First-principles calculation of the electronic band of ZnO doped with C

Using the first-principles approach based upon the density functional theory (DFT), we have studied the electronic structure of wurtzite ZnO systems doped with C at different sites. When Zn is substituted by C, the system turns from a direct band gap semiconductor into an indirect band gap semiconductor, and donor levels are formed. When O is substituted by C, acceptor levels are formed near the top of the valence band, and thus a p-type transformation of the system is achieved. When the two kinds of substitution coexist, the acceptor levels are compensated for all cases, which is unfavorable for the p-type transformation of the system.     

纤锌矿GaN/AlxGa1-xN量子阱中激子能量

考虑了纤锌矿GaN/Al<,x>Ga<,1-x>N量子阱(QW)材料中空穴带质量和光学声子模的各向异性以及声子频率随波矢变化的效应,采用改进的LLP变分法计算了纤锌矿氮化物QW中激子的基态能量和结合能.给出了激子的基态能量和结合能随着QW宽度和Al组分变化的函数关系,并对闪锌矿和纤锌矿GaN/Al<0.3>Ga<,0....     

纤锌矿GaN/AlxGa1-xN量子阱中自由极化子能级

采用Lee-Low-Pines (LLP)变分法研究了纤锌矿GaN/Al0.3Ga0.7N量子阱中自由极化子能量和电子-声子相互作用对自由极化子能量的影响.理论计算中考虑了量子阱中定域声子模(Confined phonon modes)和半空间声子模(Half-space phonon modes)的影响以及电子有效质...     

The electronic and magnetic properties of wurtzite Mn∶CdS,Cr∶CdS and Mn∶Cr∶CdS∶ first principles calculations

In this article, density functional theory (DFT) based on generalized gradient approximation (GGA) and GGA+U, U is Hubbard term, is used to study the electronic properties of CdS doped with different dopants (Cr, Mn). The calculations are carried out for Mn-doped CdS, Cr-doped CdS, and co-doping of Mn/Cr in CdS simultaneously. It is found that hopping of electrons is possible with Cr:CdS and Mn:Cr:CdS while Mn:CdS does not allow the hopping of electrons. Moreover, double exchange interactions are observed in Cr:CdS and d-d super-exchange interactions are observed in Mn:CdS. Now the problem becomes interesting when one magnetic ion (Cr) supporting double exchange interactions and another ion (Mn) supporting d-d super-exchange interactions are doped simultaneously in the same system (CdS). The co-doped CdS is more stable even at high Curie temperature due to p-d double exchange interactions and d-d super exchange interactions. Furthermore, the Cr-3d and Mn-3d states present in-between the band gap are responsible for inner shell transitions and hence for optical properties. Therefore, the co-doped system is taken into account to enhance its applications in the field of spintronic and magneto-optical devices.     

热处理温度对CuInS2粉体物相、形貌及光吸收性能的影响

采用溶剂热法在不同反应体系和温度下,制备了一系列Cu In S2(CIS)粉体。CIS粉体的物相、形貌、光吸收性能分别用X射线衍射(XRD)仪、场发射扫描电镜(FESEM)、透射电镜(TEM)、紫外-可见光谱仪(UV-Vis)等手段进行了表征。结果表明,180℃时乙醇-硫脲体系所得"绣球"状CIS粉体为黄铜矿结构,而乙二胺-硫化钠体系则为"花簇"状纤锌矿结构,升高溶剂热温度,两者形貌均往"球体"演变;结合XRD,差热(DSC)分析表明纤锌矿CIS具有往黄铜矿CIS转变的趋势,物相转变温度约为453℃;受物相转变影响,纤锌矿CIS的带隙值由黄铜矿的1.43 e V减小至1.35 e V,其可见光吸收能力增强。同时探讨了CIS物相的转变机理。     

纳米粉ZnO的制备及低温热容研究

采用液相沉淀新方法制备了ＺｎＯ纳米晶超微粉末,ＸＲＤ和ＴＥＭ分析结果表明,平均粒径为１８ｎｍ,纤锌矿晶相结构,粒径分布范围较窄．化学分析和ＩＣＰ联合测定,其纯度＞９９．９％．在７８～３７０Ｋ温区,用高精密全自动量热仪测定了热容,拟合出热容随温度变化的多项式方程： Ｃ_ｐ＝ ４０．０４２＋ ２４．５５４Ｘ＋ ０．９３０３３Ｘ^２＋ ２．１６４９Ｘ^３一 １．８３８９Ｘ^４;并与粗晶 ＺｎＯ热容文献值进行比较,从能量的角度分析了各热容曲线不同的原因．