Development of Pulsed Laser Deposition Method with Ions in the Plume Controlled by HV Pulses

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TiN thin films were prepared in the nitrogen gas environment and DLC films were prepared in vacuum by using the KrF Excimer pulsed laser deposition (PLD) method. During depositing the films, negative high voltage pulses, -0.5kV〜-6kV amplitude and 20μs duration and synchronized with the laser, were applied to the substrate holder to accelerate the ions in the plasma plume toward the substrate. The effects of the pulses on the deposited films were investigated by characterizing the film properties using EPMA, UV-visible absorbance spectrometer, FTIR, nanoindentator, AFM etc. TiN plasma plumes were diagnosed by the emission spectroscopy to investigate ionic species, and the number density profiles of C_2 and C_3 in the carbon plasma plumes were measured by the 2D-LIF method.In the case of TiN film deposition, application of pulses to the substrate holder increased the atomic ratio N/Ti of the films from 0.5 to 1.1 and decreased their resistivity from 30mΩ・cm to 7mΩ・cm. As for the DLC films, by applying -0.5kV pulses, optical band gap of the films increased from 1.0eV to 1.3eV and absorbance due to sp^3C also increased. The nanoindentation results showed the hardness of the DLC films prepared with -0.5kV pulses was tenfold larger than that prepared without pulses.The results of the optical measurement showed that emission from the ionic species increased and the species were energized by applying pulses. The 2D-LIF measurement showed the C_2 and C_3 in the carbon plasma plumes were localized near the target and exist until about 3μs after ablation. Their kinetic energy was small and the profiles of C_2 was affected by pulses applied to the substrate holder.It was found that applying negative pulses in the PLD method improved the chemical, optical and physical properties of the deposited films.