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Coherently strained GeSi/Si(001) islands were overgrown with a Si capping layer of different thicknesses at temperature 300 °C. The structures of the islands and the Si capping layer were investigated by high resolution transmission electron microscopy. The shapes of the embedded islands were well preserved, whereas planar defects were observed exactly over the islands in the capping layers. The strain energy in regions over the islands accumulated with increasing thickness of the Si capping layer, resulting in the formation of the planar defects. By means of a two-step deposition in which 20-nm-thick Si capping layer was first deposited at a low temperature of 300 °C followed by 70-nm-thick Si capping layer deposition at a high temperature of 640 °C, the defect-free Si capping layer with flat surface can be obtained. [ABSTRACT FROM AUTHOR]

SnO2 nanowires were prepared in an Au-catalyzed VLS growth process by thermal evaporation. The NO sensing properties of the resistive gas sensor based on the SnO2 nanowires was found to be improved obviously after the SnO2 nanowires were treated by Ar-O2 plasma. The responses of the gas sensors to 10, 20, 30, 40, 50 ppm NO gas increased from 8.4, 10.6, 12.6, 14.2, 16.1% to 44.2, 91.9, 108.0, 118.1, 157.4% at 100 °C, respectively. The selectivity of the gas sensors to NO gas against NO2, NH3, CH4, H2 and O2 was also enhanced greatly. The characterization by X-ray diffraction, transmission electron microscopy and X-ray photoelectron spectroscopy revealed that the enhanced gas sensing properties can be attributed to the rough surfaces, the resultant dangling bond and free lattice sites, and the Sn3O4 grains appearing on the surface of the Ar-O2 plasma treated SnO2 nanowires. [ABSTRACT FROM AUTHOR]

The transport behavior of Au-Si droplets near the Si(001) surface at elevated temperatures is investigated using transmission electron microscopy. It has been found that Au-Si droplets move differently under different temperatures, which lead to the formation of SiOx surface islands on top of droplets, and result in the lateral movements of smaller droplets away from their corresponding surface islands. Since Au droplets have been widely used as catalysts to induce semiconductor nanowires, this study provides insight behavior of Au containing droplets on semiconductor surfaces, which is critical for understanding the formation mechanisms of semiconductor nanowires. [ABSTRACT FROM AUTHOR]

The misfit dislocations in [001] Ge(Si)/Si islands grown at 700°C were investigated using transmission electron microscopy. 30° partial misfit dislocations are found both in the island/ substrate interface and near the island surface. Since the 30° partial leads the movement of the 60° dissociated misfit dislocation in a (001) compressively strained system such as (001) GeSi/Si, a generation mechanism of misfit dislocations through partial misfit dislocations half loops is proposed. [ABSTRACT FROM AUTHOR]

Ge(Si)/Si(001) coherent islands grown at 700 °C by molecular beam epitaxy were investigated using transmission electron microscopy. [001] on-zone bright-field diffraction contrast imaging and image simulation techniques were used to investigate the structure of these coherent islands. Comparison of simulated and experimental images indicates nonuniform composition distribution within the coherent islands when the islands were grown at high temperatures (700 °C), but uniform composition for growth at lower temperatures (600 °C). © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]