氢稀释制备的非晶碳膜的绿光和蓝光发射

在电容耦合式PECVD系统中，以CH4和H2为气源，通过控制H2的流量制备了一系列氢化非晶碳膜（a-C:H)样品。利用傅里叶变换红外光谱（FTIR）、光致发光谱（PL）和吸收谱对a-C:H膜的结构及光学性质进行了研究。结果表明：氢稀释可以在一定程度上减少碳的sp^2团簇的形成，增大它的光学带隙，并改变薄的微结构。与此同时，光致发光峰随郑 光学带隙的增大而蓝移；当光学带隙增大2．72eV时，出现了2．4eV（绿光）和2．97eV(蓝光）组成的发光峰。

Green and Blue Light Emitting from Hydrogenated Amorphous Carbon Films Diluted by Hydrogen

Hydrogenated amorphous carbon films have many unique properties, they have attracted much attention because of their applications in many kinds of optoelectronic devices such as light emitting diodes and field emission devices. It was well known that the film structures and properties were varied in a wide range by changing many factors such as hydrogen content and treatment. In this paper, the influence of hydrogen dilution on the optical properties of a-C: H films was studied. The a-C: H films were prepared in a capacitance coupled plasma enhanced vapor chemical deposition system at 13. 56MHz. The gas mixture of CH4 and H2 was used as source and the flow rate of the H2 was changed. The structures and optical properties were investigated by Fourier-transform infrared spectra, photoluminescence spectra and optical absorption spectra. It was concluded that hydrogen dilution can, to some extent, etch the weak bonds in films, decrease the size of sp2 clusters, and increase the sp3 C-Hn con- tent which results in the increase of the optical band gap of a-C: H films. The optical band gap increased from 2. 57eV to 2. 72eV with increasing hydrogen dilution ratio. Consequently, the PL peak energy has a blue shift from 2. 5eV to 2. 75eV under the excitation with 3.54eV light. The further increase of the hy- drogen dilution will induce the change of the bonding configurations in the carbon films, which results in the multiple PL bands in the luminescence spectra at room temperature. The a-C: H films include both sp3 C-C, C-H and sp2 carbon related clusters. The C=C bonds can exist in the form of olefinic chains, six- fold ring aromatic species et al. Under different hydrogen dilution conditions, the main C= C structure in the sp2 clusters was different, which induces the different structures and optical properties of a-C:H films.