Chemical vapour deposition of hard a-C:H films from CH2I2

Abstract

Abstract Hydrogen containing amorphous carbon (a-C:H) films were deposited on Si(100) substrates by thermal decomposition of CH2I2. The coatings were hard, smooth, adherent and had a density of 1.8 g cm−3. The temperature dependence of the deposition process was studied between 750–1400 K at a partial pressure of 360 mTorr, where the apparent activation energy was determined to be 44 kJ mol−1. The partial pressure dependence of the process, which was studied between 36–390 mTorr at a temperature of 945 K, followed first order reaction kinetics. Transmission electron microscopy and Raman spectroscopy indicated that the a-C:H consisted of small (∼ 7 A) graphite like clusters embedded in an amorphous matrix. The morphology was investigated by atomic force microscopy. The deposited material was smooth and no grain boundaries were observed. The iodine content in the films was studied by Rutherford backscattering spectroscopy, energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy. The hydrogen content was determined by nuclear reaction analysis. The a-C:H films were free from iodine and the hydrogen content was 4–15 at% depending on the deposition temperature.