Studies of thin FeAlN films prepared by different techniques

The microstructure, morphology, and magnetic properties of FeAlN films deposited by reactive rf magnetron sputtering with subsequent treatment by three techniques, namely, in situ, ex situ (with the sputtering and annealing processes separated), and thermal crystallization of amorphous alloys, have been studied. FeAlN films prepared by the ex situ technique exhibit the best soft magnetic characteristics. Thermal crystallization of amorphous alloys produced films with properties having the highest thermal stability. Films 800-to 1000-nm thick were found to have the best soft magnetic properties. The dependences of the properties of FeAlN films on nitrogen content and annealing temperature were established. The conditions favoring the preparation of thin nanostructured FeAlN films featuring the best soft magnetic characteristics (saturation induction B _S = 1.8 T, coercivity H _C = 1.2 Oe, magnetic susceptibility μ₁ (1 MHz) = 3400) were determined.     

Low-temperature growth of polycrystalline Ge thin film on glass by in situ deposition and ex situ solid-phase crystallization for photovoltaic applications

Poly-crystalline germanium (poly-Ge) thin films have potential for lowering the manufacturing cost of photovoltaic devices especially in tandem solar cells, but high crystalline quality would be required. This work investigates the crystallinity of sputtered Ge thin films on glass prepared by in situ growth and ex situ solid-phase crystallization (SPC). Structural properties of the films were characterized by Raman, X-ray diffraction and ultraviolet-visible reflectance measurements. The results show the transition temperature from amorphous to polycrystalline is between 255 °C and 280 °C for in situ grown poly-Ge films, whereas the transition temperature is between 400 °C and 500 °C for films produced by SPC for a 20 h annealing time. The in situ growth in situ crystallized poly-Ge films at 450 °C exhibit significantly better crystalline quality than those formed by solid-phase crystallization at 600 °C. High crystalline quality at low substrate temperature obtained in this work suggests the poly-Ge films could be promising for use in thin film solar cells on glass.     

椭圆偏振光谱实时在线监测与离线分析微晶硅薄膜的生长

采用甚高频等离子体增强化学气相沉积技术高速沉积了有无籽晶层两个系列微晶硅薄膜,通过椭圆偏振光谱、拉曼光谱和XRD对薄膜进行了分析,发现采用籽晶层后,在薄膜沉积初期有促进晶化的作用;由于籽晶层减少了薄膜的诱导成核时间,提高了薄膜的沉积速率,对比了实时在线和离线椭圆偏振光谱两种测量状态对分析微晶硅薄膜的影响,研究发现,当薄膜较薄时,实时在线测量得到的薄膜厚度小于离线下的数值;当薄膜较厚时,两种测量条件下得到的薄膜厚度差异较小;实时在线条件下得到的表面粗糙度要大于离线条件下得到的数值,这是由于薄膜暴露在大气中后表面有硅氧化物生成,对表面有平滑作用.     

Role of the mercury pressure during reaction synthesis of Hg(Re)-based superconducting films

Thin films of mercury based superconductors were prepared on the R-plane sapphire with a CeO₂ buffer layer using a two step process involving the deposition of the Hg-free precursor and ex situ mercuration in the sealed quartz tube. For the thin film preparation, a method with no contact between the mercury source and the precursor film was used for mercuration. We studied the influence of the basic parameters of the mercuration (annealing time, temperature and partial pressure of the mercury) regarding the composition and superconducting properties of prepared Hg-based films to determine appropriate conditions for this mercuration method. We found out that an increased partial pressure of mercury inhibited the creation of the parasitic Re-based phase and supported the crystallization of the superconducting phase. The advantage of this mercuration method is higher reproducibility as well as its capability to prepare high quality thin large areas films. Presented at 5-th International Conference Solid State Surfaces and Interfaces, November 19–24, 2006, Smolenice Castle, Slovakia     

Electrical measurements of nanoscale bismuth cluster films

A range of percolating atomic cluster films, with nanoscale overall dimensions, have been studied using a combination of in situ and ex situ electrical transport measurements, together with field emission electron microscopy and atomic force microscopy. Bismuth clusters with mean diameter 20 nm were deposited between electrical contacts defined by electron beam lithography. The morphology of the films can be understood within percolation theory, and the electrical measurements show complex behaviour characteristic of both percolation effects and modification of the cluster films by current flow and by oxidation.     

Effect of growth defects on microwave properties in epitaxial Ba0.5Sr0.5TiO3 thin films grown on (001) MgO by pulsed laser deposition

Ba_0.5Sr_0.5TiO₃ (BSTO) films have been grown heteroepitaxially on (001) MgO substrates by pulsed laser deposition (PLD) to fabricate microwave phase shifters for the wide frequency range 45 MHz–50 GHz. Both as-grown and ex situ annealed films have a cube on cube epitaxial relationship with ?100?BSTO//?100?MgO. Threading dislocations are the dominant defects, mostly with Burgers vectors b = ?101?. Growth at 10^?1 mbar oxygen pressure, compared to 10^?4 mbar, resulted in significantly better properties. Ex situ annealing of the film grown at 0.1 mbar resulted in a reduction of 40% in threading dislocation density and a 40% increase in dielectric tunability.     

Thermal stability of amorphous SiOC/crystalline Fe composite

We examined the thermal stability of amorphous silicon oxycarbide (SiOC) and crystalline Fe composite by in situ and ex situ annealing. The Fe/SiOC multilayer thin films were grown via magnetron sputtering with controlled length scales on a surface-oxidized Si (100) substrate. These Fe/SiOC multilayers were in situ or ex situ annealed at temperature of 600 °C or lower. The thin multilayer sample (~10 nm) was observed to have a layer breakdown after 600 °C annealing. Diffusion starts from low groove angle triple junctions in Fe layers. In contrast, the thick multilayer structure (~70 nm) was found to be stable and an intermixed layer (Fe_xSi_yO_z) was observed after 600 °C annealing. The thickness of the intermixed layer does not vary as annealing time goes up. The results suggest that the Fe_xSi_yO_z layer can impede further Fe, Si and O diffusion, and assists in maintaining morphological stability.     

SiC film growth on Si(111) by supersonic beams of C 60

The development of electronic devices based on Silicon Carbide (SiC) has been strongly limited by the difficulties in growing high quality crystalline bulk materials and films. We have recently elaborated a new technique for the synthesis of SiC on clean Si substrates by means of supersonic beams of C₆₀: the electronic and structural properties of the film can be controlled by monitoring the beam parameters, i.e. flux and particles energy and aggregation state. SiC films were grown in Ultra High Vacuum on Si(111)-7×7, at substrates temperatures of 800 ^° C, using two different supersonic beams of C₆₀: He and H₂ have been used as seeding gases, leading to particles energy of 5 eV and 20 eV, respectively. Surface characterisation was done in situ by Auger and X-Ray photoelectron spectroscopy, as well as by low energy electron diffraction and ex situ by atomic force microscopy technique. SiC films exhibited good structural and electronic properties, with presence of defects different from the typical triangular voids. Received 20 November 2001     

Analysis of strain relaxation process in GaInN/GaN heterostructure by in situ X‐ray diffraction monitoring during metalorganic vapor‐phase epitaxial growth

Strain relaxation in a GaInN/GaN heterostructure is analyzed by combining in situ X‐ray diffraction (XRD) monitoring and ex situ observations. Two different characteristic thicknesses of GaInN films are defined by the evolution of in situ XRD from the full width at half‐maximum of symmetric (0002) diffraction as a function of GaInN thickness. This in situ XRD measurement enables to clearly observe the critical thicknesses corresponding to strain relaxation in the GaInN/GaN heterostructure caused by the formation of surface pits with bent threading dislocations and the generation of misfit dislocations on GaInN during growth. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Superconducting BSCCO thin films obtained by MBE

Summary We realized BSCCO thin films withT _c(R=0)=88 K using the Molecular Beam Epitaxy (MBE) technique. The stoichiometric control is reached by a multilayer deposition technique in which Ca−Cu−Sr−Bi are sequentially deposited using the two effusive cells and the two e-guns present in the system. EDS and X-ray analyses are used to cross-check the obtained results, after theex situ in air annealing. The recent acquisition of an atomic oxygen source will allow in the close future the completelyin situ realization of BSCCO thin films. Paper presented at the ?VII Congresso SATT?, Torino, 4–7 October 1994.     

Oxidation and thermal annealing effects on native and ion-irradiated PbTe films grown by molecular beam deposition

Investigations are reported into the effect of low-pressure oxygen exposure and thermal annealing on the carrier transport properties of native and 350 eV Ar⁺ bombarded PbTe films. The electrical measurements were madein situ on MBD-grown PbTe films without breaking vacuum. On native surfaces, oxidation was initially sustained by diffusion of a donor species from the film bulk to the surface, where reaction with oxygen occured. This diffusion process was apparently inhibited on ion irradiated films and direct doping of the film surface effected a gradual reduction in the ion-induced electron accumulation resident at the film surface. The native properties and behavioural characteristics of the films could be recovered by thermal annealing of the ion-irradiated and/or oxidized films at 300–350 °C.     

多晶Si0.9654Mn0.0346:B薄膜的磁性研究

利用磁控溅射和快速热处理的方法制备了Mn,B共掺的多晶硅薄膜(Si_0.9654Mn_0.0346:B).磁性和结构研究发现薄膜有两个铁磁相.低温铁磁相来源于杂相Mn₄Si₇,高温铁磁相(居里温度T_C～250K)是由Mn原子掺杂进入Si晶格导致.晶化后的薄膜利用射频等离子体增强化学气相沉积系统(PECVD)进行短暂(4min)的氢化处理后发现,薄膜的微结构没有发生变化而饱和磁化强度却随着 关键词： 磁性半导体 硅 氢化     

Nanoscratch studies of SiGe epitaxial layer damage on the Si substrate

The present study evaluates the wear performance of silicon-germanium (SiGe) epitaxial growth of thin films, in which the in situ scratch profile is followed by ex situ atomic force microscopy (AFM) examinations. The wear evaluation of SiGe films was carried out at different constant loads (2000, 4000, and 6000 μN) with the same sliding speeds. The microstructural morphology was observed by means of transmission electron microscopy (TEM)Findings show that annealing treatments of SiGe films exhibit the highest scratch resistance at 400 °C compared to that of the as-deposited sample. The main characteristic of SiGe film is its ability to withstand wear resistance; observations show that moderate compressive residual is beneficial to the film, since it can suppress crack initiation. The annealing treatments of SiGe films revealed the resultant adhesive and cohesive failure mechanism.     

Ferromagnetism dependence on hole carriers in polycrystalline silicon films co-doped with Mn and B

Polycrystalline Si_0.96Mn_0.04:B films were prepared by cosputtering deposition followed by rapid thermal annealing for crystallization. The films are ferromagnetic with Curie temperatures of about 250 K. Through the approach of microwave plasma enhanced chemical vapor deposition, the films were treated by hydrogen plasma and boron plasma. After the plasma treatments, the structural properties of the films did not change, while both the saturation magnetization and hole concentration in the films changed. The correlation between the magnetic properties and the transport properties of the Si_0.96Mn_0.04:B films suggests that free hole carriers play an important role in Si:Mn diluted magnetic semiconductors.     

Fabrication of atomically smooth SrRuO3 thin films by laser molecular beam epitaxy

High-quality SrRuO₃ (SRO) thin films and SrTiO₃/SRO bilayer were grown epitaxially on SrTiO₃ (STO)(001) substrates by laser molecular beam epitaxy. The results of in situ observation of reflection high-energy electron diffraction and ex situ X-ray diffraction ϑ-2ϑ scan indicate that the SRO thin films have good crystallinity. The measurements of atomic force microscopy and scan tunneling microscopy reveal that the surface of the SRO thin film is atomically smooth. The resistivity of the SRO thin film is 300 μΘ·cm at room temperature. Furthermore, the transmission electron microscopy study shows that the interfaces of STO/SRO and SRO/STO are very clear and no interfacial reaction layer was observed. The experimental results show that the SRO thin film is an excellent electrode material for devices based on perovskite oxide materials. Supported by the National Natural Science Foundation of China (Grant No. 10334070)     

Intercalative polymerization of cyclic esters in layered silicates: thermal vs. catalytic activation

Poly(ε-caprolactone) layered silicate nanocomposites were synthesized by in situ intercalative ring-opening polymerization (ROP) of ε-caprolactone. The polymerization was promoted by thermal or catalytic initiation starting from either non-modified natural sodium-montmorillonite (MMT-Na) or montmorillonite modified by different ammonium cations bearing either non-functional alkyl chains or chains terminated by carboxylic acid or hydroxyl functions. The resulting compositions were analyzed by small-angle X-ray diffraction and transmission electron microscopy. The clay dispersion depended on the structure of the alkyl ammonium. Exfoliated nanocomposites were formed when hydroxyl-containing alkyl ammonium was used; otherwise, partially intercalated/partially exfoliated structures were observed. Moreover, owing to the inherent catalytic properties of the montmorillonite surface, it was also possible to prepare intercalated nanocomposites by in situ polymerization of ε-caprolactone in presence of non-modified montmorillonite-Na (MMT-Na) without any added catalyst.     

The influence of the rhenium in the precursor film on the properties of the thin superconducting films based on thallium

Thin films of thallium based superconductors have been prepared on a CeO₂ buffered R-plane sapphire as well as on a LaAlO₃ substrate using an RF magnetron sputtering and an ex situ thallination in a one zone configuration. We have studied the influence of the presence of the rhenium in the precursor film on structural and electrical properties of the final films. Our results show that the presence of the rhenium in the precursor films caused the significant changes in the morphology of the prepared films.     

Features of the formation of a perovskite phase in thin polycrystalline Pb(Zr,Ti)O<Subscript>3</Subscript> films

The structure and dielectric properties of thin lead zirconate titanate Pb(Zr,Ti)O₃ films grown ex situ on a silicon substrate are studied using various methods (X-ray analysis, raster electron microscopy, atomic-force microscopy, optical microscopy, and dielectric measurements). It is shown that, upon increase in the crystallization temperature, the growth texture of the films changes, leading to a change of their dielectric parameters.     

Tribological Behavior of Fluorinated and Nonfluorinated Polyimide Films

In this study a series of polyimide (PI) films were synthesized from fluorinated and nonfluorinated monomers which contained diamines and dianhydrides. The influence of fluorine-containing groups on the glass transition temperature (T _g) and tribological properties of the PI films was investigated. The wear mechanism for the different kinds of PI polymers was comparatively discussed. T _g was characterized by dynamic mechanical analysis and the tribological changes were evaluated by friction and wear tests as well as scanning electron microscopy (SEM) analysis of the worn surfaces. Fourier transform infrared (FTIR) has been used to study the structures of the PI polymers. Experimental results indicated that the fluorine groups influenced the thermal behavior (T _g) of the PI films. Nonfluorinated PI films have lower friction coefficient and wear rate compared with the fluorinated ones. It was also found that the tribological properties of the PI films were closely related with the applied load. The friction coefficients and wear rates reduced with increasing the applied load.     

Preparation of ultrathin gold films by oxygen-ion sputtering and their optical properties

The optical and electrical properties of gold films of thickness varying from less than 1 to 8 nm are studied. The films are obtained by sputtering with argon ion and oxygen ion beams. It is shown that the properties of the films are independent of the type of ions used for sputtering. The 1-to 5-nm-thick films are continuous and offer a high transparency. Sputtering by oxygen ion beams is used to produce NiO_x/Au ohmic contacts to p-GaN.