物理升华法生长ZnO晶体的研究

Zinc oxide（ZnO） has a wide band gap, high stability and a high thermal operating range that makes it a suitable material as a semiconductor for fabricating light emitting diodes（LEDs） and laser diodes, photodiodes, power diodes and other semiconductor devices. Recently, a new crystal growth for producing ZnO crystal boules was developed, which was physical vapor transport（PVT）, at temperatures exceeding 1500 ？C under a certain system pressure. ZnO crystal wafers in sizes up to 50 mm in diameter were produced. The conditions of ZnO crystal growth, growth rate and the quality of ZnO crystal were analyzed. Results from crystal growth and material characterization are presented and discussed. Our research results suggest that the novel crystal growth technique is a viable production technique for producing ZnO crystals and substrates for semiconductor device applications.     

VEGF提高MCAO/R小鼠的EPCs表达及促进脑梗死的康复

目的：观察局灶性脑缺血再灌注模型（MCAO/R）小鼠外周循环中血管内皮祖细胞（EPCs）的数量变化,并应用血管内皮生长因子（VEGF）动员小鼠自体骨髓中的EPCs,达到治疗脑梗死的目的。方法：以MCAO/R小鼠为研究对象,通过腹腔注射VEGF动员体内的EPCs,（每日一次,持续一周）,在动员过程中的第1d、4d、7d、14d从内眦静脉采血,使用流式细胞仪检测MCAO/R组及MCAO/R＋VEGF组小鼠外周血中EPCs的数量;然后断头取脑,用免疫组化法检测新生血管的密度,并对脑组织TTC染色后计算并比较小鼠脑梗死体积的变化。结果：MCAO/R＋VEGF组在动员过程中,外周血中的EPCs在给药第1d开始增加,第4d达到高峰并持续到第7d,第14d高峰持续存在;并且在这四个时间点上,MCAO/R＋VEGF组与其它两组比较均具有统计学意义（P〈0.01）。新生血管密度：MCAO/R＋VEGF组1d开始有新生血管生成,4d血管新生明显,14d达高峰,且各时间点MCAO/R＋VEGF组血管新生数量明显多于MCAO/R组。TTC染色后通过图像分析系统计算脑梗死体积：MCAO/R＋VEGF组在给药第14d较第1d、4d、7d梗死灶体积明显缩小（P〈0.01）,且MCAO/R＋VEGF组在给药第4d,7d、14d的梗死灶体积较同时间点的MCAO/R组有显著缩小（P〈0.01）。结论：在急性脑缺血/再灌注损伤的情况下,应用VEGF能显著动员小鼠骨髓中的EPCs,增强出生后的血管新生,达到缩小梗死灶,治疗脑梗死的目的。     

Selective Photothermal Tumor Therapy Using Nanodiamond‐Based Nanoclusters with Folic Acid

This paper describes the fabrication and evaluation of folic acid (FA)‐conjugated nanodiamond (ND) nanoclusters for selective photothermal tumor therapy. ND nanoclusters with surface carboxyl groups are aminated using ethylenediamine and conjugated with FA via carbodiimide chemistry. The temperature of an aqueous ND dispersion (10 μg mL^?1) is increased to 54 °C upon laser exposure for 5 min. FA‐ND nanoclusters are preferentially taken up by KB cells (folate receptor positive) compared to WI‐38 (folate receptor negative) cells, suggesting specificity for tumor cells that overexpress folate receptors. Cell viability tests reveal that FA‐ND nanoclusters effectively and selectively ablate KB cells upon near‐infrared (NIR) laser exposure. In addition, fluorescence microscopy images confirm that only KB cells treated with FA‐ND nanoclusters are ablated in a spot (200 μm in diameter) by NIR laser exposure. In an animal model, a large amount of FA‐ND nanoclusters is accumulated into tumor tissue, resulting in dramatically reduced tumor volume post‐NIR laser exposure as compared to ND nanoclusters.     

Synchronous Growth of High‐Quality Bilayer Bernal Graphene: From Hexagonal Single‐Crystal Domains to Wafer‐Scale Homogeneous Films

The precise control of the domain structure, layer thickness, and stacking order of graphene has attracted intense interest because of its great potential for nanoelectronics applications. Much effort has been devoted to synthesize semiconducting Bernal (AB)‐stacked bilayer graphene because of its tunable band structure and electronic properties that are unavailable to single‐layer graphene. However, fast growth of large‐scale bilayer graphene sheets with a high AB‐stacking ratio and high mobility on copper poses a tremendous challenge, which has to overcome the self‐limiting effect. This study reports a low‐cost but facile method to rapidly synthesize bilayer Bernal graphene by atmospheric pressure chemical vapor deposition using polystyrene as the feedstock. The bilayer graphene grains and continuous film obtained are of high quality and exhibit field‐effect hole mobilities as high as 5700 and 2200 cm² V^?1 s^?1 at room temperature, respectively. In addition, a synchronous growth mechanism of bilayer graphene is revealed by monitoring the growth process, resulting in a high surface coverage of nearly 100% for a near‐perfect AB‐stacking order. This new synthesis route is significant for industrial application of bilayer graphene and investigation of the growth mechanism of graphene by the chemical vapor deposition process.     

A new N-type doping precursor for MOCVD-IMP growth of detector quality MCT

A new indium precursor, triisopropyl indium (TIPIn), has been used for doping MCT at low carrier concentrations. Previous attempts using indium organometallics resulted in a strong memory effect where residual doping would persist for many growth runs. Introducing TIPIn on the tellurium inject line resulted in a similarly strong memory doping but this was not observed when feeding the dopant in on the cadmium injection line. The TIPIn is believed to have been forming a low volatility adduct with diisopropyl tellurium (DIPTe) in the feed line and to have continued to evaporate at a low but significant rate. By keeping the TIPIn and DIPTe precursors separate until they entered the reactor, the desired low 10¹⁵ cm⁻³ carrier concentration and flat indium profiles could be achieved with good reproducibility. Good electrical characteristics were measured for these layers with Auger limited lifetime >1 μs at 77K.     

CdTe and HgTe surface growth kinetics for molecular and metalorganic molecular beam epitaxy

The surface growth kinetics of CdTe and HgTe have been investigated during molecular and metalorganic molecular beam epitaxy. The surface growth kinetics was studied through in-situ measurements of the growth rate as a function of flux ratio and substrate temperature on the (001), (111)B, and (211)B CdTe surface orientations. For the (001) and (111)B CdTe growth kinetics, the existence of low binding energy surface precursor sites was proposed for both molecular and atomic growth species before lattice incorporation. Intensity oscillations were observed during HgTe growth on misoriented (111)B surfaces and during CdTe growth on the (211)B orientation. The (211)B surface reconstructions displayed both vicinal and singular surface characteristics, depending on the growth flux ratio.     

Substrate issues for the growth of mercury cadmium telluride

Close lattice matching and lattice compatibility with mercury cadmium telluride (MCT) make CdTe and related alloys ideal substrate materials for growth of MCT layers for the purpose of making high-performance second-generation infrared detectors. However, the limitations in the properties of CdTe and the difficulties in its bulk growth have prompted extensive research in the area of alternative substrates. Some basic relevant characteristics of substrates such as sapphire, GaAs, and silicon are compared and the possibilities and problems associated with each material are analyzed in the light of the most recent results in the field.     

波导系统模式的分析与鉴别

介绍了现有各种模式分析的方法,比较了它们各自的特点,认为模式耦合鉴别方法具有实时性与动态性的优点,尤其适合高功率微波系统应用。     

Oxygen-related photoluminescence quenching in selectively grown GaN nanocolumns: Dependence on diameter

This work reports on the effects of air exposure on the photoluminescence intensity of GaN nanocolumns, with diameters ranging from below 40 nm up to around 230 nm, grown selectively on GaN/sapphire and GaN/Si(111). The high control of dimensions provided by selective area growth epitaxy allowed for a better study of the relationship between the observed phenomena, namely the photoluminescence intensity quenching due to oxygen photo-adsorption, and the nanocolumns properties (morphology and dimensions). For nanocolumns with diameters below 120 nm and lengths of about 300 nm, photoluminescence intensity dropped by more than 90% of the initial value, while for shorter nanocolumns a reduced drop value was found.     

An Electroabsorption Modulator Monolithically Integrated with a Semiconductor Optical Amplifier and a Dual-Waveguide Spot-Size Converter

A semiconductor optical amplifier and electroabsorption modulator monolithically integrated with a spot-size converter input and output is fabricated by means of selective area growth,quantum well intermixing,and asymmetric twin waveguide technology.A 1550～1600nm lossless operation with a high DC extinction ratio of 25dB and more than 10GHz 3dB bandwidth are successfully achieved.The output beam divergence angles of the device in the horizontal and vertical directions are as small as 7.3°×18.0°,respectively,resulting in a 3.0dB coupling loss with a cleaved single-mode optical fiber.