BITS Faculty Publications
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Item Development of PIC-FDTD code for beam-wave interaction study in ‘PASOTRON’(IEEE, 2015-01) Sarkar, NiladriPlasma-assisted high power microwave source `PASOTRON' is being developed at a few places internationally to utilize plasma channel transport of the beam through Slow Wave Structure (SWS) to significantly reduce the size and weight in conventional linear high power microwave (HPM) sources by eliminating the need for the applied axial magnetic field [1-2]. In this device, very strong non-linear interaction between electron beam and electromagnetic wave can occur, thus making analytical design very cumbersome. Consequently, a particle simulation code is very much required to make its design simpler. We have made an efforts to study beam wave interaction in plasma filled SWS, which is a backward wave oscillator (BWO). The aim is to develop a particle-in-cell finite-difference-time-domain (PIC-FDTD) code [3] using MATLAB for the simulation of beam-wave interaction in the PASOTRON. The updating equations for electromagnetic fields are formulated using FDTD in cylindrical coordinate system since the SWS geometry is axially symmetric. In order to examine the field configuration in 3D, a field solver is implemented using the BOR-FDTD (Body of revolution FDTD) [4]. The results are being compared with MAGIC [5] tool software to validate the analysis. The results of this analysis will be presented.Item Application of the self-consistent quantum method for simulating the size quantization effect in the channel of a nano-scale dual gate MOSFET(AIP, 2015-06) Sarkar, NiladriSelf-Consistent Quantum Method using Schrodinger-Poisson equations have been used for determining the Channel electron density of Nano-Scale MOSFETs for 6nm and 9nm thick channels. The 6nm thick MOSFET show the peak of the electron density at the middle where as the 9nm thick MOSFET shows the accumulation of the electrons at the oxide/semiconductor interface. The electron density in the channel is obtained from the diagonal elements of the density matrix; [ρ]=[1/(1+exp(β(H − μ)))] A Tridiagonal Hamiltonian Matrix [H] is constructed for the oxide/channel/oxide 1D structure for the dual gate MOSFET. This structure is discretized and Finite-Difference method is used for constructing the matrix equation. The comparison of these results which are obtained by Quantum methods are done with Semi-Classical methods.Item Application of the Density Matrix Formalism for Obtaining the Channel Density of a Dual Gate Nanoscale Ultra-Thin MOSFET and its Comparison with the Semi-Classical Approach(World Scientific, 2020) Sarkar, NiladriDensity Matrix Formalism using quantum methods has been used for determining the channel density of dual gate ultra-thin MOSFETs. The results obtained from the quantum methods have been compared with the semi-classical methods. This paper discusses in detail the simulation methods using self-consistent schemes and the discretization procedures for constructing the Hamiltonian Matrix for a dual gate MOSFET consisting of oxide/semiconductor/oxide interface and the self-consistent procedure involving the discretization of Poisson’s equation for satisfying the charge neutrality condition in the channel of different thicknesses. Under quantum methods, the channel densities are determined from the diagonal elements of the density matrix. This successfully simulates the size quantization effect for thin channels. For semi-classical methods, the Fermi–Dirac Integral function is used for the determination of the channel density. For thin channels, the channel density strongly varies with the values of the effective masses. This variation is simulated when we use Quantum methods. The channel density also varies with the asymmetric gate bias and this variation is more for thicker channels where the electrons get accumulated near the oxide/semiconductor interface. All the calculations are performed at room temperature (300K).