Epitaxial growth and structural characterization of Pb(Fe1/2Nb1/2)O3 thin films

We have grown lead iron niobate thin films with composition Pb(Fe_1/2Nb_1/2)O₃ (PFN) on (0 0 1) SrTiO₃ substrates by pulsed laser deposition. The influence of the deposition conditions on the phase purity was studied. Due to similar thermodynamic stability spaces, a pyrochlore phase often coexists with the PFN perovskite phase. By optimizing the kinetic parameters, we succeeded in identifying a deposition window which resulted in epitaxial perovskite-phase PFN thin films with no identifiable trace of impurity phases appearing in the X-ray diffractograms. PFN films having thicknesses between 20 and 200 nm were smooth and epitaxially oriented with the substrate and as demonstrated by RHEED streaks which were aligned with the substrate axes. X-ray diffraction showed that the films were completely c-axis oriented and of excellent crystalline quality with low mosaicity (X-ray rocking curve FWHM?0.09°). The surface roughness of thin films was also investigated by atomic force microscopy. The root-mean-square roughness varies between 0.9 nm for 50-nm-thick films to 16 nm for 100-nm-thick films. We also observe a correlation between grain size, surface roughness and film thickness.     

Deposition of ZnO multilayer on LiNbO3 single crystals by DC-magnetron sputtering

Zinc oxide (ZnO) thin films were deposited on LiNbO₃ (LN) single crystals with 200 nm thicknesses by three different ways, where coating of zinc (Zn) film was followed by thermal oxidation for four, two, and one steps with 50, 100, and 200 nm thicknesses repeatedly. Sample, which was produced at 4-step of deposition and oxidation of Zn layer, showed high transmittance and low structural defect due to a lower photoluminescence intensity and Urbach energy. Average grain size in X-ray diffraction (XRD), scanning electron microscopy (SEM) micrograph, and atomic force microscopy (AFM) images for multilayer of ZnO was lower than monolayer of ZnO thin films. Applying multilayer coating technique leads to decrease of surface roughness and scattering on light on surface and fabrication of LiNbO₃ waveguides with lower optical loss.     

Strain due to nickel diffusion into hydrogen-terminated Si(1 1 1) surface

We studied the affection of thin (i.e., 0.2–0.8 nm) Ni films on hydrogen-terminated Si(1 1 1) substrate surface by using strain-sensitive X-ray diffraction. It was reported that Ni deposition onto hydrogen-terminated Si surface apparently does not cause film growth, but rather diffuses into the Si crystal, creating an “Ni diffusion layer” up to Ni deposition 0.8 nm thick. Measured rocking curves of the Si 1 1 3 reflection and integrated intensities of the rocking curves for the substrate provide information about the evolution of the strain field introduced near the substrate surface during Ni diffusion into the substrate. Comparing the measured and calculated rocking curves indicates that compression of the {1 1 1} spacing of the Si occurs gradually up to an Ni thickness of 0.6 nm, and that above this thickness, strain relaxation occurs.

We found that the slope of the integrated intensity of the rocking curve versus X-ray wavelength correlates to the strain field near the surface, in the same way that the shape of the rocking curves correlate to the strain field near the surface. Dynamical diffraction calculations indicate that measurement of the slope of the integrated intensity of the rocking curve versus X-ray wavelength is useful for strain analysis, because the dependence is not only sensitive to strain fields, but is also insensitive to the effect of absorption by the overlayer, which otherwise would cause deformation of the shape of the rocking curve.     

Improved surface morphology of flow-modulated MOVPE grown AIN on sapphire using thin medium-temperature AIN buffer layer

High-temperature (HT) AIN films were grown on (0 0 0 1) sapphire by low-pressure flow-modulated (FM) metal organic vapor phase epitaxy (MOVPE) with and without inserting a thin medium-temperature (MT) AIN layer. To suppress parasitic reactions between the sources of trimethylaluminum (TMA) and ammonia (NH₃), TMA and NH₃ was introduced to the reactor of MOVPE by alternating supply way. Surface morphology and crystalline quality were characterized by a scanning electronic microscopy (SEM), atomic force microscopy (AFM) and X-ray rocking curve (XRC) measurements of (0 0 0 2) and (10-12) diffractions. The AFM and SEM measurements indicated that the thin MT-AIN layer had a strong influence on the surface morphology of the HT-AIN films. The surface morphology became quite smooth by inserting the thin MT-AIN layer and surface RMS roughness values were 0.84 nm and 13.4 nm for the HT-AIN films with and without inserting the thin MT-AIN buffer layer, respectively. By etching the samples in aqueous KOH solution, it was found that the polarity of AIN films was different, the HT-AIN film with the thin MT-AIN layer could not be etched, indicating that the film had an Al-polar surface; however, the film without the MT-AIN layer was etched, which was explained that that film had a N- or mixed-polar surface. The mechanism for the origin of the different polarity of HT-AIN with and without the thin MT-AIN layer was proposed and discussed in detail.     

Surface chemical states of barium zirconate titanate thin films prepared by chemical solution deposition

Ba(Zr_0.05Ti_0.95)O₃ (BZT) thin films grown on Pt/Ti/SiO₂/Si(1 0 0) substrates were prepared by chemical solution deposition. The structural and surface morphology of BZT thin films has been studied by X-ray diffraction (XRD) and scanning electron microscope (SEM). The results showed that the random oriented BZT thin film grown on Pt/Ti/SiO₂/Si(1 0 0) substrate with a perovskite phase. The SEM surface image showed that the BZT thin film was crack-free. And the average grain size and thickness of the BZT film are 35 and 400 nm, respectively. Furthermore, the chemical states and chemical composition of the films were determined by X-ray photoelectron spectroscopy (XPS) near the surface. The XPS results show that Ba, Ti, and Zr exist mainly in the forms of BZT perovskite structure.     

Low-temperature growth of Y2O3 thin films by ultraviolet-assisted pulsed laser deposition

Thin Y₂O₃ films have been grown on (100) Si using an in-situ ultraviolet-assisted pulsed laser deposition (UVPLD) technique. When compared to conventional pulsed laser deposited (PLD) films under similar conditions, the UVPLD-grown films exhibited better structural and optical properties, especially those grown at lower substrate temperatures, from 200 °C to 400 °C. X-ray diffraction investigations showed that the films grown were highly crystalline and textured. According to X-ray photoelectron spectroscopy and Rutherford backscattering spectrometry investigations, UVPLD-grown Y₂O₃ films have a better overall stoichiometry and contain less physisorbed oxygen than the conventional PLD-grown films. The refractive index values, measured in the range 300-750 nm by using variable-angle spectroscopic ellipsometry, were similar to those of a reference Y₂O₃ film.     

单晶Si表面离子束溅射沉积Co纳米薄膜的研究

采用离子束溅射沉积法，在单晶Si基片上制备了不同厚度(1—100nm)的Co纳米薄膜.利用原子力显微镜、X射线光电子能谱(XPS)仪和X射线衍射仪对不同厚度的Co纳米薄膜进行了分析和研究.结果表明：当薄膜厚度为1—10nm时，沉积颗粒形态随薄膜厚度增加将由二维生长的细长胞状过渡到多个颗粒聚集成的球状.当膜厚大于10nm时，小颗粒球聚集成大颗粒球，颗粒球呈现三维生长状态.表面粗糙度随膜厚的增加呈现先增加后减小的趋势，在膜厚为3nm时出现极值.XPS全程宽扫描和窄扫描显示：薄膜表面的元素成分为Co，化学态分别 关键词： 离子束沉积 纳米薄膜 X射线光电子能谱 X射线衍射     

Formation of gold nanoparticles in heat-treated reactive co-sputtered Au-SiO2 thin films

In this work, formation of gold nanoparticles in radio frequency (RF) reactive magnetron co-sputtered Au-SiO₂ thin films post annealed at different temperatures in Ar + H₂ atmosphere has been investigated. Optical, surface topography, chemical state and crystalline properties of the prepared films were analyzed by using UV-visible spectrophotometry, atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and X-ray diffractometry (XRD) techniques, respectively. Optical absorption spectrum of the Au-SiO₂ thin films annealed at 800 °C showed one surface plasmon resonance (SPR) absorption peak located at 520 nm relating to gold nanoparticles. According to XPS analysis, it was found that the gold nanoparticles had a tendency to accumulate on surface of the heat-treated films in the metallic state. AFM images showed that the nanoparticles were uniformly distributed on the film surface with grain size of about 30 nm. Using XRD analysis average crystalline size of the Au particles was estimated to about 20 nm.     

Low-temperature growth of epitaxial ZnO films on (001) sapphire by ultraviolet- assisted pulsed laser deposition

ZnO thin films have been grown on thin Si₃N₄ membranes and (001) sapphire substrates by an ultraviolet-assisted pulsed laser deposition (UVPLD) technique. The microstructure of the films grown on Si₃N₄ membranes, investigated by transmission electron microscopy, showed that crystalline and textured films can be grown by UVPLD at a substrate temperature of only 100 °C. For deposition temperatures higher than 400 °C, ZnO films grown on sapphire substrates were found to be epitaxial by Rutherford backscattering (RBS) and X-ray diffraction measurements. The minimum yield of channeling RBS spectra recorded from films deposited at 550 °C was around 2% and the FWHM of the rocking curve for the (002) diffraction peak was 0.17°; these values are similar to those recorded from ZnO layers grown by conventional PLD at 750 °C.     

Laser Induced Damage Threshold at 355 and 1064nm of Ta2O5 Films of Different Phases

Ta2O5 films axe deposited on fused silica substrates by conventional electron beam evaporation method. By annealing at different temperatures, Ta2 O5 films of amorphous, hexagonal and orthorhombic phases are obtained and confirmed by x-ray diffractometer （XRD） results. X-ray photoelectron spectroscopy （XPS） analysis shows that chemical composition of all the films is stoichiometry. It is found that the amorphous Ta2 O5 film achieves the highest laser induced damage threshold （LIDT） either at 355 or 1064nm, followed by hexagonal phase and finally orthorhombic phase. The damage morphologies at 355 and 1064nm are different as the former shows a uniform fused area while the latter is centred on one or more defect points, which is induced by different damage mechanisms. The decrease of the LIDT at 1064nm is attributed to the increasing structural defect, while at 355nm is due to the combination effect of the increasing structural defect and decreasing band gap energy.     

The characterization of fluorocarbon films on NiTi alloy by magnetron sputtering

Fluorocarbon films were deposited on nickel-titanium (NiTi) alloy substrate by radio-frequency (RF, 13.56 MHz) magnetron sputtering using a polytetrafluoroethylene (PTFE) target. The deposition parameters of fluorocarbon films including the RF power, the working gas pressure and Ar flow rate were systematically studied. The structure of the deposited films was studied by attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS). The surface morphology of the deposited films was measured by atomic force microscopy (AFM). The mechanical properties of the deposited films were characterized by a nanoindenter. C-Fx and C-C units were found in the deposited fluorocarbon films, which corresponded to the results of XPS. The surface roughness of the fluorocarbon film was 7.418 nm (Ra).     

Improvement of Field Emission Characteristics of Copper Nitride Films with Increasing Copper Content

A copper nitride （Cu3N） thin film is deposited on a Si substrate by the reactive magnetron sputtering method. The XPS measurements of the composite film indicate that the Cu content in the film is increased to 80.82 at. % and the value of the Cu/N ratio to 4.2：1 by introducing 4% 112 into the reactive gas. X-ray diffraction measurements show that the film is composed of Cu3N crystallites with an anti-ReO3 structure. The effects of the increase of copper content on the field emission characteristics of the Cu3N thin film are investigated. Significant improvement in emission current density and emission repeatability could be attributed to the geometric field enhancement, caused by numerous surface nanotips, and the decrease of resistivity of the film.     

Adjusting chemical bonding of hard amorphous CSixNy thin films by N*-plasma-assisted pulsed laser deposition

Hard amorphous carbon silicon nitride thin films have been grown by pulsed laser deposition (PLD) of various carbon silicon nitride targets by using an additional nitrogen RF plasma source on [100] oriented silicon substrates at room temperature. The influence of the number of laser shots per target site on the growth rate and film surface morphology was studied. Up to about 30 at. % nitrogen and up to 20 at. % silicon were found in the films by Rutherford backscattering spectroscopy (RBS) and X-ray photoelectron spectroscopy (XPS). The XPS of the films showed a clear correlation of binding energy to the variation of PLD parameters. The films show a universal hardness value up to 23 GPa (reference value for silicon substrate 14 GPa) in dependence on target composition and PLD parameters. The results emphasise the possibility of variation of chemical bonding and corresponding properties, such as nanohardness, of amorphous CSi_xN_y thin films by the plasma-assisted PLD process.     

Photosensitivity of nanocrystalline ZnO films grown by PLD

We have studied the properties of ZnO thin films grown by laser ablation of ZnO targets on (0 0 0 1) sapphire (Al₂O₃), under substrate temperatures around 400 °C. The films were characterized by different methods including X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and atomic force microscopy (AFM). XPS analysis revealed that the films are oxygen deficient, and XRD analysis with θ-2θ scans and rocking curves indicate that the ZnO thin films are highly c-axis oriented. All the films are ultraviolet (UV) sensitive. Sensitivity is maximum for the films deposited at lower temperature. The films deposited at higher temperatures show crystallite sizes of typically 500 nm, a high dark current and minimum photoresponse. In all films we observe persistent photoconductivity decay. More densely packed crystallites and a faster decay in photocurrent is observed for films deposited at lower temperature.     

AlCl3-induced crystallization of amorphous silicon thin films

It is reported that the direct contact between Al and amorphous silicon (a-Si) enhances the crystallization of a-Si films. But the polycrystalline silicon (poly-Si) films crystallized by the direct contact of Al metal film suffer the problems of rough surface. In our study, we utilized the AlCl₃ vapor during the a-Si films deposition instead of Al metal film to enhance crystallization. X-ray diffraction (XRD) shows that the AlCl₃ vapor so successfully enhanced the crystallization of a-Si films that the crystallization was completed in 5 h at 540 °C. And the orientation of the poly-Si film deposited with AlCl₃ vapor is much more random than that of annealed with Al metal under layer. But the average grain size is much larger than that. Moreover, the surface of the AlCl₃-induced crystallized poly-Si film was much smoother than that of the Al-induced poly-Si film. The Al and Cl incorporation into the poly-Si film was confirmed using X-ray photoelectron spectroscopy (XPS) and found that the quantity of Al and Cl incorporated into the Si film was below the detection limit of XPS.     

MSLM调制组件的电光性能

对设计并制作的[M_gF₂+(ZrO₂/SiO₂)]膜系·LiNbO₃·ITO/玻璃结构的MSLM用调制组件的综合电光性能进行了实验测定。结果表明,其反射半波电压V_πR为1.2kV±0.1kV,反射率达99%,峰值次级电子发射系数为5.8。用其制作的光导址MSLM具有良好的功能与性能。     

XPS depth profiling study on the passive oxide film of carbon steel in saturated calcium hydroxide solution and the effect of chloride on the film properties

X-ray photoelectron spectroscopy (XPS) was used to study the properties of passive oxide film that form on carbon steel in saturated calcium hydroxide solution and the effect of chloride on the film properties. The thickness of the oxide films was determined to be approximately 4 nm and was not affected by the exposure time. Near the film/substrate interface the concentration of the Fe²⁺ oxides was higher than the concentration of the Fe³⁺ oxides; the layers near the free surface of the film mostly contained Fe³⁺ oxides. Chloride exposure decreased the thickness of the oxide films and changed their stoichiometry such that near the film/substrate interface Fe³⁺/Fe²⁺ ratio increased.     

Auger electron/X-ray photoelectron and cathodoluminescent spectroscopic studies of pulsed laser ablated SrAl2O4:Eu,Dy thin films

Auger electron/X-ray photoelectron and cathodoluminescent (CL) spectroscopic studies were conducted on pulsed laser deposited SrAl₂O₄:Eu²⁺,Dy³⁺ thin films and the correlation between the surface chemical reactions and the decrease in the CL intensity was determined. The Auger electron and the CL data were collected simultaneously in a vacuum chamber either maintained at base pressure or backfilled with oxygen gas. The data were collected when the films were irradiated for 14 h with 2 keV electrons. The CL emission peak attributed to the 4f⁶5d¹ → 4f⁷ transitions was observed at ∼521 nm and the CL intensity of the peaks degraded at different rates in different vacuum conditions. X-ray photoelectron spectroscopy (XPS) data collected from degraded films suggest that strontium oxide (SrO) and aliminium oxide (Al₂O₃) were formed on the surface of the film as a result of electron stimulated surface chemical reaction (ESSCR).     

LaNiO3 under-electrode layers for the growth of textured (Pb0.4Zr0.6)TiO3 thin films using pulsed laser deposition

We investigated the structural properties of LaNiO₃ thin films of three different thicknesses deposited by pulsed laser deposition on Si(001) mainly by using a synchrotron X-ray scattering measurement. The LaNiO₃ thin films were grown with the (00l) preferred growth direction, showing completely random distribution in the in-plane direction. In the early stage of the growth, the film was almost unstrained. However, as the film grew further, tensile strain was markedly involved. Also its surface became rougher but its crystalline quality improved significantly with increasing film thickness. A completely (00l)-oriented (Pb_0.4Zr_0.6)TiO₃ thin film was successfully grown on such a LaNiO₃/Si(001) substrate at a substrate temperature of 350 °C by using the same pulsed laser deposition. Our results show that the LaNiO₃ film can serve effectively as a bottom electrode layer for the preparation of a well-oriented (Pb_0.4Zr_0.6)TiO₃ thin film on Si substrates.     

Surface analysis of the nanostructured W-Ti thin film deposited on silicon

The W-Ti thin films are deposited by the dc Ar⁺ sputtering of W(70%)-Ti(30%) a.t. target on silicon substrates. The surface composition and structure of the thin film, previously exposed to air, was carried out. The surface structure was undertaken using grazing incidence X-ray diffraction (GIXRD), and compared to that of the thin film interior. The surface morphology was determined by the Scanning Tunneling Microscopy (STM). The surface composition and chemical bonding of elements on the Ti-W film were analyzed by X-ray photoelectron spectroscopy (XPS) and Low Energy Ion Scattering (LEIS). The measurements show that the overlayer of metallic oxides TiO₂ and WO₃ is formed. The first atomic layer is occupied by TiO₂ only, and its thickness is estimated to about 3.2 ± 0.4 nm. The strong surface segregation of Ti is triggered by the surface oxidation, which is confirmed by the thermodynamical considerations.