Ge dots formation using Si(100)-c(4×4) surface reconstruction

Abstract

An effect of Si(100)-c(4×4) surface reconstruction by using sub-monolayer carbon reaction was investigated to form Ge dots on a Si (100) substrate. Samples were prepared by a solid-source molecular beam epitaxy system with an electron beam gun for carbon (C) sublimation and a Knudsen cell for Ge evaporation. C of 0.1 to 0.5ML was deposited on Si (100) at the substrate temperature of 200˚C, followed by a high-temperature treatment at 1000˚C to react C with Si. Ge equivalent to 3nm thick was subsequently deposited at 450˚C. The densest dots were obtained for C coverage of 0.25ML because the Si surface was stabilized by C for c(4×4) reconstruction without leaving excessive C. To investigate effects of Ge deposition thickness and temperature on Ge dot morphology, Ge equivalent to 3 to 5nm thick was deposited at 400 and 450˚C in the case of 0.25-ML C. The most uniform and densest Ge dots were formed at the Ge deposition thickness and temperature of 4nm and 400˚C, respectively. These results indicate that the Ge deposition should be optimized along the condition of the surface reconstruction via the C–Si reaction.