Characterization of temporal response, spectral responsivity and its spatial uniformity in photoconductive diamond detectors

Three photoconductive diamond detectors with highly oriented diamond (HOD) films fabricated by the same process were characterized with respect to temporal response, spectral responsivity and its spatial uniformity over the wavelength range from 190 to 250 nm. Temporal measurements showed a drift in the baseline, suggesting the presence of deep level carrier traps. The responsivity of specimen No. 2 was more than twice those of the other two specimens, but it showed an unpredictable current fluctuation. It was found that the spatial uniformities of all the specimens were too low for radiometric purposes. A prominent peak, thought to be due to photoemission, was found in the responsivity spatial distribution of specimen No. 3 under a negative applied voltage.     

Wide-gap layered oxychalcogenide semiconductors: Materials, electronic structures and optoelectronic properties

Applying the concept of materials design for transparent conductive oxides to layered oxychalcogenides, several p-type and n-type layered oxychalcogenides were proposed as wide-gap semiconductors and their basic optical and electrical properties were examined. The layered oxychalcogenides are composed of ionic oxide layers and covalent chalcogenide layers, which bring wide-gap and conductive properties to these materials, respectively. The electronic structures of the materials were examined by normal/inverse photoemission spectroscopy and energy band calculations. The results of the examinations suggested that these materials possess unique features more than simple wide-gap semiconductors. Namely, the layered oxychalcogenides are considered to be extremely thin quantum wells composed of the oxide and chalcogenide layers or 2D chalcogenide crystals/molecules embedded in an oxide matrix. Observation of step-like absorption edges, large band gap energy and large exciton binding energy demonstrated these features originating from 2D density of states and quantum size effects in these layered materials.     

Gold Nitride: Preparation and Properties

We review the currently known methods of producing gold nitride and report on the influence of electrically isolated substrates on the growth of gold nitride films by reactive ion sputtering (RIS). It is found that isolation of the substrate decreases grain size and increases nitrogen content, the latter attributed to longer nitrogen ion lifetime on the surface of the growing film. The chemical reactivity of gold nitride is compared with that of pure gold films using the adsorption of 1-dodecyl mercaptan (CH₃(CH₂)₁₁SH) as a model system and it is found that there is no significant difference between gold films and gold nitride in terms of Au–S binding. However, gold nitride nanoparticles are suggested to be worthy of further investigation in terms of their catalytic properties.

Preliminary studies of In surface diffusion on the W(1 1 0) surface

The growth of In onto W(1 1 0) was observed at room temperature by means of low-energy electron diffraction and photoemission from core levels and valence levels. Surface diffusion of In onto the W(1 1 0) surface was studied by using ESCA imaging property of SCIENTA ESCA200 instrument at the temperature range of 400-550 K.     

GaAs阴极激活铯源质量对成像器件性能的影响

为了解决三代微光器件研究中出现的阴极灵敏度低、光电发射不均匀、稳定性差等问题,重点开展了铯源质量对阴极性能产生影响的试验研究。结果表明,激活铯源纯度、装配结构、铯源与阴极距离对阴极光电发射灵敏度、均匀性影响最大。铯源出口孔径多少大小及射出方向是阴极产生暗班的主要原因。在铯源材料成分结构与阴极距离确定之后,阴极灵敏度的高低主要决定于对铯源的除气工艺,通过对铯源除气工艺进行优化,制备出了阴极灵敏度大于1700μA/lm三代微光器件。     

MoSi_2硅化物的形成及电子结构的研究

利用XPS、UPS、AES、X-光衍射和拉曼散射等技术,研究了在稳态热退火条件下共溅射的Mo-Si合金膜,硅化物的形成及电子结构特性.     

Effect of oxygen plasma treatment on air exposed MoOx thin film

Oxygen plasma (OP) treatment on air exposed molybdenum oxide (MoO_x) has been investigated with ultraviolet photoemission spectroscopy (UPS) and angle resolved X-ray photoemission spectroscopy (AR-XPS). It was found that the work function (WF) reduction of MoO_x by air exposure can be recovered partially by OP treatment on the surface. The overall recovery was measured to be slightly more than 64%, which was adequate to provide a hole extraction layer to many hole-conducting organic materials. The incompleteness of the WF recovery could be attributed to the formation of a very thin layer of oxygen rich absorbents on top of the evaporated MoO_x film after OP treatment. AR-XPS showed that OP treatment shifted the core levels of oxygen and molybdenum about 0.1 eV toward the lower binding energy (BE), and confirmed the existence of oxygen deficiency in the evaporated MoO_x film. We also investigated the electronic energy level evolution of copper phthalocyanine (CuPc) on MoO_x/ITO by UPS. With the deposition of CuPc on OP treated MoO_x we observed band bending and the highest occupied molecular orbital (HOMO) level of CuPc was almost pinned to the Fermi level, which indicates the possibility of efficient hole injection with the OP treated MoO_x film.     

Tunable self-assembly of one-dimensional nanostructures with orthogonal directions

High-temperature exposure of a Mo(110) surface to borazine (HBNH)₃ leads to the formation of two distinctly different self-assembling nanostructures. Depending on the substrate temperature during preparation, either well-aligned, ultra-thin boron nanowires or a single-layer stripe structure of hexagonal boron nitride forms. Both structures show one-dimensional (1D) characteristics, but in directions perpendicular to each other. It is also possible to grow the two phases in coexistence. The relative weights are controlled by the sample temperature during preparation.     

On the correlation between morphology and electronic properties of copper phthalocyanine (CuPc) thin films

The morphology of vacuum deposited copper phthalocyanine (CuPc) thin films surface deposited on Si(111) have been studied using the contact mode Atomic Force Microscope (AFM). The influence of substrate temperature during deposition and of the post-deposition UHV annealing on surface roughness as well as on the average and maximum grain height was determined. The observed changes of surface morphology were in a good correlation with the shift of surface Fermi level position in the band gap after O₂ exposure determined in our recent photoemission studies.     

碱金属Cs和Na与GaAs(100)界面相互作用的光电子能谱研究

用光电子能源谱技术（XPS和UPS）研究了金属Cs和Na与GaAs（100）的界面形成。实验结果表明，Cs和Na吸附在GaAs（100）表面时，衬底As向外扩散，形成混合相。在Na吸附的表面，As扩散程度比Cs吸附的表面大。随着复盖层厚度增加，吸附层开始金属化。