Characterization studies of diamond-like carbon films grown using a saddle-field fast-atom-beam source

• Published in: Journal of vacuum science & technology. A, Vacuum, surfaces, and films Vacuum, surfaces, and films, 2000-09, Vol.18 (5), p.2302-2311
• Main Authors: Sarangi, D., Panwar, O. S., Kumar, S., Bhattacharyya, R.
• Format: Article
• Language: English
• Subjects: Atomic beams; Auger electron spectroscopy; Composition effects; Ellipsometry; Fourier transform infrared spectroscopy; Scanning electron microscopy; X ray photoelectron spectroscopy
• ISSN: 0734-2101; 1520-8559
• DOI: 10.1116/1.1289699

In this article, we report results of an extensive characterization study involving scanning electron microscopy, spectroscopic ellipsometry (SE), photothermal deflection spectroscopy (PDS), x-ray photoelectron spectroscopy, x-ray Auger electron spectroscopy (XAES), current–voltage (I–V) measurements, hydrogen content evaluated from Fourier transform infrared spectroscopy and elastic recoil detection analysis, and also measurement of stress and hardness of diamond-like carbon (DLC) films. These films were grown using methane ( CH 4 ), acetylene ( C 2 H 2 ) gases, and benzene ( C 6 H 6 ) vapors into a saddle-field fast-atom-beam (FAB) source. DLC films formed by the saddle-field FAB source technique exhibit extremely low residual stress (0.12–0.26 GPa) and high Knoop hardness (9–22 GPa) measured at 50 g load. The values of optical constants (n, k, ε 1 , ε 2 ) evaluated from SE, characteristic energy of band tail (Urbach energy, E 0 ) evaluated from PDS studies, sp 2 percentage evaluated from XAES data, the density of states [N(E F )] derived from space-charge-limited conduction, and the hydrogen content are found to decrease, and the sp 3 /sp 2 ratio evaluated are found to increase with the increase of carbon-to-hydrogen ratio in the hydrocarbon gases/vapors used for growing DLC films by this technique. The values of E 0 , N(E F ), hydrogen content, and sp 3 /sp 2 ratio of these DLC films are found to be in the range of 180–280 meV, 1–6×10 17   eV −1  cm −3 , 3–8 at. % and 5.2–12.3, respectively, which are lower than the values of E 0 (300–500 meV), N(E F ) (∼10 18   eV −1  cm −3 ), and hydrogen content (15–40 at. %) and higher than sp 3 /sp 2 ratio (1.3–2.5) of DLC films grown by the more conventional rf self-bias technique reported in the literature.