Epitaxial CuInS2 on Si(111) using di-tert-butyl disulfide as sulphur precursor

In a new approach, we introduce a combination of chemical (CBE) and molecular beam epitaxy (MBE) of CuInS2 (CIS) on hydrogen-terminated Si(111) using di-tert-butyl disulfide (TBDS) as sulphur precursor. The films are analysed in situ with photoelectron spectroscopy and low-energy electron diffraction (LEED). Ex situ, the samples are investigated with X-ray diffraction (XRD) and scanning electron microscopy (SEM). We find that, at growth temperatures of 300 °C, no carbon is incorporated into the deposited film. Furthermore, on the In-rich side of the CuInS2 preparation, we additionally observe Cu2In. However, the valence band structure remains that of a typical CuInS2 film. During the growth in the Cu-rich regime, segregation of Cu2S occurs which can be identified by the shifting of the valence band edge towards the Fermi level. Epitaxial growth of CuInS2 is assumed for both regimes. LEED patterns and XRD data support the epitaxial relation Si{111}∣∣CuInS2{112}.