Influence of RF PACVD process parameters of diamond-like carbon films on optical properties and nano-hardness of the films

• Published in: Diamond and related materials 2008-07, Vol.17 (7), p.1655-1659
• Main Authors: Smietana, M., Szmidt, J., Korwin-Pawlowski, M.L., Miller, N., Elmustafa, A.A.
• Format: Article
• Language: English
• Subjects: Chemical vapor deposition (including plasma-enhanced cvd, mocvd, etc.); Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Diamond-like carbon; Exact sciences and technology; Fullerenes and related materials; diamonds, graphite; Materials science; Mechanical and acoustical properties; Mechanical properties; Methods of deposition of films and coatings; film growth and epitaxy; Optical properties; Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation; Optical properties of specific thin films; Physical properties of thin films, nonelectronic; Physics; Plasma CVD; Specific materials; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties)
• ISSN: 0925-9635; 1879-0062
• DOI: 10.1016/j.diamond.2008.01.111

This paper discusses the mechanical and optical properties of diamond-like carbon (DLC) films deposited onto p-type silicon substrates in order to use them in field of photonics. The influence of Radio Frequency Plasma Assisted Chemical Vapour Deposition (RF PACVD) process parameters, such as the negative self-bias voltage of RF powered electrode and source gas composition (methane and argon) on the index of refraction, extinction coefficient, thickness, and roughness determined by spectroscopic ellipsometry, and on nano-hardness and Young's modulus determined by MTS XP nanoindentation method is examined. It was shown that self-bias voltage, in its range ensuring the most diamond-like character of the film, has significant impact on both the mechanical and optical parameters of the film. In the infrared range, the refractive index is less dependent on self-bias voltage than in visible range. Taking into consideration the optical absorption, it's better to use argon as a gas accompanying hydrocarbon, which reduces the absorption, especially in the infrared range. On the other hand incorporation of argon gave slightly thinner and softer films and also increases roughness for high values of self-bias voltage. In general argon reduces the influence of self-bias voltage variations to film's properties. We also conclude that Young's modulus and hardness depend on the process condition, and generally decrease with increasing bias voltage in the investigated range.