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

已知最硬的材料是金刚石和立方氮化硼。最近的计算表明，假设的β-C_3N_4可能和钻石一样硬。这使得氮化碳（以下简称CN）薄膜的合成活性激增。通过化学气相沉积、离子束辅助沉积和反应磁控溅射等不同的沉积技术制备了不同的CN膜。纯β-C_3N_4的合成仍然是一个开放的挑战。在这项研究中，我们开发了一种新的脉冲激光沉积（PLD）方法，该方法具有交叉磁场，离子束源和直流偏压来合成CN薄膜。激光束聚焦在高纯度（99.999%以上）石墨靶上。在重复频率为10 Hz的36000次激光脉冲后，完成沉积过程。采用场发射扫描电镜（FE-SEM）、俄歇电子能谱（AES）、原子力显微镜（AFM）、能量色散x射线分析仪（EDX）、傅里叶变换红外光谱（FT-IR）和微拉曼光谱仪对样品进行分析。采用1034光电二极管阵列的光学多通道分析仪（OMA）检测了脉冲Nd: YAG激光辐照产生的等离子体羽流的光发射。N/C组成比受衬底温度和衬底偏置电压的影响。FT-IR测量表明存在一个C≡N三键。FE-SEM观察表明，液滴中存在若干螺旋结构颗粒。采用PLD法制备了CrC、WC、Sin、Tie、cBN、Sin、TaN等硬质薄膜和SnO_2、WO_3气敏薄膜。实验表明，PLD工艺是制备氮化物、碳化物和氧化物等陶瓷薄膜的一种简单有效的技术。对可编程逻辑器件工艺的科学研究和工业应用具有重要意义。

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.