Amit Chauhan

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Charles University, Prague

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Papers by Amit Chauhan

Estimation of CHF Margins for Nuclear Rod Bundles in a Radially Expanded Pressure Tube

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In-induced stable ordering of stepped Si(553) surface

Applied Surface Science, 2015

The growth mechanism and adsorbate-induced surface morphology of metal atoms on semiconducting su... more The growth mechanism and adsorbate-induced surface morphology of metal atoms on semiconducting surfaces crucially determines the electronic and physicochemical properties of these metal/semiconductor systems. In this study, we investigate the kinetically controlled growth of indium (In) atoms on the high index stepped Si(553)-7 × 7 surface and the thermal stability of various novel In-induced superstructural phases formed during adsorption/desorption process. Auger electron spectroscopy analysis reveals that In adsorption at room temperature (RT) and at 350 • C, with a controlled incident flux of 0.0016 ML/s, proceeds in the Stranski-Krastanov growth mode where two dimensional (2D)/three dimensional (3D) islands are formed on top of two complete monolayers. At higher substrate temperature up to 450 • C, the growth of In atoms occurs in the form of islands on the bare Si(553) surface, and In coverage is limited to the sub-monolayer regime. During the thermal desorption of the RT grown In/Si(553) system, the In clusters rearrange themselves and an unusual "cluster to layer" transformation occurs on top of the stable monolayer. In situ low energy electron diffraction analysis during adsorption and desorption shows the development of various coverage and temperature dependent In-induced superstructural phases on Si(553) surface, such as: (8 × 2) after annealing at 520 • C with coverage 0.5 ML, (8 × 4) after annealing at 580 • C (∼1 ML coverage) and (553)-7 × 1 + (111)-√ 3 × √ 3-R30 • at 0.3 ML (630 • C). These adsorbate-induced superstructural phases could potentially be utilized as templates for pattern assisted growth of various exotic 1D/2D structures for optoelectronics and photovoltaic applications.

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Kinetically Controlled Growth and Thermal Stability of Potassium on Reconstructed High Index Si(5512) 2 x 1 Surface

Materials Focus, 2014

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An improved trust calculation method for mobile Ad Hoc Network

2010 First International Conference On Parallel, Distributed and Grid Computing (PDGC 2010), 2010

Abstract Securing a Wireless Ad Hoc Network is one of the major concerns for the researchers. Due... more Abstract Securing a Wireless Ad Hoc Network is one of the major concerns for the researchers. Due to wide-ranging characteristics of the ad-hoc networks, it is always at a risk to internal as well as external attacks. Many solutions have been proposed and currently ...

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A Comparative Photoelectron Spectroscopic Analysis of MBE and MOCVD Grown Epitaxial GaN Films

Science of Advanced Materials, 2015

ABSTRACT The report presents X-Ray Photoelectron Spectroscopic analysis of as-received and cleane... more ABSTRACT The report presents X-Ray Photoelectron Spectroscopic analysis of as-received and cleaned MBE and MOCVD grown undoped epitaxial GaN films. We correlate observed changes in electronic structure and surface properties after employing a newly derived approach to clean GaN surfaces. The adopted approach is a combination of two different standard cleaning procedures consisting of ex-situ wet chemical (HCl) etching followed by an in-situ ultrahigh vacuum anneal (up to 750 °C), and successfully yielded a clean and stoichiometric GaN surface. The method was employed to investigate cleanliness of MBE and MOCVD grown GaN films and it was observed that major contaminants such as carbon and oxygen were significantly removed from the surface. XPS analysis revealed that MBE grown films show higher amount of surface contamination than the MOCVD grown films but can also be cleaned more efficiently. Thermal annealing (≥ 750 °C) resulted in the dissociation of GaN bonds and accumulation of metallic gallium on the surface on MOCVD grown GaN films, which was confirmed by core level as well as the valence band spectra. The n O/n N ratio of the films reduced drastically from 1.79 to 0.04 and 0.73 to 0.09 after cleaning with the stoichiometry (N:Ga) of 1.0 ± 0.04 and 1.1 ± 0.05 for MBE and MOCVD grown GaN films respectively. The VB maximum position of MBE and MOCVD grown films was observed to be shifted from 2.9 ± 0 eV to 2.2 ± 0.1 eV and 2.8 ± 0.1 eV to 1.4 ± 0.1 eV after cleaning of the surface.

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Amit Chauhan

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