反应溅射TiN纳米晶薄膜的结构特征和耐蚀性

利用直流反应溅射技术在不锈钢和硅基体上沉积了TiN纳米晶薄膜,采用场发射扫描电镜(FESEM)、X射线衍射(XRD)和电化学阻抗谱(EIS)技术研究了薄膜的表面形貌、相结构和耐蚀性与偏压的关系。结果表明,TiN薄膜的表面结构明显取决于所施加的偏压,适当提高偏压有利于获得细小、均匀、致密和光滑的膜层。XRD分析发现,TiN薄膜为面心立方结构,其择优取向为(111)面。实验显示,对应0V和-35V偏压的薄膜为欠化学计量比的,而偏压增加至-70V和-105V时的薄膜为化学计量比的TiN。EIS结果表明,较高偏压下的TiN薄膜几乎在整个频率范围内均表现为容抗特征,其阻抗模值明显高于低偏压下的膜层,这主要与较高偏压下的薄膜具有相对致密的微结构有关。较低偏压的TiN薄膜因结构缺陷较多其耐蚀性低于基体不锈钢。EIS所揭示的薄膜结构特征与FESEM观测结果一致。可见,减少穿膜针孔等结构缺陷有利于改善反应溅射TiN纳米晶薄膜耐蚀性。

Microstructure and Corrosion Resistance of Reactively Sputtered Nanocrystalline TiN Thin Films

Nanocrystalline TiN thin films were deposited on stainless steel and silicone substrate under different negative bias voltages by direct current reactive sputtering. The microstructure and corrosion behavior were investigated by field emission scanning electron microscopy (FESEM), X-ray diffraction, and electrochemical impedance spectroscopy (EIS). The experimental results showed that the surface microstructure was dictated by the negative bias voltage, and proper high negative bias voltages were beneficial to produce a fine, dense, uniform and smooth film. The TiN film belonged to fcc structure and its preferential orientation was (111) plane independent of bias voltages applied. The films produced at -70 V and -105 V bias voltages were stoichiometric TiN while these produced at lower bias voltages were under stoichiometric. It was found that the EIS for the films produced at higher negative bias voltages exhibited distinctive capacitance loops almost in the whole range of frequency, and the absolute values of impe-dance increased with increasing bias voltages, resulting from the less defective and more compact film. The lower bia-sed films possessed lower corrosion resistance than that of stainless steel substrate. The structure feature revealed by EIS was in consistence with the FESEM observation results. The above results show that it is of great significance for corrosion protection to decrease the film pores or large structural defects in the sputtered TiN films.