低补偿度n-Hg1-xCdxTe的磁致金属-绝缘体相变和相变后的温度激活输运行为

报道了ｘ＝０．２１４组份、低补偿度（Ｋ《１）ｎ－Ｈｇ_1-xＣｄ_xＴｅ晶体在０．３─３０Ｋ温度范围，０─７Ｔ强磁场下的横向磁阻、电子霍耳迁移率、霍耳系数测量结果，观测到了磁致金属－绝缘体相变和相变后的温度激活输运行为。分析实验数据，提出：低补偿度、组份：ｘ＝０．２附近的ｎ－Ｈｇ_1-xＣｄ_xＴｅ，磁致金属－绝缘体相变（ＭＩＴ）发生的机理是载流子在浅施主杂质态上的磁冻结；发生磁冻结的前提是热冻出（ｔｈｅｒｍａｌ ｆｒｅｅｚｅ 关键词：     

Keldysh-Faisal-Reiss理论的一些改进

提出在Ａ规范下将终态库仑相互作用（即以库仑波函数代替平面波）适当地加进Ｋｅｌｄｙｓｈ-Ｆａｉｓａｌ-Ｒｅｉｓ（缩写为ＫＦＲ）理论的方法，证明这样改进的ＫＦＲ理论有正确的低强度行为，最后与Ｅ规范下的对应结果进行了比较． 关键词：     

稀磁半导体Cd_（1－x）Fe_xTe的磁光光谱

在７０－３００Ｋ温度范围内测量了组分ｘ为０．０１和０．０４的Ｃｄ１－ｘＦｅｘＴｅ及ＣｄＴｅ的法拉第效应随入射光子能量的变化，首次获得了Ｃｄ１－ｘＦｅｘＴｅ在布里渊区Γ点和Ｌ点的有效ｇ因子及其与温度的关系。给出了Ｆｅ２＋离子与载流子间的ｓｐ－ｄ交换作用常数Ｎ０（β－α）＝（－１．５７±０．０３）ｅＶ。     

Femtosecond Spectroscopy on Simple Molecular Systems: Pump-Probe and Cars Techniques

ＦｅｍｔｏｓｅｃｏｎｄＳｐｅｃｔｒｏｓｃｏｐｙｏｎＳｉｍｐｌｅＭｏｌｅｃｕｌａｒＳｙｓｔｅｍｓ：Ｐｕｍｐ┐ＰｒｏｂｅａｎｄＣａｒｓＴｅｃｈｎｉｑｕｅｓＷ．Ｋｉｅｆｅｒ，Ｇ．Ｋｎｏｐｐ，Ａ．Ｍａｔｅｒｎｙ，Ｒ．Ｐａｕｓｃｈ，Ｍ．Ｓｃｈｍｉｔｔ，ａｎｄＨ...     

Te—Se—I玻璃及添加As和Ge元素的结构,性能与量子化学计算研究

用自洽场离散变分Ｘα（ＳＣＦ－Ｘα－ＤＶ）量子化学计算方法研究了Ｔｅ－Ｓｅ－Ｉ玻璃及添加Ａｓ和Ｇｅ元素的体系，讨论了结构、性能与化学键之间的关系。计算表明离子键和共价键强度的次序都是Ｇｅ－Ｓｅ〉Ａｓ－Ｓｅ〉Ｔｅ－Ｓｅ，与相应的玻璃转变温度的实验结果一致。含有一配位碘原子的Ｔｅ－Ｉ键比含有二配位碘原子的Ｔｅ－Ｉ键强。Ａｓ－Ａｓ和Ａｓ－Ｉ键比两类Ｔｅ－Ｉ键都强。较强的Ａｓ－Ａｓ和Ａｓ－Ｉ键取代较弱的Ｔ     

论^6A1基态中Kramers能级的翻转与Hoshina猜想

半导体晶体ＺｎＯ、ＣｄＳ和ＣｄＳｅ具有相似的晶体结构，然而掺入其中的Ｆｅ（Ⅲ）离子却表现出完全不同的基态分裂特征，按顺序ＺｎＯ∶Ｆｅ（Ⅲ）→ＣｄＳ∶Ｆｅ（Ⅲ）→ＣｄＳｅ∶Ｆｅ（Ⅲ）其重要的ＥＰＲ参量Ｄ，将由负值转变成正值，这一变化将导致６Ａ１基态中Ｋｒａｍｅｒｓ能级｜±５／２〉、｜±３／２〉、｜±１／２〉的次序发生翻转。这种奇异的电子能级结构转换现象至１９６７年报道以来迄今未得到合理地解释。Ｈｏｓｈｉｎａ猜想这一现象可能与配位体离子的自旋－轨道耦合系数有关。本文用共价自旋－轨道耦合机制来解释这一能级翻转现象并论证Ｈｏｓｈｉｎａ猜想的正确性     

HgCdTe阳极氧化膜及界面XPS分析

通过电子能谱仪对经阳极氧化表面钝化工艺处理的的ＨｇＣｄＴｅ表面所生成的氧化膜有界面进行深度分析研究，结果表明，该氧化膜中Ｔｅ和Ｃｄ的单质成分存在，氧化膜中的氧化物形式为ＴｅＯ２，ＣｄＴｅ２Ｏ５和ＨｇＴｅ２Ｏ５；在界面中，随着剖析深度的增加Ｔｅ２Ｏ＾２－５，向ＴｅＯ＾２－３过渡。     

2：17型结构Gd—Fe—Co—Ga化合物的结构与磁性

用电弧熔炼的方法制备了Ｇｄ２（Ｆｅ１－ｘＣｏｘ）１５Ｇａ２（０≤ｘ≤１０）和Ｇｄ２（Ｆｅ０８Ｃｏ０２）１７－ｙＧａｙ（０≤ｙ≤８）化合物，通过Ｘ射线衍射和磁性测量手段研究了它们的结构和磁性．实验结果表明它们都是２∶１７型结构的单相化合物．Ｇｄ２（Ｆｅ１－ｘＣｏｘ）１５Ｇａ２的单胞体积Ｖ随Ｃｏ含量的增加单调下降，而居里温度ＴＣ单调上升，１５Ｋ下的饱和磁化强度Ｍｓ随Ｃｏ含量的增加开始时略有增大，在ｘ＝０２时出现极大值，然后单调下降；对Ｇｄ２（Ｆｅ０８Ｃｏ０２）１７－ｙＧａｙ的样品，随Ｇａ含量的增加单胞体积增加，居里温度和饱和磁化强度单调下降．用Ｃｏ替代Ｆｅ，或用Ｇａ替代Ｆｅ和Ｃｏ都能导致Ｆｅ或Ｃｏ次晶格出现室温单轴各向异性，这可能与Ｇａ原子的择优占位有关．     

NiI等电子数序列KrⅨ－RhⅩⅧ原子参数的计算

利用可得到的实验结果，假设能级的实验值与ＨＦＲ方法的计算值之差随有效核电荷的变化可用函数进行最小二乘拟合，对ＫｒⅨ─ＲｈⅧ３ｄ－４ｐ、４ｓ－４ｐ、４ｐ－４ｄ的能级和波长进行计算，并给出各谱线的ＨＦＲ理论振子强度。     

NiI等电子数序列KrⅨ－RhⅩⅧ原子参数的计算

利用可得到的实验结果，假设能级的实验值与ＨＦＲ方法的计算值之差随有效核电荷的变化可用函数进行最小二乘拟合，对ＫｒⅨ─ＲｈⅧ３ｄ－４ｐ、４ｓ－４ｐ、４ｐ－４ｄ的能级和波长进行计算，并给出各谱线的ＨＦＲ理论振子强度。     

Pool-Frenkel thermoelectric modulation of exciton photoluminescence in GaSe crystals

Effect of external field on the exciton photoluminescence of GaSe crystals has been investigated and it has been observed that the PL is quenched with the applied field. The changes observed in the PL spectra have been analyzed with impact exciton, Franz-Keldysh and Pool-Frenkel effects. From the analyses of the experimental data, it has been found that the intensity of direct free, indirect free and bound exciton peaks decreased exponentially with the square root of applied field as I∼exp-β√E. The energy positions of emission peaks were found to shift to longer wavelength with the applied field as ΔE∼β√E. From these findings, the Pool-Frenkel thermoelectric field effect is seen to be the dominant mechanism in the variation of exciton PL with the applied field even though the impact exciton and Franz-Keldysh effects contribute.     

Absorption edge shift: Internal electric field model

The shift of the optical absorption edge caused by defect-induced electric fields through Redfield's internal Franz-Keldysh mechanism is discussed for semiconductors and insulators.     

Influence d'un fort champ electrique statique sur le spectre d'absorption du polyester mylar

Electrical fields induce a shift towards lower frequencies of the absorption spectrum of mylar, this shift, proportional to the square of the field, is three orders of magnitude smaller than a typical Franz-Keldysh effect and is sensitive to the relative orientation of the static field with respect to the polarization vector of the light. We suggest that the measured shift is mostly due to Stark effects in this amorphous material. This kind of measurement could be used to estimate the degree of crystalline order in partially amorphous solids.     

Dislocation-induced shift of the absorption edge in silicon

The optical absorption edge shift in deformed silicon containing a high density of dislocations (N_D ≈ 10¹⁰ ? 10¹¹ cm^?2) is observed at room temperature. This effect is attributed to which fields which affect the absorption edge via the internal Franz-Keldysh mechanism.     

A 125Te and 23Na NMR investigation of the structure and crystallisation of sodium tellurite glasses

125Te static nuclear magnetic resonance (NMR) and 23Na and 125Te magic angle spinning (MAS) NMR have been used, in conjunction with X-ray diffraction, to examine the structure and crystallisation behaviour of glasses of composition xNa2O.(1-x)TeO2 (0.075 x 0.4). The MAS NMR 23Na spectra from the glasses are broad and featureless but shift by approximately +5 ppm with increased x, i.e. as the system becomes more ionic. The static 125Te NMR spectra show an increase in axial symmetry with increasing x, indicating a shift from predominantly [TeO4] to [TeO3] structural units. The 23Na and 125Te spectra from the crystallised samples have been fitted to obtain information on the sites in the metastable crystal phases, which are the first to form on heating and which are therefore more closely related to the glass structure than thermodynamically stable crystal phases. New sodium tellurite phases are reported, including a sodium stabilised, face centred cubic phase related to delta-TeO2; a metastable form of Na2Te4O9 containing 3 sodium and 4 tellurium sites; and a metastable form of Na2Te2O5 containing 2 sodium sites. There is evidence of oxidation of TeIV to TeVI occurring in glasses with high values of x and, at x=0.40 and 0.50 (outside the glass forming range), some sodium metatellurate (Na2TeO4) is formed at the same time as sodium metatellurite (Na2TeO3). The 125Te shift is very sensitive to environment within the sodium tellurite system, covering more than 320 ppm, with anisotropies varying from 640 to 1540 ppm. The lack of features in the 125Te spectra of the glass phases, combined with the large shift range and high but variable anisotropy, means than it is not possible to obtain a unique fit to any presumed species present. Furthermore, the chemical shift anisotropy parameters for three of the four Te sites in the Na2Te4O9 phase are found to lie outside the range used for previous simulations of glass spectra.     

双光子吸收的Franz-Keldysh效应

从实验上证实Hg_0.695Cd_0.305Te 光电二极管空间电荷区中存在双光子吸收的Franz-Keldysh效应.利用一个皮秒Nd:YAG激光器抽运的光学参量产生器和差频产生器作为激发光源,测量了入射波长为λ₀=7.92μm的脉冲激光所激发的光响应随入射光强的变化关系.脉冲光响应峰值强度随入射光强的增大呈现二次幂函数增强趋势.采用等效RC电路模型将脉冲光伏信号峰值与入射光强相关联,得到空间电荷区中强电场下单光束 关键词： Franz-Keldysh效应 碲镉汞 双光子吸收 脉冲光伏信号     

溅射气压对Ge2Sb2Te5薄膜光学常数的影响

实验研究了氩气气压对溅射制备的Ge2 Sb2 Te5 薄膜的光学常数随波长变化的影响 ,结果表明 :随薄膜制备时氩气气压的增加 ,Ge2 Sb2 Te5 薄膜的折射率n先增大后减小 ,而消光系数k先减小后增大。二者都随波长的变化而变化 ,且在长波长范围变化较大 ,短波长范围变化较小 ,解释了溅射气压对Ge2 Sb2 Te5 薄膜的光学常数影响的机理     

Laser-induced above-band-gap transparency in GaAs

We report the observation of large (approximately 40%) laser-induced above-band-gap transparency in GaAs at room temperature. The induced transparency is present only during the pulse width of the driving midinfrared laser pulses and its spectral shape is consistent with a laser-induced blueshift of the band edge. Our simulations based on the dynamic Franz-Keldysh effect reproduce the salient features of the experimental results, demonstrating, in particular, that the amount of the band edge shift is approximately given by the ponderomotive potential.     

Time resolved calorimetry of te films during pulsed laser annealing

Using a pyroelectric thin-film calorimeter the temperature of 30 nm thick Te films during pulsed laser annealing was studied in real-time. A XeCl excimer laser pumped dye laser with Raman shifter was utilized to study the wavelength and energy dependence. No significant wavelength dependence was noticed. Depending on the pulse energy, however, melting, boiling and crystallization of the Te films was observed. These findings support a strictly thermal model for laser annealing and optical recording with Te based media. In addition boiling was identified as the prevalent mechanism for the loss of material.     

Structure and luminescence properties of tellurium(IV) complex compounds

Using the tellurium(IV) complex compounds as an example, we study the interrelation between the geometric structure and spectral luminescence properties. We find that, in the series of compounds of Te(IV), which are characterized by the island octahedral coordination of Te(IV) ions, the luminescence intensity depends on the degree of distortion of the Te(IV) coordination polyhedron, the Stokes shift, and the energy of the luminescence transition. We revealed that the considered series of Te(IV) compounds possess reversible thermochromic properties.