Hydrogenated amorphous silicon nitride deposited by DC magnetron sputtering

Hydrogenated amorphous silicon nitride thin films are deposited by DC magnetron sputtering in argon, and molecular hydrogen and nitrogen mixture. The samples are characterized by electrical measurements and by optical transmission. The physicochemical structure is studied by FTIR spectrum analysis. The results show that both nitrogen and hydrogen are incorporated. The ratio [N]/[Si] increases with increasing hydrogen partial pressure. The deposited films are used in MIS structures. The capacitance–voltage characteristics are carried out. The deposited samples present a large gap and show a nearly chemical stoichiometric composition.     

Cu-In-O composite thin films deposited by reactive DC magnetron sputtering

Cu-In-O composite thin films were deposited by reactive DC magnetron sputtering at room temperature. The samples were characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), UV/vis spectrophotometer, four-probe measurement and Seebeck effect measurement, etc. The samples contain Cu, In and O. The ratios of Cu to In and O to In increase with increase in O₂ flow rates. The ratio of Cu to In is over 1 and this suggests that Cu is in excess. The obtained Cu-In-O thin films are very possibly made of rhombohedral In₂O₃ and monoclinic CuO. Transmittance of the films decreases with increase in O₂ flow rate. The decrease in transmittance results from increase in Cu content in the films. The optical band gap of all the samples is estimated to be 4.1-4.4 eV, which is larger than those of In₂O₃ and CuO. The sheet resistance of the films decreases with increase in O₂ flow rate. Conductivity of the films is a little low, due to the addition of Cu and the poor crystalline quality of the film. The conduction behavior of the films is similar to that of In₂O₃ and the conduction mechanism of Cu-In-O thin films is through O vacancy.     

Nickel induced lateral crystallization behavior of amorphous silicon films

Nickel induced lateral crystallization of amorphous silicon with and without electric field has been studied. Dendritic silicon growth behavior is observed, with crystallites of a few hundred nanometers in width and up to a few microns in length. The behavior can be understood from the preferential epitaxial growth of silicon from the (1 1 1) facets of the NiSi₂ precipitate, which forms during the early stage of the annealing process. The dendritic growth fronts are different with and without electric field in the nickel induced lateral crystallization process. Electric field is found to be beneficial in increasing the lateral crystallization rate and improving the film crystallinity. Joule heating plays an important role as well to enhance the lateral crystallization.     

直流磁控反应溅射法制备的钒氧化物薄膜及其光谱研究

用直流磁控反应溅射法和不同基底温度下在玻璃底上沉积微纳结构的氧化钒薄膜,通过X射线衍射、电子扫描显微镜、UV-Vis透射、红外和拉曼光谱研究了薄膜的结构特性.在低温下制备的薄膜表现出高的光学透过特性,在基底温度低于200℃下制备的薄膜具有无定形结构,而在基底温度高于200℃时制备的薄膜具有多晶结构.薄膜的光学参数使用经...     

利用等离子体辅助脉冲磁控溅射实现 多晶硅薄膜的低温沉积

本文报道了利用电感耦合等离子体辅助中频直流脉冲磁控溅射在温度300 ℃ 以下沉积氢化多晶硅薄膜的制备方法. 利用拉曼散射、X射线衍射、透射电子衍射和傅里叶红外光谱对多晶硅薄膜进行了表征. 详细研究了氢气在沉积过程中所起的作用, 并结合Langmuir探针和发射光谱等等离子体诊断方法, 对辅助等离子体源在多晶硅薄膜制备过程中所起到的作用进行了讨论.     

The effect of hydrogen on copper nitride thin films deposited by magnetron sputtering

Copper nitride thin films were deposited on Si (1 0 0) wafers by reactive magnetron sputtering at various H₂/N₂ ratios. X-ray diffraction measurements show that the films are composed of Cu₃N crystallites with anti-ReO₃ structure and exhibit preferred orientation of [1 0 0] direction. Although the relative composition of the films has obviously changes with the H₂/N₂ ratios, the orientations of the films keep almost no changes. However, the grain size, lattice parameter and composition of the films are strongly dependent on the H₂/N₂ ratios. The copper nitride films prepared at 10% H₂/N₂ ratios show poor stability and large weight gain compared to the copper nitride films prepared at 0% H₂/N₂ ratios.     

Photoluminescence analyses of hydrogenated amorphous silicon nitride thin films

Silicon-rich hydrogenated amorphous silicon nitride (a-SiN_x:H) films were grown by plasma enhanced chemical vapor deposition (PECVD) with different r=NH₃/SiH₄ gas flow ratios. The optical absorption characteristics were analyzed by Fourier transform infrared (FTIR) and UV-visible transmittance spectroscopies. The recombination properties were investigated via photoluminescence (PL) measurements. As r was increased from 2 to 9, the PL emission color could be adjusted from red to blue with the emission intensity high enough to be perceived by naked eye at room temperature. The behaviors of the PL peak energy and the PL band broadness with respect to the optical constants were discussed in the frame of electron-phonon coupling and band tail recombination models. A semiquantitative analysis supported the band tail recombination model, where the recombination was found to be favored when the carriers thermalize to an energy level at which the band tail density of states (DOS) reduces to some fraction of the relevant band edge DOS. For the PL efficiency comparison of the samples with different nitrogen contents, the PL intensity was corrected for the absorbed intensity fraction of the incident PL excitation source. The resulted correlation between the PL efficiency and the subgap absorption tail width further supported the band tail recombination model.     

溅射制备非晶氮化镓薄膜的光学性能

采用直流磁控溅射方法在不同的氩气-氮气（Ar-N₂）气氛中制备了非晶氮化镓（a-GaN）薄膜. X射线衍射分析（XRD）和拉曼光谱（Raman）表明薄膜具有非晶结构. 通过椭偏光谱（SE）得到薄膜的折射率和厚度都随着氩气分量的增多而增大. 紫外—可见光谱（UV-Vis）的测量得到,当氩气分量R,即Ar/（Ar+N₂）,为0%时,薄膜的光学带隙为3.90eV,比晶体GaN （c-GaN） 的较大,这主要是由非晶结构中原子无序性造成的;而当R关键词： 非晶氮化镓 溅射 光学带隙 带尾态     

Dynamics of hydrogen in hydrogenated amorphous silicon

The problem of hydrogen diffusion in hydrogenated amorphous silicon (a-Si:H) is studied semiclassically. It is found that the local hydrogen concentration fluctuations-induced extra potential wells, if intense enough, lead to the localized electronic states in a-Si:H. These localized states are metastable. The trapping of electrons and holes in these states leads to the electrical degradation of the material. These states also act as recombination centers for photo-generated carriers (electrons and holes) which in turn may excite a hydrogen atom from a nearby Si-H bond and breaks the weak (strained) Si-Si bond thereby apparently enhancing the hydrogen diffusion and increasing the light-induced dangling bonds.     

脉冲激光晶化超薄非晶硅膜的分子动力学研究

利用准分子脉冲激光晶化非晶硅薄膜是制备高密度尺寸可控的硅基纳米结构的有效方法之一.本文将脉冲激光对非晶硅超薄膜的影响处理为热传导问题,采用了基于Tersoff势函数的分子动力学方法模拟了在非晶氮化硅衬底上2.7 nm超薄非晶硅膜的脉冲激光晶化过程.研究了不同激光能量对非晶硅薄膜晶化形成纳米硅的影响,发现在合适的激光能量窗口下,可以获得高密度尺寸可控的纳米硅薄膜,进而模拟了在此能量作用下非晶硅膜中成核与生长的机理与微观过程,并对晶化所获得的纳米硅薄膜的微结构进行了分析. 关键词： 非晶硅 分子动力学 脉冲激光晶化     

Structural characterization and optical properties of UO2 thin films by magnetron sputtering

Uranium dioxide films were deposited on Si (1 1 1) substrates by dc magnetron sputtering method at different sputtering parameters. The structure, morphology and chemical state of the films were studied by field emission scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and atomic force microscopy. Influences of film thickness on the microstructure and optical properties were investigated. Experimental results show that the film crystallites are preferentially oriented with the (1 1 1) planes. The average grain size increases with increasing film thickness. AFM images show that the root mean square roughness of the films is between 1.2 nm and 2.1 nm. Optical constants (refractive index, extinction coefficient) of the films in the wavelength range of 350-1000 nm are obtained by ellipsometric spectroscopy. The result shows that the refractive index decreases with the increasing film thickness, while extinction coefficient increases with the film thickness.     

Low-temperature deposition of transparent conducting ZnO:Zr films on PET substrates by DC magnetron sputtering

Transparent conducting zirconium-doped zinc oxide (ZnO:Zr) films were firstly deposited on polyethylene terephthalate (PET) substrates with ZnO buffer layers by DC magnetron sputtering at room temperature. Dependence of physical properties of ZnO:Zr films on deposition pressure was systematically studied. All the deposited films were polycrystalline and (1 0 0) oriented. When deposition pressure increases from 1 to 2.5 Pa, the crystallinity of the films improves and the resistivity decreases. While deposition pressure increases from 2.5 to 3.5 Pa, the crystallinity of the films deteriorates and the resistivity increases. The lowest resistivity of 1.8 × 10⁻³ Ω cm was obtained for the films deposited at the optimum deposition pressure of 2.5 Pa. All the films present a high transmittance of above 86% in the wavelength range of the visible spectrum.     

Heterogeneous crystallization of amorphous silicon expedited by external force fields: a molecular dynamics study

Applying a molecular dynamics simulation technique with the Tersoff potential, we investigate the isothermal crystallization processes of amorphous silicon (a-Si). To obtain a realistic amorphous structure, a rapid quenching process from liquid-phase at 3500 K to solid-phase at 500 K is simulated at a rate of 10¹² K/s and the Voronoi analysis is conducted to observe atomic structural changes during this cooling process. This amorphous structure is utilized to simulate the crystallization processes at various process temperatures with and without external force fields. While homogeneous crystallization of a-Si could not be achieved readily, it is shown that the heterogeneous crystallization can be significantly accelerated by external force fields. This enhancement is owing to increased molecular jumping frequencies associated with the molecular potential energies being increased by external excitations, rather than due to thermal mechanisms normally found in conventional solid-phase crystallization processes.     

Microstructure of microwave dielectricthin films by RF magnetron sputtering

The article describes the microstructure and morphological properties of microwave dielectric ceramic thin films. These thin films were successfully prepared on SiO₂ (1 1 0) single-crystal substrates by radio frequency magnetron-sputtering system. The microstructure and morphology of the thin films were characterized by X-ray diffraction, scanning electron microscopy, atomic force microscopy, and transmission electron microscopy. The results show that the main phase is Ba_0.5Sr_0.5Nb₂O₆,which has a tetragonal perovskite structure, a long strip pattern, and uniform crystal-grain size of about 2-3 μm in length when annealed under 1150 °C for 30 min in an O₂ atmosphere. These thin films are of excellent crystallization quality, with a polycrystalline and dense structure.     

Effect of Ar in the source gas on the microstructure and optoelectronic properties of microcrystalline silicon films deposited by plasma-enhanced CVD

Hydrogenated microcrystalline silicon films have been prepared by plasma-enhanced chemical vapor deposition technique using silane diluted in H₂ or H₂ + Ar. The microstructures for silicon films have been evaluated by Raman scattering spectroscopy, X-ray diffraction and Fourier-transform infrared spectroscopy. Optical characterization has been done by UV-vis spectroscopy. It is found that the addition of Ar in diluent gases efficiently improves the deposition rate and crystallinity due to an enhanced dissociation of the source gas and the energy of deexcitation of Ar* released within the growth zone. Meanwhile, the enhanced crystallinity and the reducing of hydrogen ion bombardment with increasing Ar dilution lead to the polymerization and also a bad passivation of the hydrogen which cause the widening of the optical gap and increase of defect states in the μc-Si films. The absorption coefficient and dark conductivity are found to decrease basically with increasing Ar dilution corresponding to the widening optical gap and more defects. That the activation energy increases with increasing Ar dilution or decreasing hydrogen dilution is due to the fact that more defect states lead to a pulling down of the Fermi level.     

Surface passivation of crystalline silicon by sputter deposited hydrogenated amorphous silicon

This letter shows that intrinsic hydrogenated amorphous silicon (a‐Si:H) films deposited by RF magnetron sputtering can provide outstanding passivation of crystalline silicon surfaces, similar to that achieved by plasma enhanced chemical vapour deposition (PECVD). By using a 2% hydrogen and 98% argon gas mixture as the plasma source, 1.5 Ω cm n‐type FZ silicon wafers coated with sputtered a‐Si:H films achieved an effective lifetime of 3.5 ms, comparable to the 3 ms achieved by PECVD (RF and microwave dual‐mode). This is despite the fact that Fourier transform infrared spectroscopy measurements show that sputtering and PECVD deposited films have very different chemical bonding configurations. We have found that film thickness and deposition temperature have a significant impact on the passivation results. Self‐annealing and hydrogen plasma treatment during deposition are likely driving forces for the observed changes in surface passivation. These experimental results open the way for the application of sputtered a‐Si:H to silicon heterojunction solar cells. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

非平衡磁控溅射法类金刚石薄膜的制备及分析

利用非平衡磁控溅射物理气相沉积技术制备了光滑、致密、均匀的类金刚石薄膜.分析沉积工艺参数对所得类金刚石薄膜的电学特性的影响以及溅射粒子的大小、能量、碰撞及沉积过程中的相变机理后认为：溅射粒子越小、与环境气体分子的碰撞次数越多、与衬底相互作用时具有适当动量等，能够有效提高薄膜中sp^３杂化碳原子的含量.利用拉曼光谱 、纳米力学探针、红外光谱、扫描电镜等分析了所得类金刚石膜的结构、力学及光学性能、 表面形貌等特征.结果表明，类金刚石膜中sp^３杂化碳原子的含量较高，显微硬 度大于11GPa，薄膜光学透过率达到89.4％，折射系数为1.952，沉积速率为0.724μm/h，表 面光滑、致密、均匀，不存在明显的晶粒特征. 关键词： 非平衡磁控溅射 类金刚石膜 拉曼光谱 红外光谱     

Magnetic anisotropy properties of CoZrNb thin films deposited on PET substrate by magnetron sputtering

Soft magnetism and magnetic anisotropy properties of CoZrNb thin films deposited on polyethylene terephthalate (PET) substrate by magnetron sputtering were investigated. As the film thickness increases, the coercivity of films decreases from 7 to 4 Oe. It exhibits an in-plane uniaxial magnetic anisotropy as the thickness of CoZrNb thin films increases. An easy axis is observed in CoZrNb films along the direction transverse to the rolling direction of the polymer web.     

Field emission property of copper nitride thin film deposited by reactive magnetron sputtering

Copper nitride (Cu₃N) thin film was deposited on silicon (Si) substrate by reactive magnetron sputtering method. X-ray diffraction measurement showed that the film was composed of Cu₃N crystallites with anti-ReO₃ structure and exhibited preferential orientation of [1 0 0] direction. The field emission (FE) result showed that Cu₃N film had a turn-on electric field of about 3 V/μm at a current density of 1 μA/cm² and a current density of 700 μA/cm² was obtained at the electric field of 24 V/μm. The emission mechanism inferred by Fowler-Nordheim (FN) plot is shown as following: thermal electron emission at low field region and tunneling electron emission at high field region.     

Effects of flow ratios on surface morphology and structure of hydrogenated amorphous carbon films prepared by microwave plasma chemical vapor deposition

A series of hydrogenated amorphous carbon (a-C:H) films were deposited on silicon substrates by microwave plasma chemical vapor deposition technique with a mixture of hydrogen and acetylene. The effects of flow ratio of hydrogen to acetylene on surface morphology and structure of a-C:H films were investigated using surface-enhanced Raman spectroscopy and scanning probe microscope (SPM) in the tapping AFM mode. Raman data imply a transition from graphite-like phase to diamond-like bonding configurations when the flow ratio increases. AFM measurements show that the increase in hydrogen content, to some extent, can smoothen the surface morphology and decrease the RMS roughness. Excessive hydrogen is found to cause the formation of polymeric hydrocarbon clusters in the films and reduce deposition rate.