Fabrication of Free-Standing Single-Crystal Silicon Nanostructures for the Study of Thermal Transport and Defect Scattering in Low Dimensional Systems

Free-standing wire samples have been fabricated that enable low dimensional conducting wires to be examined by transmission electron microscopy (TEM). These structures have been fabricated using a combination of gas-assisted ion beam etching and electron beam lithography, and have cross-sectional dimensions between 70 nm and 1 µm, and lengths of up to 50 µm. The free-standing wires have been examined by TEM before and after ion implantation and annealing. The results indicate that no extended defects are created in the wires, even for high doses (1016cm-3) or high beam energies (>50 keV). The reason for this is not fully understood. In addition, the fabrication process has been extended so that low temperature electrical measurements can be performed on the TEM samples. In this way it is hoped eventually to study the role of specific crystalline defects in limiting the electronic and phonon transport.