a-SiC_x:H/nc-Si:H多层薄膜的室温时间分辨光致可见发光

Time Resolution Photoluminescence of a-SiC_x∶H/nc-Si∶H Multi-layers at Room Temperature

在等离子体增强化学气相沉积(PECVD)系统中,通过控制进入反应室的气体种类逐层沉积非晶SiCx∶H(a SiCx∶H)和非晶Si∶H(a Si∶H)薄膜,然后经过高温热退火处理,成功制备了晶化纳米a SiCx∶H/nc Si∶H(多晶SiC和纳米Si)多层薄膜。利用截面透射电子显微镜技术分析了a SiCx∶H/nc Si∶H多层薄膜的结构特性。通过对晶化样品的时间分辨光致发光谱的研究,结果表明:随着退火温度的升高,发光峰位置开始出现一些红移现象;当退火温度为900℃时,样品的发光强度和发光衰减时间分别达到最大值和最小值;随着退火温度的继续升高,发光峰位置又开始出现蓝移现象。由此探讨纳米a SiCx∶H/nc Si∶H多层薄膜的发光特性和发光机理。

The intense visible photoluminescence (PL) of porous Si has attracted much interest as it opens up the possibility of fabricating light-emitting devices based on silicon technology. The effect was attributed to a quantum confinement of carriers in structures only a few nm in size, resulting in an effective increase of the apparent band-gap with respect to bulk Si. Recent years, it had been widely reported about Si and Ge nano particles embedded in SiO_2 and Si_3N_4 films, some interesting phenomenon were also reported. Since the successful synthesis of amorphous semiconductor multiple films used plasma enhanced chemical vapour deposition (PECVD) by Exxon Corporation, the technology which need little complex epitaxy has attracted much attention, as we all known, the multiple films has a strong quantum effect, and also some interface effect would be magnified compared to the single layer films, it brings some novel phenomenon. The low temperature or room temperature photoluminescence had been widely reported, and they mostly concerned about the quantum effect and interface structure, but the photoluminescence dynamics of the multiple semiconductor films had not been reported. In this paper, we have performed multiple a-SiC_x∶H/a-Si∶H films successfully by PECVD. Microstructure and time-resolved PL spectra of the samples were studied. The results showed that a significant photoluminescence peak at about 650 nm was observed, and the peak position varies with annealing temperature. A maximum intensity of PL peak and a minimum decay time (t_1) were obtained for the sample annealed at 900 ℃. The origin of luminescence was suggested and discussed.