N掺杂对非晶C薄膜的电子结构与光学性质的影响

用直流磁控溅射法制备了非晶C薄膜及N掺杂非晶C(a-C∶N)薄膜，用紫外-可见分光光谱仪、椭圆偏振仪、俄歇电子能谱(AES)等对薄膜进行了检测。结果表明：随源气体中N气含量的增加，透过率和折射率变小, 而光学带隙先增大后减小; 当薄膜中N的含量很少，N的掺入对sp3杂化C起稳定作用，使得薄膜光学带隙E_g增大。而较高量N的掺入抑制了sp3杂化C的形成，提高了薄膜中sp2键含量，使得薄膜光学带隙变小。参数D定义为俄歇电子能谱(AES)中最大正峰和最低负峰之间的距离，用俄歇电子能谱中的D值来计算薄膜的sp2键的百分含量，俄歇电子能谱(AES)表征也表明：较高量的N的掺入抑制了sp3杂化C的形成。所以应该考虑在较低N分压条件下掺N来改善非晶C薄膜的光学性能。

Influence of Nitrogen Doping on Electron Structure and Optical Properties of Amorphous Carbon Thin Films

Nitrogen doped amorphous carbon (a-C : N) thin films were prepared by DC magnetron sputtering. The films were investigated by AES, UV-Vis and ellipsometer. A parameter 'D' defined as the distance between the maximum of positive going excursion and the minimum of negative going excursion was calculated in the derivative AES spectra. The values of 'D' were used to calculate the percentage of sp2 hybrid bonds. The optical transmission and the optical band gap of the films were characterized by an UV-Vis spectrophotometer. The results showed that the optical band gap decreased and then increased with the increase of N2 gas source. The transmission and refractive index changed in reverse order. It was demonstrated that the thin film with low percentage of nitrogen was beneficial to the formation of sp3 hybrid bonds and caused the optical band gap of the thin film to increase. As a result, the thin film should be prepared under low percentage of nitrogen pressure to ensure that it possesses fine optical properties.