Study on the growth mechanism and optical properties of sputtered lead selenide thin films

Abstract

Lead selenide thin films with different microstructure were deposited on Si (100) substrates using magnetron sputtering at 50°C, 150°C and 250°C, respectively. The crystal structure of the sputtered PbSe thin films varies from amorphous crystalline to columnar grain, and then to double-layer (nano-crystalline layer and columnar grain layer) structure as the deposition temperature increases, which is due to the dominating growth mode of the thin films changes from Frank–van der Merwe (or layer-by-layer) growth mode at 50°C to Volmer–Weber (or 3D island) growth mode at 150°C, and then to Stranski–Krastanow (or 3D island-on-wetting-layer) growth mode at 250°C. The growth mechanism of the sputtered PbSe thin films is mainly dominated by the surface and strain energy contributions. Moreover, the strain energy contribution is more prominent when the deposition temperature is less than 180°C, while, the surface energy contribution is more prominent when the deposition temperature is higher than 180°C. The absorption spectra of the sputtered PbSe thin films are in 3.1–5μm range. Besides, the sputtered PbSe thin film prepared at 250°C has two different optical band gaps due to its unique double-layer structure. According to the theoretical calculation results, the variation of the band gap with the deposition temperature is determined by the shift of the valence band maximum with the lattice constant.