Microstructural and chemical transformation of thin Ti/Pd and TiD<Subscript><Emphasis Type="BoldItalic">y</Emphasis></Subscript>/Pd bilayer films induced by vacuum annealing

Using a combination of scanning electron microscopy, transmission electron microscopy (TEM), X-ray diffraction and X-ray photoelectron spectroscopy (XPS), we made a comparative study of the high-temperature annealing impact on thin titanium deuteride (TiD _y ) films covered by an ultrathin Pd layer, and on Ti/Pd bilayer films. The bilayer films were prepared under ultrahigh vacuum conditions and were in situ annealed using the same annealing procedure. It was found that the surface and the bulk morphology of both films undergo different annealing-induced transformations, leading to an extensive intermixing between the Ti and Pd layers and the formation of a new PdTi₂ bimetallic phase. Energy-filtered TEM imaging and energy-dispersive X-ray spectrometry analysis, as well as XPS depth profiling all provided evidence of a different distribution of Pd and Ti in the annealed TiD _y /Pd film compared with the annealed Ti/Pd film. Our results show that thermal decomposition of TiD _y , as a consequence of annealing the TiD _y /Pd film, modifies the intermixing process, thereby promoting Ti diffusion into the Pd-rich top layer of the TiD _y film and thus providing a more likely path for the formation of the PdTi₂ phase than in an annealed Ti/Pd film. Figure Figure Microstructural and chemical characterisation of thin TiDy/Pd film after annealing     

Structural and chemical characterisation of titanium deuteride films covered by nanoscale evaporated palladium layers

Thin titanium deuteride (TiD_y) films, covered by an ultra-thin palladium layer, have been compared with the corresponding titanium and palladium films using a combination of scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The TiD_y layers were prepared under ultra-high vacuum (UHV) conditions by precisely controlled deuterium sorption at 298 K on a Ti film evaporated onto a Si(100) substrate. Both Ti and TiD_y films were then covered in situ by a nanoscale Pd layer. It was found that a 10- to 12-nm-thick Pd layer protects the TiD_y films efficiently against extensive air interaction. The morphology of both the surface and bulk Pd/TiD_y (Ti) films have been observed using SEM and cross-sectional TEM analysis, respectively. A polycrystalline bulk morphology in both Ti and TiD_y films accompanied by a fine-grained Pd surface was observed. High-magnification cross-sectional TEM images reveal the TiD_y film to be plastically deformed leading to an increase in the roughness of the top Pd layer. Complex structures, including Moiré patterns, have been identified within the Pd/TiD_y interface. The chemical nature of this interface has been analysed after partial sputtering of the Pd top layer using XPS. Besides TiD_y and Pd, TiO and PdO were found to be the main chemical species in the interface region of the Pd/TiH_y film. The XPS valence-band spectra of the Pd/TiD_y interface reveal electronic features characteristic of a Pd–Ti bimetallic structure.     

Application of TEM and XPS in the interpretation of the kinetics of deuterium evolution from ultrathin TiD<Subscript><Emphasis Type="BoldItalic">y</Emphasis></Subscript>/Pd films evaporated on quartz

The kinetics of thermal evolution of deuterium from ultrathin TiD _y /Pd bilayer films has been studied by means of thermal desorption mass spectrometry (TDMS). Using a combination of transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy, we made a study of the complex structural and chemical transformations of the TiD _y /Pd film as a result of TDMS-induced evolution of deuterium and simultaneous annealing of this film. Both preparation and TDMS processing of the TiD _y /Pd bilayer films were performed in situ under UHV conditions. It was found that the high-temperature TDMS processing of an ultrathin TiD _y /Pd film, which was carried out in a relatively short time, leads to a significant film structure transformation. Energy-filtered TEM mapping of cross-section images and EDX analysis revealed extensive interdiffusion of Ti and Pd within the Ti–Pd bi-layer film. This process leads to a progressive change in chemical composition within the surface and subsurface area of the film during the TDMS processing. As the temperature of TDMS heating increases, segregation of Ti at the Pd top layer surface becomes significant. As a result, the kinetics of deuterium desorption is progressively changed during TDMS; at lower temperatures, the kinetics is limited by recombinative processes at the Pd surface, at temperatures beyond 500 K, it becomes dominated by interdiffusion of Ti into the Pd surface.     

Ultrathin cobalt silicide film formation on Si(100)

The interfacial reaction between ultrathin Co film and substrate Si(100) was studied by in situ XPS using monochromatized Al Kα. When the Co is deposited on Si(100) at room temperature, CoSi₂ is formed during the initial stage of Co deposition and then metallic Co starts to grow sequentially. For 8 ML Co deposition on Si(100) the interfacial reaction layer is relatively thin compared with the pure Co overlayer, which is not involved in the interfacial reaction in depth. The Co layers change rapidly to CoSi layers after annealing at 270°C, and then CoSi₂ layers form after annealing at 540°C for 2 min. The CoSi₂ layers are changed to CoSi₂ islands by post‐annealing at >650°C. Copyright © 2003 John Wiley & Sons, Ltd.     

Effect of Annealing on the Electrical Properties of CuxS Thin Films

Copper sulphide CuS was deposited on three substrates; glass, Indium Tin Oxide (ITO) and Ti by using spray pyrolysis deposition (SPD). After depositing CuS thin films on the substrates at 200 °C, they were annealed at 50, 100, 150, and 200 °C for 1 hour. Structural measurements revealed covellite CuS and chalcocite Cu₂S phases for thin films before and after annealing at 200 °C with changes in intensities, and only covellite CuS phase for thin films after annealing at 50, 100, and 150 °C. Morphological characteristics show hexagonal-cubic crystals for the CuS thin film deposited on glass substrate and plates structures for films deposited on ITO and Ti substrates before annealing, these crystals became bigger in size and there were be oxidation and some agglomerations in some regions with formation of plates for CuS on glass substrate after annealing at 200 °C. For Hall Effect measurements, thin films sheet resistivity and mobility increased after annealing while the carrier concentration decreased. Generally, the thin film deposited on ITO substrate had the lowest resistivity and the highest carrier concentration before and after annealing. The thin film deposited on Ti substrate had the highest mobility before and after annealing, which makes it the best thin film for device performance. The objective of this research is to show the improvement of thin films electrical properties especially the mobility after annealing those thin films.     

Nitridation of niobium oxide films by rapid thermal processing

The possibility of forming niobium oxynitride through the nitridation of niobium oxide films in molecular nitrogen by rapid thermal processing (RTP) was investigated. Niobium films 200 and 500 nm thick were deposited via sputtering onto Si(100) wafers covered with a thermally grown SiO₂ layer 100 nm thick. These as-deposited films exhibited distinct texture effects. They were processed in two steps using an RTP system. The as-deposited niobium films were first oxidized under an oxygen atmosphere at 450 °C for various periods of time and subsequently nitridated under a nitrogen atmosphere at temperatures ranging from 600 to 1000 °C for 1 min. Investigations of the oxidized films showed that samples where the start of niobium pentoxide formation was detected at the surface and the film bulk still consisted of a substoichiometric NbO_x phase exhibited distinctly lower surface roughness and microcrack densities than samples where complete oxidation of the film to Nb₂O₅ had occurred. The niobium oxide phases formed at the Nb/substrate interface also showed distinct texture. Zones of niobium oxide phases like NbO and NbO₂, which did not exist in the initial oxidized films, were formed during the nitridation. This is attributed to a “snow-plough effect” produced by the diffusion of nitrogen into the film, which pushes the oxygen deeper into the film bulk. These oxide phases, in particular the NbO₂ zone, act as barriers to the in-diffusion of nitrogen and also inhibit the outdiffusion of oxygen from the SiO₂ substrate layer. Nitridation of the partially oxidized niobium films in molecular nitrogen leads to the formation of various niobium oxide and nitride phases, but no indication of niobium oxynitride formation was found. Figure Schematic representation of the phase distribution in 200 nm Nb film on SiO₂/Si substrate after two steps annealing using an RTP system. The plot below represents the SIMS depth profiles of the nitridated sample with the phase assignment     

Thickness and temperature‐dependent study of Co/Si interface

Thin films of cobalt (10, 40, and 100 nm) are deposited on Si substrate by electron beam physical vapor deposition technique. After deposition, 4 pieces from each of the wafers of silicon substrate were cut and annealed at a temperature of 200°C, 300°C, and 400°C for 2 hours each, separately. X‐ray diffraction, atomic force microscopy, and transmission electron microscopy (TEM) are used to study the structural and morphological characteristics of the deposited films. To obtain TEM images, Co films are deposited on Cu grids; so far, no such types of TEM images of Co films are reported. Structural studies confirm nanocrystalline nature with hexagonal close packed structure of the deposited Co film at lower thickness, while at higher thickness, film structure transforms to amorphous with lower surface roughness value. The particle sizes in all the cases are in the range of 3 to 5 nm. Micro‐Raman spectroscopy is also used to study the phase formation and chemical composition as a function of thickness and temperature. The results confirm that the grown films are of good quality and free from any impurity. Studies show the silicide formation at the interface during deposition. The appearance of new band at 1550 cm⁻¹ as a result of annealing indicates the structural transformation from CoSi to CoSi₂, which further enhances at higher annealing temperatures.     

The effects of oxygen concentration on ultraviolet luminescence of ZnO films by sol–gel technology and annealing

ZnO thin films were successfully deposited on SiO₂/Si substrate using the sol–gel technique and annealed in various annealing atmospheres at 900 °C by rapid thermal annealing (RTA). X-ray diffraction revealed the (002) texture of ZnO thin films. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) showed that the grains of the ZnO thin film were enlarged and its surface was smoothed upon annealing in oxygen. PL measurement revealed two ultraviolet (UV) luminescence bands at 375 and 380 nm. The intensity of the emission peak at 380 nm became stronger as the concentration of oxygen in the annealing atmosphere increased. The X-ray photoelectron spectrum (XPS) demonstrated that a more stoichiometric ZnO thin film was obtained upon annealing in oxygen and more excitons were generated from the radiative recombination carriers consistently. Additionally, the UV intensity increased with the thickness of ZnO thin film.     

Surface composition of PdCuAu ternary alloys: a combined LEIS and XPS study

PdCuAu ternary alloy samples with different composition were synthesized on top of ZrO₂‐modified porous stainless steel disks by the sequential electroless deposition technique. The structure, morphology and bulk composition of the samples were characterized by X‐ray diffraction (XRD), scanning electron microscopy and energy dispersive X‐ray spectroscopy (EDX). Complete alloy formation with a pure fcc phase for the Pd₇₁Cu₂₆Au₃, Pd₇₀Cu₂₅Au₅ and Pd₆₇Cu₂₄Au₉ samples and a bcc structure for the Pd₆₂Cu₃₆Au₂ and Pd₆₀Cu₃₇Au₃ samples were obtained upon annealing at 500 °C for 120 h as revealed by XRD. A combination of low‐energy ion scattering (LEIS) and X‐ray photoelectron spectroscopy (XPS) was used to investigate the surface properties of the PdCuAu alloys. XPS results confirmed alloy formation under the annealing conditions. XPS analysis also revealed that the near‐surface regions of the alloys became enriched in Pd with respect to the bulk composition determined by EDX. In contrast, LEIS and angle‐resolved XPS analyses showed that the top‐most surface layers in all samples were copper‐rich compared with the bulk composition. This high Cu surface concentration could impart resistance to bulk sulfide formation to the PdCuAu alloy membranes. Copyright © 2015 John Wiley & Sons, Ltd.     

Biomimetic synthesis of the arachidic acid/Ag<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Cd<Subscript><Emphasis Type="Italic">y</Emphasis></Subscript>S nanocomposite films

Ag _x Cd _y S nanoparticles were obtained in arachidic acid (AA) monolayer containing Ag⁺ and Cd²⁺ under H₂S flow. The AA/Ag _x Cd _y S monolayers were deposited onto solid substrate to prepare LB films. The UV-vis spectrum showed that the LB film exhibited notable quantum-size effect. The small-angle X-ray diffraction revealed periodic structure of the LB films. The molar ratio of Ag to Cd in AA/Ag _x Cd _y S film was ca. 1 : 5 as measured by the XPS. TEM and FTIR spectroscopy showed that the head-groups of arachidic acid molecules controlled formation of Ag _x Cd _y S nanoparticles in the monolayer.     

Growth,characterization and interfacial reaction of magnetron sputtered Pt/CeO2 thin films on Si and Si3N4 substrates

Growth of magnetron sputtered Pt/CeO₂ thin films on Si and Si₃N₄ were characterized by X‐ray diffraction (XRD), field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM) and X‐ray photoelectron spectroscopy (XPS). Interaction of Pt/CeO₂ films with Si on Si and Si₃N₄ substrates was extensively investigated by XPS. XRD studies show that films are oriented preferentially to (200) direction of CeO₂. XPS results show that Pt is mainly present in +2 oxidation state in Pt/CeO₂/Si film, whereas Pt⁴⁺ predominates in Pt/CeO₂/Si₃N₄ film. Concentration of Pt⁴⁺ species is more than four times on Si₃N₄ substrate as compared with that on Si. Ce is present as both +4 and +3 oxidation states in Pt/CeO₂ films deposited on Si and Si₃N₄ substrates, but concentration of Ce³⁺ species is more in Pt/CeO₂/Si film. Interfacial reaction between CeO₂ and Si substrate is controlled in the presence of Pt. Pt/Ce concentration ratio decreases in Pt/CeO₂/Si₃N₄ film upon successive sputtering, whereas this ratio decreases initially and then increases in Pt/CeO₂/Si film. Copyright © 2015 John Wiley & Sons, Ltd.     

Structure and dielectric properties of HfO<Subscript>2</Subscript> films prepared by a sol–gel route

Mono- and multilayer HfO₂ sol–gel thin films have been deposited on silicon wafers by dip-coating technique using a solution based on hafnium ethoxide as precursor. The densification/crystallization process was achieved by classical annealing between 400 and 600 °C for 0.5 h (after drying at 100 °C). Systematic TEM studies were performed to observe the evolution of the thin film structure depending on the annealing temperature. The overall density of the films was determined from RBS spectrometry correlated with cross section (XTEM) thickness measurements. After annealing at 450 °C the films are amorphous with a nanoporous structure showing also some incipient crystallization. After annealing at 550 °C the films are totally crystallized. The HfO₂ grains grow in colonies having the same crystalline orientation with respect to the film plane, including faceted nanopores. During annealing a nanometric SiO₂ layer is formed at the interface with the silicon substrate; the thickness of this layer increases with the annealing temperature. Capacitive measurements allowed determining the value of the dielectric constant as 25 for four layer films, i.e. very close to the value for the bulk material.     

Magnetoelectric Bi3.25Nd0.75Ti3O12–La0.6Ca0.4MnO3 composite thin films derived by SOL–GEL method

Magnetoelectric (ME) Bi_3.25Nd_0.75Ti₃O₁₂–La_0.6Ca_0.4MnO₃ (BNT–LCMO) composite thin films were deposited on Pt/Ti/SiO₂/Si(100) substrates by a simple SOL–GEL method and spin-coating process with two different deposition sequences: BNT/LCMO/Pt/Ti/SiO₂/Si(BLP) and LCMO/BNT/Pt/Ti/SiO₂/Si(LBP). Our results show the composite thin films exhibit both good ferroelectric and magnetic properties, as well as a ME effect. BLP thin films have larger maximum ME voltage coefficient values than LBP structured thin films. The deposition sequence has a notable effect on the ferroelectric and magnetic properties and ME coupling behavior of the bi-layer thin films.     

Selective solvent annealing induced phase separation and dewetting in PMMA/SAN blend ultrathin films

Phase behaviors induced by solvent annealing in poly(methyl methacrylate) (PMMA) and poly(styrene‐ran‐acrylonitrile) (SAN) blend ultrathin films have been investigated by atomic force microscopy and grazing incidence small‐angle X‐ray scattering. Our results indicate that both the phase separation within the blend and the dewetting of the film induced by composition fluctuation take place upon the selective solvent annealing, producing complex structures containing upper droplets (of one phase) and mimic‐films (of the other rich‐phase). The use of acetic acid (the selective solvent for PMMA) generates PMMA mimic‐film and SAN droplets, while the introduction of DMF (exhibiting better solubility for SAN) vapor results in the formation of SAN mimic‐film and PMMA droplets. Essentially, the interaction at polymer/substrate interface, resultant wettability of selected component, solubility of PMMA and SAN in adopted solvent dominate not only the phase separation and the dewetting of the whole film but also the synergism of them. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014 , 52, 1243–1251     

ZIF-8原位负载Pd纳米粒子及其在Suzuki-Miyaura反应中的应用(英文)

将PdCl2与ZIF-8的反应原料ZnO和2-甲基咪唑按照一定的比例,采用机械化学法原位将Pd2+负载在ZIF-8上(Pd2+/ZIF-8)。然后用NaBH4将Pd2+/ZIF-8进行还原,得到均匀分散的Pd纳米颗粒(Pd/ZIF-8)。通过XRD、N2吸附、透射电镜、ICP-AES、XPS等对Pd/ZIF-8的结构、形貌、价态等进行了表征。结果表明用机械化学法原位制备的Pd/ZIF-8具有分散均匀、容易大量制备的优点。该催化剂不仅能高效催化Suzuki-Miyaura交叉偶联反应,并且能够多次循环利用。     

Initial formation of contact layers on Ni/SiC samples studied by XPS

This study deals with the quantitative assessment of the coverage and thickness of Ni silicide films formed during annealing of SiC substrates with sputtered thin films of Ni. The analytical approach involves the use of XPS and depth profiling by means of successive ion etchings and XPS analyses. For either 3 or 6 nm initial Ni film thickness, a 10 nm Ni₂Si product is formed. On top of this product, the C released is accumulated in a very thin (1–2 nm) film. In neither case, the Ni₂Si covers the whole surface, although the coverage is almost complete (～90%) in the latter case. For the greater initial Ni‐film thickness of 17 nm, the thickness of the Ni₂Si product corresponds well to the value of 25 nm expected from the Ni/Ni₂Si stoichiometric relationship. This thickness is significantly greater than a critical level and the film covers the whole surface. Carbon is similarly accumulated in a very thin layer on the top surface, although the major part of C (～70%) is found inside the main reaction product layer. Copyright © 2008 John Wiley & Sons, Ltd.     

Review on the thickness measurement of ultrathin oxide films by mutual calibration method

Mutual calibration was suggested as a method to determine the absolute thickness of ultrathin oxide films. It was motivated from the large offset values in the reported thicknesses in the Consultative Committee for Amount of Substance (CCQM) pilot study P-38 for the thickness measurement of SiO₂ films on Si(100) and Si(111) substrates in 2004. Large offset values from 0.5 to 1.0 nm were reported in the thicknesses by ellipsometry, X-ray reflectometry (XRR), medium-energy ion scattering spectrometry (MEIS), Rutherford backscattering spectroscopy (RBS), nuclear reaction analysis (NRA), and transmission electron microscopy (TEM). However, the offset value for the thicknesses by X-ray photoelectron spectroscopy (XPS) was close to zero (−0.013 nm). From these results, the mutual calibration method was reported for the thickness measurement of SiO₂ films on Si(100) by combination of TEM and XPS. The mutual calibration method has been applied for the thickness measurements of hetero oxide films such as Al₂O₃ and HfO₂. Recently, the effect of surface contamination was reported to be critical to the thickness measurement of HfO₂ films by XPS. On the other hand, MEIS was proved to be a powerful zero offset method which is not affected by the surface contamination. As a result, the reference thicknesses in the CCQM pilot study P-190 for the thickness measurement of HfO₂ films on Si(100) substrate were determined by mutual calibration method from the average XRR data and MEIS analysis. Conclusively, the thicknesses of ultrathin oxide films can be traceably certified by mutual calibration method and most thickness measurement methods can be calibrated from the certified thicknesses.     

Phase separation morphology of thin films of polystyrene/polyisoprene blends

We present the results of a study of the morphology of phase separation in a thin film blend of polystyrene (PS) and polyisoprene (PI) in a common solvent of toluene. The blend is quenched by rapid solvent evaporation using a spincoating technique rather than a temperature quench. The mass fraction of polystyrene is varied to determine the effect of the substrate on thin film phase separation morphology. We compare the phase separation morphology for very thin films of the PS/PI blend cast onto three different substrates: Si(001) with a native oxide layer (Si (SINGLEBOND) SiO_x), Si(001) etched in hydrofluoric acid (Si-H), and a Au/Pd alloy sputtered onto Si(001). We observe large differences between the morphologies of 1000 Å thick blend films on the Si(SINGLEBOND) SiO_x and Si-H substrates as the mass fraction is varied due to the difference in the wetting properties of PS on the two substrates. Smaller differences are observed between the films on the Si(SINGLEBOND) SiO_x and Au/Pd substrates only for film thicknesses h < 600 Å. © 1996 John Wiley & Sons, Inc.     

X-ray spectroscopic study of the electronic structure of boron carbonitride films obtained by chemical vapor deposition on Co/Si and CoO<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>/Si substrates

Boron carbonitride films are synthesized by chemical vapor deposition from a mixture of triethylamine borane and ammonia on a metallic or oxidized cobalt sublayer sprayed over Si(100) substrates. Scanning electron microscopy shows that the surface of a BC _x N _y /Co/Si sample has a homogeneous fine-grained structure; filamentous entities are found on the surface of the BC _x N _y /CoO _x /Si sample. The electronic structure of the films is investigated by X-ray photoelectron spectroscopy (XPS) and near-edge X-ray absorption fine structure spectroscopy (NEXAFS). An analysis of the spectra shows that BC _x N _y films are composed of graphite and hexagonal boron nitride (h-BN) regions and complex BC _x N _y O _z components with B-C, N-C, B-O, N-O, and C-O bonds. The deposition of the BC _x N _y film on the oxidized Co sublayer results in an increase in the number of C-O, N-O, B-O, and C-N bonds and a decrease of the graphite and h-BN components and in the number of C-B bonds. The XPS data are used to estimate the surface elemental composition of the BC _x N _y /CoO _x /Si sample. It is found that the film consists of 66 at.% graphite component and 3 at.% h-BN; the proportion of complex C_0.46B_0.11N_0.05O_0.38 components is 31 at.%.     

Chemical solution processing and characterization of Ba(Zr,Ti)O<Subscript>3</Subscript>/LaNiO<Subscript>3</Subscript> layered thin films

Ba(Zr,Ti)O₃/LaNiO₃ layered thin films have been synthesized by chemical solution deposition (CSD) using metal-organic precursor solutions. Ba(Zr,Ti)O₃ thin films with smooth surface morphology and excellent dielectric properties were prepared on Pt/TiO _x /SiO₂/Si substrates by controlling the Zr/Ti ratios in Ba(Zr,Ti)O₃. Chemically derived LaNiO₃ thin films crystallized into the perovskite single phase and their conductivity was sufficiently high as a thin-film electrode. Ba(Zr,Ti)O₃/LaNiO₃ layered thin films of single phase perovskite were fabricated on SiO₂/Si and fused silica substrates. The dielectric constant of a Ba(Zr_0.2Ti_0.8)O₃ thin film prepared at 700°C on a LaNiO₃/fused silica substrate was found to be approximately 830 with a dielectric loss of 5% at 1 kHz and room temperature. Although the Ba(Zr_0.2Ti_0.8)O₃ thin film on the LaNiO₃/fused silica substrate showed a smaller dielectric constant than the Ba(Zr_0.2Ti_0.8)O₃ thin film on Pt/TiO _x /SiO₂/Si, small temperature dependence of dielectric constant was achieved over a wide temperature range. Furthermore, the fabrication of the Ba(Zr,Ti)O₃/LaNiO₃ films in alternate thin layers similar to a multilayer capacitor structure was performed by the same solution deposition process.