Mahesh Kumar

Bio: Mahesh Kumar is an academic researcher from Indian Institute of Technology, Jodhpur. The author has contributed to research in topics: Molecular beam epitaxy & Heterojunction. The author has an hindex of 29, co-authored 204 publications receiving 4864 citations. Previous affiliations of Mahesh Kumar include Indian Institutes of Technology & Indian Institute of Technology Delhi.

Visualization of band offsets at few-layer MoS2/Ge heterojunction.

Abstract: The visualization of band alignment for designing heterostructures between transition metal dichalcogenides and germanium plays a vital role in a deeper understanding of carrier dynamics at the heterointerface. Here, to study the band alignment across the MoS2/Ge heterojunction, we have deposited a wafer-scale highly crystalline few atomic layers MoS2film via a highly controllable and scalable sputtering technique coupled with a post sulfurization process in a sulfur-rich environment. The Raman and XRD spectra of as-fabricated MoS2/Ge heterojunction expose the presence of highly crystalline few atomic layer MoS2on top of Ge substrate. Interestingly, we found a type-II band alignment at the MoS2/Ge heterointerface having valence band, and conduction band offset values of 0.88 and 0.21 eV, which can provide very efficient recombination through spatially confining charge carriers. The calculation of band offset parameters offers a promising way for device engineering across the MoS2/Ge heterojunction interface. Moreover, to demonstrate the practicability of the fabricated heterostructure, we explored the suitability of our device for broadband photodetection applications.

DB-CMT: A New Concurrent Multi-path Stream Control Transport Protocol

Abstract: Abstract Stream Control Transmission Protocol (SCTP) exploits multiple network interfaces to provide multi-streaming and data chunk ordering in a stream. An extended feature of SCTP, i.e., Concurrent Multi-path Transfer (CMT), bids concurrent data transmission in a multi-path data transfer environment and guarantees bandwidth aggregation, load sharing, robustness, and reliability. In such an environment, the paths usually have distinct characteristics (i.e., delay, Packet Loss Rate (PLR), and bandwidth). Thus, data chunks are received out-of-ordered at the destination. As a result, CMT causes excessive receiver buffer blocking and unnecessary congestion window ( cwnd ) reductions. Also, during the selection of the retransmission destination path (to resend a lost data chunk), CMT does not take into account vital Quality of Service (QoS) parameters such as the PLR of a path under consideration. This paper introduces a new Delay-Based Concurrent Multi-path Transfer (DB-CMT) approach that transmits data on multiple paths according to their delay. In this scheme, we present a Delay-Based Data chunk Scheduling Policy (DB-DSP), a Retransmission Path Selection Policy (RTX-CL), and a new Delay-Based Fast Retransmission Policy (DB-FRP). The simulation results show that the DB-CMT’s RTX-CL policy performs better than the well-known RTX-CWND and RTX-LOSSRATE retransmission schemes. Also, the overall performance of DB-CMT witnesses improved throughput, fewer timeouts, and reduced File Transfer Time (FTT) performances.

Coupled excitonic quasiparticles-electron-phonon and interlayer coupling in vertically and horizontally aligned MoS2

Abstract: Excitonic quasi-particles, excitons/trions/bi-excitons, and their coupling with phonons and charge carriers play a crucial role in controlling the optical properties of atomically thin semiconducting 2D materials. In this work, we...

Effects of growth temperature on nonpolar a-plane InN grown by molecular beam epitaxy

Abstract: Nonpolar a-plane InN films were grown on r-plane sapphire substrate by plasma assisted molecular beam epitaxy with GaN underlayer Effect of growth temperature on structural, morphological, and optical properties has been studied The growth of nonpolar a-plane (1 1 -2 0) orientation was confirmed by high resolution X-ray diffraction study The film grown at 500 °C shows better crystallinity with the rocking curve FWHM 067° and 085° along [0 0 0 1] and [1 -1 0 0] directions, respectively Scanning electron micrograph shows formation of Indium droplets at higher growth temperature Room tem-perature absorption spectra show growth temperature dependent band gap variation from 074–081 eV, consistent with the expected Burstein–Moss effect The rectifying behaviour of the I–V curve indicates the existence of Schottky barrier at the InN and GaN interface (© 2014 WILEY-VCH Verlag GmbH & Co KGaA, Weinheim)

Perspective on the Development of Lead-free Piezoceramics

Abstract: A large body of work has been reported in the last 5 years on the development of lead-free piezoceramics in the quest to replace lead–zirconate–titanate (PZT) as the main material for electromechanical devices such as actuators, sensors, and transducers. In specific but narrow application ranges the new materials appear adequate, but are not yet suited to replace PZT on a broader basis. In this paper, general guidelines for the development of lead-free piezoelectric ceramics are presented. Suitable chemical elements are selected first on the basis of cost and toxicity as well as ionic polarizability. Different crystal structures with these elements are then considered based on simple concepts, and a variety of phase diagrams are described with attractive morphotropic phase boundaries, yielding good piezoelectric properties. Finally, lessons from density functional theory are reviewed and used to adjust our understanding based on the simpler concepts. Equipped with these guidelines ranging from atom to phase diagram, the current development stage in lead-free piezoceramics is then critically assessed.

Room-temperature saturated ferroelectric polarization in BiFeO3 ceramics synthesized by rapid liquid phase sintering

Abstract: Single-phased ferroelectromagnet BiFeO3 ceramics with high resistivity were synthesized by a rapid liquid phase sintering technique. Saturated ferroelectric hysteresis loops were observed at room temperature in the ceramics sintered at 880 °C for 450 s. The spontaneous polarization, remnant polarization, and the coercive field are 8.9 μC/cm2, 4.0 μC/cm2, and 39 kV/cm, respectively, under an applied field of 100 kV/cm. It is proposed that the formation of Fe2+ and an oxygen deficiency leading to the higher leakage can be greatly suppressed by the very high heating rate, short sintering period, and liquid phase sintering technique. The latter was also found effective in increasing the density of the ceramics. The sintering technique developed in this work is expected to be useful in synthesizing other ceramics from multivalent or volatile starting materials.

Room-temperature gas sensing of ZnO-based gas sensor: A review

Abstract: Novel gas sensors with high sensing properties, simultaneously operating at room temperature are considerably more attractive owing to their low power consumption, high security and long-term stability. Till date, zinc oxide (ZnO) as semiconducting metal oxide is considered as the promising resistive-type gas sensing material, but elevated operating temperature becomes the bottleneck of its extensive applications in the field of real-time gas monitoring, especially in flammable and explosive gas atmosphere. In this respect, worldwide efforts have been devoted to reducing the operating temperature by means of multiple methods In this communication, room-temperature gas sensing properties of ZnO based gas sensors are comprehensively reviewed. Much more attention is particularly paid to the effective strategies that create room-temperature gas sensing of ZnO based gas sensors, mainly including surface modification, additive doping and light activation. Finally, some perspectives for future investigation on room-temperature gas-sensing materials are discussed as well.