溅射气压对氧化镓薄膜光学特性的影响

采用射频磁控溅射法在石英衬底上制备了氧化镓(Ga2O3)薄膜.利用X射线衍射仪和紫外-可见-红外分光光度计分别对Ga2O3薄膜的晶体结构和光学带隙进行了表征,并在室温下测量了 Ga2O3薄膜的光致发光(PL)谱.结果表明:制备的Ga2O3薄膜呈非晶态.吸收边随着溅射气压的增加先蓝移后红移,光学带隙值范围为5.06～5.37 eV,溅射气压为1 Pa时,制备的Ga2O3薄膜具有最大的光学带隙.在325 nm激光激发下,400 nm附近和525 nm附近处出现与缺陷能级相关的发光峰.     

NH3-Ar气氛下制备的Zn3N2薄膜的结构和光学性能

在NH3-Ar气氛下,用RF磁控溅射金属Zn靶在玻璃衬底上室温制备了Zn3N2薄膜,研究了NH3分压对Zn3N2薄膜的结构和光学特性的影响。XRD分析表明Zn3N2薄膜出现多晶结构,具有(321)择优取向。当NH3分压从5%变化到25%时,Zn3N2薄膜的间接光学带隙从2.33eV升高到2.70eV。室温下Zn3N2薄膜在437nm和459nm波长出现了发光峰,并对发光机理进行了分析。     

Characterization and ellipsometric investigation of high-quality ZnO and ZnO(Ga2O3) thin alloys by reactive electron-beam co-evaporation technique

High-quality ZnO(Ga₂O₃) thin films have been co-evaporated by reactive electron-beam evaporation in an oxygen environment. The effect of Ga₂O₃ on the structural and optical properties has been investigated. X-ray diffraction (XRD) measurements have shown that the ZnO(Ga₂O₃) alloys are c-axis-oriented. The alloy containing 28% of Ga₂O₃ showed the best crystallinity. Photoluminescence on ZnO(28%Ga₂O₃) reveals an enhancement of the ultraviolet near band edge emission at 380 nm while the intensity of the deep-level emissions weakens. A reduction of the oxygen vacancies as well as the reduction of the zinc interstitials with gallium may explain this effect. Thus, the possibility of transitions of electron in the conduction band to a deep acceptor level due to zinc interstitials may decrease. Finally, ellipsometric measurements show that the optimum weight concentration of gallium oxide in the alloys is 28%, thus correlating with the XRD and photoluminescence measurements.     

Deposition of thin Bi2Te3 and Sb2Te3 films by pulsed laser ablation

Bi₂Te₃ and Sb₂Te₃ films were obtained by pulsed laser ablation. The films were deposited in vacuum (1 × 10⁻⁵ Torr) on single crystal substrates of Al₂O₃ (0001), BaF₂ (111), and fresh cleavages of KCl or NaCl (001) heated to 453–523 K. The films were 10–1500 nm thick. The structures of the bulk material of targets and films were studied by X-ray diffractometry and transmission high-energy electron diffraction, respectively. Electrical properties of the films were measured in the temperature range of 77–300 K. It is shown that the films possess semiconductor properties. Several activation portions are observed in the temperature dependences of resistivity; the energies of activation portions depend on the film thickness and crystallite size.     

二氧化硅纳米花的制备及发光特性研究

采用磁控溅射和化学气相沉积技术制备出二氧化硅纳米花。利用扫描电子显微镜(SEM),X射线光电子能谱(XPS)和傅里叶红外吸收谱(FTIR)对上述纳米结构进行结构表征。用荧光光谱仪(PL)对其光致发光特性进行了研究。结果表明在激发波长为325nm时,在394nm处出现一个发光峰,表现出良好的发光特性。     

Ultrasound-assisted preparation of CdSe nanocrystals in the presence of Polyvinyl alcohol as a capping agent

Nanosized Polyvinyl alcohol-capped CdSe particles were prepared via a simple and fast ultrasound-assisted technique through the reaction between aqueous solutions of cadmium acetate and sodium selenosulfate. The nanoparticles are characterized using X-ray diffraction (XRD), UV–Visible spectrophotometer, Scanning electron microscope (SEM), Energy dispersive X-ray (EDAX) analysis and Fourier transform infrared (FTIR) spectrometer. XRD pattern reveals that the nanoparticles are in well-crystalline cubic phase. The broadening of diffraction peaks indicated the formation of particles in the nanometer size regime. A shift in absorption peak is observed in the spectra near 544 nm due to quantum confinement effect. Particle sizes calculated from the X-ray diffraction studies agree fairly well with those estimated from optical absorption studies. The homogeneity of the sample could be controlled by adjusting the concentration of Polyvinyl alcohol. SEM images of a specific concentration of Polyvinyl alcohol for as-prepared CdSe nanocrystals show uniform particles distribution. The particle size is found to be less than 100 nm based on the observed SEM images and the reason of this mismatch is discussed. The calculated result from XRD and optical characterizations shows that the particles size is smaller than those observed in SEM images. The elemental analysis from EDAX shows that the average atomic percentage of Cd:Se was 50:50 showing that the prepared samples are exactly stoichiometric.     

用溶胶-凝胶法制备的Cu2Bi2Cr2O8薄膜 及其光学和铁磁性能研究

以硝酸铜Cu(NO₃)₂·3H₂O、硝酸铬Cr(NO₃)₃·9H₂O、硝酸铋Bi(NO₃)₃·3H₂O和乙二醇为原料,利用溶胶-凝胶工艺在石英衬底上制备了纳米Cu₂Bi₂Cr₂O₈薄膜。通过X射线衍射(X-Ray Diffraction, XRD)和拉曼测试对样品进行了表征。结果表明,Cu₂Bi₂Cr₂O₈薄膜具有良好的光学特性,其禁带宽度为1.49 eV;在磁性测试方面,Cu₂Bi₂Cr₂O₈薄膜呈现出了良好的铁磁性。     

First investigation of metal–insulator–metal (MIM) capacitor using Pr2O3 dielectrics

Metal–insulator–metal (MIM) capacitors with Pr₂O₃ as high-k material have been investigated for the first time. We varied the thickness of the Pr₂O₃ layers as well as the bottom electrode material. The layers are characterised using X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), transmission electron microscopy (TEM) and secondary ion mass spectroscopy (SIMS). Preliminary information on the interaction of water with the films was obtained from XPS and ab initio pseudopotential calculations. The electrical characterisation shows that Pr₂O₃ MIM capacitors can provide higher capacitance densities than Si₃N₄ MIM capacitors while still maintaining comparable voltage coefficients of capacitance. The Pr₂O₃ dielectric material seems to be suitable for use in silicon RF applications.     

新型相变材料Al1.3Sb3Te使用CF4/Ar等离子体干法刻蚀

对使用CF4/Ar 混合气体刻蚀Al1.3Sb3Te的特性进行了研究。实验控制的参数是：气体流入刻蚀腔的速率,CF4/Ar 比例,O2的加入量,腔内压强以及加在底电极上的入射射频功率。总的气体流量是50sccm ,研究刻蚀速率与CF4/Ar的比例,O2加入量,腔内压强和入射射频功率的关系。最后刻蚀参数被优化。 使用优化的刻蚀参数CF4的浓度4%,功率300W,压强800mTorr,刻蚀速率达到70.8nm/min,刻蚀表面平整     

Charging effects in CdSe nanocrystals embedded in SiO2 matrix produced by rf magnetron sputtering

Charging effects in CdSe nanocrystals embedded in SiO₂ matrix fabricated by rf magnetron co-sputtering technique were electrically characterized by means of capacitance-voltage (C-V) combined with current-voltage (I-V). The presence of CdSe nanocrystals was demonstrated by X-ray diffraction technique. The average size of nanocrystals was found to be approximately 3 nm. The carriers transport in the CdSe/SiO₂ structure was shown to be a combination of Fowler-Nordheim tunnelling and Poole-Frenkel mechanisms. A memory effect was demonstrated and a retention time was measured.     

Characteristics of chalcogenide nonvolatile memory nano-cell-element based on Sb2Te3 material

Phase-change nonvolatile memory cell elements composed of Sb₂Te₃ chalcogenide have been fabricated by using the focused ion beam method. The contact size between the Sb₂Te₃ phase change film and electrode film in the cell element is 2826 nm² (diameter: 60 nm). The thickness of the Sb₂Te₃ chalcogenide film is 40 nm. The threshold switching current of about 0.1 mA was obtained. A RESET pulse width as short as 5 ns and the SET pulse width as short as 22 ns for Sb₂Te₃ chalcogenide can be obtained. At least 1000 cycle times with a RESET/SET resistance ratio >30 times is achieved for Sb₂Te₃ chalcogenide C-RAM cell element.     

The syntheses and microstructures of tabular SrTiO3 crystal

In the present paper, the microstructures of SrTiO₃ particles obtained in two different methods were examined by scanning electron microscopy (SEM) and X-ray diffraction pattern (XRD). The two synthesis techniques included a conventional mixed solid method and a molten salt synthesis method (MSS), which proceeded through two steps. In the first, precursor Sr₃Ti₂O₇ particles were synthesized. Tabular SrTiO₃ crystals were synthesized via the superposition of the SrTiO₃ basic cell on the interface of Sr₃Ti₂O₇ particles. The microstructures of SrTiO₃ particles synthesis in those two ways were quite different. The microstructures of SrTiO₃ obtained by MSS method were high purity and obviously tabular in structure. Oriented growth faces included typical (0 0 1), (1 0 0), (1 1 0), etc. The mechanism of the oriented growth of tabular SrTiO₃ could be considered as the superposition of coordination polyhedron Ti–O₆ octahedron basic cell on the interface of Sr₃Ti₂O₇ particles.     

Nanostructure effect of V2O5 buffer layer on performance of polymer-fullerene devices

Nanostructure of solar cell materials is often essential for the device performance. V₂O₅ nanobelt structure is synthesized with a solution process and further used as an anode buffer layer in polymer solar cells, resulting insignificantly improved power conversion efficiency (PCE of 2.71%) much higher than that of devices without the buffer layer (PCE of 0.14%) or with V₂O₅ powder as the buffer layer (1.08%). X-ray diffraction (XRD) results indicate that the V₂O₅ nanobelt structure has better phase separation while providing higher surface area for the P3HT:PCBM active layer to enhance photocurrent. The measured impedance spectrums show that the V₂O₅ nanobelt structure has faster charge transport than the powder material. This work clearly demonstrates that V₂O₅ nanobelt has great potential as a substitute of the conventionally used PEDOT-PSS buffer layer for high performance devices.     

Influence of the deposition parameters on the growth of SiGe nanocrystals embedded in Al2O3 matrix

Si_1−xGe_x nanocrystals (NCs), embedded in Al₂O₃ matrix, were fabricated on Si (100) substrates by RF-magnetron sputtering technique with following annealing procedure at 800 °C, in nitrogen atmosphere. The presence of Si_1−xGe_x NCs was confirmed by grazing incidence X-ray diffraction (GIXRD), grazing incidence small angle X-ray scattering (GISAXS) and Raman spectroscopy. The influence of the growth conditions on the structural properties and composition of Si_1−xGe_x NCs inside the alumina matrix was analyzed. Optimal conditions to grow Si_1−xGe_x (x∼ 0.8) NCs sized between 3 and 4 nm in Al₂O₃ matrix were established.     

微波法制备高活性H1-xSr2Nb3-xMoxO10 (x = 0, 0.05, 0.1, 0.15 and 0.2) 光催化剂

通过微波辅助法制备出高活性H1-xSr2Nb3-xMoxO10光催化材料,制备过程和时间均被大大缩短。采用X射线粉末衍射（XRD）、扫描电镜（SEM）、紫外-可见吸收吸收光谱（UV-Vis DRS）等表征其材料性能。考察了催化材料在40W汞灯辐照下催化降解甲基橙的催化性能。实验结果表明,MoO3的掺入量为15%（摩尔分数）时,材料的光催化性能最优。     

Synthesis, characterization of CeO2@SiO2 nanoparticles and their oxide CMP behavior

SiO₂ ultrafine spheres are prepared by sol-gel method using tetraethylorthosilicate and ammonia as raw materials. CeO₂-coated SiO₂ (CeO₂@SiO₂) composite nanoparticles are also synthesized through chemical precipitation method. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectrometer (XPS) and dynamic light scattering (DLS) are used to characterize the CeO₂@SiO₂ composite particles. Silicon wafer covered by thermal oxide film is polished by CeO₂@SiO₂ composite abrasives, and the polishing behavior of novel composite abrasives is characterized by atomic force microscope (AFM). The results indicate that the phases of the as-prepared CeO₂@SiO₂ composite particles are composed of cubic fluorite CeO₂ and amorphous SiO₂. CeO₂@SiO₂ composite particles have excellent spherical morphologies and uniform particle size of 150-200 nm. The particle size of CeO₂ as shell is about 10 nm. After coating, the chemical state of SiO₂ is changed due to the formation of Si-O-Ce bond. The root-mean-square (RMS) roughness within 10 × 10 μm² area of thermal oxide film after polished by CeO₂@SiO₂ composite abrasives is 0.428 nm, and material removal rate can reach 454.6 nm/min.     

Influence of oxidation temperature on the microstructure and electrical properties of Ta2O5 on Si

The effect of the oxidation temperature (673-873 K) on the microstructural and electrical properties of thermal Ta₂O₅ thin films on Si has been studied. Auger electron spectroscopy and X-ray photoelectron spectroscopy results revealed that the films are non-stoichiometric in the depth; an interfacial transition layer between tantalum oxide and Si substrate, containing presumably SiO₂ was detected. It has been found by X-ray diffraction that the amorphous state of Ta₂O₅ depends on both the oxidation temperature and the thickness of the films—the combination of high oxidation temperature (>823 K) and thickness smaller than 50 nm is critical for the appearance of a crystal phase. The Ta₂O₅ layers crystallize to the monoclinic phase and the temperature of the phase transition is between 773 and 823 K for the thinner layers (<50 nm) and very close to 873 K for the thicker ones. The electrical characterization (current/voltage; capacitance/voltage) reveals that the optimal oxidation temperature for achieving the highest dielectric constant (∼32) and the lowest leakage current (10⁻⁸ A/cm² at 1 MV/cm applied field) is 873 K. The results imply that the poor oxidation related defects are rather the dominant factor in the leakage current than the crystallization effects.     

Formation of secondary phases during crystal growth of Pb5Ge3O11

Studies of secondary phases formed during the Czochralski growth of lead germanate crystals (Pb₅Ge₃O₁₁) show that these phases form inclusions in the crystal, thereby reducing its optical quality, and can also cause twinning and cracking. Results of differential thermal analysis, energy dispersive X-ray fluorescence analysis, and X-ray diffraction studies of secondary phases are presented. The narrow stability range for Pb₅Ge₃O₁₁ shown in the phase diagram, the thermal instability of this compound, and its pronounced supercooling during crystallization suggest that equilibrium conditions are difficult to sustain and that other compounds of the PbO-GeO₂ family may form, although Pb₅Ge3O₁₁ is melting congruently. It is shown that Pb₃GeO₅ and PbGeO₃, which are both reported to melt congruently, can crystallize during the growth of Pb₅Ge₃O₁₁ forming inclusions in the crystal. The successful synthesis of these three compounds is reported. The compound Pb₃Ge₂O₇, reported in the literature, is identified as a mixture of Pb₅Ge₃O₁₁ and PbGeO₃. Experimental conditions are presented for growing single phase Pb₅Ge₃O₁₁ crystals of uniform composition and high optical quality. This paper is based on a presentation at the Conference on Preparation and Properies of Electronic Materials, Princeton, N. J., August 1975.     

暴露(002)晶面的WO3纳米片薄膜的光电催化性能

采用一步水热法,以钨酸钠(Na2WO4·2H2O)为原料,草酸(H2C2O4)为结构导向剂,在FTO衬底上制备了具有高活性(002)面的WO3纳米片薄膜.利用XRD,FESEM对薄膜的物相和形貌进行了分析,通过UV-Vis,PL对薄膜的能带结构和载流子的分离能力进行了表征,通过电化学工作站对WO3薄膜的光电性能进行了研究.分析了草酸用量对WO3 纳米片薄膜的晶体取向、形貌尺寸和光电催化性能的影响.结果表明:草酸用量为0.30 g时,WO3纳米片薄膜的(002)面衍射峰强度最高,具有良好的光电催化性能.     

BaSi2O5荧光粉中Eu2+的制备，电子结构和荧光性质

绿色发射磷光剂BaSi2O5：Eu2+是由常见的固体反应合成。在CASTEP代码中,BaSi2O5可视为存在3.2eV直能隙的媒介带隙半导体。正如预期所料的,BaSi2O5光学带隙的计算值比对应的实验值低。200-400nm宽光谱范围可以有效地激活活化的Eu2 的BaSi2O5磷光剂,当最大半宽为95nm时,500nm处有一个发射峰。浓度和发射强度的研究表明Eu2 的最优浓度是0.05mol,当Eu2 容量超过临界值时,会出现浓度淬灭。最优条件的BaSi2O5的外量子效率：在315nm、350nm和365nm的激发下,Eu2 分别是96.1%、70.2%和62.1%。样品优越的光学性能表明绿色发射磷光剂可替代白光LED。