PacSurf2016 Session TF-WeP: Thin Films Posters Session II

Superhardness Ti –Al –Si –N nanocomposite coatings were deposited on SKD 61 and inconel substrates by hybrid coating system (AIP+Sputtering) in various Si target powers for maching of aircraft mechanical parts. The relationship among microstructures, mechanical properties, and tribologiacal properties was investigated. The synthesized Ti –Al –Si –N coatings were characterized using x –ray diffraction (XRD) and x –ray photoelectron spectroscopy (XPS). These analyses revealed that the Ti –B –N –Si coatings are nanocomposites consisting of solid-solution (Ti,Al)N crystallites distributed in an amorphous SiNx matrix. The addition of Si into the Ti –Al –N coating led to percolation of amorphous SiNx and BN phases. The Ti –Al –Si –N coatings exhibited high hardness and H/E values, indicating high fracture toughness, of approximately 42 GPa and 0.097, respectively. Furthermore, the minimum friction coefficient of the Ti –Al –Si –N coatings was approximately 0.25 at low Si target powers. A systematic investigation on the microstructures, mechanical properties, and tribological properties of Ti –Al –Si –N coatings prepared from three Ti-Al composite targets and pure Si target is reported in this study.

The development of strain relaxation buffer layers between GaAs and Si(110) that controlled large lattice mismatch and surface orientation influences are expected to integrate GaAs-based optical-fiber communication devices to Si(110) wafers. The growth of Ge and GeSi layers is mainly studied on Si(001) substrates, but absorb light signal of 1.55 μm wavelength due to the narrow bandgap energy of ~0.67 eV. A two-dimensional growth technique of GaAs(110) films on Si(110) surfaces is also necessary. In this paper, we report the migration-enhanced epitaxy of n-type GaAsNSe thin films with Ga droplets prepared on Si substrate surfaces, as the strain relaxation layers between GaAs and Si(110).

GaAsNSe films were grown by using metal-organic molecular beam epitaxy (MOMBE) equipped with the nitrogen radio-frequency discharge plasma system. MO precursors used were triethylgallium, trisdimethylaminoarsenic (TDMAAs), trisdimethylaminoantimony (TDMASb), and ditertiarybutylselenide. The Si(110) substrate surfaces were thermally cleaned at 550 °C with the simultaneous supply of TDMAAs. Ga droplets were formed on Sb-terminated Si surfaces which prepared by the supply of TDMASb at the substrate temperature of 470 °C. Then GaAsNSe films were grown at the temperature of 370-510 °C. The growth process of the films was characterized by using RHEED, AFM, and x-ray diffraction methods.

Molybdenum disulfide (MoS₂) is widely used as a solid lubricant in vacuum. It produces very low friction due to its lamellar structure. However, one of the drawback of MoS₂ is weak for oxidation. Recently, the coating that MoS₂ nanoparticles are dispersed into diamond-like carbon (DLC) host matrix is proposed to overcome this problem utilizing gas barrier effect of DLC in addition, its hardness increases . Such coating is called MoS₂-containing DLC (MD). The coating shows lower friction, m ~ 0.01, than MoS₂ in vacuum when the coating is prepared under specific condition. When it shows low friction, unique transfer layer onto counter surface is formed. The structure of the transfer layer is consisted of 5 nm carbon layer on counter surface and mixed layer composed of MoS₂ and C on it. These facts clearly indicate that such specific structure is organized thanks to the coating. We have also demonstrated that low friction can be achieved depending not only on MoS₂ concentration but also bias voltage during deposition. Carbon matrix is important for achieving low friction. It is indicated that in order to form unique transfer layer, carbon has something potential to support MoS₂ to arrange lamellar structure. The purpose of this study is to clarify mechanisms of low friction.

Friction tests were conducted with ball-on-disk type apparatus in well-controlled environmental conditions. Dry nitrogen, dry oxygen and humid nitrogen gases are used to change atmospheric condition during friction tests. Various observation techniques including scanning electron microscope (SEM) and transmission electron microscope (TEM) equipped with energy dispersive X-ray spectrometer (EDS) are employed in this study.

Diamond-like carbon (DLC) films have been investigated in domestic fields because of their many attractive properties. In especially, mechanical high hardness, low wear resistance and gas barrier property of DLC films can be mentioned as the dominant advantages. DLC coating has already applied to surface finishing technology of metallic molds, cutting tools and polyethylene terephthalate (PET) bottles. In recent, many researchers have reported the characteristics of chemical stabilities, blood compatibilities and cell affinities on the DLC films. Modification of the surface condition of DLC films has been rapidly expected to demand of the advanced medical care.

In order to improve the biocompatibility of DLC films, plasma treatment of oxygen (O₂) and nitrogen (N₂) gases are proposed on the DLC surfaces¹⁾. Surface conditions of the DLC films are delicate because bonds between carbon and oxygen are not so strong. The stability of effect of plasma treatment for DLC films has to investigate by systematic approach. In this study, we investigate that stability of the surface characteristics for time of O₂ plasma treatment. DLC films were prepared on Si substrate by using r. f. plasma chemical vapor deposition ( r. f. plasma CVD ) in methane ( CH₄ ) gas. After DLC films deposition, surface modification was carried out by O₂ plasma. To evaluate stabilities of the plasma treatment on surface characteristics, surface conditions were analyzed by contact angle measurement and X-ray photoelectron spectroscopy (XPS). The cell affinity is estimated by in-vitro examination with a cell proliferation test using mouse-derived fibroblasts.

In case of contact angle measurement, DLC films without plasma treatments have water repellency and are almost constant. Hydrophilicity of surfaces immediately O₂ plasma treatments is stables for several days, after that their change to the saturation value.

From the result of XPS, intensity ratio of oxygen and carbon peak on the surfaces of the DLC films without plasma treatment is increased as function of time. In contrast, the intensity ratio between oxygen and carbon is decreased with time in case of sample with O₂ plasma treatments. The results revealed that adsorption and desorption of oxygen play important role to shift of the wettability in the plasma treatment on DLC films.

Reference

1. S. Murata, S. Ito, J. Mizuno, K. Hirakuri, K. Sato et., Phys. Ststus Soldi C9, No. 6 (2012) pp1439-1442.

Chemical states and electrical properties of the CeO₂ based compound oxide doped with SiO₂ as the promising gate stuck material for MOS devices were investigated, based on the consideration that the crystallization could be suppressed by mixing materials having different crystalline structures. The X-ray photoelectron spectroscopy (XPS) analysis revealed that the compound oxide was successfully prepared on p-type Si (100) substrates by pyrolytic MOCVD using Ce(OCEt₂Me)₄ at the substrate temperature of 350 °C for 30 min with the intermittent introduction of TEOS (TetraEthoxyOrthoSilicate) for 10 sec every 3, 5, or 10 min. The decomposition temperature of TEOS was lowered by the hydrolysis utilizing H₂O generated from Ce source decomposition. In the X-ray diffraction (XRD) patterns, the pure CeO₂ films represented the distinct cubic CeO₂ peaks, while CeO₂ peaks decreased to the trace level for the samples with TEOS introduction; the CeO₂ films with TEOS introduction were essentially amorphous.

From the X-ray photoelectron spectroscopy (XPS) spectra of Ce3d, Si2s and O1s, the average molar concentrations of SiO₂ in the films with the introduction of TEOS for 10 sec every 3, 5, or 10 min were determined to be 15%, 6% and 6%, respectively. Although TEOS was intermittently introduced during CeO₂ deposition, the distribution of Si in CeO₂ films was uniform and the amount of incorporated Si was not directly related to the TEOS supply rate. Cerium silicate formation in the film prepared with TEOS introduction was confirmed from Si2s peaks at 153.5 eV and O1s spectra appearing with the shoulder at the higher binding energy.

Hydrogen outgassing from an inside wall is the most important issue for vacuum chambers in ultrahigh vacuum (UHV) and extremely high vacuum (XHV). In addition, the behavior of hydrogen in metals should be made clear to understand the mechanisms of hydrogen embrittlement and storage. We have observed the behavior of hydrogen in metals by visualizing sequentially spatial distributions of permeated hydrogen on the surface of stainless steel membrane. The distributions of surface hydrogen were obtained using ions emitted by the method of desorption induced by electronic transition (DIET) process with the scanning electron microscope (SEM).The diffusion pass of hydrogen can be revealed from comparison of hydrogen maps obtained by this technique with the surface grain structure. In addition, physical information on permeation, which contains the processes of solution, diffusion, adsorption, is obtained by conjunction with a measurement on time dependence of permeated hydrogen pressure in the vacuum.The experimental setup is shown in Figure 1. We equipped the SEM (JEOL JAMP10) to the sample holder with hydrogen supply system and collecting electrode of DIET ions, the detection system of DIET ions and the quadrupole mass analyzer (Pfeiffer Vacuum QMG220). The collecting electrode is attached due to focusing DIET ions on the detector system. The DIET signals are measured in two-dimensional pulse counting system constructed by LabVIEW. This two-dimensional pulse counting system is synchronized with the scanning electron beam. The sample is SUS304 stainless steel, which has austenite structure with martensite dislocations caused by cold working of 20 %. The sizes of austenite grains are about 100 μm. The thickness of membrane is 200 μm. After outgassing of hydrogen in the sample (573K: 48 hours) the following experiments were performed under the outgassing temperature. The back side of SUS membrane was exposed to hydrogen (2.7×10⁵ Pa) and the permeated hydrogen on the opposite observation side was observed by DIET method. The vacuum chamber was evacuated by the sputter ion pump (100 l/s) under the experiments. The pressure was 1x10^-7 Pa under the experiment. Both H₂ and D₂ gases were used to investigate an isotope effect for permeation.

Figures 2 and 3 are the secondary electron image and the permeated hydrogen map, which is obtained by accumulating DIET ions for 50 hours at 473 K, respectively. A comparison of two kinds of image suggested that the hydrogen permeation from the inside of grain and more permeation in austenite grains than martensite grains.

[1] A.N. Itakura, et al, Applied Surface Science, 159-160 (2000) 62-66.

[2] A.N. Itakura, et al, Journal of Vacuum Society Japan, 57 (2014) 23-26.

[3] N. Miyauch, et al, Journal of Vacuume Society Japan, 58 (2015) 387-391.

Recently, carbon nitride (CNx) has gained much attention as solid lubricant in automotive engines, aerospace instruments, etc. Experimentally, one of the authors, Adachi, discovered that CNx gives super-low friction coefficient. However, the super-low friction mechanism of CNx has not been clarified experimentally. It is experimentally pointed out that CNx shows lower friction coefficient than diamond-like carbon under specific condition. It means that the role of nitrogen in CNx is very important. However, the function of nitrogen in CNx has not been elucidated. Therefore, the theoretical approach is desired to reveal the role of nitrogen in CNx. In the present study, we employed our original tribochemical reaction simulator based on the tight-binding quantum chemical molecular dynamics method [1-3]. The friction dynamics of H-terminated CNx is simulated under 1 GPa pressure. The simulation result shows low friction coefficient of 0.05. We found that hydrogen-hydrogen repulsion is source of the super-low friction. However, this reason is same with that of H-terminated diamond like carbon films. It means that the role of nitrogen has not been clarified. Then, we investigate the effect of water molecules on the friction dynamic of H-terminated CNx. It is very interesting to see the generation and evaporation of NH3 molecules by the tribochemical reaction of CNx and water. The generation and evaporation of NH3 molecules give low density diamond-like carbon thin films. Therefore, we propose that low density diamond-like carbon generated by the tribochemical reactions of CNx and water gives super-low friction coefficient.

[1] K. Hayashi, M. Kubo et al., J. Phys. Chem. C, 115 (2011) 22981.

[2] K. Hayashi, M. Kubo et al., Faraday Discuss., 156 (2012) 137.

[3] S. Bai, M. Kubo et al., RSC Adv., 4 (2014) 33739.

Our work deals with comparison of detection abilities of thin film chemiresistors based on silver phthalocyanine with metallic nanoparticles and ion mobility spectrometry. In our study we focus to the detection of widely used taggant in explosives - 2-nitrotoluene.

The sensing layers of chemiresistors were deposited by vacuum evaporation (AgPc) and DC magnetron sputtering (metallic nanoparticles) on ceramic substrates with platinum interdigital electrodes. We varied type of metallic nanoparticles (Au, Pd and Ag), their amount (equivalent thickness in the range of 1 to 50 nm) and also the deposition sequence of used techniques (bottom AgPc + top nanoparticles vs top AgPc layer - bottom nanoparticles). For underlying metal nanoparticles the substrates were heated during deposition (temperature range of 20 - 600 °C) to investigate and tailor nanoparticle shape and conductivity properties.

Growth of metallic nanoparticles was continuously monitored by in-situ resistance measurements during sputtering and annealing operations. These measurements enable also detection of percolation threshold. The morphology of prepared layers was investigated by electron microscopy.

For as-deposited layers of metal on AgPc it was found that when the amount of metal is relatively low (i.e. less than layer with equivalent thickness of 4 nm for Pd, 5 nm for Au and 8 nm for Ag) metal clusters on organic surface are created. Continuous but incompact layers are formed for slightly greater amounts of sputtered metals. Finally, continuous and compact layers were observed when equivalent thicknesses achieved ≈ 15 nm. When the layers are annealed the percolation threshold is in general shifted to greater amounts of sputtered metal.

Optimized sub-threshold layers containing metallic cluster arrays on chemiresistor substrates were used for detection of 2-nitrotoluene. The taggant vapors were detected in two modes: without or with photoactivation (λ = 266 nm). While the dc-response of AgPc/Au(10 nm) sensor to 189 ppm of non-activated 2-nitrotoluene vapors was negligible, after photoactivation the dc-response rose to 373.

Water is environmentally friendly liquid. When we used it as a lubricant, it gives very low friction. Silicon carbide and silicon nitride can produce very low friction, < 0.01, under water lubricating condition. However, one of the drawback is low load carrying capacity due to low viscosity of water. With increase of load, direct contact between the materials occurs, which leads to seizure. Some researchers have shown increase of load-carrying capacity thanks to DLC that can reduce friction under direct contact condition. Although it works as protective coating to avoid seizure, friction under such severe condition is still high, ~0.1-0.2. So, the target of this study is to produce the coating to show low friction and high load carrying capacity under water lubricating condition. To achieve the goal, we are developing SiC-containing DLC coatings.

Investigated coatings are prepared by RF generated methane plasma and DC magnetron co-sputtering of silicon carbide target (Purity: 99.99%). Silicon carbide disk is used as a substrate material. Various coatings are deposited by changing methane and argon flow rate (CH4/Ar). Composition, structural analyses and hardness are measured by Rutherford backscattering spectroscopy (RBS), X-ray photoelectron spectroscopy (XPS) and nanoindentation technique. Friction tests are performed using ball-on-disk tribometer. Silicon carbide ball is used as a counter material. Ball and disk are immersed in water and friction tests are carried out.

By changing flow rate of methane and argon, various coatings with different composition are achieved. Hardness of the coatings decreases with increase flow rate. Friction properties also vary with composition of the coatings. With CH4/Ar = 0.1, coating is removed at very beginning of the friction test. When the coating is deposited with CH4/Ar = 0.2, very low friction of 0.05 can be achieved. Almost similar friction curve is obtained with further increase of the ratio but fluctuation of the friction coefficient is also observed with CH4/Ar = 0.3. It suggests that these is optimum structure or composition of the coating. We also changed speed and load for friction tests. Surprisingly, friction coefficient of the coating with CH4/Ar = 0.2 decreases with increase of load and decrease of speed condition, meaning lower friction is obtained with more severe contact condition. According to the literature, lowering friction coefficient is due to the termination of OH bonds by reacting SiC surface with water. Thanks to the hydrogen bonding between O from OH and H from H₂O, water is captured on the frictional surface and friction force can be derived from shearing the low viscos water.

The synthesis of high quality single layer 2D MoS₂ on large area substrates remains challenging. Mechanical exfoliation is capable of producing high quality material, but it is limited to small areas, requires transfer to the device substrate, is not scalable, and is impractical for manufacturing. Chemical vapor deposition (CVD) has been shown to yield MoS₂ on a variety of substrates, but is limited by non-uniform electrical properties, poor process stability, and high deposition temperature (>600°C). A natural method for the synthesis of 2D materials is atomic layer deposition (ALD) in which alternating, purge separated, self-limiting surface reactions allow for precise thickness control, high conformality, and scalability to large surface areas. Although reports of ALD MoS₂ are beginning to emerge, ALD of single layer MoS₂ has typically required specialty sapphire substrates and high temperature (800°C) post deposition anneals and/or has been limited to small diameter wafers.

In this work, we demonstrate low temperature ALD of single to few monolayer MoS₂ uniformly across 150 mm diameter patterned SiO₂/Si and quartz substrates.¹ Purge separated cycles of MoCl₅ and H₂S precursors were used at ALD reactor temperatures ranging from 375°C to 475°C. Raman scattering measurements show clearly the in-plane (E¹_2g) and out-of-plane (A_1g) modes for ALD films deposited at 375°C or 475°C, indicating the presence of mono- to few layer MoS₂. The separation of the E¹_2g and A_1g peaks is a function of the number of ALD cycles, shifting closer together with fewer layers. Films deposited at 475°C are of much higher quality than films deposited at 375°C. While the E¹_2g-A_1g peak separation of the 375 °C film corresponds to bulk-like MoS₂, the smaller peak separation of the 475°C film suggests a thickness of approximately two monolayers. Raman polarization tests confirm the MoS₂ crystals have the desired orientation parallel to the surface. High temperature H₂S and sulfur annealed films produce a sharpening of the E¹_2g and A_1g peaks as well as the appearance of the band edge PL and spin orbit splitting peaks, a further indication of the presence of monolayer MoS₂. High resolution transmission electron microscopy images confirms the presence of monolayer to bilayer MoS₂ films. X-ray photoelectron spectroscopy indicates that a sub-stoichiometric sulfur ratio in the as-deposited films is increased to the stoichiometric S/Mo ratio after annealing in H₂S at 600°C and above. Results suggest that ALD may be a promising method for production of 2D MoS₂.

Support provided by Sharp Labs of America.

1. A. Valdivia, D.J. Tweet, and J.F. Conley, Jr., J. Vac. Sci Tech A 34, 021515 (2016).

Results about processing and characterization of gallium nitride (GaN) films grown by pulsed laser deposition technique are presented. The films were grown on sapphire (0001) and silicon (111) substrates, under the following conditions: substrate temperature of 850 °C, time deposition of 60 minutes and pressure of 4.2x10^-6 torr. A Nd: YAG laser was used with wavelength of 1064 nm, repetition frequency of 50 Hz and power of 2.8 W. To study the GaN films structural properties, X-ray diffraction was used obtaining peaks around 34.5° corresponding to GaN. To study the optical properties, UV-Vis absorption spectroscopy, photoluminescence (PL) and Raman spectroscopy were used. From the UV-Vis spectroscopy a band-gap value of 3.2 eV was obtained. Photoluminescence at room temperature was observed, the PL spectra shows two bands, one of these associated to yellow band of GaN at 2.2 eV, and the other one around 3.0 eV associated with recombination centers, such as interstitials Gallium or Nitrogen atoms. Raman shift in 722 cm^-1 was obtained corresponding to GaN in its wurtzite structure.

Passivation of a high-k/III-V interface is the most important process to be developed for future III-V-based transistors. Recently, there have been several attempts to passivate the interface defects by performing H₂ annealing after the high-k deposition on In_0.53Ga_0.47As: forming gas annealing [1] or H₂ high pressure annealing [2].

In this study, we deposited a HfO₂/Al₂O₃ gate stack using atomic layer deposition on the In_0.53Ga_0.47As substrates with different doping types and carried out H₂ high pressure annealing (400 °C) at different pressures (10 bar and 30 bar). According to the time-of-flight secondary ion mass spectrometry and X-ray photoelectron spectroscopy measurements, out-diffusion of In and Ga atoms toward the high-k film was escalated as the H₂ pressure increased. The relationship between the observed H₂-induced out-diffusion and the resulting electrical properties will be discussed.

[1] K. Tang, R. Droopad, and P. C. McIntyre, ECS Transactions, 69, 53 (2015).

[2] T.-W. Kim, H.-M. Kwon, S. H. Shin, C.-S. Shin, W.-K. Park, E. Chiu, M. Rivera, J. I. Lew, D. Veksler, T. Orzali, and D.-H. Kim, IEEE Elec. Dev. Lett. 36, 672 (2015).

The graphene consisting with carbon atoms to honeycomb structure has the excellent properties about mechanical, chemical and thermal and it has been research in a variety of fields. In order to commercialize graphene with these outstanding properties, as well as a large area, mass production is essential for precise and fast measurement. In this study, for measuring the shape and size of the oxidation graphene fast and precisely, we configured the measuring system with an optical microscope, a heating stage and 3 W level laser. Through the configured system we can keep the graphene in a vacuum and wet condition to 200 ℃ and measure the grain boundary of the oxidation graphene by irradiating the laser to locally. Later by proceeding the additional experiment and analyzing the correlation between the degree of graphene oxide and the laser irradiation time, through this process we develop the optimized visualization method of the graphene defects.

The expanding availability of narrow-wavelength deep UV lamps and powerful tools for numerical modelling afford growing opportunity to create precisely tailored organic thin films by transformation of an original substrate. Having begun with synthetic polymers (polyesters), application to natural materials (cellulose) is now proving successful, as revealed by surface spectroscopies (XPS and ToF-SIMS), AFM and wetting.

Titanium nitride (TiN) films were prepared by rf magnetron sputtering technique. The depositions were carried out by a pure N₂ plasma sputtering. Their mechanical properties, such as nano-indentation hardness, friction coefficient, and water contact angle have been investigated. XRD studies revealed that TiNx films grown at temperatures more than 360°C exhibits an intense compressive stress as compared with the films grown at temperatures less than 360°C. The orientation of TiNx films changes toward (111) orientation at 360°C due to increased ion bombardment which favors low surface energy at (111) orientation. The increase of Ts, which means the distance between target and substrate, increases the mobility of adatoms promoting closed packing structures in near thermodynamic equilibrium conditions. Thus, for high adatom mobility the TiNx films expected to grow along the (111) orientation corresponding to that with the lowest surface free energy. On the other hand, for low adatom mobility the preferred orientation is the (002) in which the highest number of atoms per unit area can be incorporated at low energy sites. The mechanical properties of TiNx films grown at a pure N₂ atmosphere strongly dependent on the Ts. The highest hardness and the smallest friction coefficient of 26 GPa and μ=0.13, respectively were in a TiNx film deposited at 400°C. This film was found to be accompanied by a water repellent surface.

This research was financially supported by the Ministry of Education (MOE) and National Research Foundation of Korea(NRF) through the Human Resource Training Project for Regional Innovation (No. 2015H1C1A1035619). This work (Grants No. C0350891) was supported by Business for Cooperative R&D between Industry, Academy, and Research Institute funded Korea Small and Medium Business Administration in 2015.

Currently, commercial temperature and humidity sensors have a low sensitivity for both sides of a high humidity and a low humidity. Moreover, because the main parts of these sensors are manufactured using polymer materials, there is the problem of a short life in environments such as high temperature or high humidity. Therefore, the next-type sensors are required in a longer life and a higher sensitivity.

As a material satisfying some of the above-mentioned function, TiO₂ was adopted. TiO₂ is an n-type oxide semiconductor, and has the stable photo-excited state and causes no autolysis. In addition, TiO₂ shows the hydrophilicity under ultraviolet irradiation. The next-type sensor with a high sensitivity is promised by the suitable junction of between a TiO₂ layer and a Cu₂O (p-type oxide semiconductor) layer.

In this study, the investigation of TiO₂ thin films on sensor characteristics and the improvement of the sensor sensitivity by using the TiO₂/NiO/Cu₂O multi-layer thin film were carried out. The rutile-type TiO₂ thin film (TiO₂-R) with a thickness of 200 nm, the anatase-type TiO₂ thin film (TiO₂-A) with a thickness of 200 nm and the TiO₂/NiO/Cu₂O (200/10/200 nm) thin film were prepared by reactive magnetron sputtering. The electric resistance of each sample was measured by changing a voltage from 0 V to 10 V. The resistance changes for a temperature and a humidity were measured by changing a temperature from 25 ℃ to 60 ℃, by changing a humidity from 30 % to 60 %. As the characteristic relating to the humidity, a water contact angle was measured by the θ/2 method. In these experiments, the photoreaction on a semiconductor characteristic was examined by irradiating the white-LED light or UV-LED light to the sample surface.

The resistances of the TiO₂-R thin film and the TiO₂-A thin film decreased by the photo-excitation under the UV-LED light irradiation. The resistance of the TiO₂/NiO/Cu₂O thin film under the white-LED light irradiation showed the value as well as that of UV-LED. The temperature coefficient of resistance of the TiO₂-R thin film, the TiO₂-A thin film and the TiO₂/NiO/Cu₂O thin film were -8354×10^-6 [/K], -5264×10^-6 [/K] and -16390×10^-6 [/K], respectively. In the case of a humidity characteristic, there was no large change in the electric resistance against the humidity change for any sample. In addition, the improvement of hydrophilicity by light irradiation was not confirmed from the water contact angle examination.

The TiO₂/NiO/Cu₂O thin film showed a superior temperature characteristic in comparison with the TiO₂-R thin film or the TiO₂-A thin film.

In recent years, various characteristics of TiO₂ have attracted considerable attention. One of their characteristics is a photocatalytic effect. The photocatalytic effect of TiO₂ shows antifouling or antimicrobial activity, and has the ability to decompose environmental pollutants. The most important characteristic as a photocatalysis of TiO₂ is well known that the photo-excited state is very stable and does not cause self-decomposition. Therefore, TiO₂ can perform the electrolysis of water by light, however a light reaction of TiO₂ is limited at ultraviolet region corresponded with only about 3 % of sunlight.

In this study, to improve the photocatalytic property of TiO₂ the double layer films were fabricated by the constitution of the TiO₂ layer with 3.0 - 3.2 eV and the Cu₂O layer with 2.2 eV in a band gap energy. In order to prevent the diffusion of Cu, an NiO or TaON layer was inserted between the TiO₂ layer and the Cu₂O layer. NiO has a high melting point, high hardness and has been used as a barrier layer in various fields. TaON is used as electrode materials for a semiconductor and light electronics devices. Each oxide layer was prepared by reactive magnetron sputtering.

The film composition and microstructure were investigated by the X-ray photoelectron spectroscopy and X-ray diffraction, respectively. The chromatic change of a methylene blue solution was applied to the measurement of the photocatalytic property. The light irradiation to the TiO₂/NiO/Cu₂O film or the TiO₂/TaON/Cu₂O film in a methylene blue solution was carried out using a commercial sterilizing lamp as ultraviolet light and an artificial sun lamp as visible light. The transmittance of a methylene blue solution was measured by a spectrophotometer.

It was confirmed that Cu on the TiO₂ surface was not observed by inserting the NiO or the TaON layer. The crystal structure of the TiO₂/Cu₂O film showed a rutile type while the ratio of rutile (110) / anatase (101) changed with the NiO film thickness. In the case of the intermediate layer of NiO, the suitable photocatalytic effect was obtained by the film with the NiO layer of 20 nm thickness, when the transmittance showed about 57 % under an artificial sun lamp and about 77 % under a sterilization lamp. In the case of the TaON layer, the suitable photocatalytic effect was obtained by the TaON layer of 10 nm thickness, when the transmittance showed about 75 % under an artificial sun lamp and about 82 % under a sterilization lamp.

X-ray Photoelectron Spectroscopy (XPS) depth profiling has been widely utilized to provide detailed elemental and chemical state information of thin films, such as those used in microelectronic devices and protective coatings. These measurements have often been combined with valence electronic information obtained using the related technique of Ultraviolet Photoelectron Spectroscopy (UPS). Such detailed and complementary information is essential when attempting to fine-tune specific thin film parameters for best device or coating performance.

While useful information is acquired from XPS and UPS in isolation, a more powerful insight into the structure of a material comes from using these two techniques in conjunction, allowing a more complete material characterisation to be performed. Previously, switching between techniques throughout the course of an experiment has been an involved and often laborious process, discouraging more widespread use. Recently the automation of UPS has allowed acquisition of XPS and UPS data at each level of a depth profile, providing a much sought after insight into the correlation between chemical and electronic structure at within a substrate at various depths.

Of particular interest is the ability to access the valence electronic structure at mixed oxide interfaces using small argon ion gas clusters, which was not previously possible due to the loss of electronic structure in semiconductors or organic materials on exposure to monatomic argon ion beams. This presentation demonstrates the wealth of information that can be acquired by performing combined XPS-UPS depth profiles and the ease with which this information can be acquired and processed, due to recent instrumentation and software developments.

Metals like copper are easily oxidized in air to form metal oxides on the surface. This is often problematic for their applications because of reduction of the electrical conductivity. We studied influence of molecular coating of organic thiol compounds on copper plates and fine particles on their oxidation resistance and electrical conductivity.

Copper and nickel surfaces were coated with thiol terminated polystyrenes (PSt-SH)s and alkanethiols by dipping copper into solutions of the thiol compounds. XPS measurements revealed that the molecular thin layer of PSt-SH lead to a resistance against oxidation. Coating with alkanethiols like 1-dodecanethiol (Dod-SH) was also effective. However, only the PSt-SH layer kept the oxidation resistance against heating at high temperature, which was also confirmed by the color change of the metal surface by heating.

We also used cyclic voltammetry (CV) to evaluate the oxidation resistance. The oxidation resistance was determined from the integral value at the anode and cathode regions in the oxidation-reduction curve. We found that the oxidation resistance of copper covered with PSt- SH was excellent at high temperatures under atmosphere and was not decreased even by heating up to 150°C.

The temperature dependences of the contact electrical resistance measured by the four-point method indicated that the electrical conductivity was not reduced for the metal surface coated with PSt-SH even at high temperatures which is consistent with the results of XPS and CV measurements.

[1] Takuya IKEDA, Kaoru ADACHI and Yasuhisa TSUKAHARA, Journal of MMIJ, Vol.132, No.2, pp.39 - 46 (2016).

[2] Takuya IKEDA, Tomoki TAKATA, Juri TAKAGI, Kaoru ADACHI, and Yasuhisa TSUKAHARA, Kobunshi Ronbunshu, Vol.73, No.2, pp.198 - 206 (2016).

[3] Juri TAKAGI, Takuya IKEDA, Kaoru ADACHI, and Yasuhisa TSUKAHARA, Kobunshi Ronbunshu, Vol.73, No.3, pp.294 - 301 (2016).

The purpose of this work is to study the influence of the abrasive slurry concentration on the coefficient of friction of thin films submitted to micro-abrasive wear. Initially, a micro-abrasive wear testing by free rotative ball equipment was designed and constructed, able to measure the coefficient of friction on the tribo-system “thin-film – abrasive slurry – ball”. After, experiments were conducted with thin films of TiN, TiC, CrN, TiAlN, HfN, ZrN, TiZrN, TiN/TiAl (multi-layer), TiHfC and TiHfCN, balls of AISI 52100 steel and abrasive slurries prepared with black silicon carbide (SiC) particles + glycerin. All tests were conducted without interruption, and the abrasive slurry was continuously agitated and fed between the ball and specimen. The tangential (T) and normal (N) forces were monitored throughout the tests and the coefficient of friction (µ) was calculated by the equation µ = T/N. The results obtained have shown that the concentration of abrasive slurry affected the actions of the abrasive wear modes (grooving abrasion or rolling abrasion) and, consequently, the magnitude of the coefficient of friction: high abrasive slurry concentration was related with low coefficient of friction.

Several works on the coefficient of friction during abrasive wear tests are available in the literature, but only a few were dedicated to the coefficient of friction in micro-abrasive wear tests conducted with rotating ball. This work aims to study the influence of titanium nitride (TiN) and titanium carbide (TiC) coatings hardness on the coefficient of friction and coefficient of wear in ball-cratering micro-abrasive wear tests. A ball of AISI 52100 steel and two specimens of AISI D2 tool steel, one coated with TiN and another coated with TiC, were used in the experiments. The abrasive slurry was prepared with black silicon carbide (SiC) particles and distilled water. Two normal forces and six sliding distances were defined, and both normal and tangential forces were monitored constantly during all tests. The movement of the specimen in the direction parallel to the applied force was also constantly monitored with the help of an electronic linear ruler. This procedure allowed the calculation of crater geometry, and thus the coefficient of wear for the different sliding distances without the need to stop the test. The coefficient of friction was determined by the ratio between the tangential and the normal forces, and for both TiN and TiC coatings, the values remained, approximately, in the same range (from μ = 0.4 to μ = 0.9). On the other hand, the coefficient of wear decreased with the increase in coating hardness.