Characterization of air-exposure/activation cycles of porous Ti-Zr-V getter film using synchrotron radiation photoemission spectroscopy

Highly porous TiZrV films on (100) Si wafers were used to study the oxidation state of a film surface after three gas-adsorption/activation cycles using synchrotron radiation photoemission spectroscopy (SRPES). The oxidation state and composition of porous TiZrV film are highly affected by the present conditions of air-exposure/activation cycles. In the porous TiZrV films after activation treatment, the C content on the surface of the films gradually increased with increasing air-exposure/activation cycles. In the porous TiZrV film after air-exposure treatment, the O content on the surface of the films decreased with increasing of air-exposure/activation cycles. The concentration of Zr on the film surface increased with increasing of air-exposure/activation cycles. These results are caused by the formation of metal carbides on the film surface.     

Oxidation study of Cr-Ru hard coatings

Cr-Ru alloy coatings with Cr content ranging from 47 to 83 at.% were deposited at 400 °C by direct current magnetron co-sputtering with a Ti interlayer on silicon substrates. With a total input power of 300 W, the Cr content in the Cr-Ru coatings increased linearly with the increasing input power of Cr. The intermetallic compound phase Cr₂Ru with columnar structure was identified for the as-deposited Cr₅₆Ru₄₄ and Cr₆₅Ru₃₅ coatings, resulting in an increase of hardness up to 15-16 GPa. To evaluate the performance of Cr-Ru coatings as a protective coating on glass molding dies, the annealing treatment was conducted at 600 °C in a 50 ppm O₂-N₂ atmosphere. The outward diffusion and preferential oxidization of Cr in the Cr-Ru coatings resulted in the variations of the crystalline structure, chemical composition distribution, and surface hardness after annealing. X-ray diffraction and transmission electron microscopy (TEM) proved that an oxide scale consisting of Cr₂O₃ formed on the free surface. Scanning electron microscopy and TEM observed the surface morphology and structural variation. The chemical composition depth profiles were analyzed by Auger electron microscopy, verifying the presence of a Cr-depleted zone beneath the oxide scale. The hardness of Cr₅₆Ru₄₄ and Cr₆₅Ru₃₅ coatings decreased to 11-12 GPa after annealing, accompanied by the replacement of the Cr₂Ru phase by the Ru phase.     

High-resolution X-ray photoemission spectroscopy study of AlN nano-columns grown by nitridation of Al nano-squares on Si(111) substrates with ammonia

The growth of AlN nano-columns by ammonium nitridation of Al nano-squares embedded in SiO₂ on Si(111) substrates was studied by high-resolution X-ray photoemission spectroscopy from a synchrotron radiation source and scanning electron microscopy (SEM). Selective nitridation of the Al nano-squares on the SiO₂ mask was obtained in the temperature window of 600 °C-700 °C. The well-shaped AlN nano-column arrays with diameters confined by the lateral size of the Al nano-squares (~ 100 nm) were observed in SEM.     

Investigation of adenine, uracil, and ribose phosphate thin films prepared by electrospray in vacuum deposition using photoemission spectroscopy

Previous results showed significant ionization energy differences between thin films of the four ribonucleic acid (RNA) polynucleotides. The experiments reported here aim at the investigation of the origin of these differences. Since the ribose phosphate backbone is common to all RNA nucleotides, the nucleobases are the most likely candidate defining the ionization energy of RNA. Consequently, experiments were performed to investigate the electronic structure and ionization energies of thin films of two nucleobases (adenine and uracil, representative for purines and pyrimidines), and ribose phosphate. These experiments were performed using x-ray and ultraviolet photoemission spectroscopy (XPS, UPS) in conjunction with an electrospray based in vacuum multi-step deposition technique. The presented results clearly demonstrate a significant ionization energy difference between the two nucleobases, qualitatively matching the previous results on the homopolymers of adenosine and uridine (poly rA, poly rU). As expected, the ionization energy of the prepared ribose phosphate thin films was much larger than those of the nucleobases.     

Improvement of InN layers deposited on Si(111) by RF sputtering using a low-growth-rate InN buffer layer

We investigate the influence of a low-growth-rate InN buffer layer on structural and optical properties of wurtzite nanocrystalline InN films deposited on Si(111) substrates by reactive radio-frequency sputtering. The deposition conditions of the InN buffer layer were optimized in terms of morphological and structural quality, leading to films with surface root-mean-square roughness of ~ 1 nm under low-growth-rate conditions (60 nm/h). The use of the developed InN buffer layer improves the crystalline quality of the subsequent InN thick films deposited at high growth rate (180 nm/h), as confirmed by the narrowing of X-ray diffraction peaks and the increase of the average grain size of the layers. This improvement of the structural quality is further confirmed by Raman scattering spectroscopy measurements. Room temperature PL emission peaking at ~ 1.58 eV is observed for InN samples grown with the developed buffer layer. The crystal and optical quality obtained for InN films grown on Si(111) using the low-growth-rate InN buffer layer become comparable to high-quality InN films deposited directly on GaN templates by RF sputtering.     

High temperature structural evolution of a CuAlNi alloy studied by in situ X-ray diffraction and isothermal mechanical spectroscopy

The purpose of this work is to study the microstructural mechanisms associated with the eutectoid transition in a ternary Cu–12 wt.% Al–3 wt.% Ni alloy. The samples have been initially annealed at 850 °C, then slowly cooled down to room temperature. The experiments have been carried out both on cooling and on heating above 500 °C using isothermal mechanical spectroscopy and X-ray diffraction (fitted with a temperature camera). On heating, a relaxation peak with a high intensity rises up above 600 °C, then on cooling, the peak totally disappears below 580 °C, the effect being reproducible. The structural analysis, undertaken in the same temperature domain, has clearly evidenced each step of the evolution, particularly the eutectoid transformation. Consequently, the damping effect seems to be associated to the presence of the high temperature β phase.     

X-ray photoelectron spectroscopy analyses of titanium oxynitride films prepared by magnetron sputtering using air/Ar mixtures

X-ray photoelectron spectroscopy (XPS) has been employed to investigate titanium oxynitride (TiN_xO_y) films prepared by d.c. magnetron sputtering using air/Ar mixtures, which allows one to perform the deposition at a high base pressure (1.3 × 10^− 2 Pa) and can reduce substantially the processing time. XPS analyses revealed that all the prepared TiN_xO_y films comprised Ti-N, Ti-N-O, and Ti-O chemical states. When the air/Ar ratio was below 0.3, nitrogen-rich TiN_xO_y films were obtained. As the air/Ar ratio was above 0.4, oxygen-rich TiN_xO_y films were formed. XPS depth profile analyses were also performed in selected specimens. It has been found that at relatively low air/Ar ratios, such as 0.5, the oxygen content of the films increased toward the film/substrate interface and when the air/Ar ratio was higher, TiN_xO_y films with large oxygen content with uniform concentrations were then formed.     

Spatially resolved X-ray spectroscopy using a flat HOPG crystal

A novel design of a 1-D imaging X-ray spectrometer is implemented, using a high efficiency HOPG (highly oriented pyrolitic graphite) Bragg crystal and a double-entrance-slit. The double slit provides self-calibration of the imaging magnification. The spatial and spectral resolutions and dispersion are characterised both analytically and by ray tracing simulations. A key feature of this approach is that it enables the X-ray spectrum to be measured over different regions of the plasma source. The application of this instrument is demonstrated in high intensity laser-foil interaction experiments.     

Implications of stimulated resonant X-ray scattering for spectroscopy,imaging, and diffraction in the regime from soft to hard X-rays

The ultrahigh peak brilliance available at X-ray free-electron lasers opens the possibility to transfer nonlinear spectroscopic techniques from the optical and infrared into the X-ray regime. Here, we present a conceptual treatment of nonlinear X-ray processes with an emphasis on stimulated resonant X-ray scattering as well as a quantitative estimate for the scaling of stimulated X-ray scattering cross sections. These considerations provide the order of magnitude for the required X-ray intensities to experimentally observe stimulated resonant X-ray scattering for photon energies ranging from the extreme ultraviolet to the soft and hard X-ray regimes. At the same time, the regime where stimulated processes can safely be ignored is identified. With this basis, we discuss prospects and implications for spectroscopy, scattering, and imaging experiments at X-ray free-electron lasers.     

X-ray diffraction and Raman scattering in SbSI nanocrystals

Lattice structure and rod-like shaped SbSI nanocrystals obtained by ball milling with rod thickness down to 70 nm, as estimated from X-ray diffraction (XRD) and electron microscopy, is similar to that of the bulk crystals. The dependence of the grain size on the milling duration is discussed in view of the chain-like crystalline structure of SbSI. Possible factors, responsible for the observed Raman line broadening, are discussed, scattering by surface phonons being considered the predominant one.     

Structural properties of low-temperature grown ZnO thin films determined by X-ray diffraction and X-ray absorption spectroscopy

The epitaxial growth of ZnO thin films on Al₂O₃ (0001) substrates have been achieved at a low-substrate temperature of 150 °C using a dc reactive sputtering technique. The structures and crystallographic orientations of ZnO films varying thicknesses on sapphire (0001) were investigated using X-ray diffraction (XRD). We used angle-dependent X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) spectroscopy to examine the variation of local structure. The XRD data showed that the crystallinity of the film is improved as the film thickness increases and the strain is fully released as the film thickness reached about 800 Å. The Zn K-edge XANES spectra of the ZnO films have a strong angle-dependent spectral feature resulting from the preferred c-axis orientation. The wurtzite structure of the ZnO films was explicitly shown by the XRD and EXAFS analysis. The carrier concentration, Hall mobility and resistivity of the 800 Å-thick ZnO film were 1.84 × 10¹⁹ cm^− 3, 24.62 cm²V^− 1s^− 1, and 1.38 × 10^− 2 Ω cm, respectively.     

Core-level X-ray photoemission spectral shift through the successive phase transitions in layered TlInS2

Temperature-dependent change in core-level electronic structures of the layered semiconductor-ferroelectric TlInS₂ with incommensurate phase has been investigated by means of X-ray photoemission spectroscopy. The temperature dependence of the relative peak position for each core level (Tl 4f, In 3d and S 2p) is found to differ very much in the regions bordering each other at the normal-incommensurate phase transition point of 218 K. The obtained data suggest that the charge distribution in TlInS₂ dramatically changes upon passing from the normal phase (T > 218 K) to the spatially modulated incommensurate phase (T < 218 K).     

X-ray analysis of polycrystalline aluminium subjected to fatigue cycling

Variations in the halfwidth values of X-ray reflections from fatigue-cycled, polycrystalline aluminium samples have been analysed. An oscillatory variation of the halfwidths with fatigue cycling has been observed. Analysis of the diffraction line profiles indicates that broadening arises mainly because of the build-up of microstrains during fatigue cycling. The present data indicate that (i) broadening due to fatigue cycling increases with glancing angle; (ii) changes in halfwidth and integral widths, due to fatigue cycling, are comparable and (iii) (b/b ₀) versusN curves for fatigue cycling under constant stress amplitude and flight loading conditions are comparable.     

High-resolution X-ray photoelectron spectroscopy study of InTe thin film in structural phase transition from amorphous to crystalline phase

We investigated the chemical states of InTe thin film in the structural phase transition from the amorphous to the crystalline phase, using high-resolution X-ray photoelectron spectroscopy with synchrotron radiation. We confirmed the structural phase transition by transmission electron microscopy. Clean amorphous InTe (a-InTe) free of oxygen impurity was obtained after Ne⁺ ion sputtering at the ion beam energy of 1 kV for 1 h. Additionally, we obtained crystalline InTe (c-InTe) from clean a-InTe by annealing at 250 °C in an ultra-high vacuum. During the transition to the crystalline phase, the binding energy of the Te 4d core-level was unchanged, but the peak width was somewhat wider than in the amorphous phase. In the case of the In 4d core-level, the chemical shift was 0.1 eV at the higher binding energy between the amorphous and crystalline phases. The valence band maximum was shifted at the higher binding energy of 0.34 eV. We assumed that the Te atom was almost fixed and that the In atoms moved in the tight binding energy state to the center of the 4-Te atoms.     

X-ray textural and microstructural characterisations by using the Combined Analysis Approach for the optical optimisation of micro- and nano-structured thin films

Nano/micro-crystalline silicon, silicon carbide and zinc selenide sputtered films are chosen to illustrate the potentialities of the X-ray Combined Analysis methodology in characterising textures, structures, residual stresses, phase amounts, twin faults, layer thicknesses and crystallite sizes and shapes. The observed textures range from weak (in Si and SiC films) to very strong (in ZnSe). In all films, crystallites are found anisotropic in shapes and sizes. In nc-Si, no residual stress is observed, but the cell parameters deviate from bulk values due to crystal size reduction. The layer thickness as probed by X-ray diffraction imposes films porosities. In unstressed SiC films the two polymorph phases (hexagonal and cubic) are present and both are textured. In ZnSe films, a ratio of around 55/45 for the cubic and hexagonal phases respectively is quantified and large tensile in-plane residual stresses reaching several hundreds of MPa calculated.     

Ultrathin film assembly of sulfobetaine-stabilized palladium nanoparticles investigated by photoemission spectroscopy

Thin films of sulfobetaine-stabilized palladium nanoparticles on a gold surface were prepared by evaporation of their colloidal water solution and investigated by ultraviolet photoemission spectroscopy. The photoemission from the thin films was found to be dominated entirely by the surfactant molecules. No photoemission from the gold substrate was observed; these facts strongly suggest the formation of uniform (hole-free) thin films of the surfactant-stabilized nanoparticles. Additional investigation of structural degradation using neon-ion sputtering also supports the film condition.     

Air gap type thin film bulk acoustic resonator fabrication using simplified process

In this study we propose a simplified process for making an air-gap-type film bulk acoustic resonator (FBAR) using the magnesium (Mg) sacrificial layer. The Mg sacrificial layer minimizes damage to other layers in the wet etching process because of its short etching time. Also the Mg sacrificial layer plays the role of etching aisle and air-gap simultaneous during the etching process. In addition, our proposed process can reduce the number of FBAR fabrication steps when compared with previous dry etching techniques. The FBAR's resonant frequency characteristics successfully show performance from 2.44 to 3.11 GHz.     

XPS and X-ray diffraction studies of aluminum-doped zinc oxide transparent conducting films

Aluminum-doped zinc oxide transparent conducting films are prepared by spray pyrolysis at different dopant concentrations. These films are subsequently characterized by X-ray diffractometric and X-ray photoelectron spectroscopic (XPS) techniques. The results are compared with those obtained from pure zinc oxide films prepared under identical conditions. X-ray diffraction measurements show an increase in lattice parameters (c and a) for aluminum-doped films while their ratio remains the same. This study also indicates that within the XPS detection limit the films are chemically identical to pure zinc oxide. However, a difference in the core-electron line shape of the Zn 2p_3/2 photoelectron peaks is predicted. An asymmetry in Zn 2p_3/2 photoelectron peaks has been observed for aluminium-doped films. The asymmetry parameters evaluated from core-electron line-shape analysis yield a value of the order of 0.04±0.01. The value is found to lie between those obtained for pure zinc oxide and has been attributed to the presence of excess zinc in the films.     

In situ synchrotron X-ray study of bainite transformation kinetics in a low-carbon Si-containing steel

The bainite transformation in a low-carbon Si-containing steel has been studied in situ by synchrotron X-rays. While the austenite is homogeneous prior to transformation, the carbon distribution becomes nonuniform as bainite plates form. This is because of the different degrees of physical isolation of films and blocks of residual austenite. The method for converting dilatational strain into bainite volume fraction, using lattice strain as a reference, during isothermal transformation was found to overestimate it. The bainitic and martensitic ferrite did not exhibit a tetragonal unit cell due to the low-carbon content of the steel and the high transformation temperature.     

Effect of rapid thermal annealing on the crystal quality and the piezoelectric response of polycrystalline AlN films

This work analyzes the effect of post-deposition rapid thermal annealing (RTA) on the crystal quality and the piezoelectric response of sputtered polycrystalline aluminium nitride (AlN) thin films. AlN films with mixed crystal texture were not significantly affected by RTA processing. However, in films exhibiting clear c-axis preferred orientation, the annealing produced a crystallization process, characterized by an increase in the grain size of the original crystallites, the growth of new small grains, and the reduction of defects. The improvement in the crystal quality was more evident in highly textured c-axis oriented films. However, the enhanced crystal quality of the films due to RTA was not accompanied by a significant improvement in the piezoelectric response. This is attributed to the presence of grains with opposite polarities that could not be rearranged through the RTA treatment.