Cd1-xMnxTe混晶的远红外吸收光谱

本文报道4.2—300K和20—400cm^-1范围内不同组份的Cd_1-xMn_xTe混晶远红外声子吸收光谱的研究结果。实验分辨了类CdTe,类MnTe剩余射线带及其TO-LO分裂,首次观察到位于混晶剩余射线吸收区内侧的低频吸收带、低x值情况下的准定域模吸收峰及其两侧的诸双声子吸收带。用缺陷晶格动力学理论估计了准定域模的出现及位置,讨论了其他吸收带的物理起源和判定。 关键词：     

Cd_(1-x)Mn_xTe混晶的远红外吸收光谱

本文报道4.2—300K和20—400cm~(-1)范围内不同组份的Cd_(1-x)Mn_xTe混晶远红外声子吸收光谱的研究结果。实验分辨了类CdTe,类MnTe剩余射线带及其TO-LO分裂,首次观察到位于混晶剩余射线吸收区内侧的低频吸收带、低x值情况下的准定域模吸收峰及其两侧的诸双声子吸收带。用缺陷晶格动力学理论估计了准定域模的出现及位置,讨论了其他吸收带的物理起源和判定。     

CdxHg1-xTe混晶的远红外反射光谱和多振子模型

在温度4.2—300K和波数15—450cm^-1范围内研究了x=0.18到0.45的不同组份的Cd_xHg_1-xTe样品的远红外反射光谱。实验观察到了类CdTe光学声子反射带的精细结构和低组份样品类HgTe反射带的复杂结构,研究了这些结构对组份和温度的关系,并用多振子模型讨论了反射光谱的这种精细结构。对实验反射光谱用经典的振子匹配方法进行了拟合计算,并从这种拟合运算获得了Cd_(x^-)Hg_1-xTe的远红外介电函数谱及其它光学常数和频率的关系。 关键词：     

Hg1-xCdxTe的低频吸收带

本文对Hg_1-xCd_xTe的低频吸收带,提出另一种解释。把Hg_1-xCd_xTe作为具有0—25％Cd(或Hg)替位杂质的HgTe(或CdTe)晶体,用格林函数计算含有一个Cd(或Hg)的HgTe(或CdTe)双原子链振动谱,进而讨论Hg_1-xCd_xTe混晶振动模的特性,结果表明Hg_1-xCd_xTe在k→0存在频率不趋于零的声学声子,它们有条件吸收远红外波段的光子,形成低频吸收带。它能说明已报道的实验上观察到的低频吸收带的主要特征,并表明对光学声子存在双模行为的其它混晶,在远红外吸收谱中很可能存在类似的低频吸收带。 关键词：     

CdxHg1-xTe混晶声子谱的远红外光谱研究

在温度4.2—300K和波数15—5OOcm^-1的范围内研究了x=0.18到0.45的不同组分的Cd_xHg_1-xTe的远红外吸收光谱。除剩余射线吸收带两侧的双声子吸收结构外,实验首次观察到一个位于波数20—50cm^-1的低频吸收带。用面间力常数的密度函数法等估计了Cd_xHg_1-xTe混晶的声子谱,并将上述低频吸收带归之于混晶导致的无序和“掺杂”诱发TA声子带模吸收效应。 关键词：     

Cd_xHg_(1-x)Te混晶的远红外反射光谱和多振子模型

在温度4.2—300K和波数15—450cm~(-1)范围内研究了x=0.18到0.45的不同组份的Cd_xHg_(1-x)Te样品的远红外反射光谱。实验观察到了类CdTe光学声子反射带的精细结构和低组份样品类HgTe反射带的复杂结构,研究了这些结构对组份和温度的关系,并用多振子模型讨论了反射光谱的这种精细结构。 对实验反射光谱用经典的振子匹配方法进行了拟合计算,并从这种拟合运算获得了Cd_(x~-)Hg_(1-x)Te的远红外介电函数谱及其它光学常数和频率的关系。     

Hg_(1-x)Cd_xTe的低频吸收带

本文对Hg_(1-x)Cd_xTe的低频吸收带,提出另一种解释。把Hg_(1-x)Cd_xTe作为具有0—25％Cd(或Hg)替位杂质的HgTe(或CdTe)晶体,用格林函数计算含有一个Cd(或Hg)的HgTe(或CdTe)双原子链振动谱,进而讨论Hg_(1-x)Cd_xTe混晶振动模的特性,结果表明Hg_(1-x)Cd_xTe在k→0存在频率不趋于零的声学声子,它们有条件吸收远红外波段的光子,形成低频吸收带。它能说明已报道的实验上观察到的低频吸收带的主要特征,并表明对光学声子存在双模行为的其它混晶,在远红外吸收谱中很可能存在类似的低频吸收带。     

静压下(CdTe)_2(ZnTe)_4-ZnTe多量子阱结构的多声子共振拉曼散射

用加静高压的方法改变光学能隙来实现共振条件。在以(CdTe)_2(ZnTe)_4短周期超晶格为阱层,(ZnTe)_(4)为垒层的多量子阱结构中观察到高达四阶的类 ZnTe 纵光学声子模的多声子共振拉曼散射。通过对拉曼位移随压力变化的分析,发现在与(CdTe)_2(ZnTe)_4短周期超晶格共振时测得的类ZnTe 纵光学声子模的频率比与 ZnTe 势垒层共振时测得的 ZnTe 纵光学声子模的频率低4cm~(-1)。并将它归结为在短周期超品格中纵光学声子模的限制效应。在与短周期超品格严格的2LO 声子出射共振条件下观察到了类 CdTe 的2LO 声子的共振拉曼峰。     

液相外延GaAs1-xPx混晶的光学声子、等离子体激元和LO声子-等离子体激元耦合模

在40—700cm^-1波数和4.2—300K温度范围内研究了不同组份液相外延n型CaAs_1-xP_x样品的红外反射谱。对反射谱进行了赝谐振子拟合与K-K关系计算。从而获得了有关描述CaAs_1-xP_x样品的光学声子模、等离子体激元、LO声子-等离子体激元耦合模的重要物理参量及红外光学常数信息。基于这些计算结果,提出了双导带谷并计及与X能谷相联系的施主能级模型,用它解释等离子体激元频率和实验观察的三支主要的耦合模的温度变化规律。 关键词：     

聚噻吩中双电子极化子附近的二维局域振动模

将聚噻吩的一维SSH孤子模型推广到二维平面,研究了聚噻吩双电子极化子附近的二维局域振动模.计算结果表明双电子极化子附近存在15个局域振动模,其中4个奇宇称模与4条强红外吸收谱线1020,1120,1200,1323cm^-1相对应,4个偶宇称模恰与4条Raman吸收峰700,1047,1175,1220cm^-1一致. 关键词：     

Far-infrared quasi-local modes of ZnTe in CdTe

We report the very far-infrared absorption spectra of the mixed-crystals Cd_1-xZn_xTe for small x in the temperature range of 4.2K–150K and the wavenumber region of 20cm⁻¹–100cm⁻¹. The quasi-local mode induced by ZnTe in CdTe and CdTe-like 2TA two-phonon creations are observed, to be best of our knowledge, for the first time. The frequencies of the modes are estimated by using the mass-defect model combined with Green's functions calculations. Besides, the temperature dependence of the absorption peak is well explained in the light of the characteristics of the modes.     

Optical constants of silver and copper indium ternary sulfides from infrared reflectivity measurements

Infrared reflection spectra are obtained in the frequency range of 50–2000 cm⁻¹ for AgIn₅S₈ and CuIn₅S₈ single crystals grown by Bridgman method. All four infrared-active modes are detected, which are in full agreement with the prediction of group-theoretical analysis. Spectral dependence of optical parameters; real and imaginary parts of the dielectric function, the function of energy losses, refractive index, absorption index and absorption coefficient were calculated from reflectivity experiments. The frequencies of transverse and longitudinal optical modes and oscillator strengths were also determined. The bands detected in IR spectra of studied crystals were assigned to various vibration types (valence and valence-deformation) on the basis of the symmetrized displacements of atoms obtained employing the Melvin projection operators.     

Raman spectra of Cd1-xMnxTe mixed crystals

Raman spectra of the mixed crystals Cd_1-xMn_xTe have been studied over the composition range 0.1 ≤ × ≤ 0.7. They show the two-mode behavior corresponding to the zone center “CdTe-like” and “MnTe-like” LO-TO modes. In addition, a first-order Raman spectrum is observed which reflects the one-phonon density of states. It is attributed to the presence of both translational and spin-disorder in these mixed crystals. We observe an intense feature of A₁ symmetry, whose peculiar lineshape suggests the occurrence of a Fano type interference between a discrete mode and an overlapping continuum of states.     

The polarized reflection and absorption spectra of perylene crystals in monomeric and dimeric forms

The electronic absorption spectra of perylene crystals in the α- and β-forms were measured by the normal incidence reflection method in the spectral region from 20 000 to 60 000 cm^?1. From the absorption spectrum polarized perpendicular to [1$\text{1}$0] axis of the α-form crystal, the bands around 24 000 cm^?1 were determined to be polarized along the long molecular axis. Two strong bands with different polarizations were observed around 50 000 cm^?1 for each of the α- and β-perylene crystals and were assigned to the transitions to the ¹B_2u and ¹B_3u states. The observed polarized absorption spectra as a whole were consistent with the theoretical results by Hummel and Ruedenberg and the reflection method was found to be suitable to the polarized absorption measurement of strong bands of crystals. The observed factor-group splittings were compared with the theoretical values, the oriented gas model being found to be applicable to the β-form crystal.     

Optical spectra and energy band structure of AgAsS2 crystals

Ground and excited states of three exciton series are observed in the region of fundamental absorption edge of AgAsS₂ crystals. The contours of exciton reflection spectra are calculated and the main parameters of excitons and energy bands are determined in the center of Brillouin zone. The optical reflection spectra are investigated at 30 K in E∥c and E⊥c polarizations in AgAsS₂ crystals in the region of 2-6 eV. The optical functions are calculated from the reflection spectra and a scheme of electronic transitions responsible for peculiarities of reflection spectra deep into the absorption band is proposed.     

Optical absorption behavior of Tl<Superscript>+</Superscript> DOPED Rb(Br<Subscript>1–<Emphasis Type="Italic">x</Emphasis></Subscript>I<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>) system

The optical absorption behavior of Tl⁺ doped Rb(Br_1–x I _x ) mixed crystals (with x = 0.00, 0.05, and 0.10) grown under vacuum by slow cooling from the melt has been studied. Absorption spectra of the mixed crystals recorded at room temperature showed that the characteristic A-absorption band of Tl⁺ ions in the Rb(Br_1–x I _x ) system (0.1 mol. %) with x = 0.00 (i.e., RbBr:Tl⁺) broadened with the iodine content towards the low energy side. Changes in the absorption spectra of the mixed crystals are due to creation of some complex centers involving Tl⁺, Br^–, and I^- ions with energy levels inside the band gap while forming the mixed crystal. The absorption spectra of gamma-irradiated mixed crystals showed the F-band, which shifted towards the low energy side due to the existence of iodine ions in the mixed crystals.     

低温相偏硼酸钡晶体的红外反射光谱

本文报道了新型非线性材料——低温相偏硼酸钡晶体在室温下两种不同偏振成份的红外反射光谱(100—4000cm^-1波段),得到了200cm^-1以上频率范围内振动模的横模和纵模频率。利用“层状分子性结构”模型,参照喇曼光谱实验结果,对该晶体内振动模的归属给出了分析指认。 关键词：