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Malik, Hitendra K.

Publications and source records attributed to Malik, Hitendra K..

10 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

Influence of N{sup +} ions on bandgap and electrical resistivity of TiN thin films

In the present work, nitrogen ions are embedded into Ti thin films (200 nm) using low energy ion beam implantation (70 keV) by varying ions fluence from 4×10{sup 15} ions/cm{sup 2} to 2×10{sup 16} ions/cm{sup 2}. For this, Ti films were grown using DC magnetron sputtering in Ar environment (power 200 W). TiN films were then characterized using versatile techniques for estimating the band gap and electrical resistivity. X-ray diffraction pattern shows shift in peaks towards higher angle with increase in nitrogen fluence that confirms the introduction of strain in Ti films. UV-Vis spectra show that band gap is reduced from 3.75 eV to 1.7 eV with increase in fluence from 4×10{sup 15} ions/cm{sup 2} to 2×10{sup 16} ions/cm{sup 2}. Furthermore, electrical resistivity also decreases from 2.67×10{sup −4} Ω.cm to 2.31×10{sup −4} Ωcm with nitrogen ion fluence. Based on these results, it can be inferred that ion implantation is an effective approach for uniform distribution of N ions in host matrix and tuning of optical and electrical properties.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2015

Influence of bias voltage on structural and optical properties of TiN{sub x} thin films

In the present work, Ti thin films were deposited on Si substrate using DC sputtering technique. Indigenous hot cathode arc discharge plasma system was used for nitriding over these samples, where the plasma parameters and work piece can be controlled independently. A mixture of H{sub 2} and N{sub 2} gases (in the ratio of 80:20) was supplied into the plasma chamber. The effect of bias voltage on the crystal structure, morphology and optical properties was investigated by employing various physical techniques such as X-ray Diffraction, Atomic Force Microscopy and UV-Vis spectrometry. It was found that bias voltage affects largely the crystal structure and band gap which in turn is responsible for the modifications in optical properties of the deposited films.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Structural and optical properties of oxygen irradiated Zn{sub 1-x}Mg{sub x}O (x = 0, 0.2) thin films

In the present study we report the effect of oxygen ion beam irradiation on the structural and optical properties of pure and 20% Mg doped ZnO thin films. These films were grown on Si substrate using RF sputtering technique. X-ray diffraction study confirms the formation of hexagonal wurtzite phase and the lattice parameter is found to reduce by Mg incorporation which further decreases after irradiation. The optical properties of the thin films using UV-Vis spectroscopy technique indicate an increment in the optical band gap with Mg incorporation as well as after irradiation.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2014

Conditions for reflection and transmission of an ion acoustic soliton in a dusty plasma with variable charge dust

Modified Korteweg-de Vries (mKdV) equations are derived for the incident, reflected, and transmitted waves in order to examine the soliton reflection and its transmission through an inhomogeneous plasma comprising ions, dust grains with fluctuating charge and two types of electrons, namely nonisothermal electrons and isothermal electrons. All the mKdV equations are coupled at the point of reflection and solved for the reflected soliton. Unlike others, a relation is established between the velocity shifts of the incident, reflected and transmitted solitons, and based on a critical value of the shift of incident soliton the strengths of the soliton reflection and transmission are talked about. Conditions are obtained for the soliton reflection and its transmission, and a comparative study is made for the two cases of fixed and fluctuating charges on the dust grains.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2014

Enhanced UV and suppressed defect related emission in yttrium doped zinc oxide

Yttrium doped ZnO (YZO) synthesized through conventional solid state reaction method using ZnO and Y{sub 2}O{sub 3} as starting material. The formation of YZO compounds were confirmed by X-ray diffraction and Raman spectroscopy. Photoluminescence measurements revealed an enhanced ultra-violet (UV) and suppressed defect related emission in YZO which is due to reduction in the concentration of the defects related to oxygen interstitials (O{sub i}) and zinc vacancy (V{sub Zn}) of ZnO.

36 MATERIALS SCIENCE↗
DOE OSTI2013

High frequency electromagnetic resistive instability in a Hall thruster under the effect of ionization

Two types of high frequency electromagnetic resistive instabilities are found to occur in a Hall thruster plasma in the presence of collisions and ionization, out of which one of lower growth rate (called lower magnitude high frequency instability (LMHFI)) is sensitive to the axial component of the wave vector. The effects of ionization, collisions, and electron drift velocity on the growth rates of these instabilities are studied in greater details. The LMHFI grows faster in the presence of ionization but shows weaker dependence on the electrons' E(vector sign)×B(vector sign) drift, contrary to the case of other instability (called higher magnitude high frequency instability) which is sensitive to the azimuthal wave number and collisions.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2013

Influence of ionization on reflection of solitary waves in a magnetized plasma

The reflection of nonlinear solitary waves is studied in a nonuniform, magnetized plasma diffusing from an ionization source along the magnetic field lines. Contribution of the ionization term is included in the continuity equation. The behavior of solitary waves is governed by modified form of Korteweg–de Vries equation (called mKdV equation). In order to investigate the reflection of solitary waves, the mKdV equations for the right and left going waves are derived, and solved by finding new transformations coupled at the point of reflection, for obtaining the expression of reflection coefficient. Contrary to the case of usual inhomogeneous plasma, the present analysis shows that a combination of usual sech{sup 2} structure and tanh structure (called the tail of soliton) arises due to the influence of ionization term. Interestingly, this tailing structure disappears after the reflection of the soliton and hence, the soliton is downshifted prominently.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2013

Microwave breakdown for the TE{sub 10} mode in a rectangular waveguide

Microwave breakdown is studied for the lowest order TE{sub 10} mode in a rectangular waveguide with the help of direct variational approach via the continuity equation along with the use of ionisation and attachment frequency. We investigate the role of the ionisation, attachment of electron with neutral gas or air molecules and the diffusion on microwave breakdown threshold in the waveguide filled with air or Ar Gas. We examine the effect of different gases and microwave parameters on the diffusion length and the breakdown threshold of electric field of continuous microwave and pulsed microwave. We also employ numerical approach for obtaining the results and compare them with the ones of variational approach.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2013

Density modification by two superposing TE{sub 10} modes in a plasma filled rectangular waveguide

Microwave and plasma interaction is examined via two fundamental TE{sub 10} modes propagating in a plasma filled rectangular waveguide after superposing at a smaller angle. The propagation of the resultant mode realized from these two modes is governed by a wave equation obtained using the Maxwell's equations. This equation is solved numerically using fourth order Runge-Kutta method for the field amplitude of the microwave in the waveguide considering the waveguide to be made up of a perfect conductor and filled with different types of initial plasma density distributions, viz. homogeneous density, linear density with gradient in the propagation direction, and the density with Gaussian profile along the waveguide width. A phenomenon similar to the duct formation by high power microwaves is found to take place, where the plasma density attains interesting profiles. These profiles can be controlled by the angle of superposition, phase difference between the fields of the two modes, microwave frequency and microwave field amplitude.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗