Preparation of five-layered Si/Si _x Ge _1-x nano-films by RF helicon magnetron sputtering

Five-layered Si/Si _x Ge _1-x films on Si(1 0 0) substrate with single-layer thickness of 30 nm, 10 nm and 5 nm, respectively were prepared by RF helicon magnetron sputtering with dual targets of Si and Ge to investigate the feasibility of an industrial fabrication method on multi-stacked superlattice structure for thin-film thermoelectric applications. The fine periodic structure is confirmed in the samples except for the case of 5 nm in single-layer thickness. Fine crystalline Si _x Ge _1-x layer is obtained from 700 °C in substrate temperature, while higher than 700 °C is required for Si good layer. The composition ratio (x) in Si _x Ge _1-x is varied depending on the applied power to Si and Ge targets. Typical power ratio to obtain x = 0.83 was 7:3, Hall coefficient, p-type carrier concentration, sheet carrier concentration and mobility measured for the sample composed of five layers of Si (10 nm)/Si _0.82 Ge _0.18 (10 nm) are 2.55 × 10 ⁶ /°C, 2.56 × 10 ¹² cm ^-3 , 1.28 × 10 ⁷ cm ^-2 , and 15.8 cm ^-2 /(V s), respectively.