Nano Structural and Thermoelectric Properties of SiGeAu Thin Films

SiGeAu thin films exhibit large thermoelectric power. Recently, the formation of SiGe nano crystal has been confirmed after annealing. In this study, we investigated the relationship between the size of the nano crystal and thermoelectric power. SiGe nano crystals were fabricated by the crystallization of amorphous SiGeAu thin films. The grain size of SiGe was around 6 nm when Au composition was 2.2 at. %. The grain size decreased with increasing Au composition up to 2.2 at.% due to metal-induced crystallization, and increased depending on Au composition over 2.2 at.% due to liquid phase crystallization. When the grain size was around 6 nm, the thin films exhibited large thermoelectric power (4.8mVK(-1)) and power factor (2.4 x 10(-2) Wm(-1) K-2). Therefore, the grain size of SiGe around 6 nm is important for obtaining the large thermoelectric power and power factor. These results indicate that the quantum size effect enhances the thermoelectric power and power factor of SiGeAu thin films. (C) 2011 The Japan Society of Applied Physics