Effect of substrate temperature and radio frequency power on compositional, structural and optical properties of amorphous germanium carbide films deposited using sputtering

• a-GexC1 − x films were grown at different substrate temperatures on Si (100) and Quartz substrates.
• X-ray photoelectron spectroscopy evidence the formation of GeC bond in the films.
• Maximum 21% of a-GexC1 − x is found using XPS peak fitting analysis for the film deposited with 250 °C ,50 W RF power.
• GeC mode is identified near 1497.2 cm− 1 in a-GexC1 − x film using Raman spectroscopy for the film deposited at 250 °C, 50 W.
• Optical band gap tuned from 2.7 eV to 1.0 eV.

Fabrication of GexC1 − x has been a big challenge because of the solubility of C in Ge. Only a small percentage of GeC bonds (11.6%) have been introduced so far. In this work, a-GexC1 − x with GeC content up to 21% has been fabricated with 50 W RF power at 250 °C by reactive sputtering methods. The effects of the radio frequency power and substrate temperature on the yield of GeC were analysed in detail. The GeC percentage by volume was found to first increase and then decrease with increasing substrate temperature. Introduction of C into the Ge matrix seems to tune the optical bandgap over a range of 2.7 eV to 1.0 eV depending on the combination of substrate temperature and radio frequency power.