X-ray sensitivity of Cd0.9Zn0.1Te detectors

The X-ray sensitivity of Cd_0.9Zn_0.1Te detectors as a function of the effective X-ray energy and bias voltage is studied. It is shown that the sensitivity grows with effective X-ray energy and much more significantly with bias voltage. The sensitivity depends on the angle the X-ray beam makes with an electric field in the detector. In the energy range 28–72 keV, the sensitivity is the highest when the X-ray beam is normal to the electric field in the detector.     

Cd0.9Zn0.1Te晶体的Cd气氛扩散热处理研究

将生长得到的Cd0.9Zn0.1Te晶体在Cd气氛下及不同的温度条件下进行了退火处理. 借助已建立的退火处理过程中Cd1-xZnxTe晶体材料电阻率及导电类型变化和扩散杂质的扩散系数之间关系的模型,结合实验数据,获得了1073 K,973 K和873 K下Cd在Cd0.9Zn0.1Te晶体中的扩散系数,并估算了其激活能. 通过使用获得的扩散系数,研究了在不同温度及饱和Cd气氛下,退火时间对Cd0.9Zn0.1Te晶体电阻率分布及导电类型等的变化的影响.     

Performance of Cd0.9Zn0.1Te X-ray detectors versus the purity of initial components

X-ray detectors made of Cd_0.9Zn_0.1Te single crystals are studied. Starting components (Cd, Zn, Te) are obtained by multistage volume distillation. Synthesized CdZnTe is finally purified by continuous vacuum sublimation. Detectors highly sensitive to X rays are produced.     

Localization of exciton excitation in planar structures Cd0.9Mn0.1Te/Cd0.7Mg0.3Te

The spectra of exciton emission in a series of periodic structures with ultrathin Cd_0.9Mn_0.1Te inclusions in the Cd_0.7Mg_0.3Te matrix have been studied. The complex structure of the luminescence spectra and their relation to the luminescence excitation spectra indicate large-scale fluctuations in thickness of narrow-band-gap layers. Two types of temperature dependences of the luminescence intensity of localized excitons are found: (1) the complete suppression of emission above 80 K and (2) the relative enhancement of temperature-insensitive low-energy band that corresponds to local bulges in planar Cd_0.9Mn_0.1Te layers.     

XPS and SRUPS study of oxygen adsorption on Cd0.9Zn0.1Te (1 1 1)A surface

Synchrotron radiation ultraviolet photoemission spectroscopy (SRUPS) and X-ray photoelectron spectroscopy (XPS) have been applied to investigate oxygen adsorption on a cadmium zinc telluride (CZT) (1 1 1)A surface. The surface chemical composition and the surface oxidation process were monitored by recording the Te 3d, O 1s, Zn 2p, Cd 4d core level peaks, and the Cd MNN Auger peak. The CZT (1 1 1)A surface was effectively oxidized by dosing oxygen directly. The typical surface state of the clean CZT (1 1 1)A surface was identified. After oxygen exposure, this surface state disappeared and a signal due to the formation of O–CZT appeared. In addition, the work function of CZT decreased with the increasing oxygen exposure.     

Fine structure of the cubic semiconductor compound Zn0.9Ni0.1S

The fine structure of a single crystal of the Zn_0.9Ni_0.1S cubic compound synthesized by the chemical transport method has been investigated at room temperature using thermal neutron diffraction. It has been found that the diffraction patterns of this compound, along with strong Bragg reflections of the facecentered cubic phase, include a system of diffuse maxima, which indicate the occurrence of a local deformation of the cubic structure by the Jahn-Teller nickel ions. Results of this experiment have been compared with the previously obtained data for the lightly doped Zn_{1 ? x} Ni _x Se single crystal (x = 0.002).     

Optical,structural and magnetic properties of Zn0.9Cd0.1S:yCo nanoparticles

Zn_0.9Cd_0.1S:yCo nanoparticles were prepared by a co-precipitation method at low temperature. The obtained products were identified to be of cubic structure without any impurity phase. Cobalt incorporation leads to an increase in the local strain value and a decrease in the lattice constants as measured from XRD. Magnetic measurements showed that cobalt was incorporated in the Zn_0.9Cd_0.1S lattice as Co²⁺ and substituted for the Zn site as there was no evidence of the presence of metallic cobalt. Transmission electron microscopy suggests the crystalline nature of nanoparticles, with average particle size of ∼3.5 nm. UV-Vis measurements showed a red shift with respect to undoped nanoparticles in energy band gap with increasing cobalt concentration. Photoluminescence spectra reveal the defect-related emissions. The decay time constant is found to be in the nanosecond regime and is attributed to the spatial confinement of photo generated electron–hole pairs.     

The effect of hydrogen on the electrical properties of n-type Pb0.9Cd0.1Te thin films

Measurements of the Hall coefficient and the d.c. conductivity were made on flash evaporated n-type Pb_0.9Cd_0.1Te epitaxial films exposed to molecular hydrogen gas at high pressures (upto 500 psi) in the temperature range 77–300 K. It has been found that the effect of hydrogen on the films is to reduce the concentration of the extrinsic carriers and to increase their mobility. It is believed that hydrogen gas removes cadmium ions and neutral cadmium atoms from these films.     

Fabrication and electrical characterization of Au/p-Si/STO/Au contact

Au/STO/p-Si/Au structure is fabricated using pulsed laser deposition technique at room temperature. The current–voltage (I–V) characteristics of the device show rectification behavior. Various junction parameters such as ideality factor, barrier height and series resistance is determined using conventional forward bias I–V characteristics, Cheung method and Norde’s function. Au/STO/p-Si/Au structure shows non-ideal diode characteristics with the value of ideality factor of ∼5.1 and barrier height of ∼0.40 eV.     

Influence of Cu doping on the microstructure,optical properties and photoluminescence features of Cd0.9Zn0.1S nanoparticles

Cd_0.9−xZn_0.1Cu_xS (0≤x≤0.06) nanoparticles were successfully synthesized by a conventional chemical co-precipitation method at room temperature. Crystalline phases and optical absorption of the nanoparticles have been studied by X-ray diffraction (XRD) and UV–visible spectrophotometer. XRD confirms the phase singularity of the synthesized material, which also confirmed the formation of Cd–Zn–Cu–S alloy nanocrystals rather than separate nucleation or phase formation. Elemental composition was examined by the energy dispersive X-ray analysis and the microstructure was examined by scanning electron microscope. The blue shift of absorption edge below Cu=2% is responsible for dominance of Cu⁺ while at higher Cu concentration dominated Cu²⁺, d–d transition may exist. It is suggested that the addition of third metal ion (Cu²⁺/Cu⁺) is an effective way to improve the optical property and stability of the Cd_0.9Zn_0.1S solid solutions. When Cu is introduced, stretching of Cd–Zn–Cu–S bond is shifted lower wave number side from 678 cm⁻¹ (Cu=0%) to 671 cm⁻¹ (Cu=6%) due to the presence of Cu in Cd–Zn–S lattice and also the size effect. The variation in blue band emission peak from 456 nm (∼2.72 eV) to 482 nm (∼2.58 eV) by Cu-doping is corresponding to the inter-band radiation combination of photo-generated electrons and holes. Intensity of red band emission centered at 656 nm significantly increased up to Cu=4%; beyond 4% it is decreased due to the quenching of Cu concentration.     

The effect of oxygen stoichiometry on electrical transport and magnetic properties of La0.9Te0.1MnOy

The effect of the variation of oxygen content on structural, magnetic and transport properties in the electron-doped manganites La_0.9Te_0.1MnO_y has been investigated. All samples show a rhombohedral structure with the space group The Curie temperature T_C decreases and the paramagnetic-ferromagnetic (PM-FM) transition becomes broader with the reduction of oxygen content. The resistivity of the annealed samples increases slightly with a small reduction of oxygen content. Further reduction in the oxygen content, the resistivity maximum increases by six orders of magnitude compared with that of the as-prepared sample, and the ρ(T) curves of samples with y=2.86 and y=2.83 display the semiconducting behavior (dρ/dT<0) in both high-temperature PM phase and low-temperature FM phase, which is considered to be related to the appearance of superexchange ferromagnetism and the localization of carriers. The results are discussed in terms of the combined effects of the increase in the Mn²⁺/(Mn²⁺+Mn³⁺) ratio, the partial destruction of double exchange interaction, and the localization of carriers due to the introduction of oxygen vacancies in the Mn-O-Mn network.     

Effects of crystallinity on laser-induced voltage effect from Zn0.9Co0.1O thin film

Co-doped ZnO epilayer films were grown by pulsed laser deposition (PLD) on vicinal cut silicon and sapphire substrates. Changes in deposition time were observed as a moderate effect on the quality of the films, and the influence of the thickness on thermoelectric signals from Zn_0.9Co_0.1O thin films were discussed. The effect of one of the main deposition parameters, the deposition time, on the crystallinity and electron mobility properties of the Zn_0.9Co_0.1O thin films grown on sapphire was investigated by means of X-ray diffraction (XRD) and laser-induced voltage (LIV) effect. It shown that the XRD rocking curve full-width half-maximun (FWHM) decreased as time increasing, and the LIV signals were observed along the tilting angle of the substrate orientation when the pulsed KrF excimer laser of 248 nm were irradiated on the films. When the films illuminated in pulse lasers, the highest signals occurred in the films with best crystalline quality, and the signals were higher in the films grown on sapphire than those on silicon substrates. It suggested that the electrical resistivity and electron mobility have close relations with not only the crystallinity but also with the interface of the thin films.     

The effect of grain size on electrical transport and magnetic properties of La0.9Te0.1MnO3

The effect of grain size on structural, magnetic and transport properties in electron-doped manganites La_0.9Te_0.1MnO₃ has been investigated. All samples show a rhombohedral structure with the space group at room temperature. The Mn-O-Mn bond angle decreases and the Mn-O bond length increases with the increase of grain size. All samples undergo paramagnetic (PM)-ferromagnetic (FM) phase transitions and the interesting phenomenon that both magnetization and the Curie temperature T_C decrease with increasing grain size is observed, which is suggested to mainly originate from the increase of the Mn-O bond length d_Mn-O. Additionally, ρ obviously increases with decreasing grain size due to the increase of both the height and width of tunneling barriers with decreasing grain size. The results indicate that both the intrinsic colossal magnetoresistance and the extrinsic interfacial magnetoresistance can be effectively tuned in La_0.9Te_0.1MnO₃ by changing grain size.     

基于Marangoni界面效应的数控化学抛光去除函数的研究

利用基于Marangoni界面效应对化学抛光去除函数的理论及实验进行研究,提出采用湿法化学抛光（刻蚀）方法为大口径高精度光学元件的加工提供新的解决途径。介绍了Marangoni界面效应及其验证实验,运用WYKO轮廓仪对熔石英基片局域刻蚀前后的粗糙度进行检测,结果表明,粗糙度基本无变化,刻蚀前后粗糙度分别为0.72 nm和0.71 nm。基于Preston假设, 建立了数控化学抛光理论模型,运用WYKO干涉仪观察实验现象可知,化学抛光刻蚀曲线基本上成平底陡峭的去除函数曲线,小磨头抛光是倒置的仿高斯函数曲线。     

基于Marangoni界面效应的数控化学抛光去除函数的研究

 利用基于Marangoni界面效应对化学抛光去除函数的理论及实验进行研究,提出采用湿法化学抛光（刻蚀）方法为大口径高精度光学元件的加工提供新的解决途径。介绍了Marangoni界面效应及其验证实验,运用WYKO轮廓仪对熔石英基片局域刻蚀前后的粗糙度进行检测,结果表明,粗糙度基本无变化,刻蚀前后粗糙度分别为0.72 nm和0.71 nm。基于Preston假设, 建立了数控化学抛光理论模型,运用WYKO干涉仪观察实验现象可知,化学抛光刻蚀曲线基本上成平底陡峭的去除函数曲线,小磨头抛光是倒置的仿高斯函数曲线。     

Effect of Zn substitution on the electrical properties of Bi2Co0.1V0.9O5.35 synthesized by sol-gel method

Samples of Bi₂V_0.9Co_0.1-xZn_xO_5.35, 0.02 ≤ x ≤ 0.08 with layered Aurivillius structure were synthesized successfully by sol-gel citrate method. Structural and electrical characterization of compositions has been investigated by X-ray diffraction, thermogravimetric analysis–differential scanning calorimetric (TGA–DSC) analysis and AC impedance spectroscopy. The tetragonal γ phase has been observed for all investigated samples. The AC impedance response of samples has been measured in the frequency range of 20 Hz to 1 MHz. The impedance for pellets decreases as thermal energy increases. The contribution of grain to the conduction process is more than that of grain boundary. The ionic conductivity and dielectric permittivity are found to be composition-dependent and increase with increasing Zn concentration. The maximum electrical conductivity observed for the composition x = 0.08 is σ = 4.51 × 10^?4 S cm^?1 at 300 °C.     

High pressure effect on the crystal and magnetic structure of Pr0.1Sr0.9MnO3 manganite

The crystal and magnetic structure of Pr_0.1Sr_0.9MnO₃ manganite has been studied by the neutron diffraction at high pressures up to 5 GPa in the temperature range 10?C295 K. At normal pressure and decreasing temperature the appearance of the C-type (T _N = 220 K) and G-type (T _N = 180 K) antiferromagnetic states occurs, which is accompanied by a structural phase transition from the cubic structure (Pm $ \bar 3 $ m space group) to the tetragonal structure (I4/mcm space group). It is shown that the temperature of the transition to the C-type antiferromagnetic phase increases with pressure with the pressure coefficient dT _N/dP = 4.0(5) K/GPa and the temperature of the transition to the G-type antiferromagnetic phase weakly depends on pressure.     

Magnetic and electrical transport properties in the self-doped manganite La0.9Mn0.9M0.1O3 (M=Mn,Zn and Ti)

The magnetic and electrical transport properties of La_0.9Mn_0.9M_0.1O₃ (M=Mn, Zn and Ti) were investigated. The temperature and magnetic field dependence of electrical resistivity (ρ) and dc magnetization were studied. All the compounds are found in rhombohedral structure. The excess oxygen in all three compounds was detected through iodometric titration. A modification in resistivity is observed when M=Mn is replaced by M=Zn and Ti. The high temperature resistivity above T_C follow variable range hopping model for both Zn and Ti compounds. For Zn doping, the observation of large field-cool effect and decrease in resistivity at room temperature and is assumed to be due to the implant of Mn⁴⁺ in Mn³⁺ matrix, which favor Mn³⁺/Mn⁴⁺ double exchange. The ferromagnetic behavior below T_C for the compound with M=Ti is correlated to the excess oxygen in it, which implants Mn⁴⁺ and thus incorporates ferromagnetic interactions. The substitutions lead to a reduction of T_c and magnetization.