用ARUPS和HREELS研究GaP(111)面的表面态

本文利用角分辨紫外光电子能谱(ARUPS)和高分辨率电子能量损失谱(HREELS)研究Ar⁺刻蚀退火处理的GaP(111)面表面态。发现与P原子悬挂键有关的本征满表面态在Г点位于价带顶下0.6eV处,而缺陷引入的空表面态位于价带顶上1.1eV处(Г点)。空表面态引起n型样品表面能带发生1.36eV弯曲。     

氢、氧终端掺硼金刚石薄膜的电子结构

利用氢微波等离子体溅射和浓酸中沸煮方法分别制备了氢、氧终端掺硼金刚石薄膜.借助X射线光电子能谱及接触角检测对两种终端薄膜表面进行了分析，通过扫描探针显微镜研究了针尖和样品间的扫描隧道谱.结果表明，氢终端掺硼金刚石表面能带向上弯曲，在高于价带顶位置存在浅受主能级；氧终端表面能带向下弯曲，带隙较宽，带隙中不存在表面态.对两种终端金刚石薄膜的导电机理进行了讨论.     

非晶态As2S8半导体薄膜的光致结构变化效应研究

实验研究了非晶态As2S8半导体薄膜在光照、退火-光照和退火-光照-退火-光照关连作用下的光折变效应及淀积态与退火态两种膜系光致体积变化现象.采用棱镜耦合技术、Raman光谱和X线衍射测试技术,确认了As2S8薄膜经紫外光辐照后薄膜密度增高、折射率增大的现象.实验表明,淀积态As2S8薄膜经紫外光照后,折射率变化的最大增量可达到0.06,而退火态As2S8薄膜经紫外光照射后,其折射率最大变化比前者要小一个数量级,约为0.005 7.淀积态和退火态两种膜系紫外光照后,体积缩小,这与As2S3非晶态薄膜的情况不同,体积变化率分别为－3.5%和－2.1%.实验还显示,退火态的As2S8薄膜存在折射率完全可逆现象.     

氢、氧终端掺硼金刚石薄膜的电子结构

利用氢微波等离子体溅射和浓酸中沸煮方法分别制备了氢、氧终端掺硼金刚石薄膜.借助X射线光电子能谱及接触角检测对两种终端薄膜表面进行了分析,通过扫描探针显微镜研究了针尖和样品间的扫描隧道谱.结果表明,氢终端掺硼金刚石表面能带向上弯曲,在高于价带顶位置存在浅受主能级;氧终端表面能带向下弯曲,带隙较宽,带隙中不存在表面态.对两种终端金刚石薄膜的导电机理进行了讨论. 关键词： 氢终端 氧终端 掺硼金刚石薄膜 电子结构     

Co/Cu(111)薄膜生长和退火过程中的扩散

利用同步辐射角分辨光电子能谱和俄歇电子能谱研究了CoCu(111)分子束外延薄膜在生长和退火过程中的电子结构.实验发现:随着Co膜厚度的增加,Cu的sdz2杂化带能级位移相应增大,证实了界面间发生了互混;退火过程中存在表面扩散,而非通过界面的体扩散.并把这两种不同过程的扩散的内在动力归结为Co的表面自由能显著大于Cu的表面自由能 关键词： 表面扩散和界面混合物形成 固体表面能 表面态和能带结构     

VC(001)弛豫表面构型与电子结构第一性原理研究

用第一性原理方法对VC(001)清洁表面的构型和电子结构进行了详细研究，与TiC(001)面类似，VC(001)面弛豫后形成表面皱褶，其表层V原子和C原子分别朝体相和真空方向移动. 能带计算结果表明，过渡金属碳化物(001)面的能带结构符合刚性带理论模型. 对于VC(001)面，表面态主要处在-30eV附近，其主要成分为表层C原子的2pz轨道. 此外，以表层V原子的3d轨道成分为主的表面态出现在费米能级附近，由于这些表面态以表面法线方向的轨道(3d２z和3dxz/dyz)为主要成分，因此在表面反应中将起到重要作用，从而体现出与TiC(001)面不同的反应性质. 关键词： 过渡金属碳化物 表面态 能带结构     

YBa_2Cu_3O_7基面电子态特性计算

用散射理论描述了 YBa2 Cu3O7( 0 0 1)面的电子能带结构。用近似到第三近邻的紧束缚模型得到了 YBCO的体电子态密度 ,Cu O及 Cu O2 的表面态密度和表面投影能带 ,进而分析了 Cu O和 Cu O2 的表面态密度的特点及与体态密度的差别。     

Nb-X(X=Y,Zr)共掺杂SnO_2电子结构的第一性原理研究

本文采用第一性原理方法研究了Nb-X(X=Y,Zr)共掺杂SnO_2能带结构与态密度,探讨了其磁性产生的机理.研究结果表明,Nb-Y共掺杂SnO_2体系自旋向上和自旋向下的能带、态密度完全对称,总磁矩为0μB;Nb-Zr共掺杂的SnO_2体系自旋向上和自旋向下的能带与态密度在费米能级处都出现了不对称的情况,出现耦合现象,其总磁矩为0.933μB;分析Nb-Y共掺杂SnO_2的能带结构与态密度得到自旋向上和自旋向下的能带禁带中的4条杂质能级来源于Nb-Y共掺杂SnO_2电子的施主与受主能级;NbZr共掺杂SnO_2体系产生磁性的原因在于Nb和Zr的d轨道的引入.     

四面体键半导体合金LMTO能带的相干势近似计算

本文提出一种无须引入可调参数的基于LMTO能带的相干势近似(CPA)计算方法。在LMTO及其虚晶近似计算中,哈密顿矩阵的矩阵元计及原子球的d态,哈密顿矩阵对角化时忽略d带对s,p能带的影响,所得能带本征态便于构成适用于CPA计算的sp杂化正交轨道且能带结构较为合理。以Ga_1-xAl_xAs为例,论证这一方法在四面体键半导体合金中的应用。计算结果表明,其重要能带及相应带隙的弯曲参数的CPA修正值是合理的。 关键词：     

CdTe(110)弛豫表面电子态的计算

利用形式散射理论，采用次近邻的紧束缚模型计算了CdTe（110）弛豫表面的电子结构，给出了总体、局域及分波态密度，并给出了表面能带．所得到的结果与实验和第一原理计算结果符合得很好．通过分析表面态的变化，指出表面发生弛豫的原因主要是阴阳离子的p态电子的相互作用加强所致． 关键词：     

The effect of illumination on dark conductivity and photoconductivity of hydrogenated amorphous silicon layered films

It is established that both the amplitude and temperature dependence of dark conductivity and photoconductivity of preilluminated high-sensitivity layered films of amorphous hydrogenated silicon (a-Si:H) prepared by cyclic deposition with layer-by-layer annealing in hydrogen plasma depend on illumination temperature. The relaxation kinetics of the dark conductivity of these films after illumination is shut off is found to be nonmonotonic. The observed effects can be explained by fast and slow changes in the distribution of energy state density below the midgap during and after illumination.     

GeSe2非晶半导体薄膜中光致结构及性能变化

运用X射线衍射分析、红外光谱分析、扫描电镜分析和透射光谱分析，研究了GeSe2非晶半导体薄膜经514.5nm波长的氩离子激光辐照后的结构及性能变化。实验结果表明，经热处理和激光辐照后，薄膜的光学吸收边均移向短波长处，这种移劝随着辐照激光强度和辐照时间的增加而增大，并且在退火薄膜中是可逆的，扫描电镜分析结果表明，薄膜在激光辐照后有微晶析出，这种微晶的析出量随着辐照激光强度的增强而增加。     

Fabrication of an intelligent superhydrophobic surface based on ZnO nanorod arrays with switchable adhesion property

The superhydrophobic ZnO surface possessing water adhesive reversibility is fabricated by a facile method. The as-prepared surface is low adhesive; however, after being irradiated by UV light through a photomask, it becomes highly adhesive. A water droplet can suspend on the irradiated surface. Further annealing the irradiated surface, water droplets can roll on the surface again. Reversible transition between the high adhesive pinning state and low adhesive rolling state can be realized simply by UV illumination and heat treatment alternately. The adhesion transition is attributed to the adsorption/desorption of surface hydroxyl groups and the organic chains rearrangement on the top surfaces of ZnO.     

Superhydrophilicity and XPS study of boron-doped TiO2

This study examines the superhydrophilicity and chemical state of boron-doped TiO₂ prepared by the ion implantation method and explores the effect of annealing on them. XRD measurements show that the implanted sample forms a polycrystalline structure of anatase with no trace of rutile. Their water-contact angles are significantly reduced upon irradiation with ultraviolet light. The Ti 2p XPS spectra of the oxide exhibit a shoulder peak at the lower binding energy side of the main peak, whereas no shoulder is observed in single-crystal and annealed TiO₂. This suggests that the titanium ions with lower valences are produced by boron doping and they disappear on subsequent annealing. The SIMS depth profile of boron in the as-implanted TiO₂ exhibits a peak at a depth of 15-20 nm, whereas this peak disappears upon annealing. The water-contact angles increased on annealing under ultraviolet light illumination. It is concluded that the improvement in the superhydrophilicity by boron doping is due to the reduction of titanium, and the deterioration of superhydrophilicity with the subsequent annealing is due to the oxidation of reduced titanium and the inward diffusion of boron.     

退火对ZnO薄膜晶体结构和ZnO/p-Si异质结光电性质的影响

采用脉冲激光沉积方法在p-Si(100)衬底卜牛长ZnO薄膜,分别在500℃、600℃和700℃下真空退火,采用X射线衍射仪研究了退火对ZnO薄膜品体结构的影响,并测量了ZnO的面电阻和ZnO/p-Si异质结的、I-V特性曲线.研究表明,随着退火温度的升高,ZnO的(002)衍射峰强度逐渐增大,半峰全宽不断减小,同时薄膜内应力减小,ZnO晶粒尺寸变大.表明高温退火有助于ZnO薄膜结晶质量的提高.在没有光照的条件下,异质结的漏电流随退火温度的增加而增大;用650 nm光照射样品时,600℃退火的样品表现出最明显的光电效应,而过高的退火温度会破坏ZnO/p-Si异质结的界面结构,使其光电流变小.所以,要得到性能良好的光电器件,应选取适当的退火温度.     

E.S.R. line-narrowing induced by light illumination in the cyclopentanyl radical trapped in a glassy matrix at 77 K

Unusual line-narrowing was found in the β-cyclopentanyl radical trapped in a glassy matrix at 77 K during exposure of the sample to red light, although the bulk temperature of the sample was unchanged by this light illumination. The infra-red band corresponding to the C-H stretching frequency of the radical seemed to be effective in this narrowing. It was also found that the narrowing reached a stationary state about 20 min after the light was turned on. Quantitative investigation of this narrowing indicates that agitation induced photodynamically by this illumination is equivalent to a thermal agitation in a sample which is in equilibrium at 50° higher. Plausible sources of this phenomenon are discussed.     

Light-enhanced reactivation of passivated boron in hydrogen treated silicon

The thermal reactivation of the boron acceptor in hydrogenated silicon is strongly enhanced if the anneals are performed under illumination. The changes of the inactive boron concentration R versus annealing time t satisfy the equation dR/dt = -rR²/(N_A − R)², where N_A is the total boron concentration. Under strong illumination the annealing parameter r is proportional to the light intensity.     

Photo-induced ESR and optical absorption edge shift in amorphous Ge-S films

Reversible shift of the optical absorption edge by the cycle of band-gap illumination and annealing has been observed for Ge-S films for the first time. Photo-induced ESR has been observed, and it is explained by two processes: (1)Increase in randomness of the structure by illumination, and (2)Trapping of free carriers excited by illumination by charged dangling bonds. The ESR signal caused by the former process does not disappear either by warming the film up to room temperature or by illuminating it with the mid-gap light, while that by the latter process disappears.     

Photo-induced degradation of a-Si: H diodes with an nin structure

Diodes with an nin structure consisting of hydrogenated amorphous silicon (a-Si:H) exhibit space-charge-limited currents. We subjected some diodes to both illumination and voltage stresses. Only the illumination treatment led to a degradation of the I(U)-characteristics. The degradation is reversible by annealing. We deduce from these findings that metastable traps are created by recombining photocarriers rather than by single-carrier trapping. The reversible diode degradation is consistent with the Staebler-Wronski effect.     

Light induced microstructure transformation in a-Si：H films

A series of a-Si:H films are deposited by hot wire assisted microwave electron cyclotron resonant chemical vapour deposition (HW-MWECR-CVD), subsequently exposed under simulated illumination for three hours. This paper studies the microstructure change during illumination by Fourier Transformation Infrared (FTIR) spectra. There are two typical transformation tendencies of microstructure after illumination. It proposes a model of light induced structural change based on the experimental results. It is found that all samples follow the same mechanism during illumination, and intrinsic structure of samples affect the total H content.