Investigation of Thermal Effects in Small Structures

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9501108 Wybourne The phase memory of electrons is maintained in samples with dimensions less than the electron-electron and electron-phonon interaction lengths. In this situation there is no dissipation in the sample, and parts of the sdample outside the classical current path influence transport phenomena associated with the electron's phase. In the proposed research, a related transport regime in which the sample dimensions are greater than the electron-electron interaction length, but less than the electron-phonon relaxation length, will be studied. In this case phase memory is lost, yet dissipation within the sample remains unlikely. To study the relationship between dissipation and sample geometry, electron transport measurements will be made on metal microstructures of different shapes under conditions far from equilibrium. Fluctuations in the electron energy loss are anticipated when the electron-phonon relaxation length approaches the sample dimensions. Dissipation in the sample is expected to be dependent on the acoustic mode confinement in the structure, especially when the confined acoustic mode energy spacing is greater than the internal energy of the electron gas. %%% Many experiments have been reported on phase coherence and ballistic electron transport for which energy dissipation occurs mainly in the circuit contacts. Little experimental work has been directed towards the onset of dissipation in microstructures (as in computer chips) that occurs when the characteristic length associated with energy loss becomes comparable to the sample dimensions. In the proposed research, electron transport measurements will be made under conditions far from equilibrium in order to study the relationship between energy dissipation and the geometry of a microstructure. The connection between dissipation and the acoustic properties of the microstructures will also be inve stigated. ***