Plasma and Fusion Research

Volume 21, 1406014 (2026)

Regular Articles

Effect of the Substrate Position and Flow Rate Ratio on the Properties of a-C:H Films Deposited by Pseudo-Spark Discharge Plasma CVD Using Acetylene and Ar

Takaharu KAMADA¹⁾, Yuto TSUKIDATE²⁾, Masayuki WATANABE³⁾, Yoshitaka NAKAMURA¹⁾, Seiji MUKAIGAWA⁴⁾

1): Industrial Systems Engineering Department, National Institute of Technology (KOSEN), Hachinohe College, Aomori 039-1192, Japan
2): Industrial Systems Engineering Advanced Department, National Institute of Technology (KOSEN), Hachinohe College, Aomori 039-1192, Japan
3): Institute of Quantum Science, Nihon University, Tokyo 101-8308, Japan
4): Faculty of Science and Engineering, Iwate University, Iwate 020-8551, Japan

(Received 27 May 2025 / Accepted 10 December 2025 / Published 14 April 2026)

Abstract

Hydrogenated amorphous carbon (a-C:H) films were deposited on silicon wafers using a pseudo-spark discharge (PSD) method. A mixture of argon and acetylene (C₂H₂) was employed as the process gas. PSD generates high-density plasma and forms a diffuse discharge due to the hollow cathode effect. The film structure was analyzed using Raman spectroscopy, while film hardness was measured using nanoindentation. Surface hybridization states and contamination levels were examined by X-ray photoelectron spectroscopy. This study investigates the optimal distance between the anode and the deposition substrate, as well as the optimal flow rate ratio using acetylene diluted with argon. The results indicated that the optimal substrate distance was 40 mm and the ideal flow rate ratio (Ar/(Ar + C₂H₂)) was 1%. Under these conditions, the a-C:H films exhibited a G-band position of 1,571 cm⁻¹, a full width at half maximum of 114 cm⁻¹ for the G peak, a deposition rate of 155 nm/h, and a hardness of 5.3 GPa.

Keywords

Hydrogenated amorphous carbon (a-C:H) film, pseudo-spark discharge (PSD), Raman spectrum, film hardness

DOI: 10.1585/pfr.21.1406014

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