Sulphide passivation of GaN based Schottky diodes

Wet chemical passivation of n-GaN surface was carried out by dipping GaN samples in ammonium sulphide diluted in aqueous and alcoholic solvent base solutions. Photoluminescence (PL) investigations indicated that sulphide solution effectively led to the reduction of GaN surface states. Increased band edge PL peak showed that S²⁻ ions are more active in alcohol based solvents. X-ray photoelectron spectroscopy revealed reduction in surface oxides by introduction of sulphide species. Ni/n-GaN Schottky barrier diodes were fabricated on passivated surfaces. Remarkable improvement in the Schottky barrier height (0.98 eV for passivated diodes as compared to 0.75 eV for untreated diodes) has been observed.     

水热合成ZnO:Cd纳米棒的微结构及光致发光特性

采用水热法制备了ZnO和不同掺杂浓度的ZnO:Cd纳米棒,通过SEM,XRD、拉曼光谱等的分析,研究了ZnO和ZnO:Cd的微结构并测试分析了其光致发光特性.结果表明,ZnO和ZnO:Cd纳米棒呈六角纤锌矿结构,Cd掺杂使得纳米棒体积更小.由于内部张应力的影响,Cd掺杂使得材料光学带隙减少.当掺杂浓度为2%时,合成的材料光致发光谱中出现了位于2.67 eV处,由导带底和Zn空位(VZn)缺陷能级跃迁造成的蓝光发射峰,并且Cd的掺入使得位于2.90 eV附近的紫光发射峰强度增强,对于研究ZnO蓝紫发光器件具有重要的意义.     

Emission properties of sequentially deposited ultrathin CH3NH3PbI3/MoS2 heterostructures

Hybrid organic-inorganic perovskite materials have obtained considerable attention due to their exotic optoelectronic properties and extraordinarily high performance in photovoltaic devices. Herein, we successively converted the ultrathin PbI₂/MoS₂ into the CH₃NH₃PbI₃/MoS₂ heterostructures via CH₃NH₃I vapor processing. Atomic force microscopy (AFM)、Scanning electron microscopy (SEM) and X-ray photoemission spectroscopy (XPS) measurements prove the high-quality of the converted CH₃NH₃PbI₃/MoS₂. Both MoS₂ and CH₃NH₃PbI₃ related photoluminescence (PL) intensity quenching in CH₃NH₃PbI₃/MoS₂ implies a Type-II energy level alignment at the interface. Temperature-dependent PL measurements show that the emission peak position shifting trend of CH₃NH₃PbI₃ is opposite to that of MoS₂ (traditional semiconductors) due to the thermal expansion and electron-phonon coupling effects. The CH₃NH₃PbI₃/TMDC heterostructures are useful in fabricating innovative devices for wider optoelectronic applications.     

AlN插入层对a-AlGaN的外延生长的影响

采用有机金属化学气相沉积(MOCVD)在r面蓝宝石衬底上生长a-AlGaN外延膜,研究了AlN插入层对a-AlGaN外延膜的应力和光学性质的影响。根据高分辨X射线衍射(HRXRD)技术和扫描电子显微镜(SEM)我们可以得到,AlN插入层有效地提高了a-AlGaN外延膜的晶体质量并减小了外延膜材料结构的各向异性。由拉曼光谱得到AlN插入层的引入减小了a-AlGaN外延膜的面内压应力,其原因是AlN插入层可以当作衬底有效的调制与减小a-AlGaN外延膜与r面蓝宝石衬底的晶格失配,从而使a-AlGaN的面内应力得到适当释放。对室温下的光致发光进行测量得到AlN插入层的使用使近带边发射峰(NBE)发生了红移,这可能是由于残余应力的减小引起。     

低阻值In掺杂CdZnTe晶体的退火改性

以Cd_(1-y)Zn_y合金作退火源,对采用改进的垂直布里奇曼法(MVB)生长的In掺杂的Cd_(0.9)Zn_(0.1)Te晶片进行退火改性.结果表明:与退火前相比,退火后晶片的成分均匀性提高,Cd、Zn和Te三种元素的含量更接近理想的化学计量比,平均红外透过率由12;提高到59;,电阻率从3.5×10~6 Ω·cm提高到5.7×10~9 Ω·cm,且在PL谱中出现了代表晶体质量的(D~0,X)发光峰.在合适的条件下对低阻值In掺杂的CdZnTe晶体进行退火改性可较好的提高晶体的性能.     

面向物流领域的本体构建研究

为适应第四方物流对相关信息资源整合的需要,实现物流知识的重享和共用,以物流领域的相关知识研究为基础,提出了采用斯坦福大学的七步法来构建出物流信息本体.该物流本体能有效解决物流信息异构问题,促进第四方物流的发展.     

PLE spectra analysis of the sub-structure in the absorption spectra of CdSeS quantum dots

The semiconductor CdSeS quantum dots (QDs) embedded in glass are analysed by means of absorption spectra, photoluminescence (PL) spectra and photoluminescence excitation (PLE) spectra. The peaks of absorption spectra shift to lower energies with the size of QD increasing, which obviously shows a quantum-size effect. Using the PLE spectra, the physical origin of the lowest absorption peak is analysed. In PLE spectra, the lowest absorption peak can be deconvoluted into two peaks that stem from the transitions of 1S_3/2--1S_e and 2S_3/2--1S_e respectively. The measured energy difference between the two peaks is found to decrease with the size of QD increasing, which agrees well with the theoretical calculation for the two transitions. The luminescence peak of defect states is also analysed by PLE spectra. Two transitions are present in the PLE, which indicates that the transitions of 1S_3/2--1S_e and 2S_3/2--1S_e are responsible for the defect states luminescence.     

Low-dimensional structures formed by irradiation of laser

Some kinds of low-dimensional nanostructures can be formed by irradiation of laser on the pure silicon sample and the SiGe alloy sample. This paper has studied the photoluminescence (PL) of the hole-net structure of silicon and the porous structure of SiGe where the PL intensity at 706nm and 725nm wavelength increases obviously. The effect of intensity-enhancing in the PL peaks cannot be explained within the quantum confinement alone. A mechanism for increasing PL emission in the above structures is proposed, in which the trap states of the interface between SiO₂ and nanocrystal play an important role.     

电场辅助电化学法沉积ZnO纳米线

采用电场辅助电化学沉积的方法成功的在阳极氧化铝模板中沉积出ZnO纳米线阵列.透射电子显微镜(TEM)、X射线衍射(XRD)测试结果表明,制备的纳米线是单晶ZnO纳米线,形貌均匀,直径大约为60nm,并且择优于(101)晶面.我们对生长过程中所加辅助电场的作用给出了初步的解释.     

聚合物基ZnO纳米线的制备和生长机理研究

采用独特的高分子溶液自组装生长方法, 在经化学镀预处理的基底上利用高分子溶液的网络络合效应制备了ZnO纳米线. 通过场发射扫描电子显微镜(FE-SEM), X射线能谱仪(EDS)等对样品的表面形貌及组成进行了观测表征. 结果显示, 纳米线直径约50 nm, 长度达到了数微米; 产物Zn、O化学计量比接近1∶1. 通过Si基底经化学镀工艺预处理和未经化学镀预处理对ZnO纳米结构、紫外吸收和PL性能影响的分析比较, 发现了化学镀Ni对于纳米线长度和直径尺寸的控制更为有效; 在PL图谱中, 经化学镀预处理的样品在中心波长385 nm出现了由激子碰撞复合所形成的近紫外发光峰. 进一步还分析了在不同的pH值和反应时间下样品的紫外吸收和光致发光性能. 通过以上实验, 讨论并提出了ZnO纳米线的生长机理及过程, 认为纳米线的生长是在化学镀催化剂和高分子双重作用下进行的.