Self-assembled Au dots in SiGe/Si layers for plasmonic application

Abstract

The concept of this study is based on self-assembled formation of voids in strained Si/SiGe heterostructures, and formation of nano-shells and nano-particles of gold through a gettering process. The gettering of vacuum deposited gold to the voids was studied using Rutherford backscattering and transmission electron microscopy. A very well defined layer of voids was formed in the strained SiGe layer at a depth of 0.5 µm as a result of helium implantation and thermal annealing. Due to strain enhanced vacancy accumulation, the voids nucleate and grow exclusively in the SiGe layer. The voids then getter large amount of Au which cover the inner walls of the voids at low temperature or precipitates into void-located nano-crystals at a temperature of 850 °C. Effects connected to structural transformations in the Si/SiGe layers during self-assembling of nano-voids and metallic dots, the optical properties of the layers, and the resulting effects of nanostructures on the spectral dependence of the photocurrent in the Si/SiGe structures are reported.