Development of Carbon Nitride (CN) Thin Film Preparation Process by Pulsed Laser Deposition

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The hardest materials known are diamond and cubic boron nitride. Recent calcurations suggested that the hypothetical, β-C_3N_4, may be as hard as diamond. This produced a surge of activity in the synthesis of carbon nitride (hereafter referred to as CN) thin films. Various CN films have been prepared by different deposition techniques including chemical vapor deposition, ion beam assisted deposition and reactive magnetron sputtering. The synthesis of pure β-C_3N_4 remains an open challenge.In this study, we develop a new pulsed laser deposition (PLD) method with a cross-magnetic field, ion-beam source and an DC bias to synthesize CN films. The laser beam was focused on the high purity (more than 99.999%) graphite targets. After 36000 laser pulses at a 10 Hz repetition rate, the deposition process was completed. All samples were analyzed by a field-emission scanning electron microscopy (FE-SEM), Auger electron spectroscopy (AES), atomic force microscope (AFM), an energy-dispersive X-ray analyzer (EDX), Fourier transform infrared spectroscopy (FT-IR) and micro-Raman spectrometer. An optical multichannel analyzer (OMA) with a 1034 photodiode array detected the optical emissions from the plasma plume generated by the pulsed Nd : YAG laser irradiation. The N/C composition ratio is affected by the substrate temperature and the substrate bias voltage. FT-IR measurement indicates the presence of a C≡N triple bond. FE-SEM observation shows that several spiral-structural particles exist in the droplets. We prepared CrC, WC, Sin, Tie, cBN, SiN, TaN films as a hard material and SnO_2, WO_3 films as a gas sensor material by PLD method. Our experiments show that the PLD process is simple and effective technique to fabricate ceramic thin films such as nitride, carbide and oxide films. It might be very important to study PLD process scientifically and industrially.