Showing papers by "Samit K. Ray published in 2002"
TL;DR: The behavior of the thermal elastohydrodynamic lubrication film in rough rolling/sliding line contacts at dynamic loads is investigated numerically in this article, where the lubricant is assumed to be a mixture of Newtonian and Ree-Eyring fluids and the maximum pressure in the contact region undergoes a noteworthy change with time due to dynamic loading and the effect of moving surface roughness.
Abstract: The behavior of the thermal elastohydrodynamic lubrication film in rough rolling/sliding line contacts at dynamic loads is investigated numerically. The lubricant is assumed to be a mixture of Newtonian and Ree-Eyring fluids. The results show that the maximum pressure in the contact region undergoes a noteworthy change with time due to dynamic loading and the effect of moving surface roughness. The variation of minimum film thickness and coefficient of friction with the composition of the lubricant is found to be dependent upon the reference viscosity ratio. The superposition of the effects of moving surface roughness and dynamic loading is shown to determine the behavior of time dependent film thickness and coefficient of friction.
26 citations
TL;DR: In this paper, Ba x Sr 1− x TiO 3 (BST) thin films have been deposited by rf magnetron sputtering on multi-layered perovskite conducting bottom electrode with or without a buffer layer on Si.
Abstract: Ba x Sr 1− x TiO 3 (BST) thin films have been deposited by rf magnetron sputtering on multi-layered perovskite conducting bottom electrode with or without a buffer layer on Si. The crystallinity and surface morphology of the deposited films have been studied using X-ray diffraction and scanning electron microscopy. Electrical properties of the BST films have been evaluated on multilayer oxide electrode using Si/MgAl 2 O 4 /LCMO/BST/Al metal-insulator-metal structure. The bottom electrode interface has shown a marked effect on the electrical properties of the BST films. Current–voltage behavior has indicated the Poole–Frenkel conduction mechanism at higher voltages.
16 citations
06 Aug 2002
TL;DR: The design and fabrication of resonators and waveguides, operating at THz frequencies are reported Resonance frequencies, mode confinement, quality factors, and stop-bands were calculated for resonators with and without photonic elements as mentioned in this paper.
Abstract: The design and fabrication of resonators and waveguides, operating at THz frequencies are reported Resonance frequencies, mode confinement, quality factors, and stop-bands were calculated for resonators with and without photonic elements The estimations show that very narrow modes can exist within the propagation bandgap of a photonic lattice Microdisk devices were designed and fabricated for high-quality whispering-gallery modes centered around 10 THz Combined with silicon-germanium quantum wells grown by molecular beam epitaxy, these resonators are promising candidates for silicon-based miniature far-infrared lasers
12 citations
TL;DR: In this paper, the authors have fabricated p-type metaloxide semiconductor field effect transistor (p-MOSFET) devices with channel lengths from 0.8-10 μm on strained Si/Si0.793Ge0.2C0.007 devices over the temperature range of 300-77 K.
Abstract: We have fabricated p-type metal–oxide semiconductor field-effect transistor (p-MOSFET) devices with channel lengths from 0.8–10 μm on strained Si/Si0.8Ge0.2/Si and partially strain compensated Si/Si0.793Ge0.2C0.007/Si heterolayers. The device characteristics, the source–drain resistance and the mobility degradation factor have been studied for control-Si, Si0.8Ge0.2 and Si0.793Ge0.2C0.007 devices over the temperature range of 300–77 K. Though a significant improvement in the drive current of Si0.793Ge0.2C0.007 devices has been observed compared to the control-Si and Si0.8Ge0.2 devices at room temperature, the performance of ternary devices at 77 K has been found to be inferior to that of binary devices. This has been found to be due to the higher source–drain resistance and mobility degradation factor of Si0.793Ge0.2C0.007 MOSFET devices at cryogenic temperature.
11 citations
TL;DR: Pseudomorphic Si-Si Raman mode vibrations on strain and composition of binary and ternary alloys have been explained with experimental and theoretically calculated results as mentioned in this paper, where the Hall hole mobility is found to increase with decreasing compressive strain or effective Ge content in the layer throughout the temperature range of 120-300 K.
Abstract: Pseudomorphic Si1-x
Ge
x
and partially strain compensated
$${\text{Si}}_{1 - x - y} {\text{Ge}}_x {\text{C}}_y $$
layers with different Ge and C fractions have been grown at 500 °C by ultra high vacuum chemical vapor deposition on Si (100) substrates The degree of strain compensation of the layers has been investigated by high resolution X-ray diffraction and simple application of the linear elasticity theory The surface morphology of the layers has been characterized by atomic force microscopy The dependence of Si–Si Raman mode vibrations on strain and composition of binary and ternary alloys have been explained with experimental and theoretically calculated results The Hall hole mobility is found to increase with decreasing compressive strain or effective Ge content in the layer throughout the temperature range of 120–300 K
9 citations
TL;DR: In this article, the room temperature Raman and IR spectra of powder and thin films (both annealed and as-deposited) of Ba 0.8 Sr 0.2 TiO 3 were compared.
9 citations
TL;DR: The potential of ZrO2 thin film as a high-K gate dielectric for scaled MOSFET devices has been studied in this article, where an equivalent oxide thickness of < 20 A with a leakage current of the order of 10-4 A/cm2 at 1 V has been obtained.
Abstract: The potential of ZrO2 thin film as a high-K gate dielectric for scaled MOSFET devices has been studied. ZrO2 has been deposited directly on a Si0.8Ge0.2 substrate by reactive RF magnetron sputtering. An equivalent oxide thickness of < 20 A with a leakage current of the order of 10-4 A/cm2 at 1 V has been obtained. Well-behaved capacitance-voltage characteristics with an interface state density of 2 × 1011 cm-2eV-1 have been achieved. The deposited dielectric exhibits low charge trapping under constant current stressing.
9 citations
TL;DR: In this article, BaxSr1−xTiO3 (BST) thin films have been deposited on silicon and platinum-coated silicon substrates with different buffer and barrier layers.
Abstract: BaxSr1−xTiO3 (BST) thin films have been deposited by r.f. magnetron sputtering on silicon and platinum-coated silicon substrates with different buffer and barrier layers. Electrical properties of BST films have been evaluated using both metal–insulator–semiconductor (MIS) and metal–insulator–metal (MIM) structures. MIS capacitor C–V and G–V characteristics have been utilized to determine the fixed charge density, interface trap density and the trap distribution in the silicon bandgap. BST films deposited on Si/SiO2/SiN/Pt and Si/SiO2/Ti/TiN/Pt multilayer bottom electrodes have been used for the fabrication of MIM capacitors. The role of bottom electrode, processing temperature and Ba to Sr ratio on the electrical properties of BaxSr1−xTiO3 films have been investigated. Current–voltage behavior has indicated an ohmic nature at lower voltages and Poole–Frenkel conduction at higher voltages. Deposited films have shown an excellent time-dependent dielectric breakdown under constant-current stressing.
7 citations
TL;DR: Nickel silicides were formed on Si (100) substrates and CVD grown Si0.9Ge0.1/Si layers by low thermal budget annealing of evaporated Ni films to evaluate their utility for ultra shallow junctions.
Abstract: Nickel silicides were formed on Si (100) substrates and CVD grown Si0.9Ge0.1/Si layers by low thermal budget annealing of evaporated Ni films to evaluate their utility for ultra shallow junctions. The phase formation and microstructure of silicides formed using conventional furnace and rapid thermal annealing were studied by x-ray diffraction, Rutherford backscattering (RBS), x-ray photoelectron spectroscopy (XPS) and atomic force microscopy. RBS simulations and XPS study revealed the formation of a ternary nickel germanosilicide phase for the SiGe alloy. The incorporation of Ge resulted in a higher temperature window for the stability of low-resistive monosilicide phase. Electrical properties of the grown silicides were characterized by four-probe resistivity and contact resistance measurements.
4 citations
TL;DR: In this paper, the hole mobility in buried SiGeC channels and the dominant scattering mechanisms in the carbon-containing Si alloy were estimated by using a simple analysis based on the inversion layer mobility model.
Abstract: Partially strain compensated Si/Si0.793Ge0.2C0.007/Si heterojunction p-MOSFET devices have been used to calculate the hole mobility in buried SiGeC channels and to estimate the dominant scattering mechanisms in the carbon-containing Si alloy. The current contribution of the buried SiGeC channel to the total drain current has been found by using a simple analysis based on the inversion layer mobility model. The 'true' effective mobility in the buried channel of the fabricated Si0.793Ge0.2C0.007 PMOSFET device has thus been extracted over a temperature range of 77–300 K. The alloy scattering limited mobility and the coefficient (Kf) associated with field-dependent mobility have been estimated from an effective mobility plot at liquid-nitrogen temperature. A quantitative estimation of C-induced alloy scattering potential is reported for the first time.
4 citations
TL;DR: In this paper, a velocity field study of holes in partially strain compensated Si/sub 0793/Ge/sub 02/C/sub 0007/ p-MOSFET devices with channel lengths ranging from 8 to 10 /spl mu/m has been carried out.
Abstract: A velocity-field study of holes in partially strain compensated Si/sub 0793/Ge/sub 02/C/sub 0007/ p-MOSFET devices with channel lengths ranging from 08 to 10 /spl mu/m has been carried out A very high effective hole velocity, 11 /spl times/ 10/sup 7/ cm/s attributed to the onset of velocity overshoot in SiGeC p-MOSFETs, is reported Significant improvement in effective hole velocity of Si/sub 0793/Ge/sub 02/C/sub 0007/, compared to that of a binary Si/sub 08/Ge/sub 02/ device, is observed this being due to C-induced strain stabilisation in the metastable SiGe layer
TL;DR: In this paper, the growth of gate-quality ultrathin oxides directly on tensile-strained Si1−yCy alloy layers has been investigated using microwave O2-plasma discharge.
Abstract: Growth of gate-quality ultrathin (<100 A) oxides directly on tensile-strained Si1−yCy alloy layers has been investigated using microwave O2-plasma discharge. The electrical properties of oxide grown on an Si0.993C0.007 layer have been studied using a metal-oxide-semiconductor structure. Fixed oxide charge density and mid-gap interface state density are found to be 2.5×1011 cm−2 and 2.0×1011 cm−2 eV−1, respectively. Oxide film exhibits hole trapping behaviour under Fowler–Nordheim constant current stressing.
05 Jun 2002
TL;DR: In this article, an intense THz emission was observed from strained SiGe/Si quantum-well structures under strong pulsed electric field, where the p-type structures were MBE-grown on n-type Si substrate and δ-doped with boron.
Abstract: An intense THz emission was observed from strained SiGe/Si quantum-well structures under strong pulsed electric field. The p-type structures were MBE-grown on n-type Si substrate and δ-doped with boron. Lines with wavelengths near 100 microns were observed in the emission spectrum. The modal structure in the spectrum gave evidence for the stimulated nature of the emission. The origin of the THz emission was attributed to intracenter optical transitions between resonant and localized boron levels.© (2002) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
TL;DR: In this paper, the authors report on far-infrared emission in the 1-12 THz frequency range from strained SiGe structures from Pseudomorphic superlattices grown by MBE at a relatively low substrate temperature of 400°C to prevent germanium segregation.
Abstract: In this paper we report on far-infrared emission in the 1–12 THz frequency range from strained SiGe structures. Pseudomorphic superlattices were grown by Molecular Beam Epitaxy (MBE) at the relatively low substrate temperature of 400°C to prevent germanium segregation. Layer thicknesses, composition, and crystallinity were confirmed by high-resolution X-ray diffraction. Devices were designed to produce confined hole states with various energy separations. Mesa devices were etched in a reactive-ion etching system and tested for edge emission over a wide range of drive currents using an FTIR spectrometer in step-scan mode. THz emission was observed in pulsed mode at current densities as low as 50 A/cm2 and at temperatures as high as 50 K, using a liquid-helium-cooled silicon bolometer detector with a lock-in amplifier. Emission spectral peaks occurred at 7.9 and 9.36 THz for two different samples, in good agreement with k·p calculations.
05 Jun 2002
TL;DR: Terahertz electroluminescence was produced by intersubband transitions in silicongermanium quantum wells as discussed by the authors, and was attributed to heavy-hole-to-light-hole transitions and demonstrates the potential for SiGe technology as terahertz emitters.
Abstract: Terahertz electroluminescence was produced by intersubband transitions in silicongermanium quantum wells. The devices were grown by solid-source molecular-beam epitaxy on high-resistivity silicon substrates, and were fabricated by standard photolithography and processing techniques. Using FTIR spectroscopy at at temperature of 5 K, electroluminescence was observed around 9 THz. The emission was attributed to heavy-hole-to-light-hole transitions and demonstrates the potential for SiGe technology as terahertz emitters.
Proceedings Article•
01 Jan 2002
TL;DR: In this paper, a comparative study of the electrical properties of some oxides e.g. Gd 2 O 3, Gd O 3 and Y O 3 has been performed for gate dielectric for strained Si 0.74 Ge 0.26 MOS devices.
Abstract: In this paper we report a comparative study of the electrical properties of some oxides e.g. Gd 2 O 3 , Ga 2 O 3 (Gd 2 O 3 ), Y 2 O 3 and Ga 2 O 3 as gate dielectric for strained Si 0.74 Ge 0.26 MOS devices. The deposited films have been characterized using EDAX, SIMS and ellipsometry. The Au / oxide / SiGe MIS structures using these insulators were examined using I-V, C-V and G-V techniques. Though Gd 2 O 3 and Y 2 O 3 showed highest resistivity and breakdown strength, Ga 2 O 3 (Gd 2 O 3 ) was found to be most effective for surface passivation of SiGe giving lowest interface state density while pure Ga 2 O 3 was incapable of passivating SiGe surface.