Growth of Strained Si1－xGex Layer by UV/UHV/CVD

Strained Si1－xGex and Si materials are successfully grown on Si substrate by ultraviolet light chemical vapor deposition under ultrahigh vacuum at a low substrate temperature of 450℃ and 480℃，respectively.At such low temperature,autodoping effects from the substrate and interdiffusion effects at each interface could be suppressed efficiently.The strained Si1－xGex and multilayer Si1－xGex /Si structures are examined by X-ray diffraction,SMIS,etc.,and it is found that the materials have good crystallinity and the rising and falling edges are steep.The technique has a capability of growing highquality Si1－xGex /Si strained layers.     

Twinning in Low-Temperature MOCVD Grown GaN on (001) GaAs Substrate

GaN buffer layers (thickness ～60nm) grown on GaAs(001) by low-temperature MOCVD are investigated by X-ray diffraction pole figure measurements using synchrotron radiation in order to understand the heteroepitaxial growth features of GaN on GaAs(001) substrates.In addition to the epitaxially aligned crystallites,their corresponding twins of the first and the second order are found in the Xray diffraction pole figures.Moreover,{111} φ scans with χ at 55°reveal the abnormal distribution of Bragg diffractions.The extra intensity maxima in the pole figures shows that the process of twinning plays a dominating role during the growth process.It is suggested that the polarity of {111} facets emerged on (001) surface will affect the growth twin nucleation at the initial stages of GaN growth on GaAs(001) substrates.It is proposed that twinning is prone to occurring on {111}B,Nterminated facets.     

Ga掺杂ZnO薄膜的MOCVD生长及其特性

利用低压MOCVD技术在(0002)蓝宝石上外延获得高质量的ZnO∶Ga单晶薄膜,并研究了Ga的不同掺杂浓度对材料电学和光学特性的影响．当Ga/Zn气相摩尔比为3.2 at%时,ZnO(0002)峰半高宽仅为0.26°,载流子浓度高达2.47e19cm－3,透射率高于90%;当载流子浓度升高时,吸收边出现明显的Burstein-Moss蓝移效应．同时室温光致发光谱显示,紫外峰位随载流子浓度的增加而发生红移,峰形展宽,这和Ga高掺杂所引起的能带重整化效应有关．当Ga/Zn比达到6.3 at%时,由于高掺杂浓度下Ga的自补偿效应导致载流子浓度下降．     

电气工程与自动化在化工生产中的应用

通过电气工程与自动化在化工生产中的应用,分析了电气工程与自动化在化工生产中存在的缺陷与问题,显示了电气工程与自动化应用的必要性,以此需要不断的提高电气工程与自动化技术,为化工安全、稳定的生产保驾护航。     

UHVCVD外延设备的热场设计

介绍了超高真空化学气相沉积(UHVCVD)锗硅外延设备的加热室设计方法,完善了相关的炉体设计,相关温度指标达到设计标准。     

纳米级三氧化二铝对碱性钨抛光液的影响

研究了纳米级三氧化二铝颗粒的加入对以二氧化硅为磨料的碱性钨抛光液的影响。首先用单一因素法分析了三氧化二铝与二氧化硅质量比对原有碱性钨抛光液的去除速率的影响,以及氧化剂体积分数和pH值对抛光液去除速率的影响,取最优值,然后对添加三氧化二铝抛光液抛光后晶圆表面粗糙度进行了测试分析。实验结果显示在三氧化二铝与二氧化硅质量比为1∶2,二氧化硅水溶胶与去离子水体积比为1∶1,氧化剂体积分数为2%,pH值为9时,去除速率达到175 nm/min,较原有碱性钨抛光液提高约1倍,表面粗糙度为2.24 nm,能满足实际生产要求。     

聚噻吩类有机聚合物材料光电性能研究进展

介绍了典型的具有光电性能的噻吩类聚合物材料,包括烷基取代聚噻吩、联苯基取代聚噻吩、芴与噻吩共聚物及一些新型的噻吩类聚合物。对它们的结构、光学性能、电致发光性能进行了归纳和总结,讨论了不同类聚噻吩的特点,对比了随取代基种类、位置及个数的不同其聚合物性能的优缺点,并对其研究和应用前景进行了展望。     

锥形图形衬底上氮化镓薄膜生长和表征

GaN films are grown on cone-shaped patterned sapphire substrates(CPSSs)by metal-organic chemical vapor deposition,and the influence of the temperature during the middle stage of GaN growth on the threading dislocation(TD)density of GaN is investigated.High-resolution X-ray diffraction(XRD)and cathodeluminescence(CL)wereusedtocharacterizetheGaNfilms.TheXRDresultsshowedthattheedge-typedislocation density of GaN grown on CPSS is remarkably reduced compared to that of GaN grown on conventional sapphire substrates(CSSs).Furthermore,whenthegrowthtemperatureinthemiddlestageofGaNgrownonCPSSdecreases,the full width at half maximum of the asymmetry(102)plane of GaN is reduced.This reduction is attributed to the enhancement of vertical growth in the middle stage with a more triangular-like shape and the bending of TDs.The CL intensity spatial mapping results also showed the superior optical properties of GaN grown on CPSS to those of GaN on CSS,and that the density of dark spots of GaN grown on CPSS induced by nonradiative recombination is reduced when the growth temperature in the middle stage decreases.     

煅烧温度和恒温时间对ZnO/AAO/Si组装体系的影响

以AAO/Si为模板,采用化学气相沉积(CVD)的方法在不同温度下,通过煅烧Zn粉和C粉的混合物制备ZnO/AAO/Si组装体系,并对其结构和性质进行了研究。扫描电镜(SEM)结果表明:随着煅烧温度的升高,AAO表面的孔洞逐渐被封堵,当温度达到900℃时,在AAO的表面出现了一层ZnO薄膜。X射线衍射(XRD)结果显示,700℃时在XRD图谱上观看到六角纤锌矿的ZnO的衍射峰,并且随着温度的升高,ZnO的衍射峰逐渐增强,当温度升至800和900℃时出现了ZnAl2O4的衍射峰。因此,化学气相沉积制备组装体系时的最适温为700℃。在700℃时煅烧不同恒温时间制备的ZnO/AAO/Si组装体系SEM图显示,随着恒温时间的延长,孔的封闭效应逐渐明显。     

Protein Engineering Strategies for Improved Pharmacokinetics

Protein therapeutics have gained momentum in recent years and become a pillar in treating many diseases and the only choice in several ailments. Protein therapeutics are highly specific, tunable, and less toxic than conventional small drug molecules. However, reaping the full benefits of therapeutic proteins in the clinics is often hindered by issues of immunogenicity and short half-life due essentially to fast renal clearance and enzymatic degradation. Advances in polymer chemistry and protein engineering allowed overcoming some of these limitations. Strategies to prolong the half-life of proteins rely on increasing their size and stability and/or fusing them to endogenous proteins (albumin, Fc fragment of antibody) to hijack physiological pathways involved in protein recycling. On the downside, these modifications might alter therapeutic proteins structure and function. Therefore, a compromise between half-life and activity is sought. This review covers half-life extension strategies using natural and synthetic polymers as well as fusion to other proteins and sheds light on genetic engineering strategies and chemical and enzymatic reactions to achieve this goal. Promising strategies and successful applications in the clinics are highlighted.