Giri P K, Bhattacharyya S, Kesavamoorthy R, Panigrahi B K, Nair K G M
Department of Physics, Indian Institute of Technology, Guwahati 781039, India.
J Nanosci Nanotechnol. 2009 Sep;9(9):5389-95. doi: 10.1166/jnn.2009.1137.
We have made systematic studies on the ultraviolet-blue photoluminescence (PL) from Ge nanocrystals (NCs) grown embedded in SiO2 matrix. Embedded Ge NCs are grown by two different methods, namely, radio-frequency magnetron sputtering (SPT) and ion implantation (IMP). For comparison, Ar implanted SiO2 layer was processed similarly and studied to isolate the contribution of Ge atoms in the observed PL. X-ray diffraction, optical Raman and low frequency Raman scattering studies confirm the presence of Ge NCs in samples prepared by SPT and IMP methods, and Si nanoclusters in Ar implanted sample. Room temperature PL studies with 325 nm excitation show very strong UV-blue emission bands in the range 342-420 nm, and PL studies with 246 nm excitation show two strong UV emission bands at approximately 285 nm and approximately 393 nm in implanted samples. Deconvolution of UV-blue bands show that most of the emission peaks are not unique to the presence of Ge in the samples. Time resolved PL studies in the blue wavelength region show a fast decay dynamics (time constant of approximately 1.0 ns), irrespective of the NC size. PL excitation spectroscopy measurements show a large Stoke's shift for the UV emission bands. Our results indicate that contrary to the literature reports, the approximately 400 nm PL emission is band is not unique to the presence of Ge in the SiO2 matrix and it is likely to originate from a defective NC/SiO2 interface, irrespective of the species of NCs. Origin of various UV emission bands is discussed in the light of the experimental findings and literature reports.
我们对嵌入SiO₂基质中生长的锗纳米晶体（NCs）的紫外-蓝光光致发光（PL）进行了系统研究。嵌入的锗纳米晶体通过两种不同方法生长，即射频磁控溅射（SPT）和离子注入（IMP）。为作比较，对以类似方式处理的氩离子注入SiO₂层进行了研究，以分离出观察到的光致发光中锗原子的贡献。X射线衍射、光学拉曼和低频拉曼散射研究证实了通过SPT和IMP方法制备的样品中存在锗纳米晶体，以及氩离子注入样品中存在硅纳米团簇。用325nm激发进行的室温光致发光研究显示，在342 - 420nm范围内有非常强的紫外-蓝光发射带，而用246nm激发进行的光致发光研究显示，注入样品中在约285nm和约393nm处有两个强紫外发射带。对紫外-蓝光带的去卷积显示，大多数发射峰并非样品中锗的存在所特有的。在蓝光波长区域进行的时间分辨光致发光研究显示出快速衰减动力学（时间常数约为1.0ns），与纳米晶体尺寸无关。光致发光激发光谱测量显示紫外发射带存在大的斯托克斯位移。我们的结果表明，与文献报道相反，约400nm的光致发光发射带并非SiO₂基质中锗的存在所特有的，并且它可能源自有缺陷的纳米晶体/ SiO₂界面，与纳米晶体的种类无关。根据实验结果和文献报道讨论了各种紫外发射带的起源。
