Effects of passivation treatment on the surface stability in indium-doped Hg0.8Cd0.2Te epilayers grown on p-Cd0.96Zn0.04Te substrates

Passivation treatment on indium-doped Hg_0.8Cd_0.2Te epitaxial layers grown on p-Cd_0.96Zn_0.04Te substrates by molecular beam epitaxy has been performed in order to improve the surface stability of the Hg_0.8Cd_0.2Te layers. Room-temperature capacitance–voltage measurements clearly revealed metal-insulator–semiconductor (MIS) behavior for the Al/ZnS/passivated Hg_0.8Cd_0.2Te layer/Cd_0.96Zn_0.04Te diodes. The fast state density and the fixed charge density of the Al/ZnS/passivated Hg_0.8Cd_0.2Te/Cd_0.96Zn_0.04Te diode with a sulfur-treated Hg_0.8Cd_0.2Te layer were smaller than those with a chemically oxidized Hg_0.8Cd_0.2Te layer. The interface state density at the ZnS/sulfur-treated Hg_0.8Cd_0.2Te interface were low at 10¹¹ eV⁻¹ cm⁻² at the middle of the Hg_0.8Cd_0.2Te energy gap. These results indicate that the Hg_0.8Cd_0.2Te epilayer is significantly passivated by sulfur treatment and that the passivated Hg_0.8Cd_0.2Te layers can be used for Hg_1−xCd_xTe-based MIS diodes and MIS field-effect transistors.     

湖北网湖^137Cs、^210Pb计年与沉积速率研究

采用放射性核素^137Cs和^210Pb计年法测定百年来湖北网湖沉积物的年代，据此计算出网湖的沉积速率．结果表明：2种计年方法测得的沉积速率基本一致，以1954年和1963年为时标，^137Cs测得的沉积速率分别为0．594cm·a^-1和0．557cm·a^-1。^210Pb计年法CIC模式计算得到网湖平均沉积速率为0．56cm·a^-1．CRS模式得到百年来网湖沉积速率变化较大，20世纪50年代以前，平均沉积速率为0．2cm·a^-1左右；50年代至80年代中期，平均沉积速率上了一个台阶，约为0．4cm·a^-1；80年代中期以后平均沉积速率攀升至约0．6cm·a^-1，网湖沉积速率变化与湖区自然环境的改变和人类活动的影响密切相关．     

N235—混合醇萃取分离稀土中的铁和铅

随着稀土在荧光和激光材料等领域的应用,对稀土纯度的要求越来越高,尤其是对非稀土杂质的含量要求越来越低。对稀土中非稀土杂质的分离去除,已有许多研究报导[1-3]。多是利用萃取剂对稀土和非稀土杂质的萃取能力不同而达到去除目的。分离因素较小,萃取级数都在20多级以上?..     

A study of the electron quenching of excimers in a KrF* laser excited by a coaxial electron beam

Measurements of the output energy, the optical pulse length and the build-up time of the laser pulse, obtained with a coaxially e-beam pumped KrF^* laser, were performed varying the total gas fill pressure, the F₂ content and the e-beam current from 1–5 bar, 0.1–0.8% and 13.3–26.6 kA, respectively. The maximum specific extraction energy amounts to 64 J/l. The large range of measurements, especially at low F₂ concentrations, reveals the necessity to extend the kinetics of the F₂ chain in the usual computer model. With the introduction of electron quenching of KrF^* and ArF^* by dissociative attachment the predictions are also for low F₂ concentration in agreement with experiments.     

Bi induced step-flow growth in the homoepitaxial growth of Au(1 1 1)

Homoepitaxial growth of Au on Bi-covered Au(1 1 1) was studied at room temperature using reflection high-energy electron diffraction (RHEED) and Auger electron spectroscopy (AES). From observations of RHEED it is found that the Au(1 1 1) (23 × 1) reconstruction structure changes to a (1 × 1) by about 0.16-0.5 ML deposition of Bi and to a (2√3 × 2√3)R30° by about 1.0 ML deposition of Bi, respectively. The surface morphology evolution by Bi deposition leads to a change of Au homoepitaxial growth behavior from layer-by-layer to step flow. This indicates that the surface diffusion distance of Au atoms on the Bi-precovered (1 × 1) and (2√3 × 2√3)R30° surfaces is longer than that on the Au(1 1 1) (23 × 1) clean surfaces. A strong surface segregation of Bi was found at top of surface. It is concluded that Bi atoms acted as an effective surfactant in the Au homoepitaxial growth by promoting Au intralayer mass transport.     

Core level spectroscopy and RHEED analysis of KGd(WO4)2 surface

Structural and electronic characterisation of mechanically polished (010) KGd(WO₄)₂ (KGW) has been produced by reflection high-energy electron diffraction (RHEED) and X-ray photoelectron spectroscopy (XPS). With XPS analysis the original element binding energies, chemical composition and valence band structure of KGW have been determined.     

Effects of diffraction conditions and processes on rheed intensity oscillations during the MBE growth of GaAs

The RHEED intensity oscillation technique has received wide-spread attention for the study of MBE growth dynamics, but insufficient consideration has been given to the diffraction conditions and processes involved. We report here a systematic investigation of the intensity oscillation behaviour as a function of diffraction parameters (azimuth, incidence angle, specular and non-specular beams), with constant growth conditions for GaAs films on GaAs (001) substrates.We show that many reported anomalies attributed to growth effects, such as phase differences and periodicity variations, can be accounted for entirely by diffraction events, provided it is realised that multiple scattering processes are the dominant cause of RHEED intensity variations during growth.The technique can provide valuable information on growth behaviour, but only if diffraction-dependent effects are first eliminated.     

Phase analysis of TaN/Ta barrier layers in sub-micrometer trench structures for Cu interconnects

The resistance behavior of TaN/Ta diffusion barrier bilayers has been investigated. The dependence of the Ta-phase on the TaN layer thickness was examined by means of X-ray micro-diffraction and resistivity measurements. Furthermore, the influence of the geometry of a damascene trench structure on the Ta-phase of the deposited TaN/Ta barrier bilayers has been studied and compared to the results obtained with blanket wafers. The influence of the Ta-phase on the via resistance of Cu interconnects is discussed.