Growth and characterization of polycrystalline Ge 1− xC x by reactive pulsed laser deposition

Abstract

Polycrystalline thin films of Ge–C were grown on Si (1 1 1) substrates by means of reactive pulsed laser deposition with methane pressure of 100 mTorr. Effect substrate temperature, T s, on C incorporation to substitutional sites ( x) in Ge 1− x C x was investigated systematically by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analyzes. The substrate temperatures were ranging from 250 to 400 °C. The substitutional C composition x in the films by XRD were estimated using the Vegard's linear law. The maximum value of x calculated by XRD was 0.032 for T s of 350 °C. The position of the C 1s peak at 283.4 eV in the XPS spectrum confirmed the germanium–carbon alloys. XRD measurements indicated that x increased with T s from 250 °C to 350 °C. At T s = 400 °C, the estimation of x was lowered. However, the C content calculated by XPS analyzes increased with T s being more these values than substitutional C composition x. XPS and XRD analyzes demonstrate that the remaining C atoms are incorporated to interstitial sites. The use of the T s plays important roles in the incorporation of substitutional C and in restraining C-cluster formation in the reactive pulsed laser deposition growth of Ge–C/Si.