Determination of interface properties between micron-thick metal film and ceramic substrate using peel test

Peel test measurements have been performed to estimate both the interface toughness and the separation strength between copper thin film and Al₂O₃ substrate with film thicknesses ranging between 1 and 15 μm. An inverse analysis based on the artificial neural network method is adopted to determine the interface parameters. The interface parameters are characterized by the cohesive zone (CZ) model. The results of finite element simulations based on the strain gradient plasticity theory are used to train the artificial neural network. Using both the trained neural network and the experimental measurements for one test result, both the interface toughness and the separation strength are determined. Finally, the finite element predictions adopting the determined interface parameters are performed for the other film thickness cases, and are in agreement with the experimental results.     

A robust and self-assembled route to synthesis of CdZn(Se<Subscript>1−x</Subscript>Te<Subscript>x</Subscript>)<Subscript>2</Subscript> photoanodes as light harvesters for photoelectrochemical solar cells

This work reports on the development of CdZn(Se_1?xTe_x)₂ thin films utilized as the photoanode for photoelectrochemical cells (PECs). It was found that the incorporation of tellurium plays an important role in determining the optostructural, morphological, compositional and PEC performance of thin films. XRD measurements showed that the deposited thin films are in the mixed phases with a nanocrystalline nature. SEM images indicated that the surface morphology is favourable for effective light absorption in the solar spectrum. The EDS spectrum confirmed that thin film deposition occured in a stoichiometric manner. A detailed quantitative study was also executed using XPS and revealed the presence of Cd²⁺, Zn²⁺, Se^2? and Te^2? elements in the deposited thin film. Finally, the deposited thin films were tested for their photoelectrochemical (PEC) performance. The PEC study illustrated that CdZn(Se_1?xTe_x)₂ thin film showed the highest power conversion efficiency (η) of 1.13% among reported values.     

Microstructural study of iron nitride thin films deposited by ion beam sputtering

An amorphous iron nitride thin film was deposited using reactive ion beam sputtering of iron by a beam of argon and nitrogen ions. Nitrogen content in the film as determined from conversion electron Mössbauer spectroscopy (CEMS) and X-ray photoelectron spectroscopy (XPS) was FeN_0.7. The mass density of the film was calculated using energy-dispersive X-ray reflectivity (EDXRR) measurements and is found to be 6.0 gm/cm³. CEMS shows that the film is nonmagnetic in nature. Morphology of the film is obtained from atomic force microscopy (AFM). The surface roughness of the film does not increase appreciably beyond that of the substrate even after a deposition of 131 nm of material with these qualities the film is a good candidate for the multilayer superstructure of a nuclear Bragg monochromator of the type ⁵⁶FeN_0.7/⁵⁷FeN_0.7.     

Interfacial adhesion energies of Ru–Mn direct plateable diffusion barriers prepared by atomic layer deposition for advanced Cu interconnects

The effects of Mn addition and post-annealing on the interfacial decohesion energies of Ru direct plateable diffusion barrier layer prepared by atomic layer deposited (ALD) for advanced Cu interconnect applications were systematically evaluated using a four-point bending test. The interfacial decohesion energy increased with the addition of Mn to the Ru thin films and further increased after post-annealing at 500 °C for 30 min in a hydrogen atmosphere, and the interfacial decohesion energies were 3.63, 6.74, and 20.09 J/m² for the as-deposited Cu/Ru/SiO₂, as-deposited Cu/Ru-4.2 at.%Mn/SiO₂, and annealed Cu/Ru-4.2 at.%Mn/SiO₂, respectively. The scanning transmission electron microscopy (STEM) and energy dispersive spectroscopy (EDS) analysis results clearly indicated that the Mn in the annealed ALD Ru–Mn film diffused toward a Ru/SiO₂ interface and Mn silicate was formed at the Ru/SiO₂ interface. Additionally, the results of the X-ray photoelectron spectroscopy (XPS) analysis clearly showed that MnSiO₃ and MnSi were formed at the Ru/SiO₂ interface. Consequently, the findings of the XPS and STEM/EDS study revealed that there was an adequate correlation between the interfacial decohesion energy and the MnSi and MnSiO₃ bond formed at the Ru–Mn /SiO₂ interface. Therefore, a properly annealed ALD Ru-4.2Mn thin film appears to be a hopeful diffusion barrier layer candidate with strong interfacial reliability for advanced Cu interconnects.

     

On structural and high temperature electrochemical properties of ZrO2 thin film coating on Zr metal produced by carbonate melt

Melt of NaCO₃ can favor oxidation of Zr to form ZrO₂ thin film on Zr surface, which is used to make Zr/ZrO₂ oxidation/reduction electrode of pH sensor for testing elevated temperature aqueous solutions. Using SEM, EPMA, XPS, EXAFS and HRTEM, we found that ZrO₂ film is tightness and solid with 20 μm thickness composed by nanometer-sized monoclinic crystals. Zr/ZrO₂ interface is characterized of zoning structure according to topography and chemical composition in five zones: oxygen-rich ZrO₂, ZrO₂, oxygen-rich Zr metal, oxygen-bearing Zr and Zr from outmost to center. Melt oxidation process of Zr involved oxidation time, air and temperature. The air is important effect on structural and electrochemical properties of ZrO₂ thin film for making elevate temperature electrochemical sensor. If oxygen air largely presented in carbonate melting process, ZrO₂ thin film is not tightness and not for oxidation/reduction electrode.     

Synthesis and optical properties of CeO<Subscript>2</Subscript> nanocrystalline films grown by pulsed electron beam deposition

The nanocrystalline cerium dioxide (CeO₂) thin films were deposited on soda lime (SLG) and Corning glass by pulsed e-beam deposition (PED) method at room temperature. The structure of the produced CeO₂ thin films was investigated by X-ray diffraction (XRD) analysis, X-ray photoelectron spectroscopy (XPS), and micro Raman spectroscopy. The surface topography of the films was examined by atomic force microscopy (AFM). Film thickness and growth morphologies were determined with FEG-SEM from the fracture cross sections. XPS studies gave a film composition composed of +4 and +3 valent cerium typical to nanocrystalline ceria structures deficient in oxygen. The ceria films were polycrystalline in nature with a lattice parameter (a) of 0.542 nm. The Raman characteristics of the source material and the films deposited were very similar in character. Raman lines for thin film and bulk CeO₂ was observed at 465 cm⁻¹. The optical properties of the CeO₂ films were deduced from reflectance and transmittance measurements at room temperature. From the optical model, the refractive index was determined as 1.8–2.7 in the photon energy interval from 3.5 to 1.25 eV. The optical indirect band gap (E _g) of CeO₂ nanocrystalline films was calculated as 2.58 eV.     

WO3 thin film prepared by PECVD technique and its gas sensing properties to NO2

Tungsten oxide films have been successfully fabricated from tungsten oxychloride (WOCl₄) precursor by using plasma enhanced vapor deposition (PECVD) technique. The films were deposited onto silicon substrates and ceramic tubes maintained at 100°C under a constant operating pressure of He-O₂ gas mixtures. The compositions and the structures of the thin films have been investigated by means of anaysis methods, such as XRD, XPS, UV and IR. The as-deposited WO₃ thin films were amorphous state and became crystalline after annealing above 400°C. The surface analysis of the films indicates that stoichiometry O/W is 2.77 : 1. The gas sensing measurements of the WO₃ thin film sensors indicate that these sensors have a high sensitivity, excellent selectivity and quick response behavior to NO₂.     

Growth of Bi2S3 film using a solution-gas interface technique

Uniform large-area Bi₂S₃ films about 0.3 μm thick were prepared using a solution-gas interface technique. The surface of a Bi(NO₃)₃ solution was exposed to H₂S gas and a thin solid film was formed. The electrical and optical properties of films prepared in this way were studied. The band gap energy of Bi₂S₃ films estimated from electrical measurements was found to be in fair agreement with the value estimated from the optical measurements.     

Investigation of superhydrophilic mechanism of titania nano layer thin film—Silica and indium oxide dopant effect

In this paper, TiO₂?CSiO₂?CIn₂O₃ nano layer thin films were deposited on glass substrate using sol?Cgel dip coating method. Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and water contact angle measurements were used to evaluate chemical structure, surface composition, hydroxyl group contents and superhydrophilicity of titania films. FTIR result indicated that Si?CO?CSi, Si?CO?CTi and Ti?CO?CTi bands formed in TiO₂?CSiO₂?CIn₂O₃ sample. According to XPS, the hydroxyl content for TiO₂, TiO₂?CSiO₂ and TiO₂?CSiO₂?CIn₂O₃ films was calculated as 11·6, 17·1 and 20·7%, respectively. The water contact angle measurements indicated that silica and indium oxide dopant improved the superhydrophilicity of titania nano film surface especially in a dark place. The enhanced superhydrophilicity can be related to the generation of surface acidity on the titania nano film surfaces. In the present state, superhydrophilicity is induced by the simultaneous presence of both Lewis and Bronsted sites.     

Investigation of chalcopyrite film growth at various temperatures: analyses from top to the bottom of the thin films

We reported a new method to investigate the phases and structures of thin film bottom parts. The films were polished by flapping papers to reach the bottoms. The surfaces and cross sections of thin films were observed by Scanning Electron Microscopy. Grazing Incidence X-ray Diffraction, Raman spectra and X-ray Photoelectron Spectroscopy (XPS) were used to investigate the phases, structures and chemical components of the surfaces and bottoms of thin films. By this method, we studied the growth processes of chalcopyrite films after the selenization at various temperatures from 270 to 600 °C. At 270 °C, a great amount of Cu–Se nodules formed at the surface, while (In,Ga)–Se stayed in the bottom. At 380 °C, a double layer structure was observed in the film. The top part was typical CuInSe₂ polycrystalline, while the bottom part contained complicated components, like CuInSe₂, Cu(In,Ga)₃Se₅, (In,Ga)Se. At 600 °C, a single layer was formed, which was composed of Cu(In,Ga)Se₂ phase. However, a higher Ga/(In+Ga) ratio was obtained towards the back contact. In addition, XPS indicated that the Mo/Cu(In,Ga)Se₂ interface was rich in Ga and Se.     

Biaxial CdTe/CaF2 films growth on amorphous surface

A continuous and highly biaxially textured CdTe film was grown by metal organic chemical vapor deposition on an amorphous substrate using biaxial CaF₂ nanorods as a buffer layer. The interface between the CdTe film and CaF₂ nanorods and the morphology of the CdTe film were studied by transmission electron microscopy (TEM) and scanning electron microscopy. Both the TEM and X-ray pole figure analysis clearly reveal that the crystalline orientation of the continuous CdTe film followed the {111}<121> biaxial texture of the CaF₂ nanorods. A high density of twin faults was observed in the CdTe film. Furthermore, the near surface texture of the CdTe thin film was investigated by reflection high-energy electron diffraction (RHEED) and RHEED surface pole figure analysis. Twinning was also observed from the RHEED surface pole figure analysis.     

Interdiffusion and compound formation in the Mo/Pd/Si thin film metallization system

The process of interdiffusion and compound formation in Mo/Pd/Si thin films was studied between 250 and 750°C via sheet resistance measurements, X-ray diffraction, Rutherford backscattering spectrometry and Auger electron spectroscopy. The results indicate that thermal annealing of the Mo/Pd/Si thin film couples between 250 and 475°C lead to PdSi interaction, Pd₂Si compound formation and consequently a small increase in the sheet resistance. In contrast, exposure of the Mo/Pd/Si thin films to temperatures higher than 475°C lead to MoPd₂Si interaction in addition to PdSi interaction, MoSi₂ compound formation and a dramatic increase in the sheet resistance. The influence of interdiffusion and compound formation on the interface morphology in the Mo/Pd/Si system was studied, and the implications of these observations to a very-large-scale integration contact metallization utilizing an Mo/Pd₂Si/Si system are discussed.     

Transformation of poly(dimethylsiloxane) into thin surface films of SiO x by UV/ozone treatment. Part II: segregation and modification of doped polymer blends

UV/ozone treatment of organic polymers having silicone additives to produce oxidized layers was achieved by doping a host polymer or prepolymer with a silicone additive, poly(dimethylsiloxane) (PDMS). The concentration of PDMS in the host polymer was low, typically in the range of 0.1–2.0% by weight. Host polymers were polyethylene, polyimide, and polyurethane. After film formation, the presence of PDMS was detected on the surface using X-ray photoelectron spectroscopy (XPS), consistent with wetting angle measurements that revealed a hydrophobic surface. The doped blend was then subjected to exposure in a UV/ozone environment such that a thin, stable barrier of SiO _x was formed at the surface of the film. Rate of film modification was monitored by XPS and measurement of advancing contact angle using deionized water. XPS measurements also showed some evidence of modified fragments of the host polymer near the surface. Significant segregation of PDMS and subsequent transformation to silicon oxides has been demonstrated to occur in these doped systems. The stability of the modified glassy surface formed by UV/ozone treatment of a commercially available epoxy formulation containing a silicone additive was shown to be superior to that obtained by other treatment techniques, e.g., oxygen plasma modification.     

Disappearance of stress singularity at interface edge due to nanostructured thin film

The purpose of this study is to examine the stress distribution near the interface between a nanostructured thin film and a solid body. We focus on a nanostructured thin film that consists of Ta₂O₅ helical nanosprings fabricated on a Si substrate by dynamic oblique deposition. The mechanical properties of the thin film are obtained by vertical and lateral loading tests using a diamond tip built into an atomic force microscope. The apparent shear and Young’s moduli, G′ and E′, of the thin film are 2-3 orders of magnitude lower than those of a conventional solid Ta₂O₅ film. Moreover, the thin film shows strong anisotropy. A finite element analysis for two types of components with different interface edges between the thin film and an elastic solid body is conducted under uniform displacement. One has a free edge where the surface-interface angle is 90°-90°, and the other has a short interface crack. These analyses indicate the absence of not only stress singularity but also high stress concentration near the free edge and the interface crack tip. The characteristic stress distributions near the interface are due to the nanoscopically discrete structure of the thin film.     

Synthesis of type-II textured tungsten disulfide thin films with bismuth interfacial layer as a texture promoter

Highly textured tungsten disulfide (WS₂) thin films have been obtained by sulfurization of tungsten trioxide. The properties of WS₂ thin films prepared with bismuth interfacial layer as texture promoter has been studied. The WS₂ thin films were found to have predominant type-II orientation. The stacking of 2H-WS₂ crystallites observed with scanning electron microscopy was not reported hitherto. The films can be pictured as an assembly of WS₂ hexagonal crystallites. The energy dispersive X-ray analysis and X-ray photoelectron spectroscopy (XPS) studies confirm that the films are stoichiometric. The XPS analysis described the local environment of the tungsten atoms and the formal oxidation states of the tungsten and sulfur atoms were + 4 and − 2. Together with the high degree of crystallinity and excellent texture of the film, a relatively smooth morphology, on submicron scale, is revealed through atomic force microscopy study. The conditions for the desired textured growth with the van der Waals planes parallel to the substrate surface are reported.     

Rietveld analysis of CaCu<Subscript>3</Subscript>Ti<Subscript>4</Subscript>O<Subscript>12</Subscript> thin films obtained by RF-sputtering

Calcium copper titanate, CaCu₃Ti₄O₁₂, CCTO, thin films with polycrystalline nature have been deposited by RF sputtering on Pt/Ti/SiO₂/Si (100) substrates at a room temperature followed by annealing at 600 °C for 2 h in a conventional furnace. The crystalline structure and the surface morphology of the films were markedly affected by the growth conditions. Rietveld analysis reveal a CCTO film with 100 % pure perovskite belonging to a space group Im3 and pseudo-cubic structure. The XPS spectroscopy reveal that the in a reducing N₂ atmosphere a lower Cu/Ca and Ti/Ca ratio were detected, while the O₂ treatment led to an excess of Cu, due to Cu segregation of the surface forming copper oxide crystals. The film present frequency -independent dielectric properties in the temperature range evaluated, which is similar to those properties obtained in single-crystal or epitaxial thin films. The room temperature dielectric constant of the 600-nm-thick CCTO films annealed at 600 °C at 1 kHz was found to be 70. The leakage current of the MFS capacitor structure was governed by the Schottky barrier conduction mechanism and the leakage current density was lower than 10^?7 A/cm² at a 1.0 V. The current–voltage measurements on MFS capacitors established good switching characteristics.     

Effect of the plasma surface treatment on an anatase TiO<Subscript>2</Subscript> film

An anatase TiO₂ film has been prepared by plasma surface treatment. TiO₂ surface thin film formed by RF reactive ion plating method was bombarded by the Ar/H₂/CH₄ mixing plasma. The following properties were changed changed by conducting the plasma surface treatment on an anatase TiO₂ film: Crystal structure, electroconductivity, chemical composition and optical characteristic. Especially, the absorption edge of a TiO₂ thin film that conducted plasma surface treatment shifted to visible light region. Therefore, it was proven that it would be able to absorb the visible light and increase the efficiency of the photocatalytic reaction.     

Titanium monoxide ultra-thin coatings evaporated onto polycrystalline copper films

We evaporated polycrystalline copper thin films of thickness between 10 and 100 nm on silicon substrates with their native oxide under ultra-high-vacuum conditions. Some of them were exposed to air for a period ranging from 1 day to 2 weeks. X-ray photoelectron spectroscopy (XPS) revealed a clean copper surface with a trace of oxygen. These films that were exposed to air presented oxides in the state Cu(II), the amount of CuO depended on the time that the film was exposed to air. Subsequently, we deposited TiO ultra-thin films on polycrystalline copper substrates. Both these thin films were formed by electron beam evaporation. XPS spectra showed that the surface of the titanium monoxide (TiO) films was contamination-free. An evaporation of 0.3 nm of TiO reduced the native oxide of the copper substrates from Cu(II) to Cu(I) or Cu(0) and transformed the TiO into TiO₂ at the interface. Low-energy ion spectroscopy showed that the complete coverage of the substrates depends on the thickness of the copper films. For 10 nm copper thin films the complete coverage occurred at 1.5 nm of TiO, and for 100 nm it occurred at 2.0 nm of TiO. In samples exposed to air, the complete coverage occurred at a film thickness slightly higher than those treated under ultra-high-vacuum conditions.     

ZnO/Al2O3 coatings for the photoprotection of polycarbonate

ZnO and ZnO/Al₂O₃ thin films were deposited by r.f. magnetron sputtering on polycarbonate (PC) films in order to protect this polymer against photodegradation. The composition, structure and optical properties of the ceramic coatings were characterised. CO₂-plasma treatments were applied to PC in order to improve the coating adhesion. The PC surface energy was characterised by wettability measurements and the chemical bonds were analysed by XPS.It was found that ZnO coatings improve the stability of PC to UV radiations and that an intermediate alumina coating inhibits the photocatalytic oxidation of PC at the PC/ZnO interface. Additionally an external alumina coating brings a high hardness to the coating.