Browsing by Author "Mourya, Satyendra Kumar"

Now showing 1 - 20 of 24

Analysis of temperature sensitive electrical performance of sputter grown Ni and Ni–Cr Schottky contacts on 4 H-SiC
(Springer, 2024-11) Singh, Dheerendra; Mourya, Satyendra Kumar; Bhatt, Upendra Mohan
This paper studies the temperature-dependent electrical transport properties of nickel (Ni) and nickel–chromium (Ni–Cr) sputtered on n-type 4 H-SiC substrate. Barrier inhomogeneities have been found to affect the electrical parameter of the Schottky barrier diode (SBD) from 323 to 423 K temperature range, We have done current–voltage characterization of Ni and Ni–Cr Schottky junctions. The barrier height , reverse saturation current , ideality factor and series resistance were obtained from I–V characteristics of Ni and Ni–Cr and these parameters are observed to be highly dependent on temperature. It has been observed that Ni–Cr contact has exhibited better electrical characteristics as well as thermal sensitivity as compared to Ni. This may be attributed to the smaller number of barrier inhomogeneities at the Ni–Cr/4 H-SiC interface. In the temperature range from 323 to 423 K, Ni and Ni–Cr-based Schottky contacts, Following observation has been noticed (a). Schottky barrier height (SBH) increased from 1.24 to 1.37 eV and 1.15 to 1.45 eV, (b). Ideality factors reduced from 3.76 to 2.61 and 3.20 to 2.53, (c). Series resistance decreased from 10.22 to 3.37 and 2.45 to 1.16 , and (d). Reverse leakage current to A and to A respectively. The V–T curves for both SBDs are investigated (for the same temperature range) to calculate their thermal sensitivity at and A, respectively. The V–T curves with linear behavior are used to calculate the thermal sensitivity coefficient , which was found to be 7.11 to 7.93 mV/K for the Ni–Cr SBD, and 7.1 to 20.01 mV/K for the Ni/4 H-SiC contacts. The sensitivity-current characteristics for the Ni/4 H-SiC SBD were found to be a non-linear comparison with Ni–Cr/4 H-SiC SBD, which may be attributed to the presence of a highly resistive and non-uniform coating of Ni at the interface.
Coexistence of Space Charge Limited and Variable Range Hopping Conduction Mechanism in Sputter-Deposited Au/SiC Metal–Semiconductor–Metal Device
(IEEE, 2023-02) Mourya, Satyendra Kumar
Despite being the cornerstone of high-temperature and high-power applications, the fabrication of silicon carbide (SiC) thin films has been a major challenge among research activities related to wide bandgap semiconductors. As almost all the reported SiC thin films produced by RF sputtering are amorphous, the growth of crystalline thin film on p-type silicon substrate at high temperature (>900 °C) is presented in this work. A metal–semiconductor–metal (MSM) device is fabricated with gold (Au) electrodes by sputtering. A unique behavior of current–voltage ( I – V ) characteristics is found in different voltage regimes. The thermionic emission model fails to explain the observed I – V characteristics. To understand the current transport mechanism in detail, I – V characteristics are carried out in the temperature range 250–380 K and divided into two voltage regimes, below and above 1 V. Below 1 V, variable range hopping mechanism (VRH) is found to be dominant and above 1 V, and ohmic conduction followed by space charge limited conduction (SCLC) is held accountable for the current transport mechanism. The analysis of both mechanisms indicates the presence of disorder states and gives valuable information about trap centers. The C – V characteristics further suggest the presence of interface states and deep traps. The advantageous implementation of this information will help to design optoelectronic, magnetic, and efficient energy storage devices to extract the maximum performance.
CsGeI3 perovskite-based solar cells for higher efficiency and stability: an experimental investigation
(IEEE, 2025-05) Mourya, Satyendra Kumar
Among the recent developments in photovoltaic technologies, perovskite solar cells (PSCs) have drawn significant attention, owing to their exceptional power conversion efficiency (PCE), cost-effectiveness, and better optoelectronic characteristics. However, the stability and presence of lead (toxicity) in PSCs remains a major challenge to their commercialization. In this study, we experimentally investigated all-inorganic, lead-free CsGeI3-based PSCs in an n-i-p configuration. The CsGeI3 films were synthesized using a one-step spin-coating technique and their crystallographic characteristics were analyzed. Furthermore, we fabricated and tested different device architectures incorporating CsGeI3 as the absorber layer with various electron transport layers (ETLs), including TiO2, ZnO, and graphene oxide (GO), while employing MoS2 as the hole transport layer. The resulting device structure was Fluorine doped Tin oxide (FTO)/(TiO2/ZnO/GO)/CsGeI3/MoS2/Ni). All fabricated devices demonstrated excellent performance, with the TiO2-based ETL device achieving the highest PCE of 10.79%. In addition, incorporating reduced graphene oxide (rGO) as an interface layer on top of the absorber layer further enhanced photovoltaic performance by approximately 3% across all configurations (achieving outstanding efficiency of 13.57%). The hydrophobic nature and high conductivity of rGO suggest its potential as a promising strategy for improving the stability and efficiency of lead-free PSCs in future applications.
Determination of optical constants including surface characteristics of optically thick nanostructured Ti films: analyzed by spectroscopic ellipsometry
(OSA Open Access, 2016) Mourya, Satyendra Kumar
In the present work, optically thick nanostructured titanium (Ti) films of thickness ranging from ∼100 to 900 nm were deposited on a glass substrate by DC magnetron sputtering at room temperature. Microstructural and surface properties of the samples were studied by x-ray diffraction and x-ray photoelectron spectroscopy (XPS). The morphological results revealed a systematic normal grain growth mechanism with increasing thickness analyzed by a scanning electron microscope. The influence of thickness on film surface roughness has been investigated by atomic force microscopy (AFM). The optical dispersion behavior was examined by spectroscopic ellipsometry (SE) over the long wavelength range of 246–1688 nm. The experimentally observed SE parameters were theoretically fitted with Drude–Lorentz and Bruggeman effective medium approximation theory. The surface properties of the Ti film measured by XPS and AFM were further accounted for in the optical model to determine optical constants (𝑛 and 𝑘) and the obtained results are expected to be the best available for bulk Ti metal.
Development of Pd-Pt functionalized high performance H2 gas sensor based on silicon carbide coated porous silicon for extreme environment applications
(Elsevier, 2019-03) Mourya, Satyendra Kumar
Present work demonstrates the hydrogen gas (H2) sensing characteristics of palladium-platinum (Pd-Pt) functionalized silicon carbide (SiC) thin film grown on porous silicon (PSi) substrate for high temperature applications. Nano-crystalline SiC thin film was deposited by RF magnetron sputtering on anodized PSi substrate. The loading of discrete ultra-thin Pd-Pt bimetallic catalytic layer was carefully controlled by varying the sputtering parameters. The proposed device architecture (Pd-Pt/SiC/PSi) revealed significant advantages, such as stable high sensing response, large tunable detection range (5–500 ppm), fast response/recovery time, excellent reproducibility, high selectivity, wide operating temperature regime (25–500 °C) and good durability. The observed high response may be ascribed to the combined effect of enhanced catalytic activity of bimetallic Pd-Pt layer and increased surface area of the proposed sensor.
Effect of annealing parameters on optoelectronic properties of highly ordered ZnO thin films
(Elsevier, 2019-09) Mourya, Satyendra Kumar
In the present work, tuning in optoelectronic properties of sputter deposited zinc oxide (ZnO) thin films on ITO coated glass substrate have been investigated as a function of annealing parameters. Although, the annealing treatment is needed to tune the optoelectronic properties of ZnO layer but it can also modify the electrical properties {a drastic change in sheet resistance (13 Ω/sq. to 23 ohm/sq.) was observed at an annealing temperature of 200 °C} of underlying ITO substrate, which restricted maximum annealing temperature to 200 °C for ZnO at ITO. Vertically standing array of ZnO nano-pipes having single crystal orientation (002) with hexagonal structure, large crystallite size (∼24 nm), lowest lattice strain (0.621%), highest surface roughness (∼16 nm), and lowest Rsh (12.3 KΩ/sq.) were obtained for sample annealed at 200 °C for 60 min. The XPS study also revealed that the sample annealed at 200 °C for 60 min contains lowest oxygen related vacancy (23.7), which favors the facile electrons transport when ZnO is used as an electron transport layer (ETL). SE and UV–Vis results revealed best optical parameters i.e., highest transmittance (T∼ 89%), refractive index (n = 1.98 at 480 nm), and band gap (Eg = 3.30 eV), for the sample annealed at 200 °C for 60 min. These results indicated that ZnO nano-pipes based ETL may be a promising candidate for low temperature, high mobility, and cost-effective optoelectronic devices.
Electronic structure of Pr2MnNiO6 from x-ray photoemission, absorption and density functional theory
(IOP, 2018) Mourya, Satyendra Kumar
The electronic structure of double perovskite Pr2MnNiO6 was studied using core x-ray photoelectron spectroscopy and x-ray absorption spectroscopy. The 2p x-ray absorption spectra show that Mn and Ni are in 4+ and 2+ states respectively. Based on charge transfer multiplet analysis of the 2p XPS spectra of both ions, we find charge transfer energies of 3.5 and 2.5 eV for Ni and Mn respectively. The ground state of Ni2+ and Mn4+ ions reveal a higher d electron count of 8.21 and 3.38 respectively as compared to the ionic values. The partial density of states clearly show a charge transfer character of the system for U − J 2 eV. The O 1s edge absorption spectra reveal a band gap of 0.9 eV, which is close to the value estimated from analysis of Ni and Mn 2p photoemission and absorption spectra. The combined analysis of nature of spectroscopic data and first principles calculations reveal that the material is a p − d type charge transfer insulator with an intermediate covalent character according to the Zannen–Sawatzy–Allen phase diagram.
Ellipsometric Investigation of Room Temperature Grown Highly-Oriented Anatase TiO2 Thin Films
(Springer, 2018-12) Mourya, Satyendra Kumar
In this article, we have reported the structural optimization and optical properties of anatase titanium dioxide (TiO2) thin films grown by direct current magnetron sputtering on a glass substrate at room temperature (RT). The x-ray diffraction measurement revealed anatase phase of TiO2 with preferred orientation (101). The morphological, compositional and topographical properties of the samples are explored by scanning electron microscopy, x-ray photoelectron spectroscopy and atomic force microscopy, respectively. The optical properties such as refractive index n, extinction coefficient k and optical bandgap Eg are determined in the broad wavelength range of 246–1688 nm using variable angle spectroscopic ellipsometry accounting for the surface properties in the optical stack model. Moreover, the nonlinear refractive index n2 and the third-order nonlinear optical susceptibility χ(3) are determined using the Tichy–Ticha relation and Wemple–Didomenico (WDD) parameters. The ratio of the carrier concentration to the effective mass N/m* has also been determined. The current research on the optical and dispersion energy parameters of RT grown anatase TiO2 thin films is expected to have a significant impact on advanced flexible optical, optoelectronic, and photonic applications.
Enhanced Optical Absorbance Of Hydrophobic Ti Thin Film: Role Of Surface Roughness
(IJMS, 2016) Mourya, Satyendra Kumar
In the present work, structural, morphological, optical and wettability properties of DC magnetron sputtered titanium (Ti) thin films have been investigated. The nanostructured Ti thin films were deposited on glass and silicon substrates at various deposition angles, θD = 0°, 30°, 45° and 60°. HCP structure of Ti thin films with preferred peak orientations (100) and (002) were revealed from XRD. It was observed that as the deposition angle increases, film thickness (~260 - 100 nm) as well as average crystallite size (~27 - 11 nm) of Ti thin films decrease. Significant changes in topography of the films, with change in deposition angle, have been observed. The optical and wettability results suggested that transmission, reflection, absorption and water contact angle of Ti thin films are strongly influenced by deposition angle due to change in its surface roughness. The large near infrared (NIR) absorbance (~ 66 - 75%) was found for the sample deposited at θD = 30°, which exhibited hydrophobic (~ 94.6°) nature with high surface roughness (~ 28 nm).
Enhanced Optical Absorption of Ti Thin Film: Coupled Effect of Deposition and Post-deposition Temperatures
(Springer, 2017-08) Mourya, Satyendra Kumar
In the present work, structural, morphological and optical properties of nanostructured titanium (Ti) thin films have been studied. The Ti thin films were fabricated on glass substrate by direct current (DC) magnetron sputtering at varying deposition and post-deposition temperatures (T DA) ranging from 373 K to 773 K. The microstructure and morphology of the Ti thin films were found to be highly dependent on T DA. The root mean square surface roughness (δ rms) was found to increase with T DA up to 673 K and then decreased at 773 K. The absorption (A) of Ti films has shown a similar trend as roughness with T DA; however, the reflection (R) has shown an opposite trend. Maximum A ~99–86% and minimum R ~1–14% were observed in the spectral range of 300–1100 nm for the sample fabricated at T DA = 673 K, which exhibited the highest δ rms ~193 nm. Due to its excellent absorption, this film may be a potential candidate for photonic applications such as a super-absorber.
High-performance self-biased Cu/SiC/Si photo-sensor with swift response for NIR/Vis photodetection
(Elsevier, 2024-08) Mourya, Satyendra Kumar
Silicon Carbide (SiC) shows great potential for use in high temperatures and harsh environments due to its promising physical properties. This report introduces a novel double depletion functional heterointerface comprising a multilayer structure of Cu/SiC/Si. High-quality nanocrystalline SiC thin films are fabricated on p-type Silicon (Si) by RF magnetron sputtering at a relatively low temperature of 900 °C as compared to conventional methods. A multilayer photo-sensor device, comprising Cu/SiC/Si layers, is fabricated through the thermal evaporation of Cu metal using a shadow mask. The device exhibits good photo-response at both 750 nm and 440 nm wavelengths. Both the junctions Cu/SiC and SiC/Si play role in generating electron-hole pairs along the depth of the device. The device exhibits a very high responsivity of 1.26 A/W and a rapid response of 94/137 ms at a wavelength of 750 nm at self-bias conditions. It also demonstrates a high responsivity of 0.46 A/W and a very fast response time of 66.8/66.4 ms for 440 nm wavelength. Owing to its impressive performance, this device distinguishes itself as a superior choice among state-of-the-art SiC-based photodetectors. Its significance lies in the robust stability of the SiC/Si junction in high-temperature settings, surpassing low bandgap materials for NIR/vis photodetectors.
Highly Sensitive and Selective H2 Gas Sensor Based on Pd-Pt Decorated Nanostructured Silicon Carbide Thin Films for Extreme Environment Application
(World Academy of Science, Engineering and Technology, 2007-01) Mourya, Satyendra Kumar
Present work describes the fabrication and sensing characteristics of the Pd-Pt decorated nanostructured silicon carbide (SiC) thin films on anodized porous silicon (PSi) substrate by RF magnetron sputtering. The gas sensing performance of Pd-Pt/SiC/PSi sensing electrode towards H2 gas under low (10–400 ppm) detection limit and high operating temperature regime (25–600 °C) were studied in detail. The chemiresistive sensor exhibited high selectivity, good sensing response, fast response/recovery time with excellent stability towards H2 at high temperature. The selectivity measurement of the sensing electrode was done towards different oxidizing and reducing gases and proposed sensing mechanism discussed in detail. Therefore, the investigated Pd-Pt/SiC/PSi structure may be a highly sensitive and selective hydrogen gas sensing electrode for deployment in extreme environment applications
Hydrogenation and Dehydrogenation of Hydrophobic Pd-Capped Vertically Aligned Porous Ti Nanoflake Thin Film
(Springer, 2018-07) Mourya, Satyendra Kumar
Hydrophobic palladium-capped vertically aligned porous titanium nanoflake (Pd/Ti) thin film has been grown on a Si substrate by DC-sputtering. The hydrogenation (0.5 bar) and dehydrogenation (100°C) kinetics of the Pd/Ti thin film have been studied in terms of their structural, morphological and optical properties. X-ray diffraction, Raman spectroscopy, scanning electron microscopy, and UV–Vis–NIR spectroscopy findings endorsed the hydrogen absorption and desorption in the Pd/Ti thin film. It was observed that the optical reflectance R decreased after hydrogenation due to the formation of dark gray-colored TiH2. Further, an increase in R was found after dehydrogenation and it became nearly equal to the R value of the as-deposited sample, which confirmed the reversible nature of Pd/Ti film towards hydrogen absorption and desorption. These investigated hydrogenation and dehydrogenation properties of the Pd/Ti thin film make this material interesting for optical hydrogen sensing and switching applications.
Nanostructured RF sputtered hexagonal ZnO nano-pebbles based electrode material for energy efficient devices
(AIP, 2020-11) Mourya, Satyendra Kumar
In the present work, we describe the synthesis and electrochromic (EC) properties of electrode material made of zinc oxide (ZnO) nano-pebbles. Highly ordered nanocrystalline nanoporous ZnO nano-pebbles electrode with crystalline hexagonal structure was synthesized on the ITO coated glass substrate using RF magnetron sputtering in a reactive atmosphere (Ar:O2::2:3) at room temperature (RT). The EC behavior of the active electrode was analyzed using UV-Vis spectroscopy and cyclic voltammetry (CV). The cyclic Voltammogram revealed the highly reversible redox characteristics with good cyclic stability at least upto 500 cycles. The proposed architecture, {Glass/ITO/ZnO nano-pebbles/1MKCl/ITO/glass} was found to be electrochemically active and exhibits wide optical modulation (26%), high reversible process, and good cyclic stability. The cathodic coloration ZnO electrode may be a potential candidate for novel and cheap energy efficient device and provide the indoor comfort with financial benefits
Optical and other physical properties of hydrophobic ZnO thin films prepared by dc magnetron sputtering at room temperature
(AIP, 2017) Mourya, Satyendra Kumar
Highly ordered and hydrophobic zinc oxide thin films have been synthesized by dc magnetron sputtering on the glass substrates at room temperature (RT). We have determined the influence of deposition parameters on the optical and other physical properties of the films, and the correlation between their microstructural and optical properties. Films have preferred (002) orientation, an average crystallite size ≤26 nm, and rms surface roughness ≤14 nm. The water contact angle of 120° exceeds previous measurements by over 10°–20°. Dispersion of the refractive index is analyzed in terms of the Wemple-DiDomenical single-oscillator model, and the third-order nonlinear optical parameters are calculated using the Tichy and Ticha relation. Refractive indices of 1.9686 at 540 nm are near the bulk value of 2.0041. Produced at RT, these highly ordered films may be promising candidates for compact optoelectronic devices.
Reduction of off-state drain current in AlN/β-Ga₂O₃ HEMT by trap state engineering
(Elsevier, 2024-05) Mourya, Satyendra Kumar; Kumar, Rahul
In this work, we report various strategies to reduce the off-state drain leakage current () in AlN/ high electron mobility transistor (HEMT) by 2D device simulation. We have investigated the effect of access region, channel doping concentration, barrier layer thickness, and trap state engineering on . The formation of a parallel channel deep into the substrate has been found to be responsible for large . All other strategies except trap state engineering have an incremental effect on . However, the device’s was reduced by around 12 orders of magnitude by trap-state engineering. Simultaneously, the on-state performance was unaffected, resulting in an elevated / current ratio of (). A steep subthreshold slope of 0.267 (V/dec) was also obtained. Further, we have investigated the impact of both donor- and acceptor-type traps on subthreshold characteristics. These promising results highlight the potential of AlN/ HEMT as a switch and for future high-power nanoelectronics applications.
The role of non-homogeneous barrier on the electrical performance of 15R–SiC Schottky diodes grown by in-situ RF sputtering
(Elsevier, 2022-10) Mourya, Satyendra Kumar
In the present work, we have demonstrated the impact of barrier inhomogeneities on the electrical characteristics of silicon carbide (SiC) based Schottky barrier diodes (SBDs). Ohmic and Schottky contacts were deposited on RF sputtered 15R–SiC film under optimized growth conditions. Forward biased current-voltage (I–V) measurement in the temperature range of 300–420 K was employed to extract the diode parameters (barrier height, ideality factor, and Richardson constant), considering the thermionic emission (TE) as dominant charge transport mechanism. The obtained value of barrier height φB and ideality factor n exhibited anomalies as compared to theoretically predicted values. It was attributed to the co-existence of multiple charge transport mechanism owing to defect induced lateral barrier inhomogeneities at the metal-semiconductor interface. Further, Gaussian distribution of φB, as established by Warner and Guttler was incorporated along with TE model to analyze the temperature dependent I–V data to understand the non-ideality in diode parameters. Eventually, the obtained diode parameters as per the modified charge transport mechanism were found to be in close alignment with the predicted values.
The Role of the Substrate on Photophysical Properties of Highly Ordered 15R-SiC Thin Films
(Springer, 2018-06) Mourya, Satyendra Kumar
We report on the structural optimization and photophysical properties of in situ RF-sputtered single crystalline 15R-SiC thin films deposited on various substrates (ZrO2, MgO, SiC, and Si). The role of the substrates on the structural, electronic, and photodynamic behavior of the grown films have been demonstrated using x-ray diffraction, photoluminescence (PL) and time-resolved photoluminescence spectroscopy. The appropriate bonding order and the presence of native oxide on the surface of the grown samples are confirmed by x-ray photoelectron spectroscopy measurement. A deep-blue PL emission has been observed corresponding to the Si-centered defects occurring in the native oxide. Deconvolution of the PL spectra manifested two decay mechanisms corresponding to the radiative recombination. The PL intensity and carrier lifetime were found to be substrate- dependent which may be ascribed to the variation in the trap-density of the films grown on different substrates.
Spin-orbit torque MRAM performance with different materials
(IOP, 2025-08) Mourya, Satyendra Kumar
spin–orbit torque (SOT) technology has emerged as a promising approach for developing advanced magnetic devices with superior performance metrics. The SOT enables efficient control of magnetic states through the generation of spin currents via spin–orbit interaction. The precise control in magnetization switching with low power consumption in SOT based devices offers advancements in memory and logic applications. This paper presents a comparative study of the various parameters related to SOT performance across a range of materials, including Bi2Se3, Pt, Ta, W, WTe2, MoTe2, and IrMN. By analyzing key material properties such as spin-Hall conductivity (SHC), resistivity, damping constant, and spin-Hall angle (SHA). We evaluate how these factors influence the efficacy of SOT applications. The critical current density and material properties are key parameters for magnetization switching. Further, we explore the retention time and temperature stability for each material. Our findings aim to identify optimal materials for SOT-based devices and provide a framework for selecting materials based on specific performance criteria. This comparative analysis contributes to the progression of SOT technology and supports the progress of next-generation spintronic devices.
Structural and optical characteristics of in-situ sputtered highly oriented 15R-SiC thin films on different substrates
(AIP, 2018-01) Mourya, Satyendra Kumar
In this work, we have reported the in-situ fabrication of nanocrystalline rhombohedral silicon carbide (15R-SiC) thin films by RF-magnetron sputtering at 800 °C substrate temperature. The structural and optical properties were investigated for the films grown on four different substrates (ZrO2, MgO, SiC, and Si). The contact angle measurement was performed on all the substrates to investigate the role of interfacial surface energy in nucleation and growth of the films. The XRD measurement revealed the growth of (1 0 10) orientation for all the samples and demonstrated better crystallinity on Si substrate, which was further corroborated by the TEM results. The Raman spectroscopy confirmed the growth of rhombohedral phase with 15R polytype. Surface characteristics of the films have been investigated by energy dispersive x-ray spectroscopy, FTIR, and atomic force microscope (AFM) to account for chemical composition, bonding, and root mean square surface roughness (δrms). The optical dispersion behavior of 15R-SiC thin films was examined by variable angle spectroscopic ellipsometry in the wide spectral range (246–1688 nm), including the surface characteristics in the optical model. The non-linear optical parameters (χ3 and n2) of the samples have been calculated by the Tichy and Ticha relation using a single effective oscillator model of Wemple and Didomenico. Additionally, our optical results provided an alternative way to measure the ratio of carrier concentration to the effective mass (N/m*). These investigated optical parameters allow one to design and fabricate optoelectronic, photonic, and telecommunication devices for deployment in extreme environment