Raj P. Dahiya

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.

Influence of bias voltage on structural and optical properties of TiNx 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 H2 and N2 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.

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 sech2 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.

Influence of N+ 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 4×1015 ions/cm2 to 2×1016 ions/cm2. 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 4×1015 ions/cm2 to 2×1016 ions/cm2. Furthermore, electrical resistivity also decreases from 2.67×10−4 Ω.cm to 2.31×10−4 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.

Inhomogeneity Effect on Solitary Structures in a Magnetized Warm Plasma: Ionization Versus Recombination

In a magnetized inhomogeneous warm plasma having ionization/recombination, usual version of the KdV equation is found to be modified by two additional terms arising due to the inclusion of ionization/recombination and the density gradient in the plasma. The density gradient in the plasma shows its dependence on the ionization/recombination rate, ion-to-electron temperature ratio, obliqueness of the magnetic field and drift velocity of the ions. In the considered plasma, only the compressive solitary structures are found to propagate corresponding to two different types of modes. A significant effect of magnetic field and ion temperature is found on these structures in both the cases of ionization and recombination, though these structures show weak dependence on the charge of the ions. Interestingly the solitons with prominent tailing structures are evolved in the plasma under the effect of stronger density gradient and higher ionization or recombination. The tailing structure with bigger size evolves in the plasma in the case of only recombination, suggesting that the exchange/transfer of energy from the main soliton to its tail is on a greater scale in the case of recombination than the case of ionization. There exists a critical value of the ionization rate at which the tailing structure associated with only the fast (not slow) solitary structure is vanished. Similarly, the tailing structure associated with only the slow (not fast) solitary structure is disappeared at a critical value of recombination rate.

Investigation of micro-structure and micro-hardness properties of 304L stainless steel treated in a hot cathode arc discharge plasma

We have established a hot cathode arc discharge plasma system, where different stainless steel samples can be treated by monitoring the plasma parameters and nitriding parameters independently. In the present work, a mixture of 70% N2 and 30% H2 gases was fed into the plasma chamber and the treatment time and substrate temperature were optimized for treating 304L Stainless Steel samples. Various physical techniques such as x-ray diffraction, energy dispersive x-ray spectroscopy and micro-vickers hardness tester were employed to determine the structural, surface composition and surface hardness of the treated samples.