纳米晶硅多层薄膜的低温调控及其发光特性

采用单-双靶交替溅射法低温沉积了纳米晶硅多层薄膜（nc-SiO_x/a-SiO_x），通过改变a-SiO_x势垒层的厚度和化学成分比例，实现了纳米晶硅多层薄膜的低温过程控制。透射电子显微镜（TEM）结果显示，a-SiO_x层太薄，不能有效阻断纳米硅生长，导致多层周期结构在后期沉积过程中受到破坏；增加a-SiO_x层厚度，周期性结构生长得以实现，但仍有部分纳米硅穿透a-SiO_x势垒层；傅里叶变换红外光谱（FTIR）分析表明，薄膜中的氧化反应以及活性氢对物相分离过程的促进作用均对纳米硅生长有影响。进而增加a-SiO_x层氧含量，纳米硅的纵向生长被成功阻断。在此基础上，通过调整nc-SiO_x层厚度实现了薄膜光学带隙调整和纳米硅粒度控制。光吸收谱分析显示，随nc-SiO_x层厚度的增加，薄膜光学带隙逐渐减小；光致发光谱表明，多层周期结构实现了纳米硅尺寸的调控，粒子尺寸为几个纳米的纳米硅表现出了较强的发光，发光机制为量子限制效应-缺陷态复合发光。

Low temperature preparation and luminescence properties of nanocrystalline silicon multilayer films

The nanocrystalline silicon multilayers(nc-SiO_x/a-SiO_x) were deposited at low temperature by single-double target alternating sputtering technology. The thickness and the chemical composition of the a-SiO_x barrier layers were regulated to control the multilayers' microstructure. Transmission electron microscopy(TEM) analysis showed that the periodic structure was disrupted during the later deposition process because the a-SiO_x layer was too thin to effectively block the growth of nc-Si. The multilayer structure was successfully prepared by increasing the thickness of the a-SiO_x layer,however,there were still a part of nc-Si particles penetrating the barrier layer. Fourier transform infrared(FTIR) spectra showed that the oxidation reaction in the film and the active hydrogen atom effected on the growth of nc-Si. Therefore,the oxygen content of the a-SiO_x layer was increased which further blocked the growth of the nc-Si. Then,the film optical bandgap was adjusted and nc-Si particles size was controlled by regulating the thickness of nc-SiO_x layer. The absorption spectra showed that the optical bandgap of the film decreased with the increase of the nc-SiO_x layer thickness. The photoluminescence(PL) spectra showed that the multilayer structure was regulated by controlling nc-SiO_x layer thickness,and the resultant nc-Si with several nanometer produced a strong luminescence,which was attributed to a complex quantum confinement effect and the defect state luminescence mechanism.