纳米铝粉点火机理的快速光谱研究

用光触发同步采集技术在多光谱系统上测定纳米铝粉与环氧丙烷快速反应的点火延迟时间和基团光谱强度,得出诱导激波作用下纳米铝粉的点火机理。X射线衍射(XRD)数据表明,等离子体方法生产的纳米铝粉由于活性较高表面有部分氧化,电子能谱(XPS)给出结果表明氧化层厚度～3nm,且其反应生成物的电子能谱显示氧化层厚度随诱导激波强度增加而相应增大。单色仪测定AlO(464.8nm)点火时间表明随诱导激波强度增大,纳米铝粉在环氧丙烷反应系统中的抛撒状态分布更均匀,颗粒受热面增大,受热率明显增大,且激波作用下铝粉表面3nm厚氧化层也极易被熔破,使内核活性铝气化与反应系统中的氧原子及含氧分子反应放热而达到点火状态。     

二维氧化锌纳米阵列的制备及光学吸收特性研究

采用漂移法,在玻璃衬底上制备出粒径分别为117,350和500 nm单层、大面积的聚苯乙烯胶体球掩膜板,在已制得的掩膜板上用射频磁控溅射的方法沉积一层氧化锌薄膜,最后用有机溶液四氢呋喃(THF)浸泡去除聚苯乙烯胶体球,获得不同粒径的二维氧化锌纳米团簇。通过扫描电子显微镜和能量色散X射线光谱仪对样品的形貌及成份进行表征,表明所制得样品为有序分布的蜂窝网状氧化锌纳米阵列。在室温下,通过吸收光谱仪测试样品在300～800 nm波长范围内的吸收光谱,结果表明对于具有不同尺寸晶粒的氧化锌纳米团簇样品,随着所采用的聚苯乙烯胶体球粒径的增大,即氧化锌纳米团簇粒径的增加,光吸收峰出现了宽化和红移;随着溅射时间的延长,即氧化锌薄膜膜厚的增加,光吸收率提高。此外,对氧化锌纳米团簇阵列的光吸收特性进行了基于离散偶极子近似的理论计算从而获得任意形状和尺寸粒子的吸收。目前,文献报道中用此理论计算各种形状的纳米金、银等金属的结果与实验结果相符,但是应用离散偶极子的近似理论计算氧化锌纳米颗粒的报道很少。应用此理论计算三角棱台形状的氧化锌光学吸收特性,根据氧化锌薄膜介电常数和膜厚的变化进行光吸收特性的模拟,并解释了实验结果。     

Growth and characterization of MOMBE grown HfO2

HfO₂ dielectric layers were grown directly on the p-type Si (1 0 0) by metalorganic molecular beam epitaxy (MOMBE). Hafnium tetra-butoxide was used as a Hf precursor and pure oxygen was introduced to form an oxide layer. The properties of the layers with different thicknesses were evaluated by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), high-resolution transmission electron microscopy (HRTEM), and capacitance–voltage (C–V) and current–voltage (I–V) analyses. XRD and HRTEM results showed that the HfO₂ films thinner than 12 nm were amorphous while the films thicker than 12 nm began to crystallize in the tetragonal and the monoclinic phases. The XPS spectra of O 1s show that the O---Si binding energies shifted to the lower binding energy with increasing the HfO₂ layer thickness. Moreover, the snap back phenomenon is observed in accumulation capacitance. These changes are believed to be linked with the decomposition of SiO and the crystallization of HfO₂ layer during the film growth.     

图谱分析退火对本征SnO2多晶薄膜性能的影响

提高CdTe太阳电池转换效率的有效途径之一是适当减薄CdS窗口层,减薄了的CdS层会严重影响电池性能,解决方法是在窗口层和透明导电膜之间加一层高阻本征SnO2薄膜。采用反应磁控溅射制备了具有高阻抗的本征SnO2薄膜,并对其进行了后处理,利用XRD,XPS等方法研究了退火前后薄膜的结构,成分及表面化学状态的变化。结果表明:经N2/O2=4:1气氛550℃(0.5h)退火后,样品由非晶态转变为四方相结构的多晶薄膜,具有(110)择优取向;XPS分析表明退火后薄膜的氧含量增加、O(1s)峰向低能方向移动,SnO被氧化成SnO2,使得薄膜的透过率增大,退火后的本征SnO2高阻膜非常适合作为过渡层应用于CdTe太阳电池中。     

MOCVD生长AlGaN薄膜的X光电子能谱

用X光电子能谱和X射线衍射谱方法分析了MOCVD生长的AlGaN薄膜的实际表面形态和晶体结构基于XPS测量结果,通过分析计算,发现实际表面除GaN外存在Ga₂O₃和Al₂O₃及其它与O有关的络合物构成的混合氧化物覆盖层,估计覆盖层厚度约1.2nmXRD结果显示生长的AlGaN薄膜为以GaN(0002)取向为主的多晶结构。     

Dependence of the optical properties of UHV deposited silver thin films on the deposition parameters and their relation to the nanostructure of the films

Silver films were deposited on glass substrates under different deposition conditions, i.e. different film thicknesses, deposition rates and deposition angles. Their optical properties were measured by spectrophotometry in the spectral range of 185–3300 nm. The Kramers–Kronig method was used to analyze the reflectivity curves of the silver films to obtain their optical constants. The influence of substrate temperature on the microstructure of thin metallic films, the structure zone model (SZM), is well established, whereas there has been some previous work on the influence of film thickness and morphology, deposition rate and deposition angle on the microstructure and morphology of thin films. An effective medium approximation (EMA) analysis was used to establish the relationship between the atomic force microscopy results, SZM predictions and EMA results, and hence the optical properties of silver thin films. The predictions of the Drude free-electron theory are compared with experimental results for dielectric functions of Ag films produced under different deposition conditions. The real part of the dielectric constant increases with film thickness and decreases with increasing deposition rate and with increasing incidence angle, whereas the imaginary part of the dielectric constant decreases with increasing film thickness and deposition rate and with decreasing incidence angle over the whole energy range measured, including the interaband and interband regions.     

Effect of substrate temperature on structural, optical and electrical properties of pulsed laser ablated nanostructured indium oxide films

Nanocrystalline indium oxide (INO) films are deposited in a back ground oxygen pressure at 0.02 mbar on quartz substrates at different substrate temperatures (T_s) ranging from 300 to 573 K using pulsed laser deposition technique. The films are characterized using GIXRD, XPS, AFM and UV-visible spectroscopy to study the effect of substrate temperature on the structural and optical properties of films. The XRD patterns suggest that the films deposited at room temperature are amorphous in nature and the crystalline nature of the films increases with increase in substrate temperature. Films prepared at T_s ≥ 473 K are polycrystalline in nature (cubic phase). Crystalline grain size calculation based on Debye Scherrer formula indicates that the particle size enhances with the increase in substrate temperature. Lattice constant of the films are calculated from the XRD data. XPS studies suggest that all the INO films consist of both crystalline and amorphous phases. XPS results show an increase in oxygen content with increase in substrate temperature and reveals that the films deposited at higher substrate temperatures exhibit better stoichiometry. The thickness measurements using interferometric techniques show that the film thickness decreases with increase in substrate temperature. Analysis of the optical transmittance data of the films shows a blue shift in the values of optical band gap energy for the films compared to that of the bulk material owing to the quantum confinement effect due to the presence of quantum dots in the films. Refractive index and porosity of the films are also investigated. Room temperature DC electrical measurements shows that the INO films investigated are having relatively high electrical resistivity in the range of 0.80-1.90 Ωm. Low temperature electrical conductivity measurements in the temperature range of 50-300 K for the film deposited at 300 K give a linear Arrhenius plot suggesting thermally activated conduction. Surface morphology studies of the films using AFM reveal the formation of nanostructured indium oxide thin films.     

Effect of vertical deposition angle on structural and optical properties of tantalum oxide nano layers deposited by electron gun evaporation

Tantalum oxide nano layers were deposition on glass substrate with different thicknesses (30, 60, 90 and 120 nm) in vertical deposition angle and high vacuum condition at room temperature by using electron gun evaporation method. There were no specific peaks in XRD patterns because of amorphous nature of these layers. AFM results show that surface roughness is reduced by increasing the thickness of the layers. FESEM images show nucleation, growth, accession and integration as interconnected islands in the lower thickness and re-nucleation at higher thicknesses (120 nm). We studied Raman spectra of the produced Ta₂O₅ amorphous layers. The calculated optical coefficients by using Kramers-Kronig relations show that with increasing film thickness, dielectric properties, absorption coefficient and band gap energy have increased.     

脉冲激光沉积制备CsPbBr3厚膜及其蓝-绿光转换性能

金属卤化物钙钛矿CsPbBr3具有优异的光学性能,是作为波长转化层在液晶显示中实现全彩显示的理想材料。为了实现高效的蓝光到绿光的光转换,采用脉冲激光沉积技术(PLD)制备CsPbBr3微米级厚膜,通过设定激光脉冲数实现膜厚的有效调控,并借助扫描电子显微镜(SEM)、X射线粉末衍射(XRD)、紫外-可见吸收光谱等测试手段对其形貌、晶体结构和光学性质进行分析。然后,将CsPbBr3微米级厚膜沉积在发射波长为460 nm的蓝光发光二极管上,并测试光转换性能。实验结果表明,制备的CsPbBr3厚膜由(100)取向的柱状晶体组成,且膜厚与激光脉冲数呈线性关系,在膜厚为2.252μm时,在460 nm的蓝光激发下实现了完全、有效绿光的发射。此外,在空气氛围(温度20℃,湿度25%)下放置18 d,光致发光强度无明显衰退。     

Enhanced light trapping for the silver nanoparticles embedded in the silica layer atop the silicon substrate

The optical properties of the structures with silver nanoparticles embedded in the silica layer atop the silicon substrate are simulated by the finite-difference time-domain method. The effects of nanoparticle size, period, silica layer thickness, and the angle of incidence of the illuminated light on optical transmissions are studied. It is found that there is the red-shift for the maximum of the total light transmitting into the silicon substrate as the silica layer thickness increases. The electric field intensity distributions and the average power densities for the structure with largest optical transmission is studied, and the strong electric field intensities are found in the silica regions surrounding to the silver nanoparticles, which can help the light energy going into the silicon substrate. By controlling the structure parameters, the optical transmissions of the structures with the silica layer can have higher optical transmissions than the cases without the silica layer. The silica layer plays the role as the graded refractive index layer between the air and the silicon substrate, and the light power from the incident wave can transmit into the silicon substrate with less optical reflections for choosing a suitable silica layer thickness. A guideline to design the structures with high optical transmissions for the solar spectra is given. This study cannot only be useful for the solar cells applications, but also other antireflection applications.     

Thickness dependence of optoelectrical properties of tungsten-doped indium oxide films

Pulsed laser deposition technique is used for deposition of tungsten-doped indium oxide films. The effect of film thickness on structural, optical and electrical properties was studied using X-ray diffraction (XRD), atomic force microscopy, UV-visible spectroscopy, and electrical measurements. X-ray diffraction study reveals that all the films are highly crystalline and oriented along (2 2 2) direction and the film crystallinity increases with increase in film thickness. Atomic force microscopy analysis shows that these films are very smooth with root mean square surface roughness of ∼1.0 nm. Bandgap energy of the films depends on thickness and varies from 3.71 eV to 3.94 eV. It is observed that resistivity of the films decreases with thickness, while mobility increases.     

The effect of PS porosity on the structure,optical and electrical properties of ZnS/PS

ZnS films were deposited on porous silicon (PS) substrates with different porosities by pulsed laser deposition (PLD). The crystalline structure, surface morphology of ZnS films on PS substrates and optical, electrical properties of ZnS/PS composites were studied. The results show that, ZnS films deposited on PS substrates were grown in preferred orientation along β-ZnS (111) direction corresponding to crystalline structure of cubic phase. With the increase of PS porosity, the XRD diffraction peak intensity of ZnS films decreases. Some voids and cracks appear in the films. Compared with as-prepared PS, the PL peak of PS for ZnS/PS has a blueshift. The larger the porosity of PS, the greater the blueshift is. A new green light emission located around 550 nm is observed with increasing PS porosity, which is ascribed to defect-center luminescence of ZnS. The blue, green emission of ZnS combined with the red emission of PS, a broad photoluminescence band (450–750 nm) is formed. ZnS/PS composites exhibited intense white light emission. The I–V characteristics of ZnS/PS heterojunctions showed rectifying behavior. Under forward bias conditions, the current density is large. Under reverse bias conditions, the current density nearly to be zero. The forward current increases with increasing PS porosity. This work lay a foundation for the realization of electroluminescence of ZnS/PS and solid white light emission devices.     

氧对于在Ar/O氛围下用近空间升华法制备的CdS薄膜的影响

采用近空间升华法（CSS）在氩/氧气氛中制备了硫化镉（CdS）多晶薄膜.利用XRD,XPS,AFM,UV-VIS光谱和四探针技术等测试和分析手段系统研究了氧对薄膜的成分、结构、光学和电学等性质的影响.结果表明,用近空间升华法制备的CdS薄膜具有六方相结构,膜层致密、均匀,平均晶粒大小约为40 nm,富硫.氧掺入后部分与镉生成氧化镉,并随着氧含量的增加,薄膜的成分有趋于化学计量比的趋势,光学带隙加宽,光暗电导比增加.此外,还利用扫描电镜（SEM）观察了CdS/CdTe断面结合光谱响应（QE）的结果讨论了氧对CdS/CdTe界面互扩散的影响.发现,随着CdS薄膜制备气氛中氧分压的升高,CdS/CdTe界面的互扩散程度降低,有利于提高器件在500—600 nm波长范围内的光谱响应.认为,氧含量的增加不但使CdS薄膜在光伏应用方面的质量得到改善,而且CdTe太阳电池器件中的CdS/CdTe界面也得到了优化. 关键词： CdS多晶薄膜 近空间升华法 窗口层 界面     

γ射线作用下氧化铪基MOS结构总剂量效应研究

使用原子层淀积方法得到了7.8 nm厚度的HfO₂薄膜并通过直接溅射金属铝电极得到了Al/HfO₂/Si MOS电容结构,测量得到了HfO₂基MOS结构在60Co γ射线辐照前后的电容-电压特性,使用原子力显微镜得到了HfO₂薄膜在辐照前后的表面微观形貌,使用X射线光电子能谱方法测量得到了HfO₂薄膜在辐照前后的化学结构变化。研究发现,使用原子层淀积方法制备的HfO₂薄膜表面质量较高;γ射线辐照在HfO₂栅介质中产生了数量级为1012 cm-2的负的氧化层陷阱电荷;HfO₂薄膜符合化学计量比,介质内部主要的缺陷为氧空位且随着辐照剂量的增加而增加,说明辐照在介质中引入了陷阱从而导致MOS结构性能的退化。     

Influence of buffer layer thickness on the structure and optical properties of ZnO thin films

A series of ZnO thin films were deposited on ZnO buffer layers by DC reactive magnetron sputtering. The buffer layer thickness determination of microstructure and optical properties of ZnO films was investigated by X-ray diffraction (XRD), photoluminescence (PL), optical transmittance and absorption measurements. XRD results revealed that the stress of ZnO thin films varied with the buffer layer thickness. With the increase of buffer layer thickness, the band gap edge shifted toward longer wavelength. The near-band-edge (NBE) emission intensity of ZnO films deposited on ZnO buffer layer also varied with the increase of thickness due to the spatial confinement increasing the Coulomb interaction between electrons and holes. The PL measurement showed that the optimum thickness of the ZnO buffer layer was around 12 nm.     

不同盖层对InAs/GaAs量子点结构和光学性质的影响

利用金属有机化合物气相沉积设备生长了不同盖层结构的InAs/GaAs量子点,采用原子力显微镜和光致发光光谱仪对量子点的结构和光学性质进行了研究.量子点层之间的盖层由一个低温层和一个高温层组成.对不同材料结构的低温盖层的对比研究表明,In组分渐变的InGaAs低温盖层有利于改善量子点均匀性、减少结合岛数目、提高光致发光强度;当组分渐变InGaAs低温盖层厚度由6.8 nm增加到12 nm,发光波长从1256.0 nm红移到1314.4 nm.另外,还对不同材料结构的高温盖层进行了对比分析,发现高温盖层采用In组分渐变的InGaAs材料有利于光致发光谱强度的提高. 关键词： 半导体量子点 盖层 组分渐变     

溶胶-凝胶法制备SiO2-TiO2平板光波导工艺研究

采用溶胶-凝胶法制备了SiO₂-TiO₂平板光波导,计算了平板光波导通光条件,分析了硅/钛溶胶-凝胶材料的热性能,观测了平板光波导的结构形貌,并测试了其通光损耗。结果表明：经过200℃,30 min干燥处理的凝胶薄膜呈疏松多孔状态,对于非对称平板波导,存在芯层通光截止厚度,而且当SiO₂-TiO₂芯层厚度为0.5 μm时,SiO₂下包层厚度至少有6 μm才能防止1550 nm波长光泄露入单晶硅衬底中。制备的光波导对于1550 nm波长光传输损耗最小值为0.34 dB/cm。     

Development of porous metal oxide thin films by co-evaporation

This paper focuses on the development of mixed metal oxide thin films and physical characterization of the films. The films were produced by co-evaporation of titanium oxide and tungsten oxide powders. This allowed the development of titanium oxide-tungsten oxide films as analyzed using XPS. Examination in the SEM and AFM showed that the films were nanoporous with the pore size and pore orientation varying as a function of the deposition angle. UV-vis spectra of the films show an increase of transmittance with increasing deposition angle which is attributed to the structure and porosity of the films. Raman analysis indicated that the as-deposited films have broad and weak Raman characteristics, attributed to the nanocrystal nature of the films and the presence of defects, and the peak broadening deceases after annealing the film, as expected.     

Interfacial electronic structure and ion beam induced effect of anatase TiO2 surface modified by Pd nanoparticles

Anatase TiO₂ surface could be modified by Pd nanoparticles using an electrochemical deposition method. Surface morphology, light absorption and interfacial electronic structures were studied by field emission scanning electron microscopy (FE-SEM), UV-visible reflectance absorption, X-ray diffraction (XRD) crystallography, and depth-profiling X-ray photoelectron spectroscopy (XPS). On the basis of XRD patterns, Pd 3d XPS and valance band spectra, the as-deposited overlayer Pd is metallic, with no detectable Pd oxides. The optical band gap of TiO₂ decreases from 3.25 to 3.14 eV upon Pd deposition. The XPS spectra with Ar⁺ ion sputtering show that 4+ oxidation state of Ti dramatically changes to lower (3+ and 2+) oxidation states. As a result of this, oxygen defects are created in the bulk while the oxygen diffuses outward to likely form hydroxyl group on the surface. The Pd 3d XPS peak shifts by +0.6 eV to a higher BE position, and the density of state at the Fermi level is more or less reduced. It appears that the overlayer Pd becomes less metallic, plausibly due to TiO₂ support and/or size effect. No critical interfacial interaction between Pd and TiO₂ was observed by XPS.     

Influences of different structures on the characteristics of H_2O-based and O_3-based La_xAl_yO films deposited by atomic layer deposition

H_2O-based and O_3-based La_xAl_yO nanolaminate films were deposited on Si substrates by atomic layer deposition(ALD). Structures and performances of the films were changed by different barrier layers. The effects of different structures on the electrical characteristics and physical properties of the La_xAl_yO films were studied. Chemical bonds in the La_xAl_yO films grown with different structures and different oxidants were also investigated with x-ray photoelectron spectroscopy(XPS). The preliminary testing results indicate that the La_xAl_yO films with different structures and different oxidants show different characteristics, including dielectric constant, equivalent oxide thickness(EOT), electrical properties, and stability.