In this paper, we study the relativistic, steady state, optically thin, advection-dominated accre... more In this paper, we study the relativistic, steady state, optically thin, advection-dominated accretion disks around the rotating black holes. We study axisymmetric and vertically averaged disks. For shear stress viscosity, the exact relations of the four-velocity with no approximation are derived. We effort to derive the general and analytic relation for density, relativistic enthalpy, temperature, pressure and inertial energy. We use the radial model for the radial component of four-velocity. In the radial model, the figures of density etc. are plotted. The influences of shear and bulk coefficients and spin of the black hole etc. are studied.
International Conference on Aerospace Sciences and Aviation Technology
Thermal decomposition of pure cyclotetramethylene tetranitramine (HMX) shows a small endothermic ... more Thermal decomposition of pure cyclotetramethylene tetranitramine (HMX) shows a small endothermic peak at 191.4°C attributed to p to a phase transition, an endothermic peak at 281°C assigned to melting of HMX followed by exothermic decomposition leading to a considerable peak at 284.3°C, and a sharp derivative thermogravimetry (DTG) peak at 282°C with 100% mass loss. The activation energy of decomposition is determined using two different techniques, thermogravimetric TG/DTG and differential scanning calorimetry DSC and three different methods of calculation Ozawa [1-3], Kissinger [2,4] and 1st order rate equation [4].
ECS Journal of Solid State Science and Technology, 2016
This study presents signal-to-noise ratio (SNR) measurements of single crystalline dots or layers... more This study presents signal-to-noise ratio (SNR) measurements of single crystalline dots or layers of SiGe/Si in multilayer structures in terms of Ge content, interfacial and layer quality. All multilayers were processed in form of mesas and the noise behavior of electrical signal was investigated by comparing the power spectral density curves and K 1/f values. The SiGe/Si multilayer structures were also characterized by the conventional material analysis tools and the results were compared to the noise measurements. The quality of SiGe/Si interface or SiGe layer was monitored by intentional exposure to oxygen in range of 2-1600 nTorr either during or prior to SiGe growth. The results demonstrated that SNR was sensitive to the interfacial and layer quality, and the Ge content in a multilayer structure. The noise level became very high when the strain fluctuated within SiGe layer and this occurred for SiGe with high Ge content or SiGe dots.
ABSTRACT Ge-Sn-Si-C alloys offer a large range of strain engineering which gives the possibility ... more ABSTRACT Ge-Sn-Si-C alloys offer a large range of strain engineering which gives the possibility to tailor the material properties for advanced photonic, electronic, photovoltaic and thermoelectric applications. The benefits of Ge-Sn-Si-C alloys are possibilities to obtain a direct-to-indirect transition (for Sn-based alloys) [1], high carrier mobility [2] and low cost process [3]. In this study, Ge1-x-y-zSnxSiyCz layers (0.01≤x≤ 0.24, 0≤y≤0.12 and 0≤z≤0.01) have successfully grown on Ge and Si by using RPCVD technique. It was demonstrated that the quality of epitaxial layers is dependent on the growth parameters, layer thickness and the quality of Ge virtual layer. It was found that a proper strain balance in the matrix during the epitaxy where the Si and Si-C is adjusted carefully compared to Sn flux improves the incorporation of Sn in Ge matrix. This is explained by the compensation of tensile strain induced by Si or Si-C with the compressive strain caused by Sn in order to obtain the minimum energy in Ge matrix. Fig. 1a and 1b show RBS spectra of two GeSnSi samples when the first one has a constant Si flux whereas the sample in Fig. 1b has a graded Si flux within GeSnSi layer. The Sn incorporation improved from 3% to 24% when Si flux was graded. Incorporation of P and B in GeSnSiC matrix has been studied and the effect of dopant concentrations on Sn content has been investigated. A low boron concentration in range of 1017 cm-3 could be incorporated in the epi-layers whereas P-doping in range of 1019 cm-3could be achieved. All Ge1-x-ySnxSiyCz layers were grown at 280-330 °C at 20 torr in a RPCVD reactor. The gas precursors were Si3H8, Ge2H6, 1% B2H6 in H2, 5% PH3 in H2, and SnCl4as Si, Ge, B, P and Sn sources, respectively. The strain in the epi-layers was measured by high-resolution x-ray reciprocal lattice maps (HRRLMs). Transmission electron microscopy (TEM) was applied to detect the defects in the epi-layers and to observe the interfacial quality. The Sn, Si and C content in the samples was measured by Rutherford backscattering spectrometry (RBS) and HRRLMs. The atomic dopant concentration in the epi-layers was measured by secondary ion mass spectrometry (SIMS). Four-probe measurements were done to determine the resistivity of the doped layers. The quality of carrier and reactant gases in terms of oxygen and water vapor was investigated by residual gas analyzer (RGA). The RGA instrument was connected to the exhaust gas output and was situated in 20 mm distance from the reactant gas chamber. A RGA spectrum reveals any absorption or desorption of molecules with accuracy of ppt range. The results showed that the level of oxygen during epitaxy was as low as 10 ppb and the contamination concetration was found as low as 1017 cm-3. This low oxygen level during epitxy is due to the high purity of trisilane, digermane and tetrachloride precursors as well as the hydrogen carrier gas. Acknowledgment The Swedish Research Council (VR) is greatly acknowledged for supporting this work. References [1] P. Moontragoon, Z. Ikonic and P.Harrison, J. Semicond. Sci. Technol. 22, p.742, 2007. [2] S. Gupta, R. Chen, B. Magyari-Kope, H. Lin, B. Yang, A. Nainani, Y. Nishi, J. S. Harris, and K. C. Saraswat, in Proc. IEDM, 11, p. 398, 2011. [3] A. Jamshidi, M. Noroozi, M. Moeen, A. Hallen, B. Hamawandi, J. Lu, L. Hultman, M. Ostling, H. H. Radamson, Surface & Coatings Technology, v 230, p.106, 2013. Fig. 1 RBS spectra for GeSnSi layers grown with a) constant Si and Sn flux b) a grading Si flux but constant Sn flux during epitaxy
2011 International Semiconductor Device Research Symposium (ISDRS), 2011
ABSTRACT Un-cooled bolometer arrays have been considered as good choices for detection of infrare... more ABSTRACT Un-cooled bolometer arrays have been considered as good choices for detection of infrared waves in the ranges of 3–5μm (MWIR: mid wavelength infrared) and 8–12μm (LWIR: long wavelength infrared). Advantages are found in their relative simplicity of mechanism and design, hence, fabrication cost, when compared to detectors working based on photon detection mechanisms. A temperature dependent resistor (or thermistor) is the core element of a bolometer. The rate of resistance dependency to temperature is a figure-of-merit for thermistor material, acting as the active element in a bolometer. This property is characterized by temperature coefficient of resistance (TCR). At the same time, for the better IR detection and imaging quality, high signal-to-noise ratio (SNR) is also sought. Different materials have been proposed and/or implemented commercially to work as thermistor materials. Among them are VOx, amorphous silicon, amorphous and poly SiGe.
ABSTRACTIn this study, the formation of Ni-(GeSn)x on strained and relaxed Ge1−xSnx (0.01≤x≤ 0.03... more ABSTRACTIn this study, the formation of Ni-(GeSn)x on strained and relaxed Ge1−xSnx (0.01≤x≤ 0.03) nanowires in contact areas has been investigated. The epi-layers were grown at different temperatures (290 to 380°C) by RPCVD technique. The strain in GeSn layers tailored through carefully chosen of growth parameters and virtual substrate. The nanowires were fabricated through both I-line and dry-etching. 15 nm Ni was deposited either on the contact areas or whole length of nanowires. The wires went through rapid thermal annealing at intervals of 360 to 550°C for 30s in N2 ambient. The results show the thermal stability and amount of particular phases were strain-dependent. The formation of Ni-GeSn was eased when GeSn layers were strain-free. When the Sn content is high the epi-layers suffer from Sn segregation. The Sn-rich surface impedes remarkably the Ni diffusion. The electrical conductivity measurement of nanowires shows low resistivity and Ohmic contact are obtained for Ni-GeSn.
The synthesis of new materials for thermal infrared (IR) detection has been an intensive research... more The synthesis of new materials for thermal infrared (IR) detection has been an intensive research area in recent years. Among new semiconductor materials, synthetic diamond has the ability to function even under very high temperature and high radiation conditions. In the present work, diamond Schottky diodes with boron concentrations in the range of 1014<B<1017cm-3 are presented as candidates for IR thermal sensors with an excellent temperature coefficient of resistance (-8.42%/K) and very low noise levels around 6.6 x10-15 V2/Hz. This enables huge performance enhancements for a wide variety of systems, e.g., automotive and space applications.
Low temperature epitaxy (LTE) in Chemical Vapor Deposition (CVD) refers to 350-650 • C interval. ... more Low temperature epitaxy (LTE) in Chemical Vapor Deposition (CVD) refers to 350-650 • C interval. This temperature range is critical for this process since the thermal and lattice mismatch (or strain relaxation) issues diminish in advanced BiCMOS processing. The modeling of the epitaxy process is a vital task to increase the understanding the growth process and to design any desired device structure. In this study, an empirical model for Si 2 H 6 /Ge 2 H 6-based LTE of SiGe is developed and compared with experimental work. The model can predict the number of free sites on Si surface, growth rate of Si and SiGe, and the Ge content at low temperatures. A good agreement between the model and the experimental data is obtained.
SiGe has been widely used for source/drain (S/D) engineering in pMOSFETs to enhance channel mobil... more SiGe has been widely used for source/drain (S/D) engineering in pMOSFETs to enhance channel mobility. In this study, selective Si 1Àx Ge x growth (0.25 x 0.35) with boron concentration of 1-3 Â 10 20 cm À3 in the process for 22 nm node complementary metal-oxide semiconductor (CMOS) has been investigated and optimized. The growth parameters were carefully tuned to achieve deposition of high quality and highly strained material. The thermal budget was decreased to 800 C to suppress dopant diffusion, to minimize Si loss in S/D recesses, and to preserve the S/D recess shape. Two layers of Si 1Àx Ge x were deposited: a bottom layer with high Ge content (x ¼ 0.35) which filled the recess and a cap layer with low Ge content (x ¼ 0.25) which was elevated in the S/D regions. The elevated SiGe cap layer was intended to be consumed during the Ni-silicidation process in order to avoid strain reduction in the channel region arising from strain relaxation in SiGe S/D. In this study, a kinetic gas model was also applied to predict the pattern dependency of the growth and to determine the epi-profile in different transistor arrays. The input parameters include growth temperature, partial pressures of reactant gases, and chip layout. By using this model, the number of test wafers for epitaxy experiments can be decreased significantly. When the epitaxy process parameters can be readily predicted by the model for epi-profile control in an advanced chip design, fast and cost-effective process development can be achieved. V
In this paper, we study the relativistic, steady state, optically thin, advection-dominated accre... more In this paper, we study the relativistic, steady state, optically thin, advection-dominated accretion disks around the rotating black holes. We study axisymmetric and vertically averaged disks. For shear stress viscosity, the exact relations of the four-velocity with no approximation are derived. We effort to derive the general and analytic relation for density, relativistic enthalpy, temperature, pressure and inertial energy. We use the radial model for the radial component of four-velocity. In the radial model, the figures of density etc. are plotted. The influences of shear and bulk coefficients and spin of the black hole etc. are studied.
International Conference on Aerospace Sciences and Aviation Technology
Thermal decomposition of pure cyclotetramethylene tetranitramine (HMX) shows a small endothermic ... more Thermal decomposition of pure cyclotetramethylene tetranitramine (HMX) shows a small endothermic peak at 191.4°C attributed to p to a phase transition, an endothermic peak at 281°C assigned to melting of HMX followed by exothermic decomposition leading to a considerable peak at 284.3°C, and a sharp derivative thermogravimetry (DTG) peak at 282°C with 100% mass loss. The activation energy of decomposition is determined using two different techniques, thermogravimetric TG/DTG and differential scanning calorimetry DSC and three different methods of calculation Ozawa [1-3], Kissinger [2,4] and 1st order rate equation [4].
ECS Journal of Solid State Science and Technology, 2016
This study presents signal-to-noise ratio (SNR) measurements of single crystalline dots or layers... more This study presents signal-to-noise ratio (SNR) measurements of single crystalline dots or layers of SiGe/Si in multilayer structures in terms of Ge content, interfacial and layer quality. All multilayers were processed in form of mesas and the noise behavior of electrical signal was investigated by comparing the power spectral density curves and K 1/f values. The SiGe/Si multilayer structures were also characterized by the conventional material analysis tools and the results were compared to the noise measurements. The quality of SiGe/Si interface or SiGe layer was monitored by intentional exposure to oxygen in range of 2-1600 nTorr either during or prior to SiGe growth. The results demonstrated that SNR was sensitive to the interfacial and layer quality, and the Ge content in a multilayer structure. The noise level became very high when the strain fluctuated within SiGe layer and this occurred for SiGe with high Ge content or SiGe dots.
ABSTRACT Ge-Sn-Si-C alloys offer a large range of strain engineering which gives the possibility ... more ABSTRACT Ge-Sn-Si-C alloys offer a large range of strain engineering which gives the possibility to tailor the material properties for advanced photonic, electronic, photovoltaic and thermoelectric applications. The benefits of Ge-Sn-Si-C alloys are possibilities to obtain a direct-to-indirect transition (for Sn-based alloys) [1], high carrier mobility [2] and low cost process [3]. In this study, Ge1-x-y-zSnxSiyCz layers (0.01≤x≤ 0.24, 0≤y≤0.12 and 0≤z≤0.01) have successfully grown on Ge and Si by using RPCVD technique. It was demonstrated that the quality of epitaxial layers is dependent on the growth parameters, layer thickness and the quality of Ge virtual layer. It was found that a proper strain balance in the matrix during the epitaxy where the Si and Si-C is adjusted carefully compared to Sn flux improves the incorporation of Sn in Ge matrix. This is explained by the compensation of tensile strain induced by Si or Si-C with the compressive strain caused by Sn in order to obtain the minimum energy in Ge matrix. Fig. 1a and 1b show RBS spectra of two GeSnSi samples when the first one has a constant Si flux whereas the sample in Fig. 1b has a graded Si flux within GeSnSi layer. The Sn incorporation improved from 3% to 24% when Si flux was graded. Incorporation of P and B in GeSnSiC matrix has been studied and the effect of dopant concentrations on Sn content has been investigated. A low boron concentration in range of 1017 cm-3 could be incorporated in the epi-layers whereas P-doping in range of 1019 cm-3could be achieved. All Ge1-x-ySnxSiyCz layers were grown at 280-330 °C at 20 torr in a RPCVD reactor. The gas precursors were Si3H8, Ge2H6, 1% B2H6 in H2, 5% PH3 in H2, and SnCl4as Si, Ge, B, P and Sn sources, respectively. The strain in the epi-layers was measured by high-resolution x-ray reciprocal lattice maps (HRRLMs). Transmission electron microscopy (TEM) was applied to detect the defects in the epi-layers and to observe the interfacial quality. The Sn, Si and C content in the samples was measured by Rutherford backscattering spectrometry (RBS) and HRRLMs. The atomic dopant concentration in the epi-layers was measured by secondary ion mass spectrometry (SIMS). Four-probe measurements were done to determine the resistivity of the doped layers. The quality of carrier and reactant gases in terms of oxygen and water vapor was investigated by residual gas analyzer (RGA). The RGA instrument was connected to the exhaust gas output and was situated in 20 mm distance from the reactant gas chamber. A RGA spectrum reveals any absorption or desorption of molecules with accuracy of ppt range. The results showed that the level of oxygen during epitaxy was as low as 10 ppb and the contamination concetration was found as low as 1017 cm-3. This low oxygen level during epitxy is due to the high purity of trisilane, digermane and tetrachloride precursors as well as the hydrogen carrier gas. Acknowledgment The Swedish Research Council (VR) is greatly acknowledged for supporting this work. References [1] P. Moontragoon, Z. Ikonic and P.Harrison, J. Semicond. Sci. Technol. 22, p.742, 2007. [2] S. Gupta, R. Chen, B. Magyari-Kope, H. Lin, B. Yang, A. Nainani, Y. Nishi, J. S. Harris, and K. C. Saraswat, in Proc. IEDM, 11, p. 398, 2011. [3] A. Jamshidi, M. Noroozi, M. Moeen, A. Hallen, B. Hamawandi, J. Lu, L. Hultman, M. Ostling, H. H. Radamson, Surface &amp; Coatings Technology, v 230, p.106, 2013. Fig. 1 RBS spectra for GeSnSi layers grown with a) constant Si and Sn flux b) a grading Si flux but constant Sn flux during epitaxy
2011 International Semiconductor Device Research Symposium (ISDRS), 2011
ABSTRACT Un-cooled bolometer arrays have been considered as good choices for detection of infrare... more ABSTRACT Un-cooled bolometer arrays have been considered as good choices for detection of infrared waves in the ranges of 3–5μm (MWIR: mid wavelength infrared) and 8–12μm (LWIR: long wavelength infrared). Advantages are found in their relative simplicity of mechanism and design, hence, fabrication cost, when compared to detectors working based on photon detection mechanisms. A temperature dependent resistor (or thermistor) is the core element of a bolometer. The rate of resistance dependency to temperature is a figure-of-merit for thermistor material, acting as the active element in a bolometer. This property is characterized by temperature coefficient of resistance (TCR). At the same time, for the better IR detection and imaging quality, high signal-to-noise ratio (SNR) is also sought. Different materials have been proposed and/or implemented commercially to work as thermistor materials. Among them are VOx, amorphous silicon, amorphous and poly SiGe.
ABSTRACTIn this study, the formation of Ni-(GeSn)x on strained and relaxed Ge1−xSnx (0.01≤x≤ 0.03... more ABSTRACTIn this study, the formation of Ni-(GeSn)x on strained and relaxed Ge1−xSnx (0.01≤x≤ 0.03) nanowires in contact areas has been investigated. The epi-layers were grown at different temperatures (290 to 380°C) by RPCVD technique. The strain in GeSn layers tailored through carefully chosen of growth parameters and virtual substrate. The nanowires were fabricated through both I-line and dry-etching. 15 nm Ni was deposited either on the contact areas or whole length of nanowires. The wires went through rapid thermal annealing at intervals of 360 to 550°C for 30s in N2 ambient. The results show the thermal stability and amount of particular phases were strain-dependent. The formation of Ni-GeSn was eased when GeSn layers were strain-free. When the Sn content is high the epi-layers suffer from Sn segregation. The Sn-rich surface impedes remarkably the Ni diffusion. The electrical conductivity measurement of nanowires shows low resistivity and Ohmic contact are obtained for Ni-GeSn.
The synthesis of new materials for thermal infrared (IR) detection has been an intensive research... more The synthesis of new materials for thermal infrared (IR) detection has been an intensive research area in recent years. Among new semiconductor materials, synthetic diamond has the ability to function even under very high temperature and high radiation conditions. In the present work, diamond Schottky diodes with boron concentrations in the range of 1014<B<1017cm-3 are presented as candidates for IR thermal sensors with an excellent temperature coefficient of resistance (-8.42%/K) and very low noise levels around 6.6 x10-15 V2/Hz. This enables huge performance enhancements for a wide variety of systems, e.g., automotive and space applications.
Low temperature epitaxy (LTE) in Chemical Vapor Deposition (CVD) refers to 350-650 • C interval. ... more Low temperature epitaxy (LTE) in Chemical Vapor Deposition (CVD) refers to 350-650 • C interval. This temperature range is critical for this process since the thermal and lattice mismatch (or strain relaxation) issues diminish in advanced BiCMOS processing. The modeling of the epitaxy process is a vital task to increase the understanding the growth process and to design any desired device structure. In this study, an empirical model for Si 2 H 6 /Ge 2 H 6-based LTE of SiGe is developed and compared with experimental work. The model can predict the number of free sites on Si surface, growth rate of Si and SiGe, and the Ge content at low temperatures. A good agreement between the model and the experimental data is obtained.
SiGe has been widely used for source/drain (S/D) engineering in pMOSFETs to enhance channel mobil... more SiGe has been widely used for source/drain (S/D) engineering in pMOSFETs to enhance channel mobility. In this study, selective Si 1Àx Ge x growth (0.25 x 0.35) with boron concentration of 1-3 Â 10 20 cm À3 in the process for 22 nm node complementary metal-oxide semiconductor (CMOS) has been investigated and optimized. The growth parameters were carefully tuned to achieve deposition of high quality and highly strained material. The thermal budget was decreased to 800 C to suppress dopant diffusion, to minimize Si loss in S/D recesses, and to preserve the S/D recess shape. Two layers of Si 1Àx Ge x were deposited: a bottom layer with high Ge content (x ¼ 0.35) which filled the recess and a cap layer with low Ge content (x ¼ 0.25) which was elevated in the S/D regions. The elevated SiGe cap layer was intended to be consumed during the Ni-silicidation process in order to avoid strain reduction in the channel region arising from strain relaxation in SiGe S/D. In this study, a kinetic gas model was also applied to predict the pattern dependency of the growth and to determine the epi-profile in different transistor arrays. The input parameters include growth temperature, partial pressures of reactant gases, and chip layout. By using this model, the number of test wafers for epitaxy experiments can be decreased significantly. When the epitaxy process parameters can be readily predicted by the model for epi-profile control in an advanced chip design, fast and cost-effective process development can be achieved. V
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