Finite size effect on the Raman frequency of phonons in nano-semiconductors

A comprehensive study on Raman spectroscopy with different excitation wavelengths, sample sizes, and sample shapes for optic phonons (OPs) and acoustic phonons (APs) in polar and non-polar nano-semiconductors has been performed. The study affirms that the finite size effect does not appear in the OPs of polar nano-semiconductors, while it exists in all other types of phonons. The absence of the FSE is confirmed to originate from the long-range Fr¨ohlich interaction and the breaking of translation symmetry. The result indicates that the Raman spectra of OPs cannot be used as a method to characterize the scale and crystalline property of polar nano-semiconductors.     

CdSe和ZnO量子点的拉曼光谱研究

本文介绍了用拉曼光谱研究CdSe和ZnO两种Ⅱ Ⅳ族量子点材料的结果,对拉曼峰进行了指认。观察到的光学声子峰位的移动被认为是由量子限制效应引起。     

水热产物γ-AlOOH在高温煅烧过程中的α相变及形貌演变

采用透射电镜(TEM)和X-射线衍射(XRD)对化学沉淀法制备的氢氧化铝凝胶及水热处理后的产物进行了在高温煅烧过程中的α相变及形貌演变的对比研究.结果表明,氢氧化铝新鲜胶体经水热处理后提高了高温煅烧时α相变的开始温度,但完成α相变的速度没有明显变化.在1150℃下煅烧1h,由水热合成的长条六角板状晶粒转变的氧化铝过渡相开始转化形成α相,形貌基本不变;在1200℃下煅烧1h,基本上完成α-Al2O3的转化,粉体为多孔的多边形片状颗粒,粒度0.6μm左右,内孔1嘶m左右;在1250℃下煅烧1h,粉体完全转化为α--Al2O3,形貌变化不大,但有轻微的烧结.