electrode Aluminum (Al) and Schottky electrode Palladium (Pd) on doped ZnO thin film were deposited through a hard mask by thermal evaporation techniques to obtain a planner Metal-Semiconductor-Metal (MSM) structure; hence present device was horizontal. The electrical characterization is used to analyze the UV detection capability of the fabricated device, and various calculated parameters include saturation current = 8.31 × 10−7 A/cm−2, ideality factor = 4.02, barrier height = 0.75 eV, etc. It was observed that forward and reversed bias current increases when exposed to Ultraviolet (UV) light. In addition, responsivity and series resistance are also reported in this paper.
Low Resistance Ohmic Contact on ZnO Thin Film Revealed by Schottky Barrier Height
Sannakashappanavar B.S., Yadav A.B., Kumar V., Murty N.V.L.N., Singh K.
Article, Silicon, 2022, DOI Link
View abstract ⏷
A high performance electronic device can be fabricated by achieving a high quality metal thin film Ohmic contact to intrinsic ZnO. In the present work, the low specific contact resistance Cr/Au metallization scheme deposited on n-type intrinsic 100 nm RF sputtered ZnO (Zinc oxide) thin film on SiO2/p-Si (100), an integrated circuit (IC) compatible substrate is utilized for the first time. Several metallization schemes were reported in the literature till date but not chromium to ZnO. Schottky Barrier height method was used to analyze the specific contact resistance which was obtained from the current-voltage characteristics. Thermionic emission carrier transport is considered at the interface for barrier height analysis. Low specific resistance was initiated in this work owing to the single-crystalline and smooth surface of the ZnO thin film revealed by X-Ray Diffraction (XRD) and Atomic Force Microscope (AFM) analysis. The simulation of the device structure was performed by using ATLAS software. The experimental result were finally compared with simulation results and were found to be in close agreement with each other.
A Theoretical Study on Palladium-ZincOxide System
Nagasai R.K.B., Suvarna Pooja B., Meher Preethi K., Sahithi Arjun R., Yadav A.B.
Conference paper, 2022 IEEE International Conference on Nanoelectronics, Nanophotonics, Nanomaterials, Nanobioscience and Nanotechnology, 5NANO 2022, 2022, DOI Link
View abstract ⏷
The Zinc-Oxide unit's properties will be investigated in combination with studies of Pd-ZnO Crystal lattice. The semi-conductor then will be emulated with software, and subsequent computations also will be performed to learn more about the lattice's different states and band structure. The computations are carried out at room temperature. The simulation is run on free open-source application Quantum Espresso, written in FORTRAN C. The main goal of this project is to simulate a Pd-ZnO Unit and compare the results to that of ZnO.
Investigation of Schottky barrier height using area as parameter: Effect of hydrogen peroxide treatment on electrical optical properties of Schottky diode
Yadav A.B., Sannakashappanavar B.S.
Article, Optical Materials, 2021, DOI Link
View abstract ⏷
RF sputtered 25 nm ZnO thin film surface treated with H2O2 has produced the Schottky diodes of improved electrical and optical properties. The enhancement is associated with adsorbed and introduced oxygen at the film's surface and in bulk while H2O2 treatment as revealed by the XPS analysis. Further, H2O2 treatment also has improved the ZnO thin film's surface morphology, crystal structure, and optical properties studied by XRD, SEM, and PL measurement. The experimentally measured energy band gap is compared with density functional theory computation-based result to find the possible cause behind the change in edge excitation energy band after treatment. Besides, an alternative method by considering the Schottky diode area as a parameter is introduced to calculate barrier height. The five diodes average barrier height, calculated by the conventional Schottky model, was lower than the barrier height obtained by this proposed method. This result is obtained for the diodes fabricated on the nontreated and treated sample. The conventional and proposed methods showed Schottky diodes potential barrier lowering under UV illumination, and it was associated with the change in carrier density and desorption of adsorbed oxygen on the ZnO surface. The treated surface's low conductivity and high oxygen concentration governed the superior UV detection capability of Schottky diodes fabricated on it. The literature demonstrates many similar studies for large thicknesses of ZnO 150–1000 nm but not on ultra-thin (25 nm) ZnO film, even though the UV light can penetrate ZnO approximately to this depth.
Synthesis of ZnO Ultra-Thin Film-Based Bottom-Gate Phototransistors for UV Detection
Sannakashappanavar B.S., Yadav A.B., Byrareddy C.R., Narasimha Murty N.V.L.
Article, Journal of Electronic Materials, 2020, DOI Link
View abstract ⏷
The present study illustrates the fabrication of ZnO ultra-thin film (25 nm)-based bottom gate phototransistors using RF sputtering and thermal evaporation on SiO2/Si substrate for UV detection. According to the literature, phototransistors have the ability to solve persistent photoconductivity (PPC). PPC increases the response time of metal oxide semiconductor-based conventional two-terminal photodetectors. Prior to transistor fabrication, the surface of the deposited ZnO thin film was treated with hydrogen peroxide (H2O2) in order to improve its crystal structure, surface morphology, energy bandgap, and electrical conductivity. The characteristics of ZnO thin film were investigated by atomic force microscope (AFM), field emission scanning electron microscopy (FESEM), x-ray diffraction (XRD), photoluminescence (PL), and x-ray photoelectron spectroscopy (XPS). The electrical and optical performance of phototransistors were investigated by measuring their output and transfer characteristics in dark and UV light. H2O2 treatment was found to be effective in producing efficient optical detection phototransistor. Optoelectronics properties (for UV detection) of the fabricated phototransistors were studied by using low-intensity and low power commercial LEDs of 365 nm wavelength.
Deposition of ZnO thin film at different substrate temperature using RF sputtering for growth of ZnO nanorods using hydrothermal method for UV detection
Sannakashappanavar B.S., Byrareddy C.R., Varma S., Pattanshetti N.A., Yadav A.B.
Conference paper, Lecture Notes in Electrical Engineering, 2020, DOI Link
View abstract ⏷
The growth properties of ZnO Nanorods was studied on different seed layers by the deposition of Zinc oxide (ZnO) thin film on SiO2/Si substrate by RF sputtering at two different conditions, i.e., one at room temperature and another at 400 °C substrate temperature. Surface morphology of the seed layer was studied by X-Ray Diffraction and Atomic Force Microscopy (AFM). Low cost hydrothermal method was employed for the growth of ZnO Nanorods on both the seed layers. The structural properties of ZnO nanorods were characterized by Field Emission Scanning Electron Microscope (FESEM). The FESEM images showed the proper alignment and orientation of ZnO nanorods grown on both the seed layers. The I-V measurements were carried out at room temperature under dark light and Ultraviolet (UV) light source. In order to examine the UV detection, MSM (Metal–Semiconductor–Metal) photodetector was fabricated and responsivity was measured for the nanorods grown on both seed layers. The better responsivity and contrast ratio of ZnO nanorods based UV detector was observed in case of 150 nm seed layer deposited at 400 °C.
Zero bias UV detection and precursor effect on properties of ZnO nanorods grown by hydrothermal method on SiO2/p-Si substrate
Yadav A.B., Parvathi P.V.L., Thabassum Shaik R.
Article, Thin Solid Films, 2019, DOI Link
View abstract ⏷
Here we present the effect of the precursor chemistry on the properties of ZnO nanorods prepared by using the hydrothermal method. The nanorods were grown over RF-sputtered 50 nm ZnO seed layers on integrated circuits compatible highly lattice mismatched SiO2/p-Si substrates. Two zinc sources namely zinc acetate and zinc nitrate were dissolved in solvent (a solution of deionized water and hexamethylenetetramine) in parallel to grow the highly conducting, vertically-aligned ZnO nanorods. Surface morphology and crystal structure of NRs were investigated using scanning electron microscope and X-ray diffraction. Nanorods synthesized in zinc acetate precursor's solution were highly crystalline and sparsely packed with well defined hexagonal top surface compared to nanorods grown in zinc nitrate precursors. Elemental composition of nanorods was studied using X-ray photoelectron spectroscopy. The oxygen and zinc observed in all the nanorods, zinc acetate synthesized nanorods show high atomic percentage of these two elements. To test the electrical and photo detection properties of the ZnO nanorods a metal semiconductor metal (MSM) structure was fabricated by depositing Ti/Au ohmic contacts over the nanorods. The MSM structure fabricated over the nanorods synthesized by using zinc nitrate precursor shows zero bias UV detection not reported up to present. The conducting properties of the nanorods were obtained from the current-voltage characteristics measurements of the MSM photosensor, and it is observed that the zinc acetate synthesized NRs were highly conducting. The UV detection capability of the MSM photosensor were tested by exposing UV light from light emitting diodes of same power and different wavelength. The ZnO NRs grown in zinc nitrate precursor shows high photosensitivity.
True Ohmic contact on RF sputtered ZnO thin film by using the nonalloy Ti/Au metallization scheme
Yadav A.B., Sannakashappanavar B.S.
Article, Journal of Alloys and Compounds, 2019, DOI Link
View abstract ⏷
Metal contact (Ohmic or Schottky) is vital for building different ZnO based IC compatible electronic devices. Literature has seen a tremendous development on metal contacts on this specific semiconductor by using a range of metallization scheme, but in all cases, ZnO film was very thick, highly doped, and deposited on Al2O3 substrate, even though this substrate is not appropriate for modern IC technology. For estimation of the specific contact resistance, transmission line method (TLM) has been used predominantly instead of Schottky barrier height (SBH) model, considering thermionic emission (TE) theory. However, SBH model is more realistic and furnishes accurate statistics of the distinct parameters of ohmic contacts compared to TLM theory, where TLM gives only specific contact resistance. So, we are presenting the electrical properties of Ti/Au nonalloy ohmic contact developed on 20 nm undoped RF sputtered ZnO thin film on SiO2/p-Si and SiO2/n-Si substrates using SBH model considering thermionic emission theory. Further, using X-ray diffraction, photo luminance, and scanning electron microscopy, we were investigated the crystal structure, energy band gap, and surface morphology of the thin film. And, current-voltage (I –V) data were measured using a semiconductor parameter analyzer. Barrier heights and other parameters of developed metallization scheme extracted from experimental I-V characteristics of the fabricated ohmic contacts considering carrier transport at the interface is governed by thermionic emission theory. It can be found that the deviation in barrier heights which are estimated from semi -log current versus voltage (ln(I)–V) characteristics and extracted from Richardson plot, because of barrier inhomogeneity, series resistance, and actual contact area. To decrease this deviation we have analyzed the barrier heights after rectify the voltage axis by considering the series resistance, but series resistance correction alone is not sufficient. Finally, lowest specific contact resistance was achieved compared to any metallization scheme using Richardson plot, this approach and structure are first time reported specifically on ZnO.
Effect of precursor chemistry on the structural and sensing properties of hydrothermally grown nanorods
Yadav A.B., Parvathi P.V.L., Thabassum S.R.
Article, Applied Physics A: Materials Science and Processing, 2019, DOI Link
View abstract ⏷
We report on the effect of precursor chemistry on ZnO nanorods (NRs) growth and their hydrogen sensing characteristics probably for the first time. We found that zinc acetate grown nanorods were dislocated at the center and showed better sensitivity towards hydrogen gas than conventional NRs without dislocation. For nanorods growth, a ZnO seed layer of thickness 80 nm was deposited by RF sputtering at room temperature over SiO2/p-Si substrate; oxidation in silicon substrate was done by the thermal oxidation method. The crystalline phases and the surface nanostructure of the ZnO thin film (seed layer) were investigated by the X-ray diffraction and atomic force microscope. The ZnO nanorods’ surface morphology and their crystalline nature were studied by SEM and X-ray diffraction. The chemical properties of the ZnO nanorods were investigated by the X-ray photoluminescence spectroscopy. Using DC sputtering and shadow mask, Ti (80 nm)/Au (100 nm) metal layers were deposited over the ZnO nanorods to fabricate a metal semiconductor metal structure for sensor fabrication. I–V characteristics of the devices were obtained by the semiconductor parameter analyzer. The hydrogen gas was exposed over the devices using mass flow controller, and it was found that device containing nanorods grown by zinc acetate shows 98% sensitivity for 24 ppm gas concentration in a nitrogen atmosphere that was the largest reported till date than with bare conventional non-dislocated NRs.
Semianalytical Threshold Voltage Model of a Double-Gate Nanoscale RingFET for Terahertz Applications in Radiation-Hardened (Rad-Hard) Environments
Singh K., Kumar S., Tiwari P.K., Yadav A.B., Dubey S., Jit S.
Article, Journal of Electronic Materials, 2019, DOI Link
View abstract ⏷
In this work, a recent device structure called double-gate (DG) nanoscale RingFET has been investigated by developing a computationally efficient foremost semianalytical threshold voltage model. Poisson’s equation has been solved using parabolic approximation to calculate surface channel potential, which has been further employed to formulate the threshold voltage of the device. This device comes under the category of edgeless transistor, which has a lot of scope in radiation harsh environment-based applications. A cutoff frequency of terahertz range up to 1.1 THz has been observed in this device, which makes it very useful for high-frequency applications. The proposed model results are extensively verified with the simulation data obtained with a three-dimensional technology computer-aided design (3D TCAD) simulator from SILVACO ATLAS™. Both the modeled and simulated results are found to be in good agreement.
Fabrication and characterization of Schottky diode on ultra thin ZnO film and its application for UV detection
Sannakashappanavar B.S., Yadav A.B., Byrareddy C.R., Murty N.V.L.N.
Article, Materials Research Express, 2019, DOI Link
View abstract ⏷
In this paper we report a Schottky contact based UV detector over ultrathin (∼25 nm) radio frequency (RF) sputtered ZnO thin film probably for the first time. The substrate used was IC compatible p-type silicon instead of widely used sapphire substrate. The surface morphology, crystal phases, optical properties of the thin film were studied by atomic force microscopy, Field emission scanning electron microscopy, x-ray diffraction and photo luminance. The planner Schottky diode (Pd/ZnO/Ti/Au) was fabricated by photolithography e-beam evaporator and DC sputtering. The electrical properties of the diode were investigated by semiconductor parameter analyzer with micro probing arrangement. Different parameters of the diode like barrier height, ideality factor and reverse saturation current were estimated from I-V characteristics using the Schottky Barrier Height theory. UV light of fixed frequencies and intensity were exposed on the diode and it was found that its different parameters were changed.
Seed layer effect on different properties and UV detection capability of hydrothermally grown ZnO nanorods over SiO2/p-Si substrate
Sannakashappanavar B.S., Byrareddy C.R., Kumar P.S., Yadav A.B.
Article, Superlattices and Microstructures, 2018, DOI Link
View abstract ⏷
Hydrothermally grown one dimensional ZnO nanostructures are among the most widely used semiconductor materials to build high-efficiency electronic devices for various applications. Few researchers have addressed the growth mechanism and effect of ZnO seed layer on different properties of ZnO nanorods grown by hydrothermal method, instead, no one has synthesized ZnO nanorod over SiO2/p-Si substrate. The aim of this study is to study the effect of ZnO seed layer and the growth mechanism of ZnO nanorods over SiO2/p-Si substrate. To achieve the goal, we have synthesized ZnO nanorods over different thickness ZnO seed layers by using the hydrothermal method on SiO2/p-Si substrate. The effects of c-plane area ratio were identified for the growth rate of c-plane, reaction rate constant and stagnant layer thickness also calculated by using a modified rate growth equation. We have identified maximum seed layer thickness for the growth of vertical ZnO nanorod. A step dislocation in the ZnO nanorods grown on 150and200nm thick seed layers was observed, the magnitude of Burges vector was calculated for this disorder. The seed layer and ZnO nanorods were characterized by AFM, XPS, UV-visible, XRD (X-ray diffraction, and SEM(scanning electron microscope). To justify the application of the grown ZnO nanorods Ti/Au was deposited over ZnO nanorods grown over all seed layers for the fabrication of photoconductor type UV detector.
Study of annealing effect on the growth of ZnO nanorods on ZnO seed layers
Sannakashappanavar B.S., Pattanashetti N.A., Byrareddy C.R., Yadav A.B.
Conference paper, AIP Conference Proceedings, 2018, DOI Link
View abstract ⏷
A zinc oxide (ZnO) seed layer was deposited on the SiO2/Si substrate by RF sputtering. To study the effect of annealing, the seed layers were classified into annealed and unannealed thin films. Annealing of the seed layers was carried at 450°C. Surface morphology of the seed layers were studied by Atomic force microscopy. ZnO nanorods were then grown on both the types of seed layer by hydrothermal method. The morphology and the structural properties of the nanorods were characterized by X-ray diffraction and Scanning electron microscopy. The effect of seed layer annealing on the growth and orientation of the ZnO nanorods were clearly examined on comparing with the nanorods grown on unannealed seed layer. The nanorods grown on annealed seed layers were found to be well aligned and oriented. Further, the I-V characteristic study was carried out on these aligned nanorods. The results supports positively for the future work to further enhance the properties of developed nanorods for their wide applications in electronic and optoelectronic devices.
Particle size effects on the hydrogen sensing properties of Pd/ZnO Schottky contacts fabricated by sol–gel method
Article, International Journal of Hydrogen Energy, 2017, DOI Link
View abstract ⏷
ZnO thin films grown on n-Si substrates using sol–gel spin coating method were annealed in Ar atmosphere at 450 °C, 550 °C and 650 °C temperatures. Three types of Pd/n-ZnO/n-Si/Ti/Al vertical Schottky diodes were fabricated using three types of ZnO films obtained by annealing at the aforementioned three different annealing temperatures for hydrogen gas sensing applications. Using thermal evaporation method, the Pd metals dots were deposited for the Schottky contacts on the annealed ZnO films while Ti and Al were sequentially deposited over the back side of the n-Si for forming the ohmic cathode contact of the diode. The XRD and SEM analyses showed that the structural and surface properties of the ZnO thin films were largely influenced by the annealing temperature. The grain size was observed to be increased with annealing temperature of the ZnO films. The increased grain size at higher annealing temperatures reduces the surface to volume ratio, number of nanoparticles in the ZnO films (and hence the number of Schottky barriers formed between a nanoparticle and Pd) and number of grain boundaries (due to merging of a number of smaller grains into a larger sized grain) which, in turn, affects the hydrogen sensing properties of the devices under consideration. This paper investigates the effects of grain size on the hydrogen sensing property, series resistance and barrier height of the Pd/ZnO film Schottky diodes in details. The highest hydrogen response was observed in the device containing the ZnO film annealed at 450 °C which was attributed to the largest surface to volume ratio owing to the smallest particle size in the ZnO film.
Sol-gel-based highly sensitive Pd/n-ZnO thin film/n-Si schottky ultraviolet photodiodes
Yadav A.B., Pandey A., Somvanshi D., Jit S.
Article, IEEE Transactions on Electron Devices, 2015, DOI Link
View abstract ⏷
High-performance ultraviolet (UV) Schottky photodiodes obtained by growing Pd Schottky contacts on the sol-gel-derived n-ZnO thin films deposited on n-Si substrates have been reported in this paper. The current-voltage (I-V) measurements of the as-fabricated Schottky photodiodes show an excellent room temperature contrast ratio (i.e., the ratio of the current under UV illumination to the dark current) of ~5.332 × 103 and responsivity (i.e., the parameter characterizing the sensitivity of the device to the UV light) of ~8.39 A/W at -5 V reverse bias voltage, respectively; when the device is illuminated by an UV source of ~650 μW output power at ~365 nm. The measured room temperature contrast ratio and responsivity are believed to be the highest among the reported values in the literature for ZnO thin film-based Schottky photodiodes using sol-gel method.
Study of post annealing effects on structural and optical properties of sol-gel derived ZnO thin films grown on n-Si substrate
Yadav A.B., Periasamy C., Jit S.
Conference paper, IOP Conference Series: Materials Science and Engineering, 2015, DOI Link
View abstract ⏷
Zinc oxide (ZnO) thin films were grown on n-type silicon (100) substrates by sol- gel spin coating technique. The prepared thin films were annealed in the presence of Ar at three different temperatures (at 450°C, 550°C and 650°C) to study the impact of annealing temperature on the structural and optical properties of the ZnO thin films. The structural, surface morphology and optical properties of the thin film were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM) and photoluminescence (PL) measurements respectively. The grown ZnO thin films are polycrystalline in nature with wurtzite hexagonal structure as evident from the XRD and SEM analyses. It further indicates that the crystalline size increases with increasing annealing temperature. The post annealing is also found to influence the optical properties in the terms of band gap energy of the ZnO thin films. The optical energy band gap was found to be decreased from 3.205 to 3.13eV as the annealing temperature is increased from 450°C to 650°C. However, our results concerning the growth of ZnO thin films on Si substrates suggest that there is an intermediate growth temperature allowing for the optimization of the ZnO film growth. The results of the study can be used as a guideline for growing ZnO thin films on n-Si substrates with a homogenous surface morphology, high surface to volume ratio and desired particle size, which are suited for optoelectronic/ gas sensing applications.
Pd schottky contacts on sol-gel derived ZnO thin films with nearly ideal richardson constant
Article, IEEE Electron Device Letters, 2014, DOI Link
View abstract ⏷
his letter reports the temperature-dependent analysis of measured I-V characteristics of Pd/ZnO thin filmbased Schottky diodes grown on n-Si (100) substrates by sol.gel method. Assuming a Gaussian distributed barrier height at the Pd/ZnO interface with a standard deviation (σ0) around a mean barrier height q&phiB,m, the analysis estimates the value of Richardson constant ∼-31.67 Acm-2K-2, which is not only very close to its theoretical value of ∼-32 Acm-2K-2 (for m.e = 0.27m0), but also the best result reported so far for ZnO-based Schottky contacts. The estimated value of the zero-bias mean barrier height (∼1.39 eV) at T = 0 K is also observed to be very close to its theoretical value of 1.42 eV (for work function of Pd = 5.12 eV and electron affinity of ZnO = 3.7 eV). © 2014 IEEE.
Effects of annealing temperature on the structural, optical, and electrical properties of ZnO thin films grown on n-Si〈100〉 substrates by the sol-gel spin coating method
Article, Acta Metallurgica Sinica (English Letters), 2014, DOI Link
View abstract ⏷
The effects of annealing temperature on the sol-gel-derived ZnO thin films deposited on n-S〈100〉 substrates by sol-gel spin coating method have been studied in this paper. The structural, optical, and electrical properties of ZnO thin films annealed at 450, 550, and 650 °C in the Ar gas atmosphere have been investigated in a systematic way. The XRD analysis shows a polycrystalline nature of the films at all three annealing temperatures. Further, the crystallite size is observed to be increased with the annealing temperature, whereas the positions of various peaks in the XRD spectra are found to be red-shifted with the temperature. The surface morphology studied through the scanning electron microscopy measurements shows a uniform distribution of ZnO nanoparticles over the entire Si substrates of enhanced grain sizes with the annealing temperature. Optical properties investigated by photoluminescence spectroscopy shows an optical band gap varying in the range of 3.28-3.15 eV as annealing temperature is increased from 450 to 650 °C, respectively. The four-point probe measurement shows a decrease in resistivity from 2.1 × 10 -2 to 8.1 × 10-4 ω cm with the increased temperature from 450 to 650 °C. The study could be useful for studying the sol-gel-derived ZnO thin film-based devices for various electronic, optoelectronic, and gas sensing applications. © 2014 The Chinese Society for Metals and Springer-Verlag Berlin Heidelberg.
Annealing-temperature effects on the properties of ZnO thin films and Pd/ZnO Schottky contacts grown on n-Si (1 0 0) substrates by vacuum deposition method
Yadav A.B., Singh K., Pandey A., Jit S.
Article, Superlattices and Microstructures, 2014, DOI Link
View abstract ⏷
The effects of annealing temperature on the properties of ZnO thin films and Pd/ZnO thin film Schottky contacts grown on the n-silicon (n-Si) substrates by vacuum evaporation technique have been reported for the first time in this paper. The as-grown ZnO thin films were annealed in the Argon gas atmosphere for a same duration of 20 min at 450 °C, 550 °C and 650 °C temperatures. The surface morphology of the films analyzed by the scanning electron microscopy and X-ray diffraction spectroscopy are observed to be modified with annealing temperature. The photoluminescence and resistivity measurements were carried out to report the effects of annealing temperature on the optical and electrical properties of the vacuum deposited ZnO thin films. The Pd Schottky contacts grown on the annealed ZnO thin films at 550 °C annealing temperature is observed to have the superior electrical characteristics over the Schottky contacts on ZnO films annealed at 450 °C and 650 °C temperatures. © 2014 Elsevier B.V. All rights reserved.
Hydrogen gas sensing properties of Pd/ZnO thin films grown on n-Si<100> substrates at room-temperature by thermal evaporation and sol-gel techniques: A comparative study
Yadav A.B., Periasamy C., Bhaumik S., Jit S.
Article, Indian Journal of Pure and Applied Physics, 2013,
View abstract ⏷
The present paper compares the room temperature hydrogen (H2) gas sensing properties of two Pd/nanocrystalline-ZnO thin film based Schottky contacts grown on n-type silicon (100) substrates by thermal evaporation and sol-gel techniques. The structural, surface and optical properties of the ZnO thin films under consideration are also presented. The Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDS) measurements have been carried out to study the surface morphologies and elementary compositions of the ZnO films,respectively. The X-ray diffraction (XRD) analysis shows that the ZnO thin films grown by both the methods are polycrystalline in nature with a hexagonal wurtzite structure. The optical band gaps of the films are estimated from the photoluminescence (PL) spectroscopy as 3.26 eV and 3.28 eV for thermal evaporation and sol-gel techniques, respectively. The current-voltage (I-V) measurements have been carried out to study the electrical and hydrogen (H2) sensing characteristics of Pd/ZnO Schottky contacts fabricated on the ZnO thin films grown by the two methods under consideration. Both the Pd/ZnO contacts under consideration are observed to have a good Schottky behaviour under dark condition and a high response to H 2 gas with relatively short response and recovery times. Device fabricated by thermal evaporation shows better performance.
Analysis of temperature dependent I-V characteristics of Pd/ZnO/n-Si schotky diode by sol-gel method
Yadav A.B., Shankar R., Kumar R., Pandey A., Jit S.
Conference paper, 2013 Annual International Conference on Emerging Research Areas, AICERA 2013 and 2013 International Conference on Microelectronics, Communications and Renewable Energy, ICMiCR 2013 - Proceedings, 2013, DOI Link
View abstract ⏷
The ZnO thin film was deposited on n-Si (100) by sol-gel and spin coating technique. Pd/ZnO/n-Si/Ti/A1 Schottky contact was fabricated by the thermal evaporation method using shadow mask technique. The ZnO thin film was annealed in Ar (argon) atmosphere at 450°C to enhance the structural and surface morphology. The structural and surface morphology of prepared ZnO thin film were characterized by the XRD and SEM and it was found that the thin film was polycrystalline in nature with homogeneous surface. The I-V characteristics of the device were analyzed by the semiconductor parameter analyzer. The semiconductor parameters were determined at different operating temperature in air atmosphere. © 2013 IEEE.
