Ravi Prakash

Saturation of number variance in embedded random-matrix ensembles.

We study fluctuation properties of embedded random matrix ensembles of noninteracting particles. For ensemble of two noninteracting particle systems, we find that unlike the spectra of classical random matrices, correlation functions are nonstationary. In the locally stationary region of spectra, we study the number variance and the spacing distributions. The spacing distributions follow the Poisson statistics, which is a key behavior of uncorrelated spectra. The number variance varies linearly as in the Poisson case for short correlation lengths but a kind of regularization occurs for large correlation lengths, and the number variance approaches saturation values. These results are known in the study of integrable systems but are being demonstrated for the first time in random matrix theory. We conjecture that the interacting particle cases, which exhibit the characteristics of classical random matrices for short correlation lengths, will also show saturation effects for large correlation lengths.

Growth and morphological evolution of c-axis oriented AlN films on Si (100) substrates by DC sputtering technique

Aluminum nitride (AlN) films were grown on Si substrates by dc magnetron sputtering in plasma containing a mixture of argon and nitrogen, using a pure aluminum target. In this paper, we studied the growth of AlN films on Si(100) substrates under varying gas ratio (N2 to Ar gas ratio) by DC reactive magnetron sputtering at moderate deposition temperature (400°C-600°C). Phase formation and orientation of the thin films were determined by Grazing Incidence X-Ray Diffraction (GIXRD). Surface morphology of the deposited thin films was investigated by Scanning Electron Microscope. Film orientations were studied by varying the gas ratio and deposition temperature to obtain (002) oriented film. The highest Texture coefficient along (002) direction (γ=3.2) is obtained for optimized growth condition at Argon to Nitrogen gas ratio 10:10 and substrate temperature 550°C. This oriented film can be used in MEMS based devices.Aluminum nitride (AlN) films were grown on Si substrates by dc magnetron sputtering in plasma containing a mixture of argon and nitrogen, using a pure aluminum target. In this paper, we studied the growth of AlN films on Si(100) substrates under varying gas ratio (N2 to Ar gas ratio) by DC reactive magnetron sputtering at moderate deposition temperature (400°C-600°C). Phase formation and orientation of the thin films were determined by Grazing Incidence X-Ray Diffraction (GIXRD). Surface morphology of the deposited thin films was investigated by Scanning Electron Microscope. Film orientations were studied by varying the gas ratio and deposition temperature to obtain (002) oriented film. The highest Texture coefficient along (002) direction (γ=3.2) is obtained for optimized growth condition at Argon to Nitrogen gas ratio 10:10 and substrate temperature 550°C. This oriented film can be used in MEMS based devices.

Effect of AlN layer on the bipolar resistive switching behavior in TiN thin film based ReRAM device for non-volatile memory application

The effect of an additional AlN layer in the Cu/TiN/AlN/Pt stack configuration deposited using sputtering has been investigated. The Cu/TiN/AlN/Pt device shows a tristate resistive switching. Multilevel switching is facilitated by ionic and metallic filament formation, and the nature of the filaments formed is confirmed by performing a resistance vs. temperature measurement. Ohmic behaviour and trap controlled space charge limited current (SCLC) conduction mechanisms are confirmed as dominant conduction mechanism at low resistance state (LRS) and high resistance state (HRS). High resistance ratio (102) corresponding to HRS and LRS, good write/erase endurance (105) and non-volatile long retention (105s) are also observed. Higher thermal conductivity of the AlN layer is the main reasons for the enhancement of resistive switching performance in Cu/TiN/AlN/Pt cell. The above result suggests the feasibility of Cu/TiN/AlN/Pt devices for multilevel nonvolatile ReRAM application.The effect of an additional AlN layer in the Cu/TiN/AlN/Pt stack configuration deposited using sputtering has been investigated. The Cu/TiN/AlN/Pt device shows a tristate resistive switching. Multilevel switching is facilitated by ionic and metallic filament formation, and the nature of the filaments formed is confirmed by performing a resistance vs. temperature measurement. Ohmic behaviour and trap controlled space charge limited current (SCLC) conduction mechanisms are confirmed as dominant conduction mechanism at low resistance state (LRS) and high resistance state (HRS). High resistance ratio (102) corresponding to HRS and LRS, good write/erase endurance (105) and non-volatile long retention (105s) are also observed. Higher thermal conductivity of the AlN layer is the main reasons for the enhancement of resistive switching performance in Cu/TiN/AlN/Pt cell. The above result suggests the feasibility of Cu/TiN/AlN/Pt devices for multilevel nonvolatile ReRAM application.

Effect of film thickness on structural and mechanical properties of AlCrN nanocompoite thin films deposited by reactive DC magnetron sputtering

In this study, the influence of film thickness on the structural, surface morphology and mechanical properties of Aluminum chromium nitride (AlCrN) thin films has been successfully investigated. The AlCrN thin films were deposited on silicon (100) substrate using dc magnetron reactive co-sputtering at substrate temperature 400° C. The structural, surface morphology and mechanical properties were studied using X-ray diffraction, field-emission scanning electron microscopy and nanoindentation techniques respectively. The thickness of these thin films was controlled by varying the deposition time therefore increase in deposition time led to increase in film thickness. X-ray diffraction pattern of AlCrN thin films with different deposition time shows the presence of (100) and (200) orientations. The crystallite size varies in the range from 12.5 nm to 36.3 nm with the film thickness due to surface energy minimization with the higher film thickness. The hardness pattern of these AlCrN thin films follows Hall-P...