用光电子能谱研究 Si/GaP(Ⅲ)异质界面的价带不连续性

介绍在改装的ADES-400型光电子能谱仪上,用Si电子束蒸发的方法生长Si/GaP(Ⅲ)界面的过程,并用光电子能谱原位地分析测量不同条件下生长的Si/GaP(Ⅲ)异质界面的形成状况和价带不连续值△E_v。讨论了△E_v与界面状况和原子能级变化的相互关系,确定了生长有序的突变Si/GaP(Ⅲ)异质界面的条件,得到此时界面的价带不连续值为0.80eV。它与理论计算值基本一致。 关键词：     

Si/ZnS极性界面能带偏移的同步辐射光电子能谱研究

用同步辐射光电子能谱测量了Si/ZnS（111）及（100）异质结的价带偏移ΔE_v．对于Si/ZnS（111）及（100）两界面，ΔE_v的实验结果均为（1.9±0.1）eV，与已有理论预期值相当符合，但与Maierhofer所报告的ZnS/Si（111）异质结测量结果之间则存在明显差别．该实验结果表明对于Si/ZnS极性界面，互逆性规则（commutativity rule）可能不成立，就此进行了讨论． 关键词：     

Hg1-xCdxTe n+-p光电二极管中的深能级及其电流机构的流体静压力研究

在流体静压力(0—2GPa)下,对Hg_1-xCd_xTe n⁺-p光电二极管(x=0.5)室温电学特性进行了实验和理论研究。通过考虑深能级压力效应及其对深能级辅助隧道电流的影响,较好地解释了实验上观察到的p-n结伏安特性在小偏压范围下呈现的“反常”压力关系。由对实验数据的理论拟合得到两个深能级:D₁(=E_v+0.75E_g)和D₂(=E_v关键词：     

应变层超晶格(InAs)n(InP)n(001)电子结构的LMTO计算

基于Linearized-Muffin-Tin Orbitals(LMTO)能带方法,采用内部求和计入空d轨道的处理,对(InAs)_n(InP)_n(001),(n=1,2,3)应变层超晶格的电子结构进行了第一性原理计算。得出了其能带结构,态密度分布(对n=1)。考察了In4d轨道对能带计算的影响,并采用冻结势方法求出了(InAs)_n(InP)_n(001),(n=1,2,3)的价带边不连续值△E_v。 关键词：     

化合物和合金中离子投影射程分布矩的计算(Ⅰ)——重离子(Z1>10)的射程分布矩

本文采用改进了的核散射函数计算了12种离子在非晶Al₂O₃,SiO₂,20/25/Nb不锈钢、UO₂和LiNbO₃等材料中的投影射程分布一次至三次矩。给出了能量范围从5keV至1MeV的离子在上述材料中的理论计算结果。将计算值与近几年的实验测量结果及Gibbons等人和Winterbon的理论计算进行了比较。结果表明,我们得到了与实验符合得更好的理论值。文中较详细地介绍了化合物和合金材料中射程分布矩的计算方法,并对改进计算精度等问题进行了简要的讨论。 关键词：     

应变层超晶格InAs/InP界面的平均键能行为与价带边不连续性

采用LMTO能带方法,对两种不同应变状态下(自由形变和以InP为衬底),应变层超晶格(InAs)₁(InP)₁(001)和与应变层超晶格的分子层相对应的应变体材料,以及无应变的体材料进行了第一原理计算,并采用冻结势方法求出了两种超晶格各分子层的平均键能。结果表明,能存在应变的情况下,异质界面两边的平均键能非常一致,且这种一致性受应变状态的影响很小,因而可以把它用来作为确定应变层超晶格价带边不连续值(△E_v)的普遍适用的参考能级。研究了应变对 关键词：     

使用CNDO/S型近似方法计算NaNO2晶体的倍频系数

本文使用CNDO/S型近似方法,计算(NO₂)^-1的单电子分子轨道,然后按基团理论的通用计算程序计算NaNO₂晶体的倍频系数,计算值和实验值符合得较好,计算结果明确指出:NaNO₂晶体倍频系数各向异性的原因来自基团的共轭π轨道,另外,本文的计算表明,有可能对非线性光学新材料探索提供计算机的预测。本文还就非线性光学效应的双能级模型作了讨论,并指出了它的局限性。 关键词：     

PtN2的结构和力学性质的第一性原理计算

采用平面波赝势密度泛函理论方法计算了PtN₂的坐标、平衡态的晶格常数、体弹模量、剪切模量和弹性常数,计算结果与已有的实验值和理论值符合较好.通过能量与体积曲线,可知ST_AA结构比黄铁矿结构具有更低的能量.根据计算结果和Pugh提出的经验判据,PtN₂是易脆的硬物质,随着压强增加PtN₂的脆性逐渐过渡到延性.两种结构的能带结构和态密度表明了黄铁矿结构的PtN₂是半导体而ST_AA 关键词： 2')" href="#">PtN₂ 第一性原理 力学性质     

β-Si3N4电子结构和红外和拉曼频率的第一性原理研究

分别用PW91,B3LYP两种密度泛函方法和全电子高斯基组对β-Si₃N₄的几何结构进行全优化(包括晶格参数和原子坐标),结果和实验值符合良好. 同时计算了能带结构和态密度.在此基础上分别用上述两种方法计算了Γ点拉曼振动频率,并按对称性进行分类,将得到的11种拉曼活性模式的频率值与实验值以及其他文献值进行了比较,进一步确定了A_g模式为中等频率,值约459cm^-1. 计算结果表明 关键词： 振动频率 密度泛函理论 电子结构 3N₄')" href="#">β-Si₃N₄     

Rh XⅢ—Cd XVI离子4s24p3—4s4p4能级与跃迁的理论计算

用HFR（Hartree-Fock with relativistic corrections）方法对Rb V—Cd XVI离子4s²4p³和4s4p⁴组态能级结构做了全面系统的理论计算研究. 通过分析能级结构参数的HFR理论计算值与基于实验能级拟合得到的计算值之比值随着原子序数Z_c变化的规律,运用广义拟合外推方法预言了这些离子能级结构参数. 由此进一步计算了Rh XⅢ,Pd XIV,Ag XV和Cd XVI离子4s²4p³（⁴S_3/2,²P_1/2,3/2,²D_3/2,5/2）和4s4p⁴（⁴P_1/2,3/2,5/2,²P_1/2,3/2,²D_3/2,5/2,²S_1/2）组态能级以及电偶极跃迁波长与振子强度. 研究表明,对于4s²4p³组态,单组态近似可以得到较满意的结果;而对于4s4p⁴组态,只有在考虑了4s²4p²4d的组态相互作用效应时,计算结果的准确性才能明显得到提高. 同时,本文还运用全相对论grasp2K-DEV程序包计算了Rh XⅢ—Cd XVI离子组态能级. 对于Rh XⅢ离子4s²4p³（²P_1/2）,Pd XIV离子4s²4p³（⁴S_3/2,²P_1/2,3/2,²D_3/2,5/2）和4s4p⁴（²P_1/2,3/2,²D_3/2,5/2,²S_1/2）,能级均无实验值;对于Ag XV和Cd XVI离子,截至目前还没实验能级数据,没有实验能级值的所有数据均仅来自本文的计算数值. 本文计算结果与已有实验值吻合得很好.     

The permittivities of PVDF/PMMA blends at hydrostatic pressure

The complex permittivities of poly(vinylidene fluoride)/poly(methyl methacrylate) (PVDF/PMMA) blends have been measured under variation of temperature T(20°-60°C), frequency v(5 Hz-300 kHz), and hydrostatic pressure p (0-260 MPa). The values can be represented by a master curve with the shift factors △p/△ log (v/Hz) = ?140 MPa at room temperature and △ (1 /T) /△ log (v/Hz) = ?2. 10^?4 K^?1 at atmospheric pressure. The dependence of the activation energy △E _A on pressure p is then given by △E _A=(100 + 0.02 MPa^?1 p) kJ/mol. Furthermore, the results indicate that the β-relaxation of PVDF is due to motions in the crystal-amorphous interphase. The interactions between the two polymers, which are miscible at all compositions, disturb the correlations between the PVDF monomer units at that location as well as the mobility of the PMMA side group.     

Temperature quenching of luminescence for linear and derivative nuclear operators

An earlier study of the thermal quenching of luminescence using the single-configurational-coordinate model is extended from Condon-approximation overlap integrals 〈u_n|v_m〉² to the linear and derivative integrals 〈u_n|z_v|v_m〉² and 〈u_n|?/?z_v|v_m〉². For non-radiative transitions, the thermally weighted nuclear factor in the transition rate is, for the linear and derivative integrals, the corresponding factor for 〈u_n|v_m〉² integrals multiplied by 2E_Xv/?ω_v and $\text{2[E}{}_{\mathrm{Xv}}\text{- E}{}_{\mathrm{p}}{}_{\mathrm{U}}\text{(T)]/}\text{h}\text{?}\text{ω}{}_{\mathrm{v}}$, respectively. E_Xv is the energy of the crossover above the initial- v-parabola minimum, and E_pU(T) is the single activation energy fitted to the nuclear factor's temperature dependence for 〈u_n|v_m〉² integrals. These multiplying factors are exact for equal parabola force constants and good approximations for unequal force constants. These multiplying factors will be difficult to distinguish experimentally. The more important considerations for fitting the model to thermal-quenching data are the parabola placement and the Condon-approximation integrals described previously.     

A-15超导化合物的d带相对移动模型

本文考虑了A₃B型A-15结构晶体场的特点,根据对势模型,求出A原子各d电子子能级间相对移动量△E_⊥,进而在LCAO方法基础上,提出了改进的RCA能带模型。并据此得到V₃B系化合物超导临界温度对△E_⊥的关系,理论曲线与实验数据大致相符。 关键词：     

Effects of annealing on localized states in amorphous Ge films

Annealing behaviors of the activation energy for the electrical conduction E_σ, that for the thermoelectric power E_s, the optical gap E^opt_g, and the spin density in evaporated amorphous Ge are investigated. E_σ is independent of E_s and E^opt_g, and the rates of variation of E^opt_g and E_s with annealing temperature are connected by △E^opt_g = 2.5△E^opt_s. It is suggested that the position of the Fermi level does not change with annealing in contrast with amorphous Si, and the edge of the localized tail state shifts with annealing.     

Transverse momentum of charged hadrons observed in deep inelastic muon scattering

The transverse momenta of charged hadrons produced in high energy muon-proton scattering have been studied. The average squared transverse momentum 〈p²_⊥〉 shows a strong dependence on z = E_h/v characteristic of intrinsic momentum effects and a significant rise as a function of s = W². The W², q², x and z dependences of the data are compared with the predictions of a perturbative QCD model.     

InxGa1-xAs-GaAs应变层量子阱结构的流体静压光荧光研究

本文报道了对分子束外延(MBE)生长的In_0.25Ga_0.75As-GaAs应变层量子阱结构在77K下的压力光荧光(PL)研究的结果。流体静压力从0到50kbar.,给出了In_0.25Ga_0.75As-GaAs应变层量子阱的Γ谷压力系数,实验观察到了量子阱中能级与势垒GaAs中X谷的能级交叉。通过对其压力行为的分析,给出了In_0.25Ga_0.75As-GaAs异质结的导带与价带跃变比:Q_c=△E_c:△E_v=0.68:0.32。对(InGa)As-GaAs应变量子阱常压下的理论分析与实验符合很好。本文也对Al_0.3Ga_0.70As-GaAs量子阱进行了讨论。 关键词：     

Theoretical methods for the calculation of Bragg curves and 3D distributions of proton beams

The well-known Bragg-Kleeman rule R _CSDA = A ⋅ E has become a pioneer work in radiation physics of charged particles and is still a useful tool to estimate the range R _CSDA of approximately monoenergetic protons with initial energy E ₀ in a homogeneous medium. The rule is based on the continuous-slowing-down-approximation (CSDA). It results from a generalized (nonrelativistic) Langevin equation and a modification of the phenomenological friction term. The complete integration of this equation provides information about the residual energy E(z) and dE(z)/dz at each position z(0 ≦ z ≦ R _CSDA). A relativistic extension of the generalized Langevin equation yields the formula R _CSDA = A ⋅ (E ₀ + E/2M ⋅ c ²)^p. The initial energy of therapeutic protons satisfies E ₀ ≪ 2M ⋅ c ²(M ⋅ c ² = 938.276 MeV), which enables us to consider the relativistic contributions as correction terms. Besides this phenomenological starting-point, a complete integration of the Bethe-Bloch equation (BBE) is developed, which also provides the determination of R _CSDA, E(z) and dE(z)/dz and uses only those parameters given by the BBE itself (i.e., without further empirical parameters like modification of friction). The results obtained in the context of the aforementioned methods are compared with Monte-Carlo calculations (GEANT4); this Monte-Carlo code is also used with regard to further topics such as lateral scatter, nuclear interactions, and buildup effects. In the framework of the CSDA, the energy transfer from protons to environmental atomic electrons does not account for local fluctuations. Based on statistical quantum mechanics, an analysis of the Gaussian convolution and the Landau-Vavilov distribution function is carried out to describe these fluctuations. The Landau tail is derived as Hermite polynomial corrections of a Gaussian convolution. It is experimentally confirmed that proton Bragg curves with E ₀ ≧ 120 MeV show a buildup, which increases with the proton energy. This buildup is explained by a theoretical analysis of impinging proton beamlets. In order to obtain a complete dose calculation model for proton treatment planning, some further aspects have to be accounted for: the decrease of the fluence of the primary protons due to nuclear interactions, the transport of released secondary protons, the dose contribution of heavy recoil nuclei, the inclusion of lateral scatter of the primary and secondary protons based on Molière’s multiple-scatter theory, and the scatter contributions of collimators. This study also presents some results which go beyond proton dose calculation models; namely, the application of the relativistic generalization of the Bragg-Kleeman rule to electrons and, in an appendix, a method to determine inelastic cross-sections of therapeutic protons in media of therapeutic interest.     

Analysis of the rotational spectrum of C3v molecules by using factorization and diagonalization of the energy matrix: Application to CH3C15N

A method is given for the analysis of the rotational spectrum in the ground and excited states of C_3v molecules; it consists in a direct diagonalization of the energy matrix including all elements whose contribution can become significant for the analysis up to the sixth order of approximation.The method of factoring the energy matrix into four submatrices A₁, A₂, E, E, according to the symmetry species of the full point group C_3v, is given. The programm enables the calculation of the rotational frequencies and also carries out by a least-squares method the fitting of the molecular constants for vibrational states v = 0 (ground state) and v_E = 1, 2, 3, and 4, separately or simultaneously over several of these states.The analysis of the rotational spectrum of CH₃C¹⁵N in the v₈ = 0, 1, 2 states is given as an example.     

关于光激射器的线宽

本文从描述光激射器工作的基本方程出发,讨论了光激射器光束线宽的“短期”(short-time)部分。通常都以下式描写这部分线宽:△v_s=(8πhv(△v′)²)/P,(1)其中△v′是谐振腔电磁模的半宽度;v为光束频率;P为输出功率。我们的主要结论可以归结为以下三点:(1)线宽主要是由与电磁模耦合的耗散体系引起的,与分子耦合的耗散体系的贡献是可以忽略的;(2)在单模近似下,只要分子的线宽比电磁模的线宽大得多,则(1)式是正确的;(3)如果多模谐振腔中激发模与其他模之间的相互作用是强的,则式(1)将被推广为 △v_s=(8πhv(△v′)²)/P+(4hv(△v′))/P somefromn=(λ′≠λ)(r_λλ′²/(rλ′),(2) 其中r_λλ′是相关弛豫系数;r_λ′是模λ′的线宽。在某些情况下,式(2)中第二项可以比其第一项还大。所以,这可能是目前关于线宽的实验结果与由式(1)计算结果不相符合的原因之一。