Potential of Multi constellation Global Navigation Satellite System in Indian Missile Test Range Applications

In this paper, the potentials of using Global Navigation Satellite System (GNSS) techniques in the complex calibration procedure of the tracking sensors for missile test range applications have been presented. The frequently used tracking sensors in test range applications are- electro-optical tracking stations (EOTS) and tracking radars. Over the years, the EOTS are used as the reference for bias estimation of the radars. With the introduction of GPS in test range applications, especially the DGPS, the reference for bias estimation got shifted to DGPS from the EOTS. However, the achievable position solution accuracy is limited to the order of a few meters for DGPS, EOTS, and Radars. With the evolution of Multi-constellation GNSS and carrier-phase based measurement techniques in satellite navigation, achievable position solution accuracies may be improved to sub-meter level. New navigation techniques like real time kinematic (RTK) and precise point positioning have the potentials for use in the calibration procedures of the missile test ranges to the accuracies of centimeter-level. Moreover, because of the availability of a large number of navigation signals over the Indian region, multi-constellation GNSS receivers can enhance signal availability, reliability, and accuracies during the calibration of missile test ranges. Currently available compact, low-cost GNSS modules also offer the possibilities of using these for cost-effective, networked RTK for dynamic calibration of test ranges reducing cost and resource requirements

Defect states assisted charge conduction in Au/MoO3¿x/n-Si Schottky barrier diode

Role of defect states of thermally evaporated molybdenum trioxide (MoO3-x) on electrical conductivity was investigated via low temperature current–voltage and capacitance–voltage measurements. To clarify the charge transport phenomena through MoO3-x, a 15 nm thin layer of MoO3-x film was used as an interface layer between gold and n-type Silicon (n-Si). The formation of an interface dipole between n-Si and MoO3-x exhibits a rectifying behaviour of Au/MoO3-x/n-Si Schottky barrier diode (SBDs). The rectifying nature of the SBDs shown up to 175 K due to proper electron extraction from valence band to conduction band via the defect states; however at =165 K the rectifying nature was not observed due to insulating behaviour of MoO3-x layer. Oxygen deficiency as a formation of defects was determined by x-ray photoelectron spectroscopy (XPS). Consequences of these defects as a function of current conduction across the MoO3-x was also confirmed by low temperature photoluminescence (PL)measurement.Peer ReviewedPostprint (author's final draft

Analysis of temperature dependent current-voltage and capacitance-voltage characteristics of an Au/V2O5/ n -Si Schottky diode

Electronic properties of Au/V2O5/n-Si Schottky device have been investigated by temperature dependent current-voltage (I-V) and capacitance-voltage (C-V) measurements ranging from 300 K to 150 K. Ideality factor (n) and barrier height (ø) for the Schottky device were obtained from I-V characteristics as 2.04 and 0.83 eV at 300 K and 6.95 and 0.39 eV at 150 K respectively. It was observed that in presence of inhomogeneity at metal-semiconductor interface, the ideality factor increases and barrier height decreases with the decrease of temperature. The Richardson constant value was estimated as 137 A-cm-2-K-2 from modified Richardson plot, which is closer to the known theoretical value of n-Si where mean value of barrier height (øb0), and its standard deviation (s0) were estimated using double Gaussian distribution (DGD) analysis. Different device parameters, namely, built-in potential, carrier concentration, image force lowering and depletion width were also obtained from the C-V-T measurements. First time use of V2O5 thin-film as an interfacial layer (IL) on Au/V2O5/n-Si Schottky diode was successfully explained by the thermionic emission (TE) theory. The interesting result obtained in this present work is the V2O5 thin-film reduced its conducting capability with decreasing temperature, while it shows a totally insulating behaviour below 150 K.Peer ReviewedPostprint (author's final draft

Characterization of transition metal Oxide/Silicon heterojunctions for solar cell applications

During the last decade, transition metal oxides have been actively investigated as hole- and electron-selective materials in organic electronics due to their low-cost processing. In this study, four transition metal oxides (V2O5, MoO3, WO3, and ReO3) with high work functions (>5 eV) were thermally evaporated as front p-type contacts in planar n-type crystalline silicon heterojunction solar cells. The concentration of oxygen vacancies in MoO3-x was found to be dependent on film thickness and redox conditions, as determined by X-ray Photoelectron Spectroscopy. Transfer length method measurements of oxide films deposited on glass yielded high sheet resistances (~109 O/sq), although lower values (~104 O/sq) were measured for oxides deposited on silicon, indicating the presence of an inversion (hole rich) layer. Of the four oxide/silicon solar cells, ReO3 was found to be unstable upon air exposure, while V2O5 achieved the highest open-circuit voltage (593 mV) and conversion efficiency (12.7%), followed by MoO3 (581 mV, 12.6%) and WO3 (570 mV, 11.8%). A short-circuit current gain of ~0.5 mA/cm2 was obtained when compared to a reference amorphous silicon contact, as expected from a wider energy bandgap. Overall, these results support the viability of a simplified solar cell design, processed at low temperature and without dopants.Peer ReviewedPostprint (published version

Transition metal oxides as hole-selective contacts in silicon heterojunctions solar cells

This work reports on a comparative study comprising three transition metal oxides, MoO3, WO3 and V2O5, acting as front p-type contacts for n-type crystalline silicon heterojunction solar cells. Owing to their high work functions (>5 eV) and wide energy band gaps, these oxides act as transparent hole-selective contacts with semiconductive properties that are determined by oxygen-vacancy defects (MoO3-x), as confirmed by X-ray photoelectron spectroscopy. In the fabricated hybrid structures, 15 nm thick transition metal oxide layers were deposited by vacuum thermal evaporation. Of all three devices, the V2O5/n-silicon heterojunction performed the best with a conversion efficiency of 15.7% and an open-circuit voltage of 606 mV, followed by MoO3 (13.6%) and WO3 (12.5%). These results bring into view a new silicon heterojunction solar cell concept with advantages such as the absence of toxic dopant gases and a simplified low-temperature fabrication process.Preprin

The effect of annealing on structural, optical and photosensitive properties of electrodeposited cadmium selenide thin films

Cadmium selenide (CdSe) thin films have been deposited on indium tin oxide coated glass substrate by simple electrodeposition method. X-ray Diffraction (XRD) studies identify that the as-deposited CdSe films are highly oriented to [002] direction and they belong to nanocrystalline hexagonal phase. The films are changed to polycrystalline structure after annealing in air for temperatures up to 450 °C and begin to degrade afterwards with the occurrence of oxidation and porosity. CdSe completely ceases to exist at higher annealing temperatures. CdSe films exhibit a maximum absorbance in the violet to blue-green region of an optical spectrum. The absorbance increases while the band gap decreases with increasing annealing temperature. Surface morphology also shows that the increase of the annealing temperature caused the grain growth. In addition, a number of distinct crystals is formed on top of the film surface. Electrical characteristics show that the films are photosensitive with a maximum sensitivity at 350 °C

Temperature dependent current-voltage characteristics of Au/n-Si Schottky barrier diodes and the effect of transition metal oxides as an interface layer

© . This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/Temperature dependent current–voltage (I¿V) characteristics of Au/n-type silicon (n-Si) Schottky barrier diodes have been investigated. Three transition metal oxides (TMO) are used as an interface layer between gold and silicon. The basic Schottky diode parameters such as ideality factor (n), barrier height () and series resistance (Rs) are calculated and successfully explained by the thermionic emission (TE) theory. It has been found that ideality factor decreased and barrier height increased with increased of temperature. The conventional Richardson plot of ln(I0/T2) vs. 1000/T is determined the activation energy (Ea) and Richardson constant (A*). Whereas value of ‘A*’ is much smaller than the known theoretical value of n-type Si. The temperature dependent I–V characteristics obtained the mean value of barrier height and standard deviation from the linear plot of vs. 1000/T. From the modified Richardson plot of ln(I0/T2) ¿ (qs)2/2(kT)2 vs. 1000/T gives Richardson constant and homogeneous barrier height of Schottky diodes. Main observation in this present work is the barrier height and ideality factor shows a considerable change but the series resistance value exhibits negligible change due to TMO as an interface layer.Peer ReviewedPostprint (author's final draft

Assessing tea plantations biophysical and biochemical characteristics in Northeast India using satellite data

Despite advancements in using multi-temporal satellite data to assess long-term changes in Northeast India's tea plantations, a research gap exists in understanding the intricate interplay between biophysical and biochemical characteristics. Further exploration is crucial for precise, sustainable monitoring and management. In this study, satellite-derived vegetation indices and near-proximal sensor data were deployed to deduce various physico-chemical characteristics and to evaluate the health conditions of tea plantations in northeast India. The districts, such as Sonitpur, Jorhat, Sibsagar, Dibrugarh, and Tinsukia in Assam were selected, which are the major contributors to the tea industry in India. The Sentinel-2A (2022) data was processed in the Google Earth Engine (GEE) cloud platform and utilized for analyzing tea plantations biochemical and biophysical properties. Leaf chlorophyll (C ab) and nitrogen contents are determined using the Normalized Area Over Reflectance Curve (NAOC) index and flavanol contents, respectively. Biophysical and biochemical parameters of the tea assessed during the spring season (March-April) 2022 revealed that tea plantations located in Tinsukia and Dibrugarh were much healthier than the other districts in Assam which are evident from satellite-derived Enhanced Vegetation Index (EVI), Modified Soil Adjusted Vegetation Index (MSAVI), Leaf Area Index (LAI), and Fraction of Absorbed Photosynthetically Active Radiation (fPAR), including the C ab and nitrogen contents. The C ab of healthy tea plants varied from 25 to 35 µg/cm 2. Pearson correlation among satellite-derived C ab and nitrogen with field measurements showed R 2 of 0.61-0.62 (p-value &lt; 0.001). This study offered vital information about land alternations and tea health conditions, which can be crucial for conservation, monitoring, and management practices. </p

Temperature dependent current-voltage characteristics of Au/n-Si Schottky barrier diodes and the effect of transition metal oxides as an interface layer

© . This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/Temperature dependent current–voltage (I¿V) characteristics of Au/n-type silicon (n-Si) Schottky barrier diodes have been investigated. Three transition metal oxides (TMO) are used as an interface layer between gold and silicon. The basic Schottky diode parameters such as ideality factor (n), barrier height () and series resistance (Rs) are calculated and successfully explained by the thermionic emission (TE) theory. It has been found that ideality factor decreased and barrier height increased with increased of temperature. The conventional Richardson plot of ln(I0/T2) vs. 1000/T is determined the activation energy (Ea) and Richardson constant (A*). Whereas value of ‘A*’ is much smaller than the known theoretical value of n-type Si. The temperature dependent I–V characteristics obtained the mean value of barrier height and standard deviation from the linear plot of vs. 1000/T. From the modified Richardson plot of ln(I0/T2) ¿ (qs)2/2(kT)2 vs. 1000/T gives Richardson constant and homogeneous barrier height of Schottky diodes. Main observation in this present work is the barrier height and ideality factor shows a considerable change but the series resistance value exhibits negligible change due to TMO as an interface layer.Peer Reviewe

Compact, Low-cost GNSS Modules for Precise Point Positioning

Global Navigation Satellite System (GNSS) uses Precise Point Positioning (PPP) technique to find out accurate geolocation information of any point. Generally, costly, geodetic GNSS receivers are used for PPP. This manuscript presents the results of studies on the usability of commercial, compact, cost-effective GNSS modules with commercial antennas for PPP in comparison to commonly used geodetic, costly receivers from India, which is a excellent location for GNSS use. Compact GNSS modules from two manufacturers are used in the study, and the encouraging results show the clear advantage of cost, size, and power requirements of such modules. The modules provide sub-cm horizontal solution accuracy which is very similar to those obtained using geodetic receivers, and around 20 cm accuracy in the vertical coordinate, which is slightly inferior to the results provided by the geodetic reveivers. Results of this novel study would be useful for implementing cost-efficient GNSS PPP in real life, in highly demanding geodetic applications including CORS establishment and PPP