不同氮流量制备Mn3CuNx薄膜及其电、磁输运性质的研究

采用对靶磁控溅射方法在单晶Si(100)基片上制备了反钙钛矿结构的Mn₃CuN_x薄膜.通过控制制备过程中的反应气体氮气(N₂) 流量(N₂/Ar+N₂), 研究了氮含量对Mn₃CuN_x薄膜结构及物理性能的影响.分别利用X射线衍射仪、俄歇电子能谱、 原子力显微镜、X射线光电子能谱、物理性能测试系统和超导量子干涉仪, 对所制备薄膜的晶体结构、成分、表面形貌和电、磁输运性质进行了测试.结果表明:制备的薄膜均为反钙钛矿立方结构,且沿 (200) 晶面择优生长.随着氮含量的增大,薄膜表面粗糙度和颗粒度尺寸逐渐增大, 导致电阻率增加.氮含量对薄膜的电输运性质没有影响,所有薄膜电阻率均随着温度的降低逐渐增大, 呈现半导体型导电行为,这与对应的块体材料结果相反.Mn₃CuN_x薄膜随着测试温度的增大发生了 亚铁磁到顺磁的磁转变,且N含量的增大降低了磁有序转变温度,主要是由于N缺陷对Mn₆N八面体结构中 磁交换作用的影响所致.     

不同氧气流量对直流磁控溅射TiO2薄膜的影响

采用直流反应磁控溅射法,以高纯Ti为靶材,高纯O₂为反应气体,制备了TiO₂薄膜.研究了氧气流量对薄膜结晶取向、表面形貌和光学性能的影响.研究发现,TiO₂薄膜主要呈锐钛矿TiO₂(101)择优取向,当氧气流量较小时,薄膜中还含有金属Ti(100),氧气流量较大时,薄膜含TiO₂(101)和TiO₂(004),成多晶态;薄膜的粗糙度和颗粒大小都随氧气流量的增大而增大;薄膜在400~1100nm可见-近红外波段有较高的透射率并且其吸收峰随着氧气流量的增大而红移,当氧气流量为5sccm时,平均透射率最高.     

ECR-PECVD制备Si3N4薄膜的光学特性研究

本文研究了ECR-PECVD制备的Si₃N₄薄膜的光学特性.得到的Si₃N₄薄膜具有光致发光效应,在280℃沉积制备的Si₃N₄薄膜的光致发光波长为400nm,具有较好的单色性.测试分析了Si₃N₄薄膜对可见光、红外光具有较高的透射性能,Si₃N₄薄膜可作为红外光的增速减反射膜.     

γ-Si3N4在高压下的电子结构和物理性质研究

采用基于密度泛函平面波赝势方法(PWP)和广义梯度近似(GGA-PW91)，计算了不同压强下γ-Si₃N₄的电子结构、光学性质和力学性质.基于计算结果，分析讨论了γ-Si₃N₄各物理参数随外压力的变化规律.计算表明，γ-Si₃N₄是一种适合于在高压条件下工作的材料.     

a-C∶H(N)薄膜结构的X射线光电子能谱分析

采用直流-射频等离子增强化学汽相沉积技术制备a-C∶H(N)薄膜，用X射线光电子能谱研究了混合气体中N₂含量对薄膜成分与结构的影响.a-C∶H(N)薄膜中含氮量可达9.09%.对a-C∶H(N)薄膜的C1s和N1s结合能谱的分析表明a-C∶H(N)薄膜的结构是由C₃N₄相镶嵌在sp²键结合的CN_x基体中组成.其中C₃N₄相中N和C原子比接近4∶3，不随薄     

正态电子偶素衰变率的实验研究

本文提出用外推N_2γ/N_3γ→0的方法测正态电子偶素的真空衰率λ₀,初步结果得到λ₀=7.034±0.013μs^－1,讨论了进一步改进实验的可能性.     

紫外波段SiO2/Si3N4介质膜分布式布拉格反射镜的制备与研究

采用光学传递矩阵方法设计了紫外波段SiO₂/Si₃N₄介质膜分布式布拉格反射镜, 并利用等离子体增强化学气相沉积技术在蓝宝石(0001)衬底上制备了SiO₂/Si₃N₄介质膜分布式布拉格反射镜. 光反射测试表明, 样品反射谱的峰值波长仅与理论模拟谱线相差10 nm, 并随着反射镜周期数的增加而蓝移. 由于SiO₂与Si₃N₄具有相对较大的折射率比, 因而制备的周期数为13的样品反射谱的峰值反射率就已大于99%. 样品反射谱的中心波长为333 nm, 谱峰的半高宽为58 nm. 样品截面的扫描电子显微镜和表面的原子力显微镜测量结果表明, 样品反射谱的中心波长蓝移是由子层的层厚和界面粗糙度的变化引起的. X射线反射谱表明,子层界面过渡层对于反射率的影响较小, 并且SiO₂膜的质量比Si₃N₄差, 也是造成反射率低于理论值的原因之一.     

第Ⅱ种强度不等的非对称两态叠加多模叠加态光场的偶数阶等阶N次方Y压缩

本文构造了由多模复共轭相干态的相反态|{-Z_j^(a)*}>_q与多模虚共轭相干态的相反态|{-iZ_j^(b)*}>_q这两者的线性叠加所组成的第Ⅱ种强度不等的非对称两态叠加多模叠加态光场|Ψ_Ⅱ^(ab)>_q,利用多模压缩态理论研究了态|Ψ_Ⅱ^(ab)>_q的任意偶数阶等阶N次方Y压缩特性.结果发现:1)在压缩阶数N取偶数,即N=2p的条件下,无论p=2m(m=1,2,3,…,…),还是p=2m+1(m=0,1,2,3,…,…),只要构成态|Ψ_Ⅱ^(ab)>_q的两个不同的量子光场态中各对应模的强度(即平均光子数)和初始相位都不相等,亦即R_j^(a)≠R_j^(b)和φ_j^(a)≠φ_j^(b)(j=1,2,3,…,q),并且 ,则当满足一定的量子化条件(或者在一些闭区间内连续取值)时,态|Ψ_Ⅱ^(ab)>_q总可呈现出周期性变化的、任意偶数阶的等阶N次方Y压缩效应.2)在N=2p且p=2m+1(m=0,1,2,3,…,…)的条件下,若R_j^(a)=R_j^(b)和φ_j^(a)=φ_j^(b)(j=1,2,3,…,q),态|Ψ_Ⅱ^(ab)>_q则可呈现出等阶N次方Y压缩简并现象.     

退火温度对N+注入ZnO:Mn薄膜结构及室温铁磁性的影响

采用射频磁控溅射法在石英玻璃衬底上制备了ZnO:Mn薄膜, 结合N⁺ 注入获得Mn-N共掺ZnO薄膜, 进而研究了退火温度对其结构及室温铁磁性的影响. 结果表明, 退火后ZnO:(Mn, N) 薄膜中Mn²⁺和N^3-均处于ZnO晶格位, 没有杂质相生成. 退火温度的升高 有助于修复N⁺注入引起的晶格损伤, 同时也会让N逸出薄膜, 导致受主(N_O)浓度降低. 室温铁磁性存在于ZnO:(Mn, N)薄膜中, 其强弱受N_O浓度的影响, 铁磁性起源可采用束缚磁极化子模型进行解释.     

CO2激光器五种混合气体压强优化

 应用遗传算法,以输出激光功率为目标函数,优化确定了普通CO₂激光器五种工作气体（CO₂, N₂, He, Xe, H₂）的最佳充气量。对1.2m长谐振腔,在15kV放电条件下,优化的充气量分别为p_CO2=1.15×133.3Pa, p_N2=7.32×133.3Pa, p_He=12.95×133.3Pa, p_Xe=0.36×133.3Pa和p_H2=0.01×133.3Pa。优化后激光功率比未优化前可提高1.27倍。     

Chiral perturbation theory for fDS/FD and BBS/BB

The decay constants for D and D_s mesons, denoted f_D and f_DS respectively, are equal in the SU(3)_V limit, as are the hadronic amplitudes for and mixing. The leading SU(3)_V violating contribution to (F_DS/F_D) and to the ration of hadronic matrix elements relevant for and mixing amplitudes are calculated in chiral perturbatiion theory. We discuss the formalism needed to include both meson and anti-meson fields in the heavy quark effective theory.     

Near-infrared bands of S2: 3Πgi-3Σu+ system

Vibrational and rotational analyses of the near-infrared bands of S₂ lying in the region 7440–8085 Å are reported. They form a new band system involving a ${}^3\text{Π}{}_{\mathrm{gi}}\text{-}{}^3\text{Σ}{}_{\mathrm{u}}{}^{\mathrm{+}}$ transition and arise from the same initial ³Π_gi state of the ³Π_gi-³Δ_ui band system reported earlier. The analyses of the bands of this system due to the isotopic molecules ³²S³⁴S and ³⁴S₂ are also reported.     

Magnetism in nanometer-thick TiOx/Co/TiOx/TiN/Si multilayered structures

Most studies on Co-doped TiO₂ system were focused on thin films grown by MBE-based methods. In this work we report the ferromagnetism of nanometer-thick-layered TiO₂/Co/TiO₂/TiN film grown on Si substrate by conventional magnetron sputtering. For the growth of TiO₂ on silicon, a non-oxide thermally stable material, TiN, was introduced to prevent Ti penetration into the Si substrate. Structural, magnetic, and transport measurements respectively by Raman, SQUID and Hall effect show that our samples are n-type semiconductors and exchange bias effect due to exchange coupling between Co and interfacial CoO. For the rapid vacuum annealed specimen, we found an enhanced loss and a Perminvar-type constricted hysteresis loop, which attributed to pinning of domain walls due to an induced anisotropy by the pair ordering in the metallic alloy of Co-Ti-Si.     

Spinor techniques for calculating pp → W±/Z0 + jets

We present techniques which enable one to calculate quickly the amplitudes for many scattering processes in the high-energy limit. As an illustration of the method, these are applied to the diagrams for $\text{p}\text{p}\text{→}\text{V}\text{+ 0, 1}\text{or}\text{2}\text{jets}$, where V = W^± or Z⁰. The form of the results lends itself to immediate numerical evaluation.     

Electrical property of HfOxNy-HfO2-HfOxNy sandwich-stack films

The effects of HfO_xN_y on the electrical property of HfO_xN_y-HfO₂-HfO_xN_y sandwich-stack (signed as SS) films were investigated. Excellent electrical performances were achieved in SS films, with a high dielectric constant of 16 and a low leakage current of ∼2 × 10⁻⁸ A/cm² at 1 MV/cm. Schottky (SK) emission and Frenkel-Poole (PF) emission are found to be the dominant mechanisms for the current conduction behavior. After a long time stress, the flat-band voltage shift in the SS film is much smaller than that in a pure HfO_xN_y film indicating fewer charge traps existed in the SS film. Based on the experiments, the new SS structure is more favorable for the improvement of electrical performances than a pure HfO_xN_y or HfO₂ structure.     

The decay process 11ΛB → π− + 11C

The branching ratios are calculated for ¹¹_ΛB decay to the ¹¹C ground and excited states below 8 MeV for two possible spin values of ¹¹_ΛB. It is found that the decay rate to the ¹¹C^★ state at E^★ = 6.48 MeV is comparable in magnitude to that leading to the ¹¹C ground state if $\text{J(}{}^{11}{}_{\mathrm{\Lambda }}\text{B}\text{) =}\text{5}\text{2}$ is assumed. This result, unlike the branching ratios calculated for the $\text{J(}{}^{11}{}_{\mathrm{\Lambda }}\text{B}\text{) =}\text{7}\text{2}$ case, is in accord with experiment and lends support to the assumption that $\text{J =}\text{5}\text{2}$ holds for ¹¹_ΛB. The necessity of the reinterpretation of some of the so-called ¹³_ΛC events in terms of ${}^{11}{}_{\mathrm{\Lambda }}\text{B}\text{→ π}{}^{\mathrm{?}}\text{+}{}^{11}\text{C}{}^1$ is indicated.     

E.P.R. in GdxCeyLa1−x−yBe13 and GdxCe−xBe13 intermetallics with high electron lattice relaxation

The bottleneck effect arising in the electron paramagnetic resonance of Gd in GdBe₁₃ and Gd_xCe_-xBe₁₃ with x ? 0.001 is removed by additions of CeBe₁₃ which displays a high electron lattice relaxation rate, tentatively attributed to an interconfiguration fluctuation of the 4f electron of Ce.     

The decay processes Λ8Li → π− + 8Be1 (∼ 17 MeV)

The branching ratio is calculated for _Λ⁸Li decay to the (2⁺) ⁸Be¹ states near 17 MeV, using intermediate coupling wave functions for _Λ⁸Li and for the relevant ⁸Be¹ states. It is pointed out that this ratio is sensitive primarily to a mixing angle ? in the _Λ⁸Li wave function. Within one standard deviation, the data allow two ranges (+0.05 to +0.25 rad and +1.10 to +1.25 rad) for the value of ?. The further requirement that there also be acceptable agreement between the angular distribution expected for the subsequent ${}^8\text{Be}{}^1\text{(? 17}\text{MeV → 2}{}^4\text{He}$ decay and the data, shifts these allowed ranges for ?, to (+0.13 to 0.40) rad and (+0.9 to +1.2) rad. It is predicted that the dominant transition should be to ⁸Be¹ (16.6 MeV), as is observed to be the case, rather than to ⁸Be¹ (16.9 MeV). The interpretation of these values for ? is discussed in some detail and their implications for intermediate coupling shell-model calculations of Λ-hypernuclear wave functions are considered.     

The 5T2g → 5Eg absorption in MgO: Fe2+

At helium temperatures two sharp lines at 9350 and 9510 cm^?1 have been observed for the first tune on the low-energy side of the broad double-peaked absorption corresponding to the ${}^5\text{T}{}_{\mathrm{2g}}\text{→}{}^5\text{E}{}_{\mathrm{g}}$ transition in Fe²⁺ at the octahedral site in MgO. The lower energy line has a half width of 4 cm^?1; Zeeman measurements show that it is of magnetic dipole origin. The Zeeman spectra are consistent with those expected for a pure electronic transition from the (⁵T_2g)T_2g ground state to the ⁵E_g excited state. The second line, with a halfwidth of ~ 35 cm^?1, a vibrational sideband.     

Lifetimes and Franck-Condon factors for the B1Πu → X1Σg+ system of Na2

Lifetimes of 24 different levels (v′, J′) in the B¹Π_u state of Na₂ have been measured with an accuracy of about 1% using a modelocked Ar⁺ laser and a modified delayed coincidence single-photon counting technique. With these lifetimes, the variation of the transition moment R(r) with internuclear distance r has been determined. The necessary Franck-Condon factors and r centroids have been calculated from spectroscopic data obtained by previous interferometric measurements of laser-induced fluorescence. The squared transition moment |R(r)|² increases between $\text{r = 2.5}\text{A}\text{?}$ and $\text{r = 6}\text{A}\text{?}$ by about 30%. Our measurements confirm the results of M. M. Hessel, E. W. Smith, and R. E. Drullinger, who used intensity measurements of Na₂ fluorescence lines for the determination of R(r).