The optoelectronic properties of CdSe:Cu photoconductive detector

Photoconductive CdSe doped with (1–5 wt%) of Cu was fabricated using the vacuum evaporation technique for thin-film preparation followed by vacuum annealing at 350°C under an argon environment for doping with copper. The electrical and detection properties as a function of Cu content were studied. It was found that the gain coefficient was increased with an increase in the Cu impurity concentration and better results were obtained for a CdSe:Cu detector of 5 wt% concentration, which showed a gain coefficient of up to 8.87×10³ for white illumination 1000 Lux. This value is much greater than the published value for pure CdSe film, possibly due to the sensitizing action of Cu centers. Additional weak but well resolved features were observed in the high-energy region of the curve depicting gain coefficients as a function of wavelength characteristics. These peaks were attributed to the 3D transition of Cu from deep levels in the valence band.     

Synthesis and growth of nonlinear infrared crystal material CdSe via seeded oriented temperature gradient solution zoning method

Single crystals of CdSe were grown by using seeded oriented temperature gradient solution zoning (STGSZ) method with the sizes of 20 mm in diameter and 80 mm in length. The crystals were characterized with X-ray diffraction, transmission spectrophotometer and infrared microscope. The transmission spectra showed that the infrared transmission is above 65% and the mean absorption was 0.01-0.04 cm-1 in the range of 2.5-20 μm.With 2.797 μm Cr, Er:YSGG laser as pumping source,experiments of optical parametric oscillator (OPO) were performed by using fabricated 5mm×5mm×30mm device crystal. The signal and idler wavelengths and the output average power were respectively 4.3 μm, 8 μm and 400 μJ. Optical-to-optical conversion efficiency was obtained by 12%.     

CdSe/ZnS量子点光纤纤芯基底的研究

量子点光纤正逐渐成为光通信领域的研究热点。首先介绍了CdSe/ZnS量子点掺杂光纤的发展历史,随后给出两种不同纤芯基底材料的CdSe/ZnS量子点掺杂光纤的制备方法,并对它们的光谱特性及发射峰值增益进行了分析比较,最后分析得出适合CdSe/ZnS量子点掺杂光纤的纤芯基底材料。CdSe/ZnS量子点掺杂光纤基底材料的研究对其他量子点光纤的研制具有一定的借鉴作用。     

Photoluminescence of CdSe nanowires grown with and without metal catalyst

We present temperature and power dependent photoluminescence measurements on CdSe nanowires synthesized via vapor-phase with and without the use of a metal catalyst. Nanowires produced without a catalyst can be optimized to yield higher quantum efficiency, and narrower and spatially uniform emission, when compared to the catalyst-assisted ones. Emission at energies lower than the band-edge is also found in both cases. By combining spatially-resolved photoluminescence and electron microscopy on the same nanowires, we show that catalyst-free nanowires exhibit a low-energy peak with sharp phonon replica, whereas for catalyst-assisted nanowires low-energy emission is linked to the presence of nanostructures with extended morphological defects.      

Infrared spectroscopy of chromium-doped cadmium selenide

The maximum optical-absorption cross section of Cr²⁺ ions was evaluated from near-infrared (NIR) absorption spectroscopy and direct measurements of the chromium concentration in Cr²⁺:CdSe crystals. The emission lifetime of the excited state, ⁵E, of Cr²⁺ was measured as a function of Cr²⁺ concentration in the 2×10¹⁷ −2×10¹⁸ ions/cm³ range and as a function of temperature from 77–300 K. Lifetime values were as high as ∼6 μs in the 77–250 K range and decreased to ∼4 μs at 300 K because of nonradiative decays. Assuming that most of the Cr dopant is in the Cr²⁺ state, an optical-absorption cross section σ_a of (1.94±0.56) × 10⁻¹⁸ cm² was calculated. Implications for laser performance are discussed.     

Influence of surface treatments on CdSe thin films in photoelectro-chemical solar energy conversion

Photovoltaic performance of semiconductor-liquid junction solar cell using electro-codeposited thin filmn-CdSe is found to improve significantly by proper surface treatments. The solid state parameters of annealed films are calculated and compared with those of unannealed film-based cells. Chemical etching is found to improve short circuit current and fill factor whereas photoelectrochemical etching technique improves the stability of photoanode in polysulphide electrolyte. Annealing promotes incipient fusion of small crystallites, thus reducing the grain boundaries which are known to act as recombination centres for minority carriers and trapping centre for majority carriers. The conversion efficiency and stability are found to improve by chemical etching of the semiconductor layer because chemical etching pins Fermi level of CdSe photoanode and promotes exchange current density.     

A novel method for the preparation of water-soluble and small-size CdSe quantum dots

A novel method for the preparation of water-soluble and small-size CdSe quantum dots has been reported under high-intensity ultrasonic irradiation. The as-prepared products have been characterized by absorption spectra, X-ray powder diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM).     

［（Cdse）_m（ZnSe）_n］_p－Znse多量子阱中的多声子散射

对用原子层外延方法，在［００１］晶向ＧａＡｓ衬底上生长的［（Ｃｄｓｅ）ｍ（Ｚｎｓｅ）ｎ］ｐ－ＺｎＳｅ应变量子阱结构，在１０～３００Ｋ温度范围内测量了喇曼散射光谱，观察到两种类ＺｎＳｅＬＯ声子限制模．利用改变样品温度和入射光能量实现了共振喇曼散射，观察到高达７阶的类ＺｎＳｅＬＯ声子模．并讨论了多声子喇曼散射和热萤光过程的区别．     

用环己烷-水两相体系优化合成CdSe量子点

采用环己烷和水组成的两相体系,合成了不同粒径大小的硒化镉量子点。用X射线粉末衍射仪（XRD）,透射电子显微镜（TEM）,荧光光谱仪和紫外可见分光光度计等测试手段对产物进行了表征,结果表明生成的量子点粒径尺寸分布均匀,为立方晶型,具有良好的荧光特性。讨论了反应物比例、反应温度、反应时间、硒单体的量等因素对CdSe量子点的粒径分布,表面缺陷,奥斯德瓦尔效应的影响。通过优化实验条件,得到了表面缺陷少,粒径分布均匀,光量子效率高的硒化镉量子点。