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Item Receiver architectures for 5g: Current status and future prospects(Springer Science and Business Media Deutschland GmbH, 2021) Kumar, A.; Sengar, B.S.; Chaudhary, S.; Pandey, S.K.; Pandey, S.K.; Hasan Raza Ansari, M.; Aaryashree, A.In this chapter, the recent progress in receiver architecture and various aspects of the available receiver architectures have been discussed. Besides, an overview of the systematic classification of architecture has been analyzed. Documentation of new possibilities and system-level trade has been closely inspected. Certainly, there is a requirement of low-power, flexible, and high-performance receiver architecture for the successful implementation of the 5G network. Different works in this regard have been considered as examples for discussing the status and prospects of architectures with respect to 5G future. Various architectures considered in this chapter can be very valuable to design 5G network in future and will expose the research community with new possibilties to explore for further improvements. © Springer Nature Singapore Pte Ltd. 2021.Item Recent advancements in growth and stability of phosphorene: Prospects for high-performance devices(CRC Press, 2022) Pandey, S.K.; Garg, V.; Izquierdo, N.; Kumar, A.Atomically thin two-dimensional (2D) materials like graphene and the transition metal dichalcogenides have made a significant impact in the field of electronics and optoelectronics devices. Graphene, however, has no bandgap, which creates hurdles for many device applications. Similarly, the modest carrier mobility of transition metal dichalcogenides makes them less suitable for high-performance electronic and optoelectronic device applications. Phosphorene, a monolayer or few-layer form of black phosphorus (BP), has attracted considerable interest owing to its unique anisotropic manner, layer-dependent direct bandgaps, high carrier mobility, and quasi-one-dimensional excitonic nature, which are not present in other abovementioned 2D materials. Phosphorene has a bandgap of ˜0.3 eV in the bulk form and can be increased with reducing layer thicknesses, approaching ˜2 eV for the monolayer. As a result, there have been stimulating reports on field-effect transistors and inverters fabricated in the material system. Phosphorene is also becoming an interesting material for solar cells and photodetectors. Despite novel properties, the development of this material itself remains in an embryonic state. One of the reasons for the slow progress is that phosphorene-based devices use either mechanical or liquid exfoliation method to deposit phosphorene from crystalline black phosphorus (c-BP). In these processes, one peels a thin layer of material from a bulk BP crystal using adhesive tape or by liquid intercalation. The exfoliation process for this material is possible due to its intralayer strong covalent bonds and interlayer weak van der Waals forces. The exfoliation method does not have the thickness, uniformity, position, orientation, and surface control needed to get repeatable experimental results. In this chapter, detailed information will be provided about phosphorene deposition using the abovementioned and other methods. Phosphorene demonstrates instability under ambient conditions, which is the main obstacle for its practical applications. Various studies have been conducted in the past to investigate the mechanism of the degradation of phosphorene and passivation techniques to resolve its problem of instability under ambient conditions. To know the various fundamental properties correctly, the stability of this 2D material is very important, which can be achieved by novel passivation strategies. Detailed passivation strategies of phosphorene are elaborated in this chapter. The effects of the passivation layers composition on the thermal stability of phosphorene are also provided. Different growth techniques are described to deposit the passivation layers without altering the properties of phosphorene. To understand the different properties of passivated phosphorene, different measurement techniques such as X-ray diffraction (XRD), Raman spectroscopy, optical microscopy, atomic force microscopy (AFM), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and high-resolution transmission electron microscopy (HRTEM) are discussed in this chapter. The effects of annealing temperatures on the properties of passivated phosphorene are discussed in detail. Finally, an overview on the utilization of phosphorene for a variety of applications is also given. A detailed study about 2D phosphorene/3D materials-based next-generation devices are presented in this chapter. The roadmaps to address present challenges for phosphorene are investigated as the properties of this material are very appropriate for next-generation devices. The information presented in this chapter will accelerate the further development of high-performance phosphorene-based electronics and optoelectronics devices. © 2022 selection and editorial matter, Ashish Raman, Deep Shekhar and Naveen Kumar; individual chapters, the contributors.Item Numerical analysis of CZTSSe solar cell with different BSF layers for performance improvement(SPIE, 2021) Prabhu, S.; Pandey, S.K.; Chakrabarti, S.This work reports the performance improvement of the CZTSSe solar cell by using a back surface field (BSF) layer between the back contact and absorber layer. Firstly, a cell model with Cadmium (Cd) free buffer structure (Mo/CZTSSe/Zn(O, S)/ZnO/ITO) is developed using SCAPS-1D software. To improve the performance, thickness and composition ratio of the absorber (CZTSSe) and buffer (Zn(O, S)) layer are optimized through simulations. The efficiency of 14.39% is achieved for a Sulphur content of 40% and 70% in CZT(SxSe1-x)4 and Zn(O1-x Sx) respectively. Further performance improvement is attempted by using a back surface field (BSF) layer between the back contact and the CZTSSe absorber layer. The P+-MoSe2, P+ - Si0.75Ge0.25, and SnSe layers are used as BSF layers to investigate their effects on performance improvement. Inclusion of the BSF layer gives further scope for optimization of the absorber layer thickness. It is observed that the use of SnSe as a BSF layer produces maximum power conversion efficiency of 17%. These findings will be helpful for the research community working in the area of high-performance and low-cost CZTSSe based solar cells. © 2021 SPIE.Item Doping of ZnMgO with phosphorus by spin-on dopant technique(SPIE, 2021) Mishra, M.; Sushama, S.; Pandey, S.K.; Chakrabarti, S.Zinc magnesium oxide is a ternary compound wide bandgap semiconductor. Incorporation of Mg into ZnO helps in increasing the of p-type conductivity by affecting the background n-type nature of ZnO. This is possible because Mg incorporation in ZnO elevates the conduction band edge which in turn increases the distance between the shallow donor level and conduction band minima, resulting increase of activation energy for background donor. In this work, we report Spin-on Dopant technique to dope phosphorus in Zn0.85Mg0.15O lattice. The undoped ZnMgO thin film (sample A) was deposited using RF sputtering. The SOD sample (sample B) was prepared using P509 spin on dopant and kept approximate 1cm above ZnMgO film at 600°C for four hours. The doped sample was annealed at temperature 700°C (sample C) in oxygen ambient to see the high temperature annealing effect on doping. In studies of high-resolution x-ray diffraction, a dominant (002) peak was observed in sample A, B, and C at 34.173°, 34.624°, and 34.638° respectively. The shifting of (002) peak at higher angle for doped samples indicates the phosphorus doping in film. The XPS spectra of phosphorus 2p peak are appears at ∼134 eV indicates the presence of P atoms as P-O bonds in ZnMgO lattice. The Donor-Acceptor pair (DAP) transition peak around 3.473eV and free Acceptor (AX°) peak around 3.588eV were found in photoluminescence spectra of sample B revels the phosphorus doping in ZnMgO. © COPYRIGHT SPIE. Downloading of the abstract is permitted for personal use only.Item Improvement in optical and elemental properties of spin-on phosphorus doped ZnO film(SPIE, 2021) Mishra, M.; Sushama, S.; Pandey, S.K.; Chakrabarti, S.SOD is a type of conventional doping technique where diffusion of dopant atom takes place from the liquid source to film by thermal annealing of sample. The study shows the SOD process is a cost effective, less destructive and an efficient way to dope ZnO film. We have doped ZnO films with phosphorus atom by simply annealing it in atmospheric furnace up to 600°C for 4 hrs. After in-situ annealing SOD process, sample has also been ex-situ annealed at 900°C in oxygen ambient for 10 secs. The elemental analysis of phosphorus 2p peak at 132.62 eV ensures the existence of P-O bond for doped sample which shows phosphorus replacing Zn and bonding with oxygen in to the lattice in order to make Pzn-2Vzn an acceptor complex. The doped samples showed the photoluminescence peak at 3.32eV and 3.35eV, which attributed to free electron to acceptor (FA) and acceptor-bound exciton (A0X) energy as an evidence of acceptor doping in ZnO film. The ex-situ annealing of doped sample further improves in passivation of deep level defects of film. All sample has (002) orientation, and a compressive stress to be found in the doped sample due to phosphorus replacing Zn, are confirmed by analysis of XRD results. © COPYRIGHT SPIE. Downloading of the abstract is permitted for personal use only.Item Improvement in performance of CZTSSe solar cell by using cadmium free buffer layers(SPIE, 2021) Prabhu, S.; Pandey, S.K.; Chakrabarti, S.Cadmium Sulphide(CdS) has been the most preferred n-type buffer layer and Indium Tin Oxide(ITO) is the popular window layer in kesterite solar cells. Cadmium being toxic and Indium being a rare earth element, continuous efforts are being made to replace these materials from kesterite solar cells structure. In this work, ZnS, ZnSe, and Zn0.8Sn0.2O are considered as possible alternatives for CdS. Similarly, Aluminium doped Zinc Oxide(AZO) is considered as an alternative for ITO. Firstly, a cell model with CdS and ITO (Mo/CZTSSe/CdS/ZnO/ITO) is developed using SCAPS-1D software. To optimise the performance parameters namely open-circuit voltage(Voc), short-circuit current density(Jsc), fill factor(FF), and the power conversion efficiency (PCE) for irradiation under normal working conditions, thickness and the composition ratio of the absorber layer(CZTSSe) are evaluated through numerical simulations. PCE of 14.51% is achieved for a 40% of Sulphur content and 2 um thickness of Cu2ZnSn(SxSe1-x)4 when CdS is used as the buffer layer. For the same structure, replacing ITO with AZO results in a PCE of 14.62%. Use of Cadmium-free buffer layers ZnS, ZnSe, and Zn0.82Sn0.18O with ITO as window layer result in PCE of 13.98%, 14.28%, and 14.53%, respectively. For the Cadmium-free buffer layers, an improvement in PCE is achieved when ITO is replaced by AZO, with the highest being 14.62% for Zn0.82Sn0.18O. This can be attributed to the smaller conduction band offset, which reduces the recombination of photogenerated carriers and improves the carrier transport in the solar cell. The above results indicate that the Zn0.8Sn0.2O and AZO can be potential candidates for the buffer layer and window layer, respectively, for high-performance and cheap kesterite solar cells. © 2021 SPIE.Item Simulation and optimization of nanostructure incorporated CZTS solar cell towards higher performance(SPIE, 2022) Prabhu, S.; Pandey, S.K.; Chakrabarti, S.Kesterite solar cells require a novel high-research implementation to replace the costlier Copper Indium Gallium Selenide (CIGS) solar cells. This study, attempts to demonstrate the performance improvement of kesterite solar cells using multiple quantum wells (MQWs). A numerical simulation approach using Atlas software from Silvaco is used. Firstly, a baseline model of the best performing Cu2ZnSnS4(CZTS) solar cell Mo/CZTS/CdS/i-ZnO/ITO with 11% power conversion efficiency (PCE) is implemented. Further, to exploit the use of MQWs, Cu2ZnSn(SxSe1-x)4 (CZTSSe) with 40% sulfur content is added as well material in a series of wells while keeping the CZTS as the barrier material. This structural modification facilitates the absorption of lower energy photons by the lower bandgap well material. Further, MQW induced quantized energy levels and higher electric fields help to increase the carrier collection, thereby increasing the solar cell's short circuit current density (Jsc) and overall power conversion efficiency (PCE). A detailed study on the effect of well and barrier thickness on the solar cell performance is done, and a well thickness of 5 nm and a barrier thickness of 10 nm was chosen for further optimization. The number of wells is also optimized to 70, which results in the highest performance of the solar cell. This structural modification and optimization remarkably improved Jsc by 48.76% (rel.) and PCE by 34.72% (rel.) compared to solar cells without nanostructures. Moreover, with an optimized structure, an external quantum efficiency (EQE) of over 95% is achieved with the optimized structure. © © 2022 SPIE.Item Effect of post-deposition annealing ambient on Gallium Oxide (Ga2O3) films(SPIE, 2022) Mishra, M.; Saha, R.; Bhowmick, S.; Pandey, S.K.; Chakrabarti, S.Gallium Oxide (Ga2O3) is an emerging wideband semiconductor which can be utilize in solar-blind photodetector and high power electronics application. Having a large bandgap and high breakdown field makes Ga2O3 material suitable for these device applications. However, the physical and the optical properties of Ga2O3 can be tailored by changing the annealing ambient and temperature, and understanding how the annealing atmosphere can affect these properties is crucial for designing a next generation optoelectronic devices. Moreover, the presence of defects and impurities can also affect the device parameters. Thus, in this work, we have investigated the influence of post deposition annealing atmosphere on the morphological, structural, and optical properties of Ga2O3 films. The prepared samples were further went through thermal annealing at 800℃ for 30 mins in Nitrogen (N2), and Oxygen (O2) ambient to achieve β-phase of Ga2O3. The structural properties of all the samples were studied by Atomic force microscopy, and X-ray diffraction while the optical properties were studies by UV-Visible, and photoluminescence spectroscopy. We have found monoclinic β-phase in the polycrystalline annealed Ga2O3 samples. The optical band gap of films were increased after annealing and highest band gap is obtained to 5.44eV in N2 annealed sample as compared to as-deposited sample (4.56eV). A broad photoluminescence spectrum ranged from 350 to 480 nm was observed, which further deconvoluted in three peaks at around 378 nm, 399 nm, and 422 nm in as-deposited sample. The same peaks with broad photoluminescence spectrum was found to be blue shifted for annealed samples as compared to the as-deposited. This study will open a new direction in future deep-UV photodetector fabrication. © 2022 SPIE.Item Reduction of oxygen vacancy related defects in RF sputtered deposited ZnO films by impurity (Phosphorus) incorporation(SPIE, 2022) Mishra, M.; Saha, R.; Bhowmick, S.; Pandey, S.K.; das Gupta, K.D.; Chakrabarti, S.ZnO is a fascinating wide gap (3.37 eV) semiconductor due to its tunable optical and electrical properties, which can be utilized for several nanodevices such as nanogenerators, photodetectors, sensors, lasers, and TFTs. In this study, we have investigated the effect of the incorporation of dopants on the native defects and corresponding optical properties of ZnO. We have prepared three samples for the current study and such samples are named samples Z-0, Z-1, and Z-2 for undoped ZnO film, undoped ZnO film annealed at 800°C, and phosphorus doped ZnO film by using spin-on dopant method at an elevated temperature of 800°C, respectively. The XRD results show a dominant peak along the (002) plane for all samples. The Room-temperature photoluminescence spectra reveal that the broad peak around 542 nm for sample Z-0 gradually shifts towards the UV region for samples Z-1 and Z-2 and appears around 509 nm and 413 nm, respectively. Significantly, such blue emission is associated with the transitions from oxygen vacancies to valence band or zinc interstitial to valance band. Also, relatively huge reductions in oxygen vacancies are observed in phosphorus doped ZnO films as compared with undoped and undoped-anneal films. Further, we have verified such reductions in oxygen vacancies with XPS O-1s spectra-related peaks (~531-532 eV) with high-temperature annealing and phosphorus doping. Therefore, such a type of oxygen vacancy reduction in ZnO films by cost-effective SOD doping technique is highly essential for developing several ZnObased functional devices. © 2022 SPIE.Item Study of Electronic and Optical Properties of Bulk and Monolayer Vanadium Di-Sulfide for Energy Storage Devices(Institute of Electrical and Electronics Engineers Inc., 2023) Yadav, A.K.; Jasil, T.K.; Pandey, S.K.In this study, the WIEN2k code implementation of the density functional theory (DFT) approach was used to examine the structural, electronic, and optical characteristics of bulk and monolayer VS2 material. For both bulk and monolayer VS2 material, we calculated the various properties including density of states, band-structure, and dielectric functions using the generalised gradient approximation (GGA). This method gives better results for the structural parameters and shows that monolayer VS2 is more favorable for energy storage devices. Additionally, we report the growth of the bulk and monolayer VS2 crystals using a chemical vapor deposition system. It was also found the crystal growth of monolayer VS2 started at the growth temperature of 690 °C. Bulk VS2 crystal growth also performed in this study. Raman spectroscopy shows a peak intensity started at 385 cm-1 for monolayer VS2 growth crystal at 690 °C. These observations show monolayer VS2 material is more suitable for energy storage devices. © 2023 IEEE.