Magnetron sputtering of Zr-Si-C thin films

The phase composition and chemical bonding of ZrC and ZrSiC films deposited by magnetron sputtering has been studied. The results show that the binary Zr-C films at higher carbon contents form nanocrystallites of ZrC in an amorphous carbon matrix. The addition of Si induces a complete amorphization of the films above a critical concentration of about 15 at.%. X-ray diffraction and transmission electron microscopy confirm that the amorphous films contain no nanocrystallites and therefore can be described as truly amorphous carbides. The amorphous films are thermally stable but start to crystallize above 500 °C. Analysis of the chemical bonding with X-ray photoelectron spectroscopy suggests that the amorphous films exhibit a mixture of different chemical bonds such as ZrC, ZrSi and SiC and that the electrical and mechanical properties are dependent on the distribution of these bonds. For higher carbon contents, strong SiC bonds are formed in the amorphous Zr-Si-C films making them harder than the corresponding binary Zr-C films.     

Determination of silicon nitride film chemical composition to study hydrogen desorption mechanisms

To go further in the comprehension of hydrogen desorption mechanisms from PECVD (Plasma Enhanced Chemical Vapour Deposited) silicon nitride, a method to determine the chemical composition of amorphous silicon nitride films using fast and non destructive characterization techniques has been developed. In particular, SiH, NH, SiSi and SiN bond concentrations are calculated from Fourier transform infra red spectroscopy, ellipsometry and mass measurement. Next, different PECVD silicon nitride films were annealed at 600 °C during 2 min. Results show that hydrogen desorption from PECVD silicon nitride depends on film mass density and main chemical reactions leading to hydrogen desorption are identified thanks to the determination of SiSi and SiN bond concentrations.     

Effects of photoirradiation in UV and VUV regions during plasma exposure to polymers

Interactions between photons irradiated from Ar-O₂ mixture plasmas and polymer surfaces were investigated on the basis of depth analyses of chemical bonding states in the nano-surface layer of polyethylene terephthalate (PET) films via hard X-ray photoelectron spectroscopy (HXPES) and conventional X-ray photoelectron spectroscopy (XPS). The PET films were exposed to photons from the Ar-O₂ mixture plasmas by covering the PET samples with MgF₂ and quartz windows as optical filters for evaluation of photoirradiation effects in ultraviolet (UV) and vacuum ultraviolet (VUV) regions. The HXPES results indicated that the degradation of the chemical bonding states due to photoirradiation in regions was insignificant in deeper regions up to about 50 nm from the surface. Whereas, conventional XPS analysis showed that CO bond, OCO bond and CO bond increased after photoirradiation in UV and VUV regions. These results suggest that the increase in oxygen functionalities (CO bond, OCO bond and CO bond) may be attributed to chemical reactions and/or terminations of scissed bonds via photodecompositions of the polymer with oxygen and/or OH species (oxygen molecules and radicals during plasma exposure and/or oxygen molecules and moisture after taking the PET samples out of the plasma reactor to the ambient air) in the vicinity of the sample surface.     

Ultraviolet irradiation effect on the properties of leakage current and dielectric breakdown of low-dielectric-constant SiOC(H) films using comb capacitor structure

Low-dielectric constant SiOC(H) films were deposited on p-type Si(100) substrates by plasma-enhanced chemical-vapor deposition (PECVD) using dimethyldimethoxy silane (DMDMS, C₄H₁₂O₂Si) and oxygen gas as precursors. To improve the physicochemical properties of the SiOC(H) films, the deposited SiOC(H) films were exposed to ultraviolet (UV) irradiation in a vacuum. The bonding structure of the SiOC(H) films was investigated by Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS). The electrical characterization of SiOC(H) films were carried out through I-V measurements using the comb-like patterns of the TiN/Al/Ti/SiOC(H)/TiN/Al/Ti metal-insulator-metal (MIM) structure. Excessive UV treatment adversely affected the SiOC(H) film, which resulted in an increased dielectric constant. Our results provide insight into the UV irradiation of low-k SiOC(H) films.     

Multiferroic properties of Co and Nd co-substituted Bi5Ti3FeO15 thin films

Co and Nd co-substituted Bi₅Ti₃FeO₁₅ thin films were prepared on Pt/Ti/SiO₂/Si substrates via metal organic decomposition method. The structural and multiferroic properties of the films were investigated. It was found that Co ions enter into the lattice and occupy the Fe site. The Bi_4.15Nd_0.85Ti₃Fe_0.5Co_0.5O₁₅ films simultaneously exhibit ferroelectric and ferromagnetic properties at room temperature, and its 2P_r and 2M_r are 38 μC/cm² and 3 kA/m, respectively. Moreover, substitutions create local ferromagnetic order and antiferromagnetic order depending on whether the local bonding is FeOCo or FeOFe/CoOCo, respectively. The competing interaction of the ferromagnetic and antiferromagnetic phases results in an interesting magnetic behavior of the films.     

A vapor phase deposition of self-assembled monolayers: Vinyl-terminated films of volatile silanes on silicon oxide substrates

Vinyl-terminated self-assembled monolayers (SAMs) offer significant flexibility for further chemical modification and can serve as a versatile starting point for a tailoring of surface properties. A vapor phase deposition of such films would offer advantages in cases where the preparation from solution is not an option or not desired, for example in connection with silicon microstructures such as micro-electromechanical systems. We show that SAMs of 9-decenyltrichlorosilane (CH₂CH(CH₂)₈SiCl₃), 10-undecenyltrichlorosilane (CH₂CH(CH₂)₉SiCl₃), 14-pentadecenyltrichlorosilane (CH₂CH(CH₂)₁₃SiCl₃), decyltrichlorosilane (CH₃(CH₂)₉SiCl₃), and octadecanetrichlorosilane (CH₃(CH₂)₁₇SiCl₃) can be prepared both from solution and from the vapor phase. The resulting layers were compared by static contact angle measurements, ellipsometry, X-ray photoelectron spectroscopy, and atomic force microscopy to determine their surface wettability, the film thickness, the smoothness and homogeneity of the respective films, and their chemical composition and each method gave films of comparable quality. Deposition of functionalized SAMs from the vapor phase is rare. Here we report the parameters for the preparation of well-ordered vinyl-terminated SAMs from the vapor phase.     

A new phase diagram for the CaOAl2O3SiO2H2O hydroceramic system at 200 °C

A new phase diagram is reported for the CaOAl₂O₃SiO₂H₂O (CASH) system at 200 °C. This system is rare in nature but has applications in cementing geothermal and deep oil wells. The phase diagram was constructed by synthesising a range of hydroceramics with CASH assemblages from oilwell cement, silica flour (quartz) and alumina (corundum). A hydroceramic is defined as any ceramic material incorporating water as H₂O or OH. At 200 °C, gyrolite, hillebrandite, jaffeite, portlandite, quartz, 11 Å tobermorite, xonotlite, hibschite and katoite were observed as product phases. The mineral assemblages produced the following three-phase triangles in the CaOAl₂O₃SiO₂ diagram: Gyr + Qtz + Xon; Crn + Tob + Xon; Crn + Hib + Xon; Crn + Hib + Jaf; Crn + Jaf + Kat; Hib + Jaf + Por; Hib + Jaf + Xon; and two reactions are found to be in progress at 200 °C. When alumina is present in the reaction mixture, the thermal stability of tobermorite is extended to higher temperature, and the crystallinity of tobermorite and xonotlite enhanced.     

Optical properties and scanning probe microscopy study of some AgAsSSe amorphous films

Doping of AsSSe amorphous films by silver photo-dissolution leads to a decrease of the optical gap and to an increase of the refractive index in forming AgAsSSe films. The difference of the optical gap and refractive index between undoped and doped films has been found in case of Ag₁₅As₂₆S₂₉Se₃₀ film up to 0.37 eV and 0.26, respectively. Transreflectance in far infrared spectral region indicates formation of AgAsS₂ and AgAsSe₂ entities in Ag₁₅As₂₆S₂₉Se₃₀ film. Scanning probe microscopy, namely atomic force microscopy, atomic force acoustic microscopy (AFAM) and Kelvin probe force microscopy (KPFM) was used for studying AgAsSSe films. It was found that silver growth is rather three dimensional and it is reminiscent of the Stranski-Krastanov growth mode. Observed silver protuberances represent silver reservoirs responsible for a local increase of silver content. Hence, the silver growth mode enhances formation of nano/meso inhomogeneities of the surface and near surface density/stiffness, seen in AFAM, and in the surface electric potential, seen in KPFM.     

Preparation and characterization of silicate nanofilms doped with europium β-diketonate complexes

Films consisting of Eu³⁺ β-diketonate complexes were deposited onto glassy substrates by means of the spin- and dip-coating techniques, using different ion/ligand ratios. Absorption spectroscopy in the infrared region revealed the typical stretching bands of the SiOSi and SiOH bonds of the inorganic matrix as well as bands relative to the CO and CH symmetric vibration of β-diketone (dibenzoylmethane). The films displayed UV-visible absorption band at 350 nm, attributed to the organic ligand. Luminescence properties were studied by photoluminescence spectroscopy. Upon ligand excitation, the emission spectra exhibited the characteristic bands of the Eu³⁺ ion corresponding to the transition from the excited state ⁵D₀ to the ground state ⁷F_J. Scanning electron microscopy confirmed the formation of a film with average thickness ranging from 80 to 100 nm. The sol-gel process and the deposition techniques resulted in the effective formation of nanofilms, which opens up perspectives for their application in photonics.     

Synthesis and structural refinement of polycrystalline ceramic powder Pr0.1Ca0.9TiO3

Perovskite structure-based ceramic precursors have a characteristic property of substitution in the ‘A’ site of the ABO₃ structure. This makes them a potential material for nuclear waste management in synthetic rock (Synroc) technology. In order to simulate the mechanism of rare earth fixation in perovskite, Pr_xCa_1−xTiO₃ (where x = 0.1) has been synthesized through ceramic route by taking calculated quantities of oxides of Ca, Ti and Pr as starting materials. The ceramic phase has been characterized by its powder diffraction pattern. The Rietveld analysis of the X-ray diffraction data has been carried out using GSAS software to achieve the convergence which gives the R_p = 5.74% and R_wp = 8.17%. The (h, k, l) values for different lattice planes have been calculated. The praseodymium substituted perovskite crystallizes in orthorhombic symmetry with space group: Pbnm, Z = 4. The unit cell parameters at room temperature are a = 5.39609(31) Å, b = 5.44869(30) Å and c = 7.6565(5) Å. The calculated and observed values of the corresponding intensities, 2θ and density of the polycrystalline powder show good agreement. GSAS-based calculation for bond distances TiO, CaO and bond angles OTiO, OCaO has been reported.     

Study of dilution of Spin-On Glass by Fourier transform infrared spectroscopy

In this work, we study the dilution of Spin-On Glass (SOG) in order to obtain high quality SiO₂ films at 200 °C, with optical and electrical characteristics similar to those of the thermally grown SiO₂. For the production of SiO₂ films we used 2-propanol and deionized water (DI) as diluents for the SOG and we compared the electrical and optical film properties with those of the films obtained from undiluted SOG. From Fourier transform infrared spectroscopy we observed a considerable reduction of SiOH (920 cm^− 1), OH (3490 cm^− 1) and CH, CO bonds (1139 cm^− 1) in the films produced from SOG diluted with DI. Besides the above, the insulator breakdown field was approximately 21 MV/cm, the refractive index and the dielectric constant were close to those of the thermally grown SiO₂. Our results suggest that the film produced from SOG diluted with DI and cured at 200 °C is an excellent candidate to be used as insulator on flexible and large-area electronics.     

Raman spectroscopic study of structure of WO3La2O3B2O3 glasses with no color and crystallization of LaBWO6

Glasses with the nominal compositions of xWO₃25La₂O₃(75 − x)B₂O₃ (mol%) with x = 15, 25, and 50 were prepared using a conventional melt quenching method, and their structure and crystallization behavior were examined from Raman scattering spectra and X-ray diffraction analyses. The glasses are colorless in the visible light region and give the optical band gap energy of 3.49-3.61 eV. The glass transition and crystallization temperatures and the thermal stability against crystallization decrease with increasing WO₃ content. The strong Raman bands at 840 and 940-960 cm⁻¹ suggest that the main coordination state of W⁶⁺ ions in the glasses is isolated (WO₄)²⁻ tetrahedral units. The formation of WO₆ octahedral units is also suggested in the glasses with high WO₃ contents. The main crystallization mechanism in the glasses is the surface crystallization, and the glass of 50WO₃25La₂O₃25B₂O₃ shows the crystallization of LaBWO₆ single phase. The present study proposes that WO₃La₂O₃B₂O₃ glasses and crystallized glasses are very interesting as optical functional materials.     

Preparation and characterization of NaSm9(SiO4)6O2 powders with infrared absorptive properties

NaSm₉(SiO₄)₆O₂ powders were synthesized by mild hydrothermal method at 180 °C for 24 h. The infrared optical properties and structure of the obtained powders were characterized. There existed two narrow and sharp absorptive bands near 943 cm^− 1 (10.6 μm). The band at 938 cm^− 1 was assigned to the stretching vibrations of SiOSm groups connecting to Q¹ species and the band at 989 cm^− 1 was attributed to the stretching vibrations of SiOSm groups linking with Q⁰ species. The reflectivity was lower than 1% from 900 to 1200 nm and reached the minimum of 0.46% at 1073 nm. The prepared powders exhibit potential to act as a new kind of absorptive material for the infrared light of 10.6 μm and 1.06 μm.     

Transmission electron microscopy of nanocomposite CrB-N thin films

This paper reports on the preparation and characterization of CrBN nanocomposite coatings for low friction, low wear and high thermostability applications. Sputtered CrBN thin films were prepared in order to obtain a composite structure consisting of hard CrB₂ and CrN crystallites as well as hexagonal BN lubricant phase by unbalanced magnetron sputtering (UBM) of a CrB₂ target in an Ar/N₂ gas discharge. Coatings, with a total thickness of 4.5-5.5 μm, were deposited at 450 °C on silicon single-crystal substrates. A nanocomposite structure was obtained by increasing the nitrogen content of the sputtering gas. The coating microstructure was investigated on selected samples by high-resolution transmission electron microscopy. The films were generally found to consist of crystallites of a 1-4 nm size embedded in amorphous matrix. This crystalline phase was identified by electron diffraction as hexagonal CrB₂ for low nitrogen content and cubic CrN for high nitrogen content. In the medium composition range, the structure was amorphous, still keeping the two-phase morphology. The use of high-resolution imaging mode helped to reveal the composition of the amorphous phase which seems predominantly to consist of boron nitride.     

Characterization of fluorite-type oxynitride phases in the R2TaON system (R = rare-earth element)

The synthesis of reactive nitridation precursors prepared using citrate complexation/calcination route has shown interest in the study of the system R₂TaON. Novel fluorite-type phases have been evidenced in the oxide series R₂TaO_5.5 (R = NdYb, Y) and oxynitride series R_2.67Ta_1.33(O,N,□)₈. Chemical and optical analyses were performed to characterize these phases, as well as structural analogies with R₂WO₆ and R₂MoO₅ oxide families.     

Enhanced scratch resistance of flexible carbon fiber-reinforced polymer composites by low temperature plasma-polymerized organosilicon oxynitride: The effects of nitrogen addition

An investigation is conducted on enhanced scratch resistance of flexible carbon fiber-reinforced polymer composites (FCFRPCs) by low temperature plasma-polymerized organo-silicon oxynitride (SiO_xC_yN_z) at varying N₂ concentrations. It is found that the organic-inorganic hybrid films (SiO_xC_yN_z) deposited on FCFRPCs using tetramethylsilane (TMS)O₂N₂ plasmas at low temperature dramatically improve the scratch resistance of FCFRPCs. Scratch resistance is greatly enhanced from an overwhelming presence of scratching (100%) on untreated FCFRPCs to a complete lack of scratching (0%) on TMSO₂N₂ plasma-polymerized FCFRPCs with steel wool for 250 cycles at 200 g loading. The scratch resistance of FCFRPCs is found to be highly dependent on their surface characteristics including hardness, surface morphology, surface compositions and chemical bonds of TMSO₂N₂ plasma-polymerized SiO_xC_yN_z.     

Bonding structure and optical properties of a-CNx:H films deposited in CH4-NH3 system

Hydrogenated amorphous carbon nitride (a-CN_x:H) films were deposited by plasma enhanced chemical vapor deposition (PECVD) in CH₄-NH₃ system. The chemical composition and bonding configuration were investigated by XPS and FTIR. The results indicated that both sp²CN and sp³CN bonds generally increased with the increase of the nitrogen concentration, and the N atoms bonded to C atoms through CN, CN and CN bonds. Remarkably, for FTIR spectra, two peaks (2125 and 2200 cm⁻¹) were obviously observed, corresponding to CN bond which was found to predominantly exist in the isonitrile structure. As more nitrogen atoms were incorporated, the optical band gap was found to vary from 1.8 to 2.5 eV. Finally, the conduction mechanisms were discussed at low and high temperature, respectively.