In2O3纳米线制备及其特性

使用管式加热炉成功地制备出In2O3纳米线.通过扫描电子显微镜可以看到样品为In2O3纳米线;X射线衍射分析证实该材料是立方结构的In2O3;X射线光电子谱分析发现该In2O3中存在大量氧缺陷;光致发光谱研究显示制得的In2O3纳米线有比较强的发光现象,主要集中在紫外光谱区.同时对反应的气相-固相(V-S)生长机理和In2O3的光致发光机理进行了详细分析.     

In situ study of the formation of silicide phases in amorphous Co-Si mixed layers

We investigate Co silicide phase formation when extra Si is added within an as deposited 50 nm Co film. The addition of Si is investigated for both the Co/SiO₂ and Co/Si(1 0 0) system. A series of 10 Co-Si mixed films with a Si content varying from 21 to 59 at.% was prepared and investigated during annealing with in situ X-ray diffraction. The oxide system is used as reference system to identify phases that initially crystallize in an amorphous mixture of a given composition. Multiple phases can nucleate, and the temperature of crystallization depends on the Co-Si atomic ratio. Upon heating of the Co(Si)/Si system, the first reaction is a similar crystallization reaction of the Co(Si) mixture. Once the first phase is formed, one has the normal system of a silicide phase in contact with an unlimited amount of Si from the substrate, and the sequential phase formation towards CoSi₂ is established. For deposited layers of composition ranging from 48%Si to 52%Si, the CoSi is the first phase to form and increasing the amount of Si leads to a remarkable improvement of the thermal stability of CoSi on Si(1 0 0). CoSi₂ nucleation was extensively delayed by 150 °C compared to the reaction observed from a pure Co film on Si(1 0 0). Electron backscatter diffraction measurements reveal that in this range, the gradual Si increase systematically leads to bigger CoSi grains (up to 20 μm). This shows that the grain size of the CoSi precursor strongly affects the nucleation of the following CoSi₂ phase. Laser-light scattering measurements suggest that adding more than 42%Si reduces the roughness of the CoSi₂ layer.     

Structural and opto-electrical properties of pyrolized ZnO-CdO crystalline thin films

A series of ZnO-CdO thin films of different molar ratios of Zn and Cd have been deposited on glass substrate at substrate temperature ~ 360 ℃ by the spray pyrolysis technique at an ambient atmosphere. X-ray diffraction (XRD) studies confirmed the polycrystalline nature of the film and modulated crystal structures of wurtzite (ZnO) and cubic (CdO) are formed. The evaluated lattice parameters, and crystallite size are consistent with literature. Dislocation density and strain increased in the film as the grain sizes of ZnO and CdO are decreased. The band gap energy varies from 3.20 to 2.21 eV depending on the Zn/Cd ratios in the film. An incident photon intensity dependent I-V study confirmed that the films are highly photosensitive. Current increased with the increase of the intensity of the light beam. The optical conductivity and the optical constants, such as extinction coefficient, refractive index and complex dielectric constants are evaluated from transmittance and reflectance spectra of the films and these parameters are found to be sensitive to photon energy and displayed intermediate optical properties between ZnO and CdO, making it preferable for applications as the buffer and window layers in solar cells.     

Maskless pendeo-epitaxial growth of GaN films

High-resolution x-ray diffraction (XRD) and atomic force microscopy (AFM) of pendeo-epitaxial (PE) GaN films confirmed transmission electron microscopy (TEM) results regarding the reduction in dislocations in the wings. Wing tilt ≤0.15° was due to tensile stresses in the stripes induced by thermal expansion mismatch between the GaN and the SiC substrate. A strong D°X peak at ≈3.466 eV (full-width half-maximum (FWHM) ≤300 μeV) was measured in the wing material. Films grown at 1020°C exhibited similar vertical [0001] and lateral [11 0] growth rates. Increasing the temperature increased the latter due to the higher thermal stability of the GaN(11 0). The (11 0) surface was atomically smooth under all growth conditions with a root mean square (RMS)=0.17 nm.     

射频磁控溅射法在柔性聚酰亚胺衬底上制备ZnS薄膜及其特性研究

为使Ⅱ-Ⅵ族化合物ZnS薄膜具有可弯曲性,选用柔性的聚酰亚胺作为衬底材料,用射频磁控溅射法沉积ZnS薄膜,对所制备薄膜的结晶结构、组分和光学特性进行分析.实验结果表明,所制备薄膜为结晶态的闪锌矿ZnS结构,择优取向为(111)晶面,晶粒尺寸为25.6 nm.薄膜组分接近化学计量比,并具有少量的S损失.薄膜在可见光区和近红外光区的平均透射率分别为82.0％和90.5％,透光特性良好.作为对比,在钠钙玻璃衬底上溅射的ZnS薄膜的结晶度高于聚酰亚胺衬底薄膜,但其透射率略低于柔性ZnS薄膜.实验结果表明了用磁控溅射法在柔性聚酰亚胺衬底上制备ZnS薄膜的可行性.     

Structural Aspects of P2-Type Na0.67Mn0.6Ni0.2Li0.2O2 (MNL) Stabilization by Lithium Defects as a Cathode Material for Sodium-Ion Batteries

A known strategy for improving the properties of layered oxide electrodes in sodium-ion batteries is the partial substitution of transition metals by Li. Herein, the role of Li as a defect and its impact on sodium storage in P2-Na_0.67Mn_0.6Ni_0.2Li_0.2O₂ is discussed. In tandem with electrochemical studies, the electronic and atomic structure are studied using solid-state NMR, operando XRD, and density functional theory (DFT). For the as-synthesized material, Li is located in comparable amounts within the sodium and the transition metal oxide (TMO) layers. Desodiation leads to a redistribution of Li ions within the crystal lattice. During charging, Li ions from the Na layer first migrate to the TMO layer before reversing their course at low Na contents. There is little change in the lattice parameters during charging/discharging, indicating stabilization of the P2 structure. This leads to a solid-solution type storage mechanism (sloping voltage profile) and hence excellent cycle life with a capacity of 110 mAh g^-1 after 100 cycles. In contrast, the Li-free compositions Na_0.67Mn_0.6Ni_0.4O₂ and Na_0.67Mn_0.8Ni_0.2O₂ show phase transitions and a stair-case voltage profile. The capacity is found to originate from mainly Ni³⁺/Ni⁴⁺ and O^2-/O^2-δ redox processes by DFT, although a small contribution from Mn⁴⁺/Mn⁵⁺ to the capacity cannot be excluded.     

ZnAl_2O_4/α-Al_2O_3衬底上GaN的生长

研究了直接在 Zn Al2 O4/α-Al2 O3 衬底上用 MOCVD法一步生长 Ga N薄膜 .利用脉冲激光淀积法在α-Al2 O3衬底上淀积了高质量 Zn O薄膜 ,对 Zn O/α-Al2 O3 样品在 110 0℃退火得到了具有 Zn Al2 O4覆盖层的 α-Al2 O3 衬底 ,并在此复合衬底上利用光加热低压 MOCVD法直接生长了纤锌矿结构 Ga N. X射线衍射谱表明反应得到的Zn Al2 O4层为 ( 111)取向 .扫描电子显微镜照片显示随退火时间从小于 3 0 min增加到 2 0 h,Zn Al2 O4表面由均匀的岛状结构衍变为突起的线状结构 ,相应的 Ga N X射线衍射谱表明 Ga N由 c轴单晶变为多晶 ,单晶 Ga N的摇摆曲线半高宽     

用SiH2Cl2沉积MEMS中的多晶硅薄膜研究

用SiH2Cl2在3种温度下进行了多晶硅薄膜的沉积,根据膜厚计算出了沉积速率,用SEM、XRD和薄膜应力测试仪对薄膜进行测试分析.证明用SiH2Cl2在950℃时可以快速沉积用于MEMS的多晶硅.     

Ni(Pt)Si硅化物温度稳定性的研究

对比研究了夹层结构N i/P t/N i分别与掺杂p型多晶硅和n型单晶硅进行快速热退火形成的硅化物薄膜的电学特性。实验结果表明,在600~800°C范围内,掺P t的N iS i薄膜电阻率低且均匀,比具有低电阻率的镍硅化物的温度范围扩大了100~150°C。依据吉布斯自由能理论,对在N i(P t)S i薄膜中掺有2%和4%的P t样品进行了分析。结果表明,掺少量的P t可以推迟N iS i向N iS i2的转化温度,提高了镍硅化物的热稳定性。最后,制作了I-V特性良好的N i(P t)S i/S i肖特基势垒二极管,更进一步证明了掺少量的P t改善了N iS i肖特基二极管的稳定性。     

ZnO薄膜的XPS研究

利用等离子体增强型MOCVD设备,在C面蓝宝石上生长出了C轴取向的未退火、生长后一次退火和生长过程中多次退火的ZnO薄膜样品,并通过X光衍射和X光电子能谱对样品进行了表征,结果表明生长过程中多次退火的样品具有较高的质量,O/Zn原子比较大,且受空气中氧和水汽的影响最小.