Silicon quantum dots thin films and superlattice in SiC matrix by co-sputtering of silicon and carbon

Silicon quantum dots (QDs) thin films and superlattice embedded in SiC matrix are prepared by co-sputtering of pure Si and C targets for all silicon tandem solar cell application. The composition of as-deposited Si_1-xC_x precursor films can be controlled by changing rf power of Si and C targets, respectively. The composition x from 0 to 0.43 is investigated by changing C power from 0 to 400W under the fixed Si power of 200W. In Raman spectrum, Si crystalline volume fraction decreases with increasing the composition and there is no phase transition from x ~ 0.38. The Si QDs with 5 - 10 nm size are clearly observed through high resolution transmission electron microscopy. From the in-situ annealing and XRD analysis, Si signal precipitates to single crystalline phase above 900°. Si-rich SiC/stoichiometric SiC superlattice shows vague interfaces owing to re-arrangement and inter-diffusion after annealing. The absorption coefficient a of the sample shifts a high energy level and appears at 1.2~1.4eV conjectured to exist Si quantum dots after annealing.