Relaxation oscillations due to plasma instabilities at frequencies ranging from a few Hz to tens of kHz have been observed in various types of plasma processing discharges. Relaxation oscillations have been observed i...Relaxation oscillations due to plasma instabilities at frequencies ranging from a few Hz to tens of kHz have been observed in various types of plasma processing discharges. Relaxation oscillations have been observed in electropositive capacitive discharges between a powered anode and a metallic chamber whose periphery is grounded through a slot with dielectric spacers. The oscillations of time-varying optical emission from the main discharge chamber show, for example, a high-frequency （- 40 kHz） relaxation oscillation at 13.33Pa, with an absorbed power being nearly the peripheral breakdown power, and a low-frequency （- 3 Hz） oscillation, with an even higher absorbed power. The high-frequency oscillation is found to ignite plasma in the slot, but usually not in the peripheral chamber. The kilohertz oscillations are modelled using an electromagnetic model of the slot impedance, coupled to a circuit analysis of the system including the matching network. The model results are in general agreement with the experimental observations, and indicate a variety of behaviours dependent on the matching conditions. In low-pressure inductive discharges, oscillations appear in the transition between low-density capacitively driven and high-density inductively driven discharges when attaching gases such as SF6 and Ar/SF6 mixtures are used. Oscillations of charged particles, plasma potential, and light, at frequencies ranging from a few Hz to tens of kHz, are seen for gas pressures between 0.133 Pa and 13.33 Pa and discharge powers in a range of 75 1200 W. The region of instability increases as the plasma becomes more electronegative, and the frequency of plasma oscillation increases as the power, pressure, and gas flow rate increase. A volume-averaged （global） model of the kilohertz instability has been developed; the results obtained from the model agree well with the experimental observations.展开更多
Low-frequency （2.72-3.70 Hz） relaxation oscillations at 100 mTorr at higher absorbed power were observed from time-varying optical emission of the main discharge chamber and the periphery. We interpret the low frequ...Low-frequency （2.72-3.70 Hz） relaxation oscillations at 100 mTorr at higher absorbed power were observed from time-varying optical emission of the main discharge chamber and the periphery. We interpret the low frequency oscillations using an electromagnetic model of the slot impedance with parallel connection variational peripheral capacitance, coupled to a circuit analysis of the system including the matching network. The model results are in general agreement with the experimental observations, and indicate a variety of behaviours dependent on the matching conditions.展开更多
Both high and low frequency relaxation oscillations have been observed in an argon capacitive discharge connected to a peripheral grounded chamber through a slot with dielectric spacers. The oscillations, observed fro...Both high and low frequency relaxation oscillations have been observed in an argon capacitive discharge connected to a peripheral grounded chamber through a slot with dielectric spacers. The oscillations, observed from time-varying optical emission of the main discharge chamber, show, for example, a high frequency （46 kHz） relaxation oscillation at 100 mTorr, with an absorbed power near the peripheral breakdown, and a low frequency （2.7-3.7 Hz） oscillation, at a higher absorbed power. The high frequency oscillation is found to ignite a plasma in the slot, but usually not in the periphery. The high frequency oscillation is interpreted by using an electromagnetic model of the slot impedance, combined with the circuit analysis of the system including a matching network. The model is further developed by using a parallel connection of variable peripheral capacitance to analyse the low frequency oscillation. The results obtained from the model are in agreement with the experimental observations and indicate that a variety of behaviours are dependent on the matching conditions.展开更多
We have observed relaxation oscillations in a capacitive discharge in Ar gas, connected to a peripheral ground chamber. The plasma oscillations observed from time-varying optical emission from the main discharge chamb...We have observed relaxation oscillations in a capacitive discharge in Ar gas, connected to a peripheral ground chamber. The plasma oscillations observed from time-varying optical emission from the main discharge chamber show, for example, a high frequency （75.37kHz） relaxation oscillation, at lOOmTorr and 8 W absorbed power, and a low frequency （2.72Hz） relaxation oscillation, lOO mTorr and 325 W absorbed power. Time-varying optical emission intensity and plasma density are also detected with a Langmuir probe. The theoretical result agrees well with experiments.展开更多
The structures and the phase transitions of ScH3 under high pressure are investigated using first-principles calcula- tions. The calculated structural parameters at zero pressure agree well with the available experime...The structures and the phase transitions of ScH3 under high pressure are investigated using first-principles calcula- tions. The calculated structural parameters at zero pressure agree well with the available experimental data. With increasing pressure, the transition sequence hcp （GdHa-type）→ C2/m →fcc→4hcp （YH3-type）→Cmcm of ScH3 is predicted first; the corresponding transition pressures at 0 K are 23 GPa, 25 GPa, 348 GPa, and 477 GPa, respectively. The C2/m symmetry structure is a possible candidate but not a good one as the intermediate state from hexagonal to cubic in ScH3. On the other hand, via the analysis of the structures of hexagonal SCH2.9, cubic ScH3, and cubic ScH2, we find that the repulsive interactions of H-H atoms must play an important role in the transition from hexagonal to cubic.展开更多
基金Project supported by the National Science Foundation of USA （Grant No ECS-0139956）.Acknowledgments The authors wish to thank Professor A. J. Lichtenberg for many useful discussions and suggestions. They acknowledge the support provided by the Lam Research Corporation, the State of California MI- CR0 Program, National Science Foundation （Grant No ECS-0139956）, and a University of California Discovery （Grant from the Industry-University Cooperative Research Program （IUCRP）. Professor Zhou Zhu-Wen performed this work as a visiting scholar in the Department of Electrical Engineering and Computer Sciences, University of California at Berkeley from May 2005 to May 2006.
文摘Relaxation oscillations due to plasma instabilities at frequencies ranging from a few Hz to tens of kHz have been observed in various types of plasma processing discharges. Relaxation oscillations have been observed in electropositive capacitive discharges between a powered anode and a metallic chamber whose periphery is grounded through a slot with dielectric spacers. The oscillations of time-varying optical emission from the main discharge chamber show, for example, a high-frequency （- 40 kHz） relaxation oscillation at 13.33Pa, with an absorbed power being nearly the peripheral breakdown power, and a low-frequency （- 3 Hz） oscillation, with an even higher absorbed power. The high-frequency oscillation is found to ignite plasma in the slot, but usually not in the peripheral chamber. The kilohertz oscillations are modelled using an electromagnetic model of the slot impedance, coupled to a circuit analysis of the system including the matching network. The model results are in general agreement with the experimental observations, and indicate a variety of behaviours dependent on the matching conditions. In low-pressure inductive discharges, oscillations appear in the transition between low-density capacitively driven and high-density inductively driven discharges when attaching gases such as SF6 and Ar/SF6 mixtures are used. Oscillations of charged particles, plasma potential, and light, at frequencies ranging from a few Hz to tens of kHz, are seen for gas pressures between 0.133 Pa and 13.33 Pa and discharge powers in a range of 75 1200 W. The region of instability increases as the plasma becomes more electronegative, and the frequency of plasma oscillation increases as the power, pressure, and gas flow rate increase. A volume-averaged （global） model of the kilohertz instability has been developed; the results obtained from the model agree well with the experimental observations.
基金Supported by the National Science Foundation of USA under Grant No ECS-0139956, and the Science Foundation of the Educational Administration of Guizhou Province under Grant No 2006215. We acknowledge the Lam Research Corporation, the State of California MICRO Program, and a UC Discovery Grant from the Industry-University Cooperative Research Program （IUCRP）.
文摘Low-frequency （2.72-3.70 Hz） relaxation oscillations at 100 mTorr at higher absorbed power were observed from time-varying optical emission of the main discharge chamber and the periphery. We interpret the low frequency oscillations using an electromagnetic model of the slot impedance with parallel connection variational peripheral capacitance, coupled to a circuit analysis of the system including the matching network. The model results are in general agreement with the experimental observations, and indicate a variety of behaviours dependent on the matching conditions.
基金Project supported by the Science Foundation of the Educational Bureau of Guizhou Province in China (Grant No ECS-2006215)the Lam Research Corporation+2 种基金the State of California MICRO ProgramNational Science Foundation (Grant No ECS-0139956)a UC Discovery Grant from the Industry-University Cooperative Research Program (IUCRP)
文摘Both high and low frequency relaxation oscillations have been observed in an argon capacitive discharge connected to a peripheral grounded chamber through a slot with dielectric spacers. The oscillations, observed from time-varying optical emission of the main discharge chamber, show, for example, a high frequency （46 kHz） relaxation oscillation at 100 mTorr, with an absorbed power near the peripheral breakdown, and a low frequency （2.7-3.7 Hz） oscillation, at a higher absorbed power. The high frequency oscillation is found to ignite a plasma in the slot, but usually not in the periphery. The high frequency oscillation is interpreted by using an electromagnetic model of the slot impedance, combined with the circuit analysis of the system including a matching network. The model is further developed by using a parallel connection of variable peripheral capacitance to analyse the low frequency oscillation. The results obtained from the model are in agreement with the experimental observations and indicate that a variety of behaviours are dependent on the matching conditions.
基金Supported by the National Science Foundation of USA under Grant No ECS-0139956, and a UC Discovery Grant from the Industry-University Cooperative Research Programme （IUCRP）.
文摘We have observed relaxation oscillations in a capacitive discharge in Ar gas, connected to a peripheral ground chamber. The plasma oscillations observed from time-varying optical emission from the main discharge chamber show, for example, a high frequency （75.37kHz） relaxation oscillation, at lOOmTorr and 8 W absorbed power, and a low frequency （2.72Hz） relaxation oscillation, lOO mTorr and 325 W absorbed power. Time-varying optical emission intensity and plasma density are also detected with a Langmuir probe. The theoretical result agrees well with experiments.
基金Project supported by the National Natural Science Foundation of China (Grant No. 11174214)the Specialized Research Fund for the Doctoral Program of Higher Education, China (Grant No. 20090181110080)+2 种基金the National Basic Research Program of China (Grant No. 2011CB808201)the Special Project for Research Conditions of High-level Talents of Guizhou Province, China (Grant No. TZJF-2008-42)the Science Foundation of Education Bureau of Guizhou Province, China (Grant No. 2010053)
文摘The structures and the phase transitions of ScH3 under high pressure are investigated using first-principles calcula- tions. The calculated structural parameters at zero pressure agree well with the available experimental data. With increasing pressure, the transition sequence hcp （GdHa-type）→ C2/m →fcc→4hcp （YH3-type）→Cmcm of ScH3 is predicted first; the corresponding transition pressures at 0 K are 23 GPa, 25 GPa, 348 GPa, and 477 GPa, respectively. The C2/m symmetry structure is a possible candidate but not a good one as the intermediate state from hexagonal to cubic in ScH3. On the other hand, via the analysis of the structures of hexagonal SCH2.9, cubic ScH3, and cubic ScH2, we find that the repulsive interactions of H-H atoms must play an important role in the transition from hexagonal to cubic.
