Preparation of Ge–C films by low-energy ion beam induced chemical vapor deposition with hexamethyldigermane

High carbon content Ge–C films were formed on (1 0 0) silicon by low-energy ion beam induced chemical vapor deposition (IBICVD) using Ar+ ion energies of 20–300 eV and gaseous hexamethyldigermane [HMDG: (CH3)3GeGe(CH3)3]. Chemical structures were characterized by Fourier transform infrared spectroscopy (FT–IR) and X-ray photoelectron spectroscopy (XPS), and IR-absorption peaks were assigned by ab initio molecular orbital calculations. While films with Ge–CH3 bonds were successfully deposited at ion beam energies of less than 200 eV, no film formation was observed at 200 eV or higher. The Ge:C atomic ratio was 0.25 as measured by XPS. In the case of a film deposited at a substrate temperature of 573 K, change in chemical structure with enhancement of hydrogen elimination was confirmed by FT–IR. Although most Ge atoms in the films bonded with C atoms, results suggest some carbon in the film constituted C–C bonds as in a graphitic phase.