调控CN_x薄膜的紫外可见波段光学性能研究

Synthesis and Optical Properties in UV-Visible Range of Carbon Nitride Thin Films

采用等离子体增强化学气相沉积(PECVD)在不同衬底温度(常温、50、100、150、200℃)下制备了碳氮(CNx)薄膜,并对其形貌、结构及光学性能进行了研究。通过扫描电镜得出随着衬底温度的升高,薄膜由疏松逐渐变得致密。X射线光电子能谱分析表明:薄膜的结合健有sp^2C=C、sp^3C-C、sp^2C=N和sp^3C-N。随着衬底温度的升高,sp^2C=C的比例没有明显变化,sp3C-C比例逐渐增大(28.6%~36.4%),sp^3C-N的比例也逐渐增大(21.4%~33.4%),而sp^2C=N的比例减小(40.2%~21%)。反射光谱和吸收光谱显示:随着衬底温度的升高,薄膜在200~800 nm波段内的反射率增大(8%~40%),吸收率减小(92%~60%)。进一步推导得到薄膜的光学带隙随着衬底温度的升高而增大(2.5~3.57 e V),主要由薄膜中sp^2C=N减少导致的。本文实现了对CN_x薄膜在紫外可见波段范围内的光学带隙的调控。

The carbon nitride （CNx） coatings were synthesized by plasma enhanced chemical vapor deposition （PECVD）. The influence of the substrate temperature （50 -200℃ ） on the mierostructures, electronic structures and optical properties of the CNx coatings was investigated with scanning electron microscopy, energy dispersive spectroscopy and X-ray photoelectron spectroscopy. The results show that the substrate temperature had a major impact. For example,as the substrate temperature increased, while sp2C = C bond little changed and spEC = N bond gradually decreased, the sp3 C-C and sp3 C-N bonds increased （28.6% - 36. 4% and 21.4% ～ 33.4% , respectively） ,and the coating became increasingly compact; the reflectivity increased （8%～ 40% ）, accompanied by a decreasing absorbance （92%～ 60% ） in 200 ～800 nm range;and the optical gap increased （2.5 ～ 3.57 eV）, simply because of a decrease of sp2C = N bond. We suggest that controlling of the substrate temperature may adjust the optical band-gap of CNx coatings in UV-visible range.