Optical emission study of the laser plasma plume produced during diamondlike carbon thin film preparation

We have studied the application of the diamondlike carbon (DLC) film as a protective coating layer for high temperature superconducting thin films. Recently, the DLC film was proposed as an attractive material for field electron emitter device. We report on spectroscopic properties of the KrF laser plasma plume produced during the DLC thin film deposition. Optical emission measurements showed appearance of such neutral and ionic species as H, C, C⁺, CH, CH⁺, C₂H⁺. Strong emission from neutral and ionic molecules CH, C₂, C₂H⁺ produced by the reaction in the gaseous phase has been observed with the ambient hydrogen gas pressure increase. The calculated velocities of CH and C₂H⁺ molecules at the distances of 10-20 mm from the target are found to be 5.0 × 10³ m/s and 9.1 × 10³ m/s, correspondingly. The properties of the DLC thin films are strongly affected by the laser plasma plume dynamics. The DLC film deposited on MgO (100) at room temperature and 200 mTorr hydrogen pressure was almost transparent in the visible light range and had an optical band energy gap of 2.0 eV, which is about half of that of a diamond.