纳米硅氧多层薄膜低温调控及其发光特性

为了研究硅量子点薄膜在太阳电池中的应用,本文采用甚高频等离子体增强化学气相沉积技术,低温制备了镶嵌有纳米晶硅(nc-Si)的纳米硅氧多层(nc-SiOx/a-SiOx)薄膜样品。TEM图显示,通过调整nc-SiOx层的厚度,实现了薄膜多层结构的低温调控。利用拉曼散射光谱(Raman)、紫外可见透射光谱以及稳/瞬态光致发光(PL)谱等检测手段对薄膜的微观结构、能带特征以及发光特性进行了分析。光吸收谱分析表明,nc-Si粒子尺寸及其a-SiOx边界层共同影响薄膜的光学带隙。稳/瞬态PL谱分析表明,多层结构发光表现为一个固定于1.19eV附近的发光峰和一个随nc-SiOx层厚度增加而发生红移的发光峰,其中固定发光峰归因于非晶SiOx网络中缺陷发光,发光衰减寿命约在4.6μs,峰位可调的发光峰为nc-Si量子限制效应-缺陷态复合发光,对应两个发光衰减过程,其中慢发光衰减寿命随nc-SiOx层厚度增加由9.9μs增加到16.5μs,快发光衰减过程基本保持不变。低温PL谱的温度依赖特性进一步表明,薄膜样品的发光主要表现为nc-Si的量子限制效应发光。

Low temperature deposition and photoluminescence properties of silicon oxide multilayer films

Nc-SiOx/a-SiOx multilayer films were deposited using very-high-frequency plasma enhanced chemical vapor deposition (VHF-PECVD), to investigate the application of silicon quantum dots in solar cells. Transmission electron microscopy (TEM) images revealed that a multilayer structure was achieved by adjusting the thickness of the nc-SiOx layer at low temperature. Based on Raman scattering, UV-visible transmission, and steady/transient photoluminescence (PL) spectra, the microstructure, energy band, and photoluminescence properties of the films were characterized, respectively. Absorption spectra analysis indicated that the combination of the nc-Si and a-SiOx matrices affected the optical band gap of the films. The PL spectra of the multilayer films exhibited two distinct peaks as the thickness of the nc-SiOx layer was increased:a peak fixed at 1.19 eV, and another red-shifted peak near 1.45 eV. The fixed PL peak originated from radiative defects in the a-SiOx matrix, which corresponds to a PL decay life of approximately 4.6 μs. The red-shifted PL peak was attributed to a complex quantum confinement effect-defect state luminescence mechanism. This is related to two PL decay processes including a slow PL decay life, which increased from 9.9 to 16.5 μs, and a fast decay life, which was constant. The temperature-dependent PL properties further signified that the origin of the PL of the multilayer films was mainly attributed to quantum confinement effects in nc-Si.