Silicon overgrowth atop low-dimensional Mg2Si on Si(111): structure, optical and thermoelectrical properties

The growth of silicon cap layers atop Mg(2)Si nanocrystallites (NCs) and Mg(2)Si two-dimensional layer with structure (2/3 root 3x2/3 root 3)-R30 degrees were studied by methods of AES, EELS, AFM, optical and Raman spectroscopy. It was established that method of solid phase epitaxy (SPE) ensures the embedding of Mg(2)Si NCs in polycrystalline quality silicon cap layer at temperatures not higher than 920 K. The increase of the temperature higher than 970 K results to the moving of silicide NCs toward the surface between silicon grains in cap layer, following their destruction and Mg desorption from the surface. The MBE method with temperatures 430-485 K was used to the embedding of continuous 2D Mg(2)Si layer with structure (2/3 root 3x2/3 root 3)-R30 degrees in silicon top layer (9-20 nm) with monocrystalline grains. Investigations of thermoelectrical properties of grown nanoheterostructures have shown that a Seebeck coefficient (alpha similar to 130 mu V/K) increases in ten times as compared with undoped silicon substrate (alpha = 10 - 15 mu V/K). (C) 2010 Published by Elsevier B.V.