MBE生长氮化镓薄膜的X光电子谱和俄歇电子谱分析

用X光电子谱和俄歇电子能谱的方法对射频等离子体辅助分子束外延(MBE)技术生长的氮化镓(GaN)薄膜进行了表面分析和深度剖析.发现薄膜实际表面存在O和C吸附层,C主要为表面污染,而O形成一定的深度分布,从而影响氮化镓薄膜的电学和光学性质.     

分子束外延GaN薄膜的X射线光电子能谱和俄歇电子能谱研究

用XPS和AES电子能谱的方法对等离子体辅助分子束外延(MBE)生长的GaN薄膜进行了表面分析和深度剖析.发现红外分子束外延(RFMBE)生长的富镓GaN薄膜实际表面存在O和C吸附层,C主要为物理吸附,而O在GaN表面形成局域化学键产生氧络合物覆盖层,并形成一定的深度分布.杂质O在GaN带隙中导带底形成杂质带同时引入深受主能级,使得带隙变窄室温光吸收谱向低能方向移动,光致发光谱出现宽带发光峰.从而影响GaN薄膜的电学和光学性质 关键词： GaN薄膜 X射线光电子能谱 俄歇电子能谱 表面分析     

Room—Temperature A1GaAsSb／InGaAsSb Multi—Quantum—Well Lasers with High Chraracteristic Temperature

Planar structure A1GaAsSb/InGaAsSb lasers operated at 2.01/zm with high characteristic temperature have been fabricated from a strained multiple quantum-well heterostructure. To decrease the free carrier induced absorption of optical mode in the mid-infrared, we design a broaden waveguide layer in the laser structures to decrease the optical mode distribution in the heavy doped cladding layer, therefore it can be absorbed easily. To enhance the characteristic temperature of laser diodes, A1 constituent up to 80% was applied to the A1GaAsSb cladding layer. The laser diodes with a threshold current density of 1.8 kA/cm2 can be pulsed operating up to 340 K. The characteristic temperature To is 125 K and 90 K in the operating temperature ranges 170-220 K and 230-340 K, resDectivelv. The emission spectrum shows a multiple longitudinal mode.     

纳米材料有机天然高分子高效复合絮凝剂实现产业化

纳米材料有机天然高分子高效复合絮凝剂是一种液态螯合树脂，它除带有-CSSN-基团之外，还含有-OH，-COOH及其他多种基团，能在常温下与工业废水中的Hg^2 ，Cd^2 ，Cu^2 ，Pb^2 ，Mn^2 ，Ni^2 ，Zn^2 ，Cr^2 ，Cr^2 等多种重金属离子迅速反应，生成水不溶性的螯合盐并形成絮状沉淀，从而达到除去重金属离子     

新型索外线吸收剂

新型紫外线吸收剂是国外最新发展起来的,它具有优良的光稳定性,广泛添加在聚乙烯、聚丙烯、聚氯乙烯、聚脂、聚苯乙烯、聚乙烯醇改性树脂、酚醛树脂、环氧树脂等10种聚合物中.也广泛应用于橡胶、塑料、合成纤维、涂料、粘合剂、日用化妆品(如护肤霜)、农药等有机物产品中,以防止紫外线对这些有机物的光降解、变质等破坏作用.分子量大约在1000以上,与材料的相溶性好.可以吸收280～40mm的紫外线.该产品工艺性好,可在45～250℃范围内加入产品中,加入量仅占0.2%～0.5%,可引起良好的防护作用.产品熔点为62±4℃.     

闭式涡轮转盘塔的传质数学模型

建立了闭式涡轮转盘塔（ＣＴＲＤＣ）的传质数学模型－简化的扩散模型,并用数值计算方法求得塔内浓度分布和传质系数Ｋｏｄａ。计算结果与实验测定值相当吻合,说明模型能较好地反映ＣＴＲＤＣ中的传质状况,可用于ＣＴＲＤＣ塔高的设计计算。     

关于包络曲线求法的一个注记

曲线族的包络线的一般求法 ,运用起来有时比较复杂 ,费时费力且容易出错。本文给出了在一些特殊场合下的特殊求法 ,使得运算大大简化。     

关于高等数学教学的思考与实践

针对高等数学地位的不断提高和我国大学招生人数逐年增加的新情况,提出了在高等数学教学中,要特别注意的几个问题。     

Possibility of Targeting Treatment for Ischemic Heart Disease With Liposome (Ⅰ)

This paper reports the basic research on the possibility of using targeting treatment for ischemic heart disease with liposome as drug carrier. Studies have been performed on isolated rat cardiomyocytes, or isolated perfused rat and rabbit hearts. Results show that cardiomyocytes may interact with liposome through fusion, endocytosis, adsorption and molecular exchange of phospholipid. Forms of cellular uptake of liposome depend chiefly on the physicochemical properties of liposomes. Anoxia changes the pattern of liposome uptake by cardiomyocytes and increases uptake of liposomes. Uptake of liposomes, especially of positively charged liposomes by ischemic myocardium is significantly increased. The quantity of increase of liposome uptake is in the following order: ischemia-reperfusion area>peripheral area of the infarct>non-ischemic area>infarcted area. The above results indicate that liposome as drug carrier might promote the delivery of drug into ischemic myocardium and cardiomyocytes.     

Surface Properties of Unintentionally Doped GaN Film and Its Contact Behaviour with Ni／Cr／Au Compound Metals

The surface properties of GaN films grown by plasma-assisted molecular beam epitaxy were investigated by using x-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy, while the depth profile was analysed by the Ar ion sputtering method.The contaminants carbon and silicon are chiefly adsorbed onto the surface while oxygen and aluminium diffuse into the bulk to distribute in a certain depth. The mixture oxides is roughly 0.1μm in thickness. Based on the analytical results of XPS of the GaN films, the Ni/Cr/Au interdigital metal-semiconductor-metal (MSM) structure has been fabricated. It has been found that the contact behaviour of the Ni/Cr/Au/undoped GaN exhibits a linear I-V characteristic under dark and 362-um light excitation without annealing treatment. The lower resistance of the MSM structure has also been observed.