Be掺杂对ZnO电子结构和光学性质的影响

基于密度泛函理论(DFT)第一性原理计算了Zn1-xBexO化合物的电子结构和光学性质.计算结果表明Zn1-xBexO带隙随掺杂浓度的增加而变大.这种现象主要是由于价带顶O2p随掺杂量x的增加几乎保持不变,而Zn4s随掺杂最x的增加向高能端移动.光学介电函数虚部计算结果表明:在2.0,6.76eV位置随掺杂浓度的增加蜂形逐渐消失,是由于Be替代Zn导致Zn3d电子态逐渐减少所致;而9.9eV峰彤逐渐增强,是由于逐渐形成的纤锌矿结构Beo的价带O2p到导带Be2s的跃迁增加所致.     

Zn掺杂和Sn空位对p型SnO2电子结构和光学性能的影响

用第一性原理计算了本征SnO2、Zn掺杂SnO2、带Sn 空位(VSn)的SnO2和Zn-VSn共掺杂 SnO2的电子结构和光学性能。结果表明,Zn 原子替位SnO2中的Sn原子后费米能级进入价带,价带顶的空能态由Zn 3d和O 2p态组成,Zn掺杂SnO2显示p型半导体性能。 带Sn空位的Zn掺杂SnO2的相对空穴数量较Zn掺杂SnO2的相对空穴数量有明显增加,Sn空位有助于增加Zn掺杂SnO2的p型导电性。Zn掺杂SnO2在可见光区域有明显的光吸收,带Sn空位的Zn掺杂SnO2的光吸收较Zn掺杂SnO2明显增强,吸收光谱发生蓝移。     

AZO透明导电薄膜的结构与光电性能

采用射频溅射工艺制备了Zn1-xAlxO透明导电薄膜。通过XRD、UV透射和电学性能测试等分析手段,研究了Al浓度对薄膜的组织结构和光电性能的影响规律。结果表明:薄膜具有c轴择优取向,随着Al浓度的增加,(002)衍射峰向高角度移动,峰强度逐渐减弱,x(Al)为15%掺杂极限浓度。x(Al)为2%时,薄膜电阻率是3.4×10–4Ω.cm。随着掺杂量x(Al)从0增加到20%,薄膜的禁带宽度从3.34 eV增加到4.0 eV。     

N掺杂p型MgZnO薄膜的制备与性能研究

利用磁控溅射设备,Mg0.04Zn0.96O陶瓷靶材,以高纯的氮气与氩气混合气体作为溅射气体,在石英衬底上沉积获得了N掺杂p型Mg0.07Zn0.93O薄膜,薄膜的电阻率为21.47Ω·cm,载流子浓度为8.38×1016 cm-3,迁移率为3.45cm2/(V·s)。研究了该薄膜的结构与光学性能。实验结果显示,其拉曼光谱中出现了位于272和642cm-1左右与NO相关的振动模。低温光致发光光谱中,可以观察到位于3.201,3.384和3.469eV的3个发光峰,其中位于3.384eV的发光峰归因为导带电子到缺陷能级的复合发光,而位于3.469eV的发光峰归因为受主束缚激子(A0X)的辐射复合,这说明该N掺杂MgZnO薄膜的空穴载流子主要来自NO受主的贡献。     

H_2O在Si(100)-(2×1)表面上的吸附和氧化

利用AES以及HeI(21.2eV)和同步辐射(138.5eV)光电子谱研究了H_2O在Si(100)-(2 ×1)表面上的室温吸附、高温退火效应以及开始氧化的过程.AES的测量结果表明,H_2O在这种表面上的粘附系数很大,在350K下,当曝汽量约为2L时就达到饱和,其覆盖率θ=1/2.价带区域的光电子谱出现三个由于H_2O吸附而引起的特征峰,低于价带顶分别为6.2、7.2和11.5eV.350K下的 H_2O吸附导致Si 2p能级的结合能增加0.8±0.1eV,相当于一个Si原子同一个氧原子键合的情况.在 640K下退火后,出现Si 2p的第二个化学位移峰,其位置比体内Si 2p 峰约低 1.8eV,表明这时的 H_2O已经完全离解,一部分Si原子同两个氧原子键合(可能是桥键方式). 在 870K下退火,得到Si 2p的四个化学位移峰,说明氧已经贯穿进Si的体内,形成SiO_x(x=1、2、3和4).当退火温度进一步提高到T(?)970K时,恢复Si的清洁表面,表明氧被完全脱附.     

生长于Pt/Ti/SiO2/Si衬底的ZnxNi(1-x)Mn2O4薄膜的结构与光学性质

采用化学溶液法在Pt/Ti/SiO2/Si衬底上生长了ZnxNi1-xMn2O4（ZNMO, x=0, 0.05, 0.1, 0.15, 0.2, 0.25）尖晶石氧化物薄膜。X射线衍射(XRD) 与场发射扫描电子显微镜(FESEM) 分析结果表明,Zn的掺杂浓度对ZNMO薄膜的结晶性和微结构有明显影响。用椭圆偏振光谱仪测量分析了ZNMO薄膜在300-1100nm波段的光学常数,并讨论了Zn掺杂对折射率n和消光系数k的影响。在薄膜的拉曼光谱中观测到两个峰A1g与F2g,A1g模式的相对峰位随着Zn的掺杂浓度x的增大而减小。由于晶格应变与晶格失配,拉曼峰峰位随Zn掺杂浓度的变化而轻微移动。     

有机／无机光电探测器的AFM和XPS分析

采用真空蒸发沉积，在室温下制备了PTCDA／p—Si有机／无机异质结样品。对其表面用原子力显微镜(AFM)研究表明，PTCDA薄膜具有岛状形态结构。经X光电子能谱(XPS)分析表明，在PTCDA分子中，C原子有两种束缚能态，其结合能力分别为285．3eV和288．7eV；O原子与C原子相邻，一些O原子通过双键与C原子相结合，另外的O原子则通过单键与2个C原子相结合。经Ar^ 束溅射研究界面电子状态表明，随溅射时间增加，C1s和O1s峰逐渐减弱，而Si 2p和Si 2s峰渐渐增强。C1s和Si 2p谱峰随着溅射时间的增加而逐渐向低束缚能力方向移动。由于荷电效应和碳硅氧烷(C—Si—O)及SiO2的存在，Ols谱峰随溅射时间的增加先向高束缚能方向移动，然后向低束缚能方向移动。     

Sm2O3掺杂对BZN基陶瓷介电性能的影响

研究了Sm2O3掺杂的Bi2O3-ZnO-Nb2O5(BZN)基陶瓷(Bi1.5–SmxZn0.5)(Zn0.5Nb1.5)O7(0≤x≤1.5,BSZN)的结构x和介电性能。实验采用传统的固相反应法制备陶瓷样品,XRD分析样品的相结构。结果表明:未掺杂的BZN陶瓷其结构为立方焦绿石单相;当Sm2O3掺杂量较少(0相似文献   

用第一性原理研究F掺杂β-Ga2O3的电子结构和光学性质

研究F掺杂浓度对β-Ga2O3的几何结构、电子结构和光学性质的影响。F掺杂β-Ga2O3在富Ga条件下容易制备,随F掺杂浓度的提高,F掺杂β-Ga2O3的稳定性增强,结构参数变大。F掺杂β-Ga2O3是一种n型半导体材料,导带中的占据态由Ga 4s、Ga 4p和O 2p态组成,占据态随F掺杂浓度的增加而增加。随F掺杂浓度的提高,F掺杂β-Ga2O3的禁带宽度收缩,占据态展宽。F掺杂β-Ga2O3的吸收谱呈现陡峭的带边吸收和宽的吸收带。随F掺杂浓度的提高,F掺杂β-Ga2O3的带边吸收蓝移,宽带吸收的强度增强。宽带吸收是由导带中的占据态向空态带内跃迁产生的。     

Ga-N共掺氧化锌纳米线阵列制备及发光性能研究

采用化学气相沉积法（CVD）以一氧化氮（NO）和氧化镓（Ga2O3）为掺杂源,在c轴取向单晶蓝宝石衬底上外延生长镓氮（Ga-N）共掺氧化锌（ZnO）纳米线阵列。利用SEM, XRD, HRTEM, XPS, PL等测试手段对掺杂后的ZnO纳米线阵列进行结构、成分和光学性能表征。结果表明,Ga-N共掺ZnO纳米线阵列保持六方纤锌矿结构,沿（002）方向择优生长;掺杂元素在样品中均匀分布。随着掺杂浓度增加,纳米线由六棱柱结构转变为尖锥层状结构,长度由2 μm减小到1 μm,锥度增加至0.95;N 1s/Ga 2p/Zn 2p峰结合能向低能态方向移动。PL光谱分析表明,所有样品均出现紫外发光峰和绿光发光峰,不同掺杂浓度的缺陷发光强度不同。     

Structure and optical properties of ZnSeO alloys with O composition up to 6.4%

II–VI-O type alloy semiconductor ZnSeO (O composition up to 6.4%) is grown by molecular beam epitaxy. O composition increases with O₂ flow rate. Several XRD peaks are observed when O composition is 2–4%, indicating phase separation. Growth at low temperature results in higher O composition. Photoluminescence intensity of ZnSeO lattice matched to GaAs is much stronger than that of ZnSe and peak shifts to lower energies with increasing O composition. Photoreflectance spectroscopy is performed to investigate the band gap energy. The band gap energy investigated by photoreflectance decreases with increasing O composition due to large band gap bowing even when phase separation occurs. The bowing parameter is estimated as 8.4 eV.     

Theoretical investigation of excitonic gain in ZnO--Mg/sub x/Zn/sub 1-x/O strained quantum wells

Free-excitonic gain of wurtzite ZnO--Mg/sub x/Zn/sub 1-x/O quantum wells(QWs) is studied theoretically. The valence band structure of ZnO--Mg/sub x/Zn/sub 1-x/O QWs with the consideration of biaxial strain and exciton-phonon interaction is calculated based on a 6/spl times/6 Hamiltonian. From the available experimental data, the band offset ratio and conduction band deformation potential of ZnO--Mg/sub x/Zn/sub 1-x/O QWs are found to be 60/40 and -6.8eV, respectively. The influence of biaxial strain on the peak free-excitonic gain of ZnO--Mg/sub x/Zn/sub 1-x/O QWs for various well-width and mole fraction of Mg is also investigated.     

Ultraviolet photoluminescence from undoped and zn doped AlxGa1−xN with x between 0 and 0.75

The origin of the abrupt decrease withx both in electron concentration and in mobility of Al_xGa_1−xN in the range ofx between 0.4 and 0.6 was investigated by photoluminescence from epitaxial layers covering the entire range of alloy composition. Band edge luminescence from undoped layers was observed out to anx value of 0.75. Whenx was larger than 0.2, a peak 0.2–0.5 eV below the band edge peak was also observed both from undoped and from Zn doped samples. This is tentatively ascribed to an unidentified acceptor (or acceptors) related to the presence of Al. No luminescence which could be attributed to a deep native donor defect was observed in semi-insulating Al_xGa_1−xN layers. When Zn was added in the lowx range of the alloys, a broad band 0.5–0.8 eV below the band edge peak was observed as well as a relatively narrow peak.     

膜厚对氧化钒薄膜结构和光学性质的影响

利用真空热蒸发在石英基片上制备了不同厚度的氧化钒薄膜, 研究厚度对薄膜的结构、形貌和光学特性的影响。薄膜的结构由X射线衍射(XRD)仪和拉曼(Raman)光谱仪测得, 表面形貌用原子力显微镜(AFM)观测。利用分光光度计测量薄膜的光学透射率, 并且采用Forouhi-Bloomer模型与修正的德鲁德(Drude)自由电子模型相结合的方法拟合透射率来确定薄膜的折射率、消光系数和带隙。结果表明, 热蒸发的氧化钒薄膜呈非晶态, 薄膜的主要成分为五氧化二钒, 且含有少量的二氧化钒。薄膜表面的颗粒粘结在一起, 随着薄膜厚度的增加, 薄膜表面粗糙度以及颗粒尺寸变小, 膜层表面平整度越来越好, 颗粒之间的空隙变小, 导致折射率随膜厚的增加而增大, 消光系数减小。另外, 随着薄膜厚度从200 nm增加到450 nm, 光学带隙从2.67 eV减小到2.45 eV。     

VUV-ellipsometry on BexZn1−xSe and BeTe

We have determined the dielectric function of BeTe and Be_xZn_1−xSe for the full composition range (0≤x≤1) by spectroscopic ellipsometry in the ultraviolet- and vacuum ultraviolet-range. The spectra show pronounced features in the photon energy range between 2.7 and 25 eV. For BeTe, we assign the main structures to interband transitions from the heavy and light hole bands to the lowest conduction band at high symmetry points in the Brillouin zone. The spectral positions of the interband critical points agree with quasiparticle excitations obtained by a GW calculation. We extracted the dielectric function of BeTe in the transparent regime below the fundamental gap E₀ at 4.2 eV from our experimental data using the three-phase model (vacuum/BeTe/GaAs). By comparing the ZnSe spectra (x=0) to literature data, we assign the observed structures to interband transitions at specific points or regions of the Brillouin zone. The corresponding assignment for BeSe is made by tracking the dependence of these structures on Be content x from x=0 to x=1. E₀ has the steepest slope dE₀/dx and exhibits a bowing vs x. For samples with a large Zn content (x<0.2) two structures show up at high energies (15.7 and 16.9 eV) which have not been observed before. We assign these structures to transitions from the Zn 3d bands to a higher conduction band at the L point and at the γ point.     

ZnO纳米棒/薄膜结构的电沉积制备及性能

以阳离子表面活性剂——十六烷三甲基氯化铵(CTAC)作为添加剂,采用电沉积法在氧化铟锡玻璃基板上制备了ZnO薄膜。并研究了CTAC含量对阴极电流密度、结构、表面形貌、化学态和光学性能的影响。实验发现阴极电流密度和(002)择优取向随CTAC含量的增加而增加。电沉积氧化锌薄膜的表面形貌随CTAC含量的增加由小晶粒变为纳米棒,这表明CTAC在控制表面形貌方面有很重要的作用。X-射线光电子能谱表明Zn2p3/2,Zn2p1/2,O1s的峰位分别为1020.78eV、1046.88eV和530.8eV。CTAC对电沉积的影响可能是由于CTAC的吸附作用改变了不同晶面的表面能和生长动力学。此外,研究了ZnO薄膜的光学性能,结果表明当CTAC含量为3.0mmol/L时,薄膜具有较好的透光性和紫外发射性能。添加不同含量CTAC的ZnO薄膜禁带宽度介于3.27～3.52eV。     

Revisit of the band gaps of rutile SnO2 and TiO2: a first-principles study

From the recent experimentally observed conduction band offset and previously reported band gaps,one may deduce that the valence band offset between rutile SnO2 and TiO2 is around 1 eV,with TiO2 having a higher valence band maximum.This implication sharply contradicts the fact that the two compounds have the same rutile structure and the Γ3^+ VBM state is mostly an oxygen p state with a small amount of cation d character,thus one would expect that SnO2 and TiO2 should have small valence band offset.If the valence band offset between SnO2 and TiO2 is indeed small,one may question the correctness of the previously reported band gaps of SnO2 and TiO2.In this paper,using first-principles calculations with different levels of computational methods and functionals within the density functional theory,we reinvestigate the long-standing band gap problem for SnO2.Our analysis suggests that the fundamental band gap of SnO2 should be similar to that of TiO2,i.e.,around 3.0 eV.This value is significantly smaller than the previously reported value of about 3.6 eV,which can be attributed as the optical band gap of this material.Similar to what has been found in In2O3,the discrepancy between the fundamental and optical gaps of SnO2 can be ascribed to the inversion symmetry of its crystal structure and the resultant dipole-forbidden transitions between its band edges.Our results are consistent with most of the optical and electrical measurements of the band gaps and band offset between SnO2 and TiO2,thus provide new understanding of the band structure and optical properties of SnO2.Experimental tests of our predictions are called for.     

XPS Investigation on Surface and Interface Electronic States of Alq3／ITO

The surface and interface electronic states of tris-(8-hydroxyquinoline)aluminum(Alq3)/indium-tin oxid(ITO)were measured and analyzed by X-ray photoelectron spectroscopy(XPS).The results indicated that, in Alq3 molecule,the binding energy(Eb)of Al atoms is 70.7eV and 75.1eV,corresponding to Al(O)and Al(Ⅲ）,respectively;The binding energy of C is 285.8eV,286.3eV,and 286.8eV,corresponding to C of C-C group,C-O,and C-N bond,respectively,N is the main peak locating at 401.0eV, corresponding to Natom of C-N=C.Oatoms mainly bond o H atom,with the binding energy of 533.2 eV.As the sputtering time of Ar^ ion bearn increases,Al2p,C1s,N1s,O1s,Ind3d5/2 and Sn3d5/2 peaks slightly shift towards lower binding energy,and Al2p,C1s and N1s peaks get weaker,which contributed to diffusing the oxygen,indium and tin in ITO into Alq3 layr.     

Near-edge conduction band electronic states in SiGe alloys

Spatially resolved electron energy loss spectroscopy (EELS) measurements in GeSi alloys illustrate the relationship of atomic structure to local electronic structure. Extending earlier measurements, where electronic structure was found to be controlled by composition in relaxed alloys, measurements in anisotropically strained alloys show splitting of normally degenerate band edges into two components. In a strained Si quantum well, this allows the engineered band offset to be followed from the GeSi substrate through the well to the alloy-capping layer. In the high-mobility conduction channel, the band edge is found to be very sharp, in spite of obvious composition roughness. Near a misfit dislocation under the Si well, the band edge can shift by as much as 0.25 eV due to local strain. Within the core of the defect, however, strictly local behavior dominates the observations. Local conduction band splitting and in-gap states are both observed.