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Search Results: 1 - 10 of 295559 matches for " V. G. Karpov "
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Coupled electron--heat transport in nonuniform thin film semiconductor structures
V. G. Karpov
Physics , 2012, DOI: 10.1103/PhysRevB.86.165317
Abstract: A theory of transverse electron transport coupled with heat transfer in semiconductor thin films is developed conceptually modeling structures of modern electronics. The transverse currents generate Joule heat with positive feedback through thermally activated conductivity. This can lead to instability known as thermal runaway, or hot spot, or reversible thermal breakdown. A theory here is based on the optimum fluctuation method modified to describe saddle stationary points determining the rate of such instabilities and conditions under which they evolve. Depending on the material and system parameters, the instabilities appear in a manner of phase transitions, similar to either nucleation or spinodal decomposition.
Electric field driven insulator-to-metal phase transitions
M. Nardone,V. G. Karpov
Physics , 2011,
Abstract: We show that strong enough electric fields can trigger nucleation of needle-shaped metallic embryos in insulators, even when the metal phase is energetically unfavorable without the field. This general phenomenon is due to the gigantic induced dipole moments acquired by the embryos which cause sufficient electrostatic energy gain. Nucleation kinetics are exponentially accelerated by the field-induced suppression of nucleation barriers. Our theory opens the venue of field driven material synthesis. In particular, we briefly discuss synthesis of metallic hydrogen at standard pressure.
Electric field induced nucleation: An alternative pathway to metallic hydrogen
M. Nardone,V. G. Karpov
Physics , 2011,
Abstract: Electric field induced nucleation is introduced as a possible mechanism to realize a metallic phase of hydrogen. Analytical expressions are derived for the nucleation probabilities of both thermal and quantum nucleation in terms of material parameters, temperature, and the applied field. Our results show that the insulator-metal transition can be driven by an electric field within a reasonable temperature range and at much lower pressures than the current paradigm of P > 400 GPa. Both static and oscillating fields are considered and practical implementations are discussed.
Thermodynamics of second phase conductive filaments
V. G. Karpov,M. Nardone,M. Simon
Physics , 2011, DOI: 10.1063/1.3592983
Abstract: We present a theory of second phase conductive filaments in phase transformable systems; applications include threshold switches, phase change memory, and shunting in thin film structures. We show that the average filament parameters can be described thermodynamically. In agreement with the published data, the predicted filament current voltage characteristics exhibit negative differential resistance vanishing at high currents where the current density becomes a bulk material property. Our description is extendible to filament transients and allows for efficient numerical simulation.
Hot spot runaway in thin film photovoltaics and related structures
V. G. Karpov,A. Vasko,A. Vijh
Physics , 2013, DOI: 10.1063/1.4818975
Abstract: We show that thin film diode structures, such as photovoltaics and light emitting arrays, can undergo zero threshold localized thermal runaway leading to thermal and electrical nonuniformities spontaneously emerging in originally uniform systems. The linear stability analysis is developed for a system of thermally and electrically coupled two discrete diodes, and for a distributed system. These results are verified with numerical modeling that is not limited to small fluctuations. The discovered instability negatively affects the device performance and reliability. It follows that these problems can be mitigated by properly designing the device geometry and thermal insulation.
Field induced nucleation in the presence of a metal electrode
V. G. Karpov,R. E. E. Maltby,I. V. Karpov,E. Yalon
Physics , 2015,
Abstract: We consider the effect of metal electrodes on the polarizability and nucleation of metal phases responsible for the operations of the emerging solid state memory. Our analysis is based on the image charge approach. We find results for point dipoles in static and oscillatory fields as well as an erect cylindrical nucleus near metal surfaces in resistive switching memories. We predict a large increase in polarizability and nucleation rate due to the metal electrode effects.
Plasmonic mediated nucleation of resonant nano-cavities in metallic layers
V. G. Karpov,M. Nardone,A. V. Subashiev
Physics , 2012, DOI: 10.1063/1.4737654
Abstract: We predict plasmonic mediated nucleation of pancake shaped resonant nano-cavities in metallic layers that are penetrable to laser fields. The underlying physics is that the cavity provides a narrow plasmonic resonance that maximizes its polarizability in an external field. The resonance yields a significant energy gain making the formation of such cavities highly favorable. Possible implications include nano-optics and generation of the dielectric bits in conductive films that underlie the existing optical recording phase change technology.
Evidence of rapid tin whisker growth under electron irradiation
A. C. Vasko,G. R. Warrell,E. Parsai,V. G. Karpov,Diana Shvydka
Physics , 2015,
Abstract: We have investigated the influence of electric field on tin whisker growth. Sputtered tin samples were exposed to electron radiation, and were subsequently found to have grown whiskers, while sister control samples did not exhibit whisker growth. Statistics on the whisker properties are reported. The results are considered encouraging for substantiating an electrostatic theory of whisker growth, and the technique offers promise for investigating early stages of whisker growth in general and establishing whisker-related accelerated life testing protocols.
Опыт лечения илеоцекальных инвагинаций у детей (RUS)
Nikolaev A.V.,Staroverova G.A.,Karpov S.A.
Saratov Journal of Medical Scientific Research , 2007,
Abstract: The authors present the result of analysis of treated 903 children with ileocecal intussusception and suggest medicaldiagnostic regimen. The priority method of treated ileocecal intussusception in children is pneumatically disinvagination during 10 hours after beginning anal bleeding.
Dissipative soliton protocols in semiconductor microcavities at finite temperatures
D. V. Karpov,I. G. Savenko,H. Flayac,N. N. Rosanov
Physics , 2014, DOI: 10.1103/PhysRevB.92.075305
Abstract: We consider exciton polaritons in a semiconductor microcavity with a saturable absorber in the growth direction of the heterostructure. This feature promotes additional nonlinear losses of the system with the emergence of bistability of the condensate particles number on the nonresonant (electrical or optical) excitation intensity. Further we demonstrate a new type of bright spatial dissipative exciton-polariton soliton which emerges in the equilibrium between the regions with different particle density. We develop protocols of soliton creation and destruction. The switch to a soliton-like behavior occurs if the cavity is exposed by a short strong laser pulse with certain energy and duration. We estimate the characteristic times of soliton switch on and off and the time of return to the initial cycle. In particular, we demonstrate surprising narrowing of the spatial profile of the soliton and its vanishing at certain temperature due to interaction of the system with the thermal bath of acoustic phonons. We also address the role of polariton-polariton interaction (Kerr-like nonlinearity) on formation of dissipative solitons and show that the soliton may exist both in its presence and absence.
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