Growth of fcc(111) on bcc(110): Influence of growth and annealing temperature on epitaxy and surface morphology for Pd on Cr

The effects of growth versus annealing temperature on epitaxial relationship and surface morphology were studied for Pd(111) films on Cr(110) surfaces. While the epitaxial orientation of the Pd films depends on film thickness as well as on growth temperature, subsequent annealing has no effect on the epitaxial orientation. Instead, additional annealing of room temperature grown films takes the surface morphology from an island to a terrace shape, which was not observed for samples directly grown at elevated temperatures. These different effects that growth and annealing temperature have, help understanding the resulting structure and morphology of the heteroepitaxial system.     

Annealing effects on the plasmonic excitations of metal/metal interfaces

The effects of the annealing procedure at 400-450 K on the electronic properties of nanoscale thin films of Ca, Au and Ag grown on Cu(1 1 1) at room temperature were probed by high-resolution electron energy loss spectroscopy measurements. Ca surface plasmon underwent to a significant red-shift upon annealing, due to the oxidation of the topmost Ca layer. Water strongly interacted with the CaO interface at room temperature. Au surface plasmon disappeared upon annealing the gold film, as a consequence of the formation of an Au-Cu alloy. Ag surface plasmon red-shifted both in the annealed adlayer and with increasing temperature compared with the frequency recorded for the as-deposited silver film.     

Effects of post-thermal annealing temperature on the optical and structural properties of gold particles on silicon suboxide films

In this work, silicon suboxide (SiO_x) thin films were deposited using a RF magnetron sputtering system. A thin layer of gold (Au) with a thickness of about 10 nm was sputtered onto the surface of the deposited SiO_x films prior to the thermal annealing process at 400 °C, 600 °C, 800 °C and 1000 °C. The optical and structural properties of the samples were studied using scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), X-ray diffractometry (XRD), Fourier transform infrared spectroscopy (FTIR) and optical transmission and reflection spectroscopy. SEM analyses demonstrated that the samples annealed at different temperatures produced different Au particle sizes and shapes. SiO_x nanowires were found in the sample annealed at 1000 °C. Au particles induce the crystallinity of SiO_x thin films in the post-thermal annealing process at different temperatures. These annealed samples produced silicon nanocrystallites with sizes of less than 4 nm, and the Au nanocrystallite sizes were in the range of 7-23 nm. With increased annealing temperature, the bond angle of the Si-O bond increased and the optical energy gap of the thin films decreased. The appearance of broad surface plasmon resonance absorption peaks in the region of 590-740 nm was observed due to the inclusion of Au particles in the samples. The results show that the position and intensity of the surface plasmon resonance peaks can be greatly influenced by the size, shape and distribution of Au particles.     

热处理对ZnO/Au薄膜结构和压电特性的影响

通过射频磁控溅射在氧化硅片表面沉积ZnO/Au薄膜,并通过不同的热处理方式对薄膜进行退火。为了研究退火对ZnO/Au薄膜结构和压电特性的影响,采用X射线衍射分析（XRD）、光学显微镜、场发射扫面电镜（FESEM）和压电力分析仪对薄膜退火前后的材料特性进行了分析。研究发现,热处理能够改善ZnO/Au薄膜的结晶质量。特别是在氮气保护氛围下慢速退火后,薄膜结晶质量有明显改善。但是,热处理导致了薄膜的压电系数d33和d31降低。分析认为,热处理过程中Au原子在ZnO中的易迁移特性破坏了ZnO/Au薄膜的压电性能。     

Segregation at the surface of an Au/Pd alloy exposed to CO

We use density functional theory (DFT) with the generalized gradient approximation (GGA) and the revised Perdew-Burke-Ernzerhoff (rPBE) functional, to study the surface composition of the (1 1 1) and (1 0 0) dilute Pd/Au alloy. We find that the energy of Pd atoms is lower when they substitute an Au atom in the bulk than when they substitute an Au atom in the surface layer, or when they are adsorbed on the surface. Whether they are in the surface layer or in the bulk, the Pd atoms interact very weakly with each other. CO adsorbs on the Pd atom in the surface layer and the energy of this complex is lower than that of CO in gas and Pd atom in the bulk. The interaction between the PdCO complexes formed when CO adsorbs on a Pd atom imbedded in the surface layer, is also negligible. We use these energies, equilibrium thermodynamics, and a simple lattice-gas model to examine the equilibrium composition of the surface layer, as a function of temperature, CO pressure and the Pd/Au ratio. We find that the surface Pd concentration for a nanoparticle of an Au/Pd alloy differs from that in a bulk sample. The difference is due mainly to the fact that in a nanoparticle the migration of Pd atoms to the surface depletes the bulk concentration while in a large sample; the bulk provides an infinite source of Pd atoms to populate the surface sites. This system is of interest because Pd/Au alloys are selective catalysts for vinyl acetate synthesis when the Pd concentration on the surface is very low.     

Preferred orientations in nano-gold/silica/silicon interfaces

Gold in contact with silicon substrates Si(1 0 0), Si(1 1 1), and SiO₂ is studied by thermal evaporation and annealing in N₂ using the modified sphere-plate technique. The final orientation distribution of crystalline Au films grown on Si substrate systems that incorporate a native amorphous oxide layer of silica and Au on amorphous silica (SiO₂ glass) substrates is influenced by preferred orientations and twinning. Experimental evidence suggests that the orientation of Au{1 1 1} close packed planes (multiply twinned) was found to be of low-energy as the annealing temperature was increased to 530 °C and 920 °C. Additional orientations were observed for Au{1 0 0} on Si(1 0 0) substrates and Au{1 0 0}, {1 1 0}, and {3 1 1} on SiO₂ substrates. After annealing at 920 °C the size distribution of the gold particles was determined to be within the range of 20-800 nm while the morphology of gold surface appears spherical to faceted in character. These results show similarities to recent findings for smaller nano-size 1D particles, islands and thin Au films on silicon annealed over lower temperature ranges.     

Hydrogen Permeability of a Foil of Pd–Ag Alloy Modified with a Nanoporous Palladium Coating

Thin films with the composition Pd–23% Ag are obtained via magnetron sputtering. The magnetron sputtering of Pd–50% Zn films with subsequent diffusion annealing and etching of the active component is used to modify the surfaces of palladium–silver films to improve their hydrogen permeability. Modifying the surfaces of the resulting Pd–Ag films using a nanoporous palladium coating with a predominant distribution of particles ranging from 0 to 50 nm allows a hydrogen flux density of up to 0.4 mmol s^?1 m^?2 to be achieved for sufficiently thin palladium membranes (<10 μm) under conditions of low temperature (<90°C) and pressure (<0.6 MPa). Experimental evidence is gathered that under these conditions, the velocity of hydrogen transport is limited by dissociative–associative processes at membrane boundaries and can be greatly (by an order of magnitude) increased, due to acceleration of the limiting stage of the process via the formation of a palladium nanoporous coating on the film’s surface.     

Structure and composition of gallium nitride films produced by processing gallium arsenide single crystals in atomic nitrogen

Thin GaN films are grown on (001) single-crystal GaAs substrates processed in an atmosphere of active nitrogen radicals. Auger electron spectroscopy is applied to take the depth profiles of the basic chemical elements that enter into the composition of the epitaxial GaN films and single-crystal GaAs substrates. It is found that the surface composition of the GaN films is characterized by considerable nonstoichiometry (the excess nitrogen achieves ≈9%), which is caused by the presence of atomic nitrogen in the discharge chamber. With a high-resolution X-ray diffraction method, the structural perfection of the epitaxial layers is investigated. It is shown that low-temperature annealing (at temperatures below 700°C) is responsible for the formation of cubic GaN films on the (001) surface of cubic GaAs, whereas higher temperature annealing results in the growth of the hexagonal films.     

几种元素的界面插层对Ta/NiFe/Ta的各向异性磁电阻效应的影响

文章中,通过磁控溅射制备了界面处插入4d,5d元素薄层(包括Ru,Pd,Ag和Au)的Ta/NiFe/Ta多层膜,并对它们的磁输运和磁性以及微结构进行了测试和表征.结果显示,Pd和Pt一样界面效应显著,能有效地提高NiFe薄膜退火前后的AMR比值,并抑制磁性死层.表面能比较小、熔点相对低的插层材料Ag,Au在退火过程中容易通过晶界扩散,强烈破坏其AMR性能.对于熔点高、表面能比较大的插层材料如Ru,磁性死层同样得到了抑制,NiFe薄膜的温度稳定性也可以得到提高.结果表明界面插层从界面电子自旋-轨道散射、界面死层和界面原子扩散等方面深刻影响NiFe薄膜的AMR. 关键词： 各向异性磁电阻 界面效应 原子扩散     

Impact of thermal annealing on physical properties of vacuum evaporated polycrystalline CdTe thin films for solar cell applications

A study on impact of post-deposition thermal annealing on the physical properties of CdTe thin films is undertaken in this paper. The thin films of thickness 500 nm were grown on ITO and glass substrates employing thermal vacuum evaporation followed by post-deposition thermal annealing in air atmosphere within low temperature range 150–350 °C. These films were subjected to the XRD, UV‐Vis NIR spectrophotometer, source meter, SEM coupled with EDS and AFM for structural, optical, electrical and surface topographical analysis respectively. The diffraction patterns reveal that the films are having zinc-blende cubic structure with preferred orientation along (111) and polycrystalline in nature. The crystallographic parameters are calculated and discussed in detail. The optical band gap is found in the range 1.48–1.64 eV and observed to decrease with thermal annealing. The current–voltage characteristics show that the CdTe films exhibit linear ohmic behavior. The SEM studies show that the as-grown films are homogeneous, uniform and free from defects. The AFM studies reveal that the surface roughness of films is observed to increase with annealing. The experimental results reveal that the thermal annealing has significant impact on the physical properties of CdTe thin films and may be used as absorber layer to the CdTe/CdS thin films solar cells.     

CVD两步法生长ZnO薄膜及其光致发光特性

用CVD两步法在常压下于p型Si(100)衬底上沉积出具有较好择优取向的多晶ZnO薄膜。在325nm波长的光激发下,室温下可观察到显著的紫外光发射(峰值波长381nm)。高温退火后氧空位缺陷浓度增加,出现了一个450~600nm的绿光发光带,发光峰值在510nm。作为比较,用一步法生长的ZnO薄膜结晶质量稍差。在其PL谱中不仅有峰值波长389nm的紫外发射而且还出现了一个很强的蓝光发光中心(峰值波长437nm),退火后同样产生绿光发光带。对这两种绿光发光带的发光机制进行了研究,认为前者源于VO,而后者与O_Zn有密切的关系。     

Effect of annealing on the surface and band gap alignment of CdZnS thin films

Effects of the annealing temperature on structural, optical and surface properties of chemically deposited cadmium zinc sulfide (CdZnS) films were investigated. X-ray diffraction (XRD) results showed that the grown CdZnS thin films formed were polycrystalline with hexagonal structure. Atomic force microscopy (AFM) studies showed that the surface roughness of the CdZnS thin films was about 60-400 nm. Grain sizes of the CdZnS thin films varied between 70 and 300 nm as a function of annealing temperature. The root mean square surface roughness of the selected area, particular point, average roughness profile, topographical area of roughness were measured using the reported AFM software. The band gaps of CdZnS thin films were determined from absorbance measurements in the visible range as 300 nm and 1100 nm, respectively, using Tauc theory.     

退火时间对MgB_2超导薄膜的影响

在多晶A l2O3衬底上,以B2H6作为硼源,化学气相沉积先驱B薄膜,采用Mg扩散方法,在不同退火时间条件下制备了MgB2超导薄膜。通过电阻-温度曲线测量、X射线衍射分析和扫描电子显微镜形貌观测方法,研究了退火时间对MgB2薄膜的超导特性、晶体结构、表面形貌的影响。     

Morphology and photoluminescence study of electrodeposited ZnO films

ZnO films on ITO substrates and Au coated ITO substrates were fabricated by using electrodeposition technique. We carried out the experiments by adjusting the concentration of solution, potential, substrate, and temperature. The effect of temperature on the growth of the film has been examined. SEM images have shown that there are several kinds of grown competitions for the deposition of ZnO films, but three kinds of them are dominant. One is the discrete hexagonal column structure, the other is the pentagonal structure, and the third one is of well-oriented hexagonal columns with well-aligned structure. The explanation on the grown competition is discussed. ZnO hexagonal column structures with well-aligned and well-perpendicular to the surface were successfully obtained on Au/ITO substrate in aqueous solvent of electrolyte. Clearly the main columns in the film were obtained by increasing the temperature. Its photoluminescence (PL) study at low temperature exhibited the optical properties as wurtzite ZnO and indicated the existence of macrocrystalline ZnO. A better quality of ZnO columnar structures after annealing was demonstrated from PL analysis and discussion on the existence of 370 nm, 384 nm and 639 nm in the emission bands before and after annealing.     

热处理对立方相结构Mg0.57Zn0.43O合金薄膜表面和组成的影响

MgZnO合金具有可覆盖日盲紫外波段的禁带宽度和晶格匹配的单晶衬底,是理想的日盲紫外探测材料.由于MgO和ZnO分属立方相和六角相,分相问题使高质量单一相MgZnO难以获得.热处理是提高薄膜结晶质量的有效手段.利用MOCVD方法制备了单一立方相Mg0.57Zn0.43O合金薄膜,研究了薄膜的退火行为对薄膜结构和光学性能...     

Correlation between microstructure and optical properties of nano-crystalline TiO2 thin films prepared by sol-gel dip coating

Titanium dioxide thin films have been prepared from tetrabutyl-orthotitanate solution and methanol as a solvent by sol-gel dip coating technique. TiO₂ thin films prepared using a sol-gel process have been analyzed for different annealing temperatures. Structural properties in terms of crystal structure were investigated by Raman spectroscopy. The surface morphology and composition of the films were investigated by atomic force microscopy (AFM). The optical transmittance and reflectance spectra of TiO₂ thin films deposited on silicon substrate were also determined. Spectroscopic ellipsometry study was used to determine the annealing temperature effect on the optical properties and the optical gap of the TiO₂ thin films. The results show that the TiO₂ thin films crystallize in anatase phase between 400 and 800 °C, and into the anatase-rutile phase at 1000 °C, and further into the rutile phase at 1200 °C. We have found that the films consist of titanium dioxide nano-crystals. The AFM surface morphology results indicate that the particle size increases from 5 to 41 nm by increasing the annealing temperature. The TiO₂ thin films have high transparency in the visible range. For annealing temperatures between 1000 and 1400 °C, the transmittance of the films was reduced significantly in the wavelength range of 300-800 nm due to the change of crystallite phase and composition in the films. We have demonstrated as well the decrease of the optical band gap with the increase of the annealing temperature.     

Charging of metal atoms on ultrathin MgO/Mo(100) films

The chemical activity of supported metal nanoclusters is enhanced by electronic charging induced by the interaction with surface defects. We use density functional theory plane wave calculations to show that charging of metal atoms with high electron affinity like Au is possible also in the absence of defects by atom deposition on ultrathin MgO films (1 to 3 layers) grown on Mo(100). The Au 6s level falls below the Fermi level of Mo, leading to electron transfer from Mo to Au by direct tunneling through the insulating MgO film. The effect is not observed for Pd, whose 5s empty level falls just above the Fermi level of Mo, or for thicker MgO films.     

室温生长MgO底层诱导(001)取向FePt薄膜的有序化过程对FePt成分的依赖

室温下通过磁控溅射在表面热氧化的Si基片上生长了MgO/Fe_xPt_100-x双层膜和Fe_xPt_100-x单层膜系列样品，Fe_xPt_100-x的原子成分x=48—68.研究了热处理前后不同成分FePt薄膜的晶体结构和磁性的变化，尤其是MgO底层的引入对FePt的晶体结构和磁性的影响 关键词： FePt(001)薄膜 0相')" href="#">L1₀相     

Structural properties of TiN films grown on stainless steel substrates by a reactive radio-frequency sputtering technique at low temperature

TiN thin films were grown on stainless steel substrates by using the reactive radio-frequency magnetron-sputtering technique at relatively low temperature (200°C) using Ti and N₂. The deposition rate of the TiN film increased linearly with increasing applied radio-frequency power, and it decreased with increasing partial-pressure ratio of the N₂ gas to the Ar gas. Scanning electron microscopy (SEM) showed that the surfaces of the TiN films had very smooth morphologies. The TiN thin film had good stoichiometry for a partial-pressure ratio of 0.05. The stoichiometry of the TiN films and the interface qualities of the TiN/stainless steel heterostructures were investigated by Auger electron spectroscopy (AES) measurements. Auger depth profiles indicated that the compositions of the as-grown films consisted of titanium and nitrogen uniformly distributed throughout the films and that the films exhibited smooth interfaces. The interface quality of the TiN films to the stainless steel substrates were improved by annealing. These results indicate that annealed TiN thin films grown on stainless steel substrates hold promise for potential applications in advanced ceramic devices.     

Study on morphology and photoluminescence of Au/SiO2 nanocomposite films

Au/SiO₂ nanocomposite films were fabricated on Si (111) substrates by radio frequency (RF) magnetron sputtering technique and annealing at different temperature for 20 min (mode A) and at 1000 °C for different annealing time (mode B). The nanocomposite films were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and photoluminescence (PL). SEM results demonstrate that the size of Au crystallites in mode A first increases and then decreases, on increasing annealing temperature, according to the results of XRD spectra. Analysis of PL spectra in mode B shows that the intensity of the emission peak at 440 nm and 523 nm early increases and late decreases, with increasing annealing time at 1000 °C. The origin of the emission peak at around 440 nm was related to the size and quantity of Au particles and one of the emission peak at around 523 nm was related to the nanostructure of films in agreement with SEM imagines. Experimental results indicated that morphology, microstructure and luminescence of Au/SiO₂ nanocomposite films showed close affinity with annealing temperature and annealing time.