Frictional and morphological properties of AuMoS2 films sputtered from a compact target

AuMoS₂ films 0.02–1.2 μm thick were sputtered from a target compacted from 5 wt.% Au plus 95 wt.% MoS₂ to investigate the frictional and morphological film growth characteristics. The gold dispersion effects in MoS₂ films are of interest to increase the densification and strengthening of the film structure. Three microstructural growth stages were identified on the nano-micro-macrostructural level. During sliding both sputtered AuMoS₂ and sputtered MoS₂ films have a tendency to break within the columnar region. The remaining or effective film, about 0.2 μm thick, performs the lubrication. The AuMoS₂ films displayed a lower friction coefficient with a high degree of frictional stability and less wear debris generation compared with pure MoS₂ films. The more favorable frictional characteristics of the AuMoS₂ films are attributed to the effective film thickness and the high density packed columnar zone which has a reduced effect on the fragmentation of the tapered crystallites during fracture.     

Hot-water treatment of sol–gel derived SiO2–TiO2 microparticles and application to electrophoretic deposition for thick films

SiO₂–TiO₂ spherical microparticles of about 0.7 μm in diameter were prepared by the sol–gel method. Anatase nanocrystals were formed in the microparticles and their specific surface area was increased after a hot-water treatment at 90 °C. From the changes in the concentration of I₂ photocatalytically generated from KI aqueous solution, the activity of the SiO₂–TiO₂ microparticles was found to increase with increasing the hot-water treatment time. Particulate, thick films were electrophoretically deposited on indium tin oxide (ITO)-coated glass substrates using the anatase nanocrystal-precipitated SiO₂–TiO₂ microparticles. The thickness of the electrophoretically deposited particulate film increased to be approximately 10 μm with an increase in applied voltage. The resultant thick film showed a high photocatalytic activity.     

SiO2 layer thickness effects on the (001) texture of FePtCu:SiO2 nanocomposite films

The influence of SiO₂ layer thickness of (Fe₅₂Pt₄₈)₈₈Cu₁₂:SiO₂ multilayer nanocomposite films on their structural and magnetic properties were investigated. The films were deposited on (001) textured FePt films, and then annealed at 873 K. The crystalline texture of (Fe₅₂Pt₄₈)₈₈Cu₁₂:SiO₂ films changes drastically with respect to the thickness of the SiO₂ layers. In the film with 50-Å thick SiO₂ layers, the (111) peak was strong although the (001) orientation is dominant, and self-organized spherical FePtCu particles were formed in the SiO₂ matrix. However, in the film with 19-Å thick SiO₂ layers, flat FePt grains with perfect (001) orientation were obtained. In addition, twins with different crystalline orientations were seen in the above films with different thicknesses of the SiO₂ layers. Accordingly, different perpendicular hysteresis loops were obtained.     

Alteration of internal stresses in SiO2/Cu/TiN thin films by X-ray and synchrotron radiation due to heat treatment

A break of wiring by stress-migration becomes a problem with an integrated circuit such as LSI. The present study investigates residual stress in SiO₂/Cu/TiN film deposited on glass substrates. A TiN layer, as an undercoat, was first deposited on the substrate by arc ion plating and then Cu and SiO₂ layers were deposited by plasma coating. The crystal structure and the residual stress in the deposited multi-layer film were investigated using in-lab. X-ray equipment and a synchrotron radiation device that emits ultra-high-intensity X-rays. It was found that the SiO₂ film was amorphous and both the Cu and TiN films had a strong {1 1 1} orientation. The Cu and TiN layers in the multi thick (Cu and TiN:1.0 μm)-layer film and multi thin (0.1 μm)-layer film exhibited tensile residual stresses. Both tensile residual stresses in the multi thin-layer film are larger than the multi thick-layer film. After annealing at 400 °C, these tensile residual stresses in both the films increased with increasing the annealing temperature. Surface swelling formations, such as bubbles were observed in the multi thick-layer film. However, in the case of the multi thin-layer films, there was no change in the surface morphology following heat-treatment.     

Properties of indium tin oxide films deposited on unheated polymer substrates by ion beam assisted deposition

The optical, electrical and mechanical properties of indium tin oxide (ITO) films prepared on polyethylene terephthalate (PET) substrates by ion beam assisted deposition at room temperature were investigated. The properties of ITO films can be improved by introducing a buffer layer of silicon dioxide (SiO₂) between the ITO film and the PET substrate. ITO films deposited on SiO₂-coated PET have better crystallinity, lower electrical resistivity, and improved resistance stability under bending than those deposited on bare PET. The average transmittance and the resistivity of ITO films deposited on SiO₂-coated PET are 85% and 0.90 × 10^− 3 Ω cm, respectively, and when the films are bent, the resistance remains almost constant until a bending radius of 1 cm and it increases slowly under a given bending radius with an increase of the bending cycles. The improved resistance stability of ITO films deposited on SiO₂-coated PET is mainly attributed to the perfect adhesion of ITO films induced by the SiO₂ buffer layer.     

Preparation and properties of antioxidative BaO–B<Subscript>2</Subscript>O<Subscript>3</Subscript>–SiO<Subscript>2</Subscript> glass-coated Cu powder for copper conductive film on LTCC substrate

In this study, uniform BaO–B₂O₃–SiO₂ glass coatings on micro Cu powders with different glass/Cu ratio were prepared by sol–gel method. The pastes prepared with the glass-coated Cu powders were screen printed on low temperature co-fired ceramic (LTCC) substrate. Then the dry films on substrate were binder-burned-out at 400 °C in air and co-fired at 910 °C in N₂ atmosphere. During the binder-burning-out process, the oxidization of the films with 9 and 11 wt% glass was slight because of the improvement of oxidization resistance of the glass-coated Cu powders. Moreover, the sintered film with 9 wt% glass coating showed no crystal phase of copper oxide and had small sheet resistance of 1.3 mΩ/□, which can be used as good conductive thick film on LTCC substrate for microelectronic packaging.     

Thanks to our referees

We successfully developed a new process for making strong smooth thick SiO₂ films on hemispherical Kovar mandrels of various sizes designed for multishell laser fusion targets. The surface finish obtainable with a SiO₂ coating 13 μm thick on a mandrel 260 μm in diameter is approximately 30 nm peak to peak, with a few defects approximately 0.3 μm deep. The r.f. magnetron sputtered SiO₂ films were dense and crystalline.     

Effect of SiO2 buffer layer thickness on the properties of ITO/Cu/ITO multilayer films deposited on polyethylene terephthalate substrates

Transparent conductive ITO/Cu/ITO films were deposited on polyethylene terephthalate (PET) substrates with a SiO₂ buffer layer by magnetron sputtering using three cathodes at room temperature. The effect of the SiO₂ buffer layer thickness on the electrical and optical properties of ITO/Cu/ITO films was investigated. The ITO/Cu/ITO film deposited on the 40 nm thick SiO₂ buffer layer exhibits a sheet resistance of 143Ω/sq and transmittance of 65% at 550 nm wavelength. Highly transparent ITO/Cu/ITO films with a transmittance of 80% and a sheet resistance of 98.7Ω/sq have been obtained by applying −60 V substrate bias.     

A study on crack propagation and electrical resistance change of sputtered aluminum thin film on poly ethylene terephthalate substrate under stretching

This work is designed to study crack development and resistance changes in aluminum thin films under stretching. Crack development and relative electrical resistance change (?R/R₀) of aluminum thin film on 127-μm poly ethylene terephthalate substrates were investigated as a function of engineering strain. Four thicknesses were considered for the aluminum thin films: 50, 100, 200, and 500 nm. The engineering stress-engineering strain curves were very similar for all thicknesses. Three strain rates were considered in this study: 0.1 min^− 1, 0.5 min^− 1 and 1.0 min^− 1. Before the yield point, there was no stress difference under different strain rates. However, after the yield point, stress was higher at a higher strain rate. It was found that ?R/R₀ was very sensitive to the film thickness. Optical microscope images at high magnification showed that cracks were observed at 2% strain for 100, 200, and 500 nm-thick films and at 8% strain for the 50 nm-thick films. Short lateral cracks (perpendicular to the original cracks) were observed at 20% strain for the 100 and 200 nm thick films and at 30% for the 500 nm thick films.     

Spectrographic ellipsometry study of a liquid crystal display substrate consisting of thin films of SiO2, polyimide and indium tin oxide on glass

Variable angle spectrometric ellipsometry at room temperature is used to determine thin film parameters of substrates used in liquid crystal displays. These substrates consist of sequential thin films of polyimide (PI), on indium tin oxide (ITO),on SiO₂ deposited on a glass backing approximately 1.1 mm thick. These films were studied by sequentially examining more complex systems of films (SiO₂, SiO₂-ITO, SiO₂-ITO-PI). The SiO₂ layer appears to be optically uniform and flat. The ITO film is difficult to characterize. When this surface film's lower surface is SiO₂ and upper surface is an air-ITO-interface it is found that including surface roughness and variation of the optical properties with ITO thickness in the model improved the fit; suggesting that both phenomena exist in the ITO films. However, the surface roughness and graded nature of optical properties could be not determinable by ellipsometry when the ITO is coated with a polyimide film. The PI films are ellipsometrically flat and over the wavelength range from 500 to 1400 nm the real refractive index of polyimide films varying in thickness between 25 and 80 nm is well modeled by a two-term Cauchy model with no absorption. The ellipsometric thickness of the ITO layer is the same as the profilometric thickness; however, the ellipsometric thickness of the polyimide layers is roughly 10 nm larger than that obtained from the profilometer. These final observations are consistent with the literature.     

Effect of SiO2 buffer layer thickness on the properties of ITO/Cu/ITO multilayer films deposited on polyethylene terephthalate substrates

Transparent conductive ITO/Cu/ITO films were deposited on polyethylene terephthalate (PET) substrates with a SiO₂ buffer layer by magnetron sputtering using three cathodes at room temperature. The effect of the SiO₂ buffer layer thickness on the electrical and optical properties of ITO/Cu/ITO films was investigated. The ITO/Cu/ITO film deposited on the 40 nm thick SiO₂ buffer layer exhibits a sheet resistance of 143Ω/sq and transmittance of 65% at 550 nm wavelength. Highly transparent ITO/Cu/ITO films with a transmittance of 80% and a sheet resistance of 98.7Ω/sq have been obtained by applying −60 V substrate bias.     

Enhanced electrical properties of PZT thick films prepared by sol–gel technique through step-by-step crystallization process

[Pb(Zr_xTi_1-x)O₃: PZT] films at morphotropic phase boundary composition (x = 0.52) were deposited on bare Si, ZrO₂/Si and Pt/Ti/SiO₂/Si substrates by sol–gel spin on technique. Films deposited on the bare Si and ZrO₂/Si substrates had low degree of crystallization and micro cracks. Well crystallized films with smooth microstructure were obtained on Pt/Ti/SiO₂/Si substrates. Further, the thickness of the films on Pt/Ti/SiO₂/Si substrate was increased up to ~1 μm by step-by-step crystallization process. The single perovskite phase of the above films was confirmed with X-ray diffraction analysis. Films had enhanced dielectric properties at room temperature and the dielectric constant values were comparable to those of bulk values at Curie temperature (T_c) from the temperature dependent dielectric measurements. Films exhibit higher remnant polarization (P_r) and lower coercive field (E_c) values. Further, capacitance–voltage (C–V), current–voltage (I–V) measurements and rough estimation of piezoelectric coefficient of the films were carried out.     

Effect of SiO2 passivation overlayers on hillock formation in Al thin films

Hillock formation in Al thin films with varying thicknesses of SiO₂ as a passivation layer was investigated during thermal cycling. Based on the stress measurements and the number of hillocks, 250 nm thick SiO₂ was thick enough to suppress the hillock formation and the suppression of hillock at 250 nm passivation and the lack of suppression at thinner passivation is related to the presence/absence of protection against the diffusive flow of atoms from the surrounding area to the surface due to the biaxial compressive stresses present in the film through the weak spots in the passivation layer. The stress state of Al films measured during annealing (the driving force for hillock formation) did not vary much with SiO₂ thickness. A small number of hillocks formed during the plasma enhanced chemical vapor deposition of SiO₂ overlayers at 300 °C.     

Thin films of SiO<Subscript>2</Subscript> and hydroxyapatite on titanium deposited by spray pyrolysis

Wet spray pyrolysis of fine, well-dispersed a SiO₂ sol was used for the deposition of thin films of silicon dioxide. The sol was obtained by hydrothermal precipitation of silicon acid from a solution at pH = 10. The morphology, roughness, phase composition, chemical homogeneity and the mechanism of the films were investigated by SEM, EDS and IR spectroscopy. The obtained results show a complete covering of the titanium substrate with SiO₂ after 3 h of deposition. It was observed that the film thickness increased from 3 to 19 μm, the roughness of the film decreased from 12 to 3 μm, while the morphology of the deposit changed considerably. A hydroxyapatite film was prepared on the so-obtained SiO₂ thin film by spray pyrolysis deposition and its morphology and phase composition were investigated.     

Microstructure developments of F-doped SiO2 thin films prepared by liquid phase deposition

This study presents a systematic investigation of the microstructure dependence of liquid phase deposition (LPD) of SiO₂ films on solution parameters and deposition temperature. The corresponding deposition rate and film roughness were also evaluated under various deposition conditions. Smooth and sufficiently dense SiO₂ films, which are the prerequisite for reliable low-k dielectric applications, were deposited on both silicon and fluorine-doped tin oxide coated glass substrates from supersaturated hydrofluorosilicic acid (H₂SiF₆) solution with the addition of boric acid (H₃BO₃). It is shown that H₂SiF₆ acid controls the surface morphology and grain structure through surface reaction while H₃BO₃ acid prompts bulk precipitation in solution. For the 208-nm thick SiO₂ film, the breakdown field exceeded 1.9 MV/cm and the leakage current density was on the order of 10^− 9 A/cm² at 4 V, indicating excellent insulating properties of LPD SiO₂ films. The strong presence of Si-O-Si and some Si-F with little Si-OH bond as shown in FT-IR spectra indicate that the LPD SiO₂ films have mostly a silica network with some fluorine (F) content. F-doping was self-incorporated into the silica films from the H₂SiF₆ solution during deposition process.     

Piezoelectric properties of PZT films prepared by the sol-gel method and their application in MEMS

Pb(Zr_0.52Ti_0.48)O₃ (PZT) piezoelectric thin films with thickness of 0.7-2.2 μm were prepared on Pt/Ti-coated SiO₂/Si (0.5 μm/300 μm) substrates by the sol-gel method. The piezoelectric coefficient e₃₁ of the PZT thin film was − 12.5 ± 0.3 C/m², which is evaluated by measuring the tip displacement of PZT-coated cantilevers of the dimensions 50 mm long, 4 mm wide, and 0.3 mm thick. The prepared PZT films demonstrated excellent piezoelectric properties and have large potential applications in MEMS devices. Micro-machined ultrasonic sensors, in which PZT-coated membrane functioned as sensing element, were fabricated and their properties were also characterized.     

Thick films of monocrystalline silicon on SiO2 obtained via embedding SiO2 stripes in bulk silicon

A method is presented for obtaining thick films of single-crystal Si on SiO₂ stripes patterned on bulk silicon. We use a classical deposition of a 0.5 μ m poly-Si coating on patterned stripes of SiO₂ grown on 4″ wafers. A controlled sinking of the SiO₂ stripes into the bulk is obtained, via melting the top surface of the substrate. The thick films of single-crystal Si obtained on SiO₂ (typically 20–40 μm in thickness) are free of defects and exhibit the same surface roughness as before crystallization.     

Photoluminescence optimization of Er-doped SiO2 films synthesized by radiofrequency magnetron sputtering with energetic treatments during and after deposition

By radiofrequency magnetron sputtering co-deposition we synthesized Er:SiO₂ film 0.5 μm thick on silica substrates, with Er content < 0.3 atomic %. By changing the preparation condition (during deposition we have used an additional negative bias voltage applied to the substrates for inducing a low-energy ion bombardment, with or without a contemporary heating) and by varying the thermal treatment after the synthesis (the best conditions were 1 h in the range 700-800 °C, in air) we have obtained an Er:SiO₂ system with an intense photoluminescence emission at λ = 1.54 μm. The best-performing Er:SiO₂ samples obtained by sputtering have shown a photoluminescence response comparable to that of the typical Er:SiO₂ thin film systems obtained by conventional techniques used in applicative framework.     

Preparation and antibacterial activities of Ag-doped SiO<Subscript>2</Subscript>–TiO<Subscript>2</Subscript> composite films by liquid phase deposition (LPD) method

In the present study, Ag/SiO₂–TiO₂ thin films on ceramic tiles with glazed surface were successfully prepared by a liquid phase deposition method (LPD) at a low temperature. The Ag/SiO₂–TiO₂ thin films obtained were homogenous, well adhered and colored by interference of reflected light. The films were characterized by scanning electron microscopy and X-ray diffraction. From these analysis data, it was found that silver (Ag) nanoparticles were trapped in SiO₂–TiO₂ matrix. The antibacterial effects of Ag/SiO₂–TiO₂ thin films against S. aureus and E. coli were examined by the so-called antibacterial-drop test. The bactericidal activity for the above bacteria cells was estimated by relative number of bacteria survived calculated from the number of viable cells which form colonies on the nutrient agar plates. The Ag/SiO₂–TiO₂ thin films had an excellent antibacterial performance. Atomic absorption spectroscopy (AAS) was used for the quantitative determination of the Ag ion concentration releasing from the Ag/SiO₂–TiO₂ thin film. The releasing rate of Ag ions from the Ag/SiO₂–TiO₂ film is 0.123 μg/mL during 192 h. The antibacterial effect of Ag/SiO₂–TiO₂ thin film before and after aging in a weathering chamber for 48 h was compared and the results show that the antibacterial activity is not compromised after weathering.     

Studies of BaTiO3 thin films on different bottom electrode

BaTiO₃ (BT) thin films were prepared on Pt/Ti/SiO₂/Si and Ru/Ti/SiO₂/Si substrates by a modified sol-gel technique. The microstructure of the films was characterized by atomic force microscopy (AFM), X-ray diffraction (XRD) and Raman spectroscopy. The results showed that BT thin films crystallized with perovskite structure. Compared to BT film on Pt/Ti/SiO₂/Si substrate, BT thin film deposited on Ru electrode has similar dielectric constant, while it has higher dielectric loss. C–E curve for BT film on Pt/Ti/SiO₂/Si was more symmetrical around zero-bias field than C–E curve for BT film on Ru/Ti/SiO₂/Si substrate. The tunability was 52.02% for BT film on Pt electrode, which was 33.42% on Ru electrode, at 275 kV/cm and room temperature. The leakage current density of BT on Pt electrode was about an order of magnitude lower than BT film on Ru electrode at the applied electrical field below 150 kV/cm. The leakage conduction mechanism was investigated.