Search

High crystalline quality heteroepitaxial diamond films were successfully formed by using grid-patterned growth on Ir with dc plasma CVD. The crystalline qualities were evaluated by X-ray diffraction, Raman spectroscopy, and etch pit method. Flat {100} diamond films without unepitaxial crystals were formed through epitaxial lateral overgrowth with grid-patterned nucleation region of 100-μm spacing. Omega-rocking curves using X-ray diffraction showed obvious improvement in tilt and twist components for wider grid-spacing. For 100-μm grid spacing, the lowest tilt and twist were 0.064 and 0.043°, respectively. The average dislocation density of 9 × 106 cm−2 for the diamond film grown with grid spacing of 100 μm was the lowest ever in reported values for heteroepitaxial diamond. A correlation between the distribution of crystallinity and dislocation was discussed from the results of etch pit method, Raman mapping and TEM observation. Finally, the crystallinity was compared with single crystal diamonds grown by CVD and HPHT. By using grid-patterned nucleation, the quality of heteroepitaxial diamond on Ir has reached in the range of homoepitaxial diamond film.

Key factors in C 1s photoelectron spectroscopy for realistic samples of single crystal diamonds are remarked. Basic equations for angle-dependent photoelectron spectroscopy applied to single crystal diamond samples are described in Appendix A. Carbon 1s photoelectron spectroscopic works so far reported for hydrogen-terminated and oxygen-terminated diamond (001) and (111) samples were reviewed placing special attention on surface C 1s components with reference to the key factors. The results showed diversity in C 1s photoelectron spectra so far reported. We had three specific subjects of the study in C 1s XPS; the first is that we have reconfirmed the phenomenon that surface conductive layers resumed when smooth non-doped CVD C(111)-O samples were annealed in vacuum [Diam.Rela.Mate.18(2009)206]. A single C 1s XPS surface component was found for a smooth C(111)-O sample before the vacuum-anneal, which was attributed to surface carbon atoms in C O H bonding. The second subject is that dependence of C 1s XPS spectra on surface sensitivity has been measured for all the samples with different surface roughness of C(001)-O, C(111)-O, C(001)-H, and C(111)-H. The results were converted to the energy difference between the Fermi-level (Ef) and valence band maximum (Ev) on the probing depth from the surface. All the samples showed downward bending of Ev toward the surface. For the C(001)-H samples, this was a reconfirmation of previous work [Surf.Sci.604(2010)1148]. For the C(001)-H and C(111)-H samples, various degrees of downward band bending toward surface were observed and analyzed with two-dimensional band simulation. It was concluded that another source of holes such as shallow acceptors is present in a deeper region of the surface in addition to holes very close to surface caused by the charge-transfer-doping. The third subject is that C 1s XPS spectra for superconducting C(111)-O samples showed a lattice distortion of ~9 monolayers near the surface.

To study the influence of crystal orientation on the electrochemical properties of boron-doped diamond (BDD), electrodes comprising (100) and (111) homoepitaxial single-crystal layers of BDD were i...

IntroductionThe COVID-19 pandemic has had a profound impact on the mental health of people around the world. Anxiety related to infection, stress and stigma caused by the forced changes in daily life have reportedly increased the incidence and symptoms of depression, anxiety disorder and obsessive-compulsive disorder. Under such circumstances, telepsychiatry is gaining importance and attracting a great deal of attention. However, few large pragmatic clinical trials on the use of telepsychiatry targeting multiple psychiatric disorders have been conducted to date.MethodsThe targeted study cohort will consist of adults (>18 years) who meet the DSM-5 diagnostic criteria for either (1) depressive disorders, (2) anxiety disorders, or (3) obsessive-compulsive and related disorders. Patients will be assigned in a 1:1 ratio to either a “telepsychiatry group” (at least 50% of visits to be conducted using telemedicine, with at least one face-to-face treatment [FTF] every six months) or an “FTF group” (all visits to be conducted FTF, with no telemedicine). Both groups will receive the usual treatment covered by public medical insurance. The study will utilize a master protocol design in that there will be primary and secondary outcomes for the entire group regardless of diagnosis, as well as the outcomes for each individual disorder group.DiscussionThis study will be a non-inferiority trial to test that the treatment effect of telepsychiatry is not inferior to that of FTF alone. This study will provide useful insights into the effect of the COVID-19 pandemic on the practice of psychiatry.Trial RegistrationjRCT1030210037, Japan Registry of Clinical Trials (jRCT)

INTRODUCTION: The COVID-19 pandemic has had a profound impact on the mental health of people around the world. Anxiety related to infection, stress and stigma caused by the forced changes in daily life have reportedly increased the incidence and symptoms of depression, anxiety disorder and obsessive-compulsive disorder. Under such circumstances, telepsychiatry is gaining importance and attracting a great deal of attention. However, few large pragmatic clinical trials on the use of telepsychiatry targeting multiple psychiatric disorders have been conducted to date. METHODS: The targeted study cohort will consist of adults (>18 years) who meet the DSM-5 diagnostic criteria for either (1) depressive disorders, (2) anxiety disorders, or (3) obsessive-compulsive and related disorders. Patients will be assigned in a 1:1 ratio to either a "telepsychiatry group" (at least 50% of treatments to be conducted using telemedicine, with at least one face-to-face treatment [FTF] within six months) or an "FTF group" (all treatments to be conducted FTF, with no telemedicine). Both groups will receive the usual treatment covered by public medical insurance. The study will utilize a master protocol design in that there will be primary and secondary outcomes for the entire group regardless of diagnosis, as well as the outcomes for each individual disorder group. DISCUSSION: This study will be a non-inferiority trial to test that the treatment effect of telepsychiatry is not inferior to that of FTF alone. This study will provide useful insights into the effect of the COVID-19 pandemic on the practice of psychiatry. TRIAL REGISTRATION: jRCT1030210037, Japan Registry of Clinical Trials (jRCT). ispartof: CONTEMPORARY CLINICAL TRIALS vol:111 ispartof: location:United States status: published

A detailed study of diamond growth on diamond microneedles was conducted using micro-Raman spectroscopy of the microneedle and coalescence regions to approach the production of freestanding diamond substrate by heteroepitaxy with the microneedle growth method. The high-density non-diamond-phase carbon is contaminated in the initial stage of overgrowth of diamond on diamond microneedles, but this completely disappears through the quick recovery of the crystallinity of the overgrown diamond layers during the coalescence with the lateral direction growth. We also point out the possibility that a strong driving force is applied to the dislocations generated at the regrowth point and at the coalescence front to enhance the mutual annihilation of dislocations. In addition, we reveal that the stress state changes from compressive stress in the initial diamond layers to a nearly stress-free state in the bulk layers on the microneedles through a momentary tensile stress state at the regrowth point at the tip of the microneedle. Overall results indicate the strong feasibility of producing freestanding, stress-free, single-crystal diamond substrate by heteroepitaxy.

Dislocation propagation during epitaxial lateral overgrowth (ELO) of diamond on Ir using stripe nucleation with two different orientations was investigated by cross-sectional Transmission Electron Microscopy and Etch Pit Method. In case of 〈100〉 stripes with diamond {100} growth sector, [001] dislocation and large inclined dislocation were observed. For 〈110〉 stripes with {111} growth sector, dislocation bending was observed with [110] propagation preferred. These results demonstrate that stripe direction in ELO affects dislocation propagation during diamond growth. The control of growth sector can be used to influence the dislocation distribution in heteroepitaxial diamond.

A new concept for producing freestanding diamond substrate by heteroepitaxy is proposed. Thick diamond growth by heteroepitaxy is often prevented by heteroepitaxial-strain-related substrate bowing as it leads to substrate cracking. The possibility of using diamond microneedles as a mechanism to neglect and/or exploit substrate bowing is discussed in this new concept; the self-breaking effect of the microneedles is proposed as an application to prevent the main bulk diamond layers from cracking. With an aim toward the realization of this concept, the present study shows the first two important experimental verifications through a homoepitaxial experiment with a high-pressure high-temperature diamond substrate: (1) fabrication of high-aspect-ratio diamond microneedles (2 and 100 μm in diameter and length, respectively) by a thermo-chemical etching reaction and (2) overgrowth of diamond on the microneedles with air gaps remaining between microneedles after continuous diamond film overgrowth. We also detail a growth scheme that illustrates how continuous diamond films are created from the microneedles. The strong feasibility for applying the concept in actual heteroepitaxy is suggested through the present study.

The classification of etch pits formed by hydrogen plasma etching on heteroepitaxial diamond has been done by cross-sectional transmission electron microscope (TEM). We demonstrated that the origin of etch pit was mainly [001] threading dislocation. From invisibility criterion of dislocation contrast in TEM observation, this dislocation was identified as edge and 45° mixed dislocation. The correlation between dislocation types and etch pit shape was discussed.

Although Ti-based ohmic contacts are often used in the fabrication of diamond electronic devices, researches on the barrier height (ϕB) of this contact are very limited and no consistent values have been reached. In this study, a direct determination of ϕB was performed using X-ray photoelectron spectroscopy. An array of μm-size Ti/Au ohmic electrodes was made on a lightly boron-doped p-type diamond (001) surface, and C 1 s and Au 4f7/2 XPS spectra were measured. The peak binding energies of the spectra from the sample and from reference samples were compared, and ϕB was determined to be ~ 0.63 ± 0.13 eV for the p-type diamond (001). The result is compared with those of previous works and discussed. Prime novelty statement The Ti-based ohmic contacts are often used in the fabrication of diamond electronic devices. Although reasonably low specific contact resistances between 10− 5 and 10− 7 Ωcm2 at room temperature have been obtained for the Ti-based ohmic contacts, the barrier height of the contact has not been determined consistently. In this study, the barrier height of the Ti-based ohmic contact on a p-type diamond (001) is directly determined by X-ray photoelectron spectroscopy to be 0.63 ± 0.13 eV.

The potential of patterned nucleation growth (PNG) technique to control the wafer bowing of free-standing heteroepitaxial diamond films was investigated. The heteroepitaxial diamond (100) films were grown on an Ir(100) substrate via PNG technique with different patterns of nucleation regions (NRs), which were dot-arrays with 8 or 13 mm pitch aligned to < 100 > or < 110 > direction of the Ir(100) substrate. The wafer bows and the local stress distributions of the free-standing films were measured using a confocal micro-Raman spectrometer. For each NR pattern, the stress evolutions within the early stage of diamond growth were also studied together with a scanning electron microscopic observation of the coalescing diamond particles. These investigations revealed that the NR pattern, in terms of pitch and direction of dot-array, strongly affects the compressive stress on the nucleation side of the diamond film and dominantly contributes to the elastic deformation of the free-standing film. This indicates that the PNG technique with an appropriate NR pattern is a promising solution to fabricate free-standing heteroepitaxial diamond films with extremely small bows.

The method of electron-beam-induced current (EBIC) was used to visualize the defect sites on a p-type (boron-doped) diamond (001) film. For this purpose, an Ag-Schottky layer (~ 2 mm × ~ 2 mm × ~ 50 nm) was deposited on the oxygen-terminated p-type diamond (001) film and used as a source of EBIC signal. The signal current of EBIC image appeared to be as large as ~ 1200 times that of the incident electron-beam current and the difference range in image intensity was also large (1–1200). The observed EBIC images showed many kinds of signatures that are possible ‘killer’ defects for Schottky devices. In order to identify ‘killer’ defects in the EBIC image, an array of Ag-dots (~ 40 × ~ 50 μm 2 ) was deposited on an oxygen-terminated p-type diamond (001) film and I–V characteristics were measured on 53 Ag-dots. The resulting I–V characteristics showed that 21 Ag-dots reside on ‘killer’ defects. Comparison between the EBIC image and the positions of Ag-dots residing on ‘killer’ defects showed that large dark dots in EBIC image correspond to the position of ‘killer’ defects. The number density of the large dark dots (i.e., ‘killer’ defects) was ~ 10 4 /cm 2 in the present sample. It is suggested that a high yield Schottky-junction device may be fabricated by avoiding these ‘killer’ defects by the use of EBIC.

Silicon-related films have gained much interest as protective coatings for transparent polymeric materials used for automotive components to improve fuel economy and reduce greenhouse gas emissions. This study aims at synthesizing transparent and hard SiOC(−H) films to improve the properties of polycarbonate. SiOC(−H) thin films were synthesized from a mixture of trimethylsilane (TrMS) and O2 gases with various mixture ratios by radio frequency plasma enhanced chemical vapor deposition (RF-PECVD) method and the characteristics of the films such as transparency, hardness and chemical bonding were investigated as a function of the mixture ratio. The transparency, hardness and chemical bonding were analyzed by ultraviolet–visible (UV–vis) spectroscopy, nanoindentation and Fourier transform infrared (FT-IR) spectroscopy, respectively. As the mixture ratio increased, an increase in hardness and a deterioration in transparency were observed, where the relative ratio of Si−(CH3)x (x = 1, 3) bonds to Si−O−Si-related bonds increased and the number of Si−O−Si bonding in the caged structure decreased. Among the sample films prepared, the film synthesized at a partial pressure ratio of TrMS gas of 60% showed an optical transparency of nearly 100% and a hardness of 6.5 GPa, which is equivalent to the hardness of conventional soda-lime glass.

There has been growing demands for amorphous carbon film which is well known as diamond-like carbon film, to be used in sliding parts of mechanical components due to their excellent physical properties. They are generally synthesized under low-pressure using expensive vacuum technology. Therefore the demand for films grows at a sluggish pace. However, the demand for films can expand substantially if it is possible to synthesize films which have excellent physical properties under atmospheric pressure. In this paper, we synthesized amorphous carbon films on high-speed steel substrates under atmospheric pressure and used C 2 H 2 and He mixture gas for process gas. From our previous study, the films synthesized under atmospheric pressure were not hard enough to apply for mechanical components. Therefore, we synthesized amorphous carbon films by heating the substrate to drive surface reaction and improve their hardness. In the result, we succeeded to synthesize the film of which the hardness was 2.6 GPa.

Diamond-like carbon films were synthesized under atmospheric pressure (AP-DLC) and their gas barrier properties and hardness were measured. The AP-DLC films were uniformly obtained by RF-plasma CVD method at room temperature with a size of 450 mm 2 . The growth rate increased as a function of C 2 H 2 concentration and the average growth rate was around 12 μm/min. The maximum deposition rate was ~ 1 μm/s, which is approximately 2000 times larger than that by low-pressure plasma CVD of 1–2 μm/h. The gas barrier properties of AP-DLC films, ~ 1 μm thick, were 5–10 times larger than those of uncoated PET substrates. The microhardness of AP-DLC films was around 3 GPa, measured by the nano-indentation method. The issue lies in the removal of macro-particles of the films to improve the microhardness and the surface roughness. In this paper, we report the physical properties of DLC films synthesized under atmospheric pressure by the radio-frequency CVD method. We also summarize a brief history of PET bottle coating by vacuum-DLC films, as well as that of the development of atmospheric pressure technology and related DLC films, focused on gas barrier properties and micro-hardness.

The flow of freshwater into the sea, termed as submarine groundwater discharge, is a key factor for understanding the hydrological cycle in both the sea and land regions. The numerous positions from which freshwater gushes out or its quantity impedes the understanding of its properties. Only sea surface information is obtained by remote sensing; however, multispectral band properties acquired from the Landsat-7 are sufficient for determining the differences between seawater and freshwater. In particular, the features extracted from the multitemporal scenes of Landsat will help determine the conditions responsible for the differences in water qualities in coastal regions. Therefore, this paper detects groundwater discharge points arising due to the difference in freshwater and seawater by using the multispectral Landsat ETM+ (Enhanced Thematic Mapper, plus) signals. This study comprises three procedures: (1) computer simulation of the flow of submarine groundwater discharge in the study area, (2) performance of preliminary experiment on the band properties of the Landsat ETM+, (3) detection of the difference in water properties by using the Landsat multispectral bands. Our experimental results obtained by the Landsat ETM+ are in considerable agreement with the realities in the study area.

Polyethylene (PE) is a semi-crystalline polyolefin widely used in consumer products and for molding materials due to its excellent thermal properties. Among its remarkable physical and chemical properties, however, one characteristic that may have limited the expansive usage of PE is its poor adhesion property. In this work, the adhesion between Diamond-like Carbon (DLC) and high-density polyethylene (HDPE) was investigated. The peel strength of DLC-deposited HDPE was found to be 20 times as high as that of non-treated HDPE. Further improvement in adhesion was observed in fluorinated DLC (F-DLC). By applying fluorine (C2F6) etching to DLC, the peel strength eventually increased up to 60 times as compared with that of pure HDPE without any pretreatment. From the surface observation and the experimental results of the surface free energy of modified HDPE, it is surmised that the mechanism behind this phenomenon is principally due to the formation of nano-scale anchors that were formed during the DLC deposition process. Further etching of the HDPE substrate by fluorine radicals eventually increased the number of the anchors, leading to a significant improvement in the adhesion between HDPE and F-DLC.

Fluorine-doped diamond-like carbon (F-DLC) has recently drawn a great deal of attention as a more non-thrombogenic coating than conventional DLC for blood-contacting medical devices. We conducted quantitative depth profiling of F-DLC film by X-ray photoelectron spectroscopy (XPS) in order to elucidate the effects of fluorine and fluorine distribution in F-DLC film in connection with the prevention of surface blood adhesion. F-DLC films were prepared on silicon substrates using the radio frequency plasma enhanced chemical vapor deposition method, and the thickness of films was ∼ 50 nm. 50-nm-thick F-DLC film samples were etched at 10-nm thickness intervals using argon plasma, and each surface was examined by XPS. Thereafter, each etched film layer was incubated with platelet-rich plasma isolated from human whole blood, and the platelet-covered area per unit area was evaluated for each surface. XPS spectra showed the localization of doped fluorine in the top-most thin layer of the film. Platelet-covered areas represented progressively larger portions of the surfaces of deeper etched layers, corresponding to the decreasing fluorine content in such sample surfaces. These results indicate that the localized fluorine in the top-most thin layer is one of the key factors in the promotion of the non-thrombogenicity of F-DLC film.

Thin DLC films coated on polymer surfaces are attracting considerable attention due to their wide applications and their interesting surface properties. When DLC films were coated on polymers, the resulting DLC-polymer composites are highly functionalized materials, some of which presenting dramatically improved gas barrier properties. In this paper, we will introduce several commonly used polymers including polyethylene terephthalate (PET), polyethylene (PE) and polypropylene (PP) for semi-crystalline polymers, and polymethyl methacyrlate (PMMA) for an amorphous polymer. The polymers were coated with thin DLC films and the gas barrier properties of the resulting DLC-polymer composites were investigated. Some of the DLC-polymer composites dramatically improved their gas barrier properties while they presented horizontal crack lines and vertical micro-buckling lines on the DLC surface when stretched to a certain strain. The gas barrier properties of the DLC-polymer composites with fractured DLC surface were also studied. It was found that the gas barrier property of the polymer substrates with lower residual strains was less damaged, when the substrates were mechanically deformed, than that of the polymer substrates with higher residual strains. When the number of the cracks increases, the strain imposed on each crack decreases, since the overall deformation is almost equally distributed to each crack while the crack spacing of each crack becomes shorter. Thus, it was found that the degradation of the gas barrier property after mechanical deformation is dependent on the residual strain of the polymers and the number of cracks on DLC films.

High gas barrier carbon films were successfully synthesized on top of polymer substrates using an atmospheric-pressure glow (APG) plasma CVD equipment by reducing the discharge area and by changing the size of the electrodes of the equipment. Homogeneous and highly stable plasma was constantly generated under an atmosphere of acetylene gas (C2H2) without using any other dilution gases such as He, Ar and N2 that are generally used in order to stabilize the plasma. The absence of the dilution gases led to form rigid carbon-to-carbon bonds. The rigid C bonds constructed dense carbon films at the very surface of the coated films with high gas barrier properties. The oxygen transmission rates of the polyethylene terephthalate (PET) film coated with this amorphous carbon (a-C:H) material was therefore dramatically improved (23 times less in transmission rate) compared with that of an uncoated PET film. The microstructures of the films were investigated by Fourier transform infrared spectroscopy (FT-IR) and the surface morphology was observed by a scanning electron microscope (SEM).

Diamond-like carbon (DLC) and fluorinated DLC (F-DLC) films were deposited on SUS316L guidewires using radio frequency (RF) plasma enhanced chemical vapor deposition (CVD), and the lubrication performance of DLC- or F-DLC-coated guidewires was then evaluated under in vitro conditions using a novel friction simulator developed for this study. Scanning electron microscopy (SEM) demonstrated that DLC or F-DLC film completely coated the specimens (SUS316L guidewires) and that polishing scars were substantially reduced. In the torturous vessel model, DLC- or F-DLC-coated guidewires exhibited significantly improved lubrication performance (by approximately 30% over that of uncoated wires). DLC and F-DLC films are thus promising candidates for lubricious coating of intravascular guidewires.

The unique properties of diamond like carbon (DLC) film, including its chemical inertness and impermeability, make it possible for new applications in food, beverage and medical market segments. Although these fields involve relatively higher risk for customers, the expected great advantages of DLC films have driven extensive efforts. In this paper, we present our recent results of development in high gas barrier polyethylene terephtalate (PET) bottles for beverage use. We also demonstrate that DLC or fluorinated DLC is a promising candidate coating material for orthopedics implants and blood contacting devices, such as artificial joints, cardiovascular interventional devices, artificial organs and pacemakers. A unique technique of plasma CVD method has been applied to deposit DLC films on the inside surface of PET bottles. The DLC-coated PET bottle exhibits extremely high gas barrier properties against oxygen, carbon dioxide and flavors compared to conventional bottles. For the practical use of PET bottles as a commodity, high speed and low cost coating are essential and lately our newly developed high speed coating machine has been successfully operated for the large production of hot tea drink bottles.

Amorphous carbon films were synthesized on top of polyethylene terephthalate (PET) substrates using atmospheric-pressure glow (APG) plasma CVD equipment which we originally designed and set up. Plasma was generated between two metal electrodes one of which was covered with a dielectric plate. By varying dielectric constant of the plate, the deposition rate of the carbon films was controlled. From the oxygen transmission test, the resulting PET coated with thin carbon films exhibited high gas barrier property. Using the material with high dielectric constant, we finally synthesized a nearly complete gas barrier films at the deposition rate of 15 sec.

Recently, gas barrier properties of diamond-like carbon (DLC) films have been investigated and are started to apply to food packaging field such as an inner coating for polyethylene terephthalate (PET) bottles. Recycling PET bottles has been promoted on environmental and economic grounds. However, it is difficult to recycle DLC-coated PET bottles because of the brownish color of DLC films. In this study, we successfully synthesized transparent and colorless DLC films on PET substrates from CH 4 and H 2 gases by the RF-CVD method. Further, we investigated the relationship between oxygen transmission and optical transparency from the viewpoint of microstructure and hardness of the films. The results showed the optical transparency were gradually improved as decreasing RF power and increasing deposition pressure. In particular, the films deposited at 15 W and 40 Pa was almost completely transparent; however the oxygen transmission increased.

A simple method of sample treatment for angle-scan X-ray photoelectron diffraction (XPD) for insulating diamond is demonstrated. The resulting XPD patterns have shown that a quantitative measure of near-surface atomic order is obtained for the insulating diamond. This simple method may be applied in principle to any insulating material, which enables non-destructive characterization of near-surface order of insulating materials by XPD.

Boron-doped diamond electrode is expected to realize high sensitive electrochemical sensors because of its unique properties such as wide potential window and low background current. Many studies of diamond electrochemistry have been already reported but most of these works were carried out using polycrystalline diamond. Because several crystal faces and many grain boundary exists, electrochemical reactions at the surface of polycrystalline diamond becomes complex. On the other hand, epitaxial diamond (nearly single crystal) is structurally uniform, we believe that boron-doped epitaxial diamond will be more ideal material in order to realize highly-sensitive and highly-reliable sensor. Furthermore, it is useful to clarify basic electrochemical reactions at the surface of diamond. Several studies have been already reported using boron-doped homoepitaxial diamond. In the case of homoepitaxial growth, HPHT (high pressure high temperature) diamond is used for substrate but available size of HPHT diamond is small and also costs much. On the other hand, heteroepitaxial growth is much easier to fabricate diamond in large size at low cost. From the viewpoint of practical use, studies on boron-doped heteroepitaxial diamond will be important. In this study, fundamental electrochemical property of hydrogen-terminated and oxygen-terminated boron-doped heteroepitaxial diamond was evaluated. There are several methods to change the surface termination of diamond from hydrogen to oxygen such as heat mixed acid, oxygen plasma, UV irradiation, anodic oxidation treatment. The treatment conditions were optimized at each method and the oxidation peak shift of potassium ferrocyanide was compared. First, non-doped epitaxial diamond(100) was grown on Ir(100)/MgO(100) substrate in thickness of 100 μm by direct current plasma enhanced chemical vapor deposition (PE-CVD) method. After the growth, Ir/MgO substrate was removed by acid treatment in order to fabricate free-standing diamond platelet. Finally, boron-doped epitaxial diamond was grown on non-doped epitaxial diamond at boron concentration of 5000 ppm. Oxidation peak potential of potassium ferrocyanide (5mM in 0.1 M sodium sulfate) was measured by cyclic voltammetry after oxidation treatment under defined condition. To optimize oxidation treatment condition, this operation was repeated until the peak potential becomes constant. For heat mixed acid treatment, sample was dipped in mixed acid (60% nitric acid:95% sulfuric acid = 3:1) at 523 K for 15 min. For anodic oxidation treatment, 0.5 M sulfuric acid was used for electrolyte and the potential was kept at 3.0 V for 5 s. From the X-ray diffraction measurement, single sharp peak at around 120 degrees which is due to diamond(004) was detected from 2theta-omega spectrum and four-fold symmetry peaks were detected from diamond{111} pole figure which indicates that the diamond was epitaxially grown on Ir/MgO substrate. When the sample was terminated by hydrogen, sharp oxidation and reduction peaks were observed from the cyclic voltammogram and its peak separation was around 70 mV which reflects a quasi-reversible reaction (very close to reversible reaction). Shift of oxidation peak was observed after both heat mixed acid and anodic oxidation treatment. By repeating heat mixed acid treatment for four times (total 60 min treatment), oxidation peak became constant and its potential was 0.42 V vs Ag/AgCl. On the other hand, repeating anodic oxidation treatment for six times (total 30 s treatment), the peak became constant at potential of 1.52 V. Heat mixed acid treatment is a well-known method to remove surface conductive layer of diamond but the peak potential at optimized treatment condition was extremely different between two methods which indicates that termination structure differs. Termination structures analyzed by X-ray photoelectron spectroscopy will be discussed. Furthermore, the results of other methods such as oxygen plasma and UV irradiation treatment will be also discussed.

Low-pressure chemical vapor deposition growth of graphene on Iridium (Ir) layers epitaxially deposited on α-Al2O3 (0001) substrates was investigated. The X-ray diffraction, Raman and reflection high energy electron diffraction characterizations revealed that graphene films were epitaxially grown on Ir(111) layers, and the in-plane epitaxial relationship between graphene, Ir(111), and α-Al2O3(0001) was graphene ⟨ 11¯00⟩//Ir⟨ 112¯⟩//α-Al2O3⟨ 112¯0⟩. The graphene on Ir(111) was electrochemically transferred onto SiO2/Si substrates. We also demonstrated the reuse of the Ir(111)/α-Al2O3(0001) substrates in multiple growth and transfer cycles.

The fabrication of a high-quality freestanding diamond substrate was successfully demonstrated via heteroepitaxy by introducing diamond micropatterns and microneedles in the early stage of growth. Micropatterns contributed to a marked reduction in the number of dislocations induced by epitaxial lateral overgrowth, and microneedles relaxed heteroepitaxial strain. Raman spectroscopy indicated the absence of nondiamond carbon inclusions in the obtained freestanding substrate. The full width at half maximum of the X-ray rocking curve for diamond (004) reflections was 0.07°, the lowest value for heteroepitaxial diamond that has been reported so far. The results provide novel insights toward realizing large-diameter single-crystalline diamond substrates.

Diamond-like carbon (DLC) films were deposited on polyethylene terephthalate (PET) substrates with the rf plasma chemical vapor deposition method using C2H2 gas and were investigated on the chemical bonding characteristics and microstructures, comparing with those on Si substrates. At the initial stage of deposition (∼10 s), the DLC films deposited on PET substrates contained more sp2 bonds and the growth rate was higher. Then, the number of sp3 bonds increased and became unchanged after 10 s of deposition. Similar results were observed for DLC films on Si substrates. When the input power of rf plasma equipment was higher, the C 1s x-ray photoelectron spectra from DLC films shifted to higher binding energy, but this shift was not observed for the films on Si substrates. Transmission electron microscope observation showed that the films were uniformly deposited on PET substrates and had amorphous structure without graphitic structure even in the restricted area.

Electron spectro-microscopic methods were applied as direct methods of determining the Schottky barrier heights (SBHs) and their spatial distribution for Au- and Ag-Schottky junctions fabricated on an acid-treated oxygen-terminated diamond (001) substrate. Metal layers were formed with two ranges of thickness (3–5 nm for thin layers and 13–100 nm for thick layers) for both Au- and Ag-Schottky junctions. Leading X-ray photoelectron spectroscopy (XPS) core-level peaks of either Au 4f7/2 or Ag 3d5/2 for the metal layers and C 1s for diamond were used as measures of the SBH. For the thick-metal samples, spatially resolved XPS measurements were performed over most of the sample surface. It was found that there is a variation in SBH on the order of 0.1 eV for the large ("high barrier") SBH values and that there are several places where the SBHs were rather small ("low barrier" junction). For the thin-metal samples, less variations in SBH were observed. The average SBH of "high barrier" junctions for the thick-metal samples appeared to be slightly (0.1 eV order) larger than that for the thin-metal samples. XPS images of leading metal core levels tuned for the "high barrier" and "low barrier" SBHs were observed. For the thick-Ag Schottky sample, the resulting Ag 3d5/2 XPS images clearly showed the locations of defective Schottly junctions. It is suggested that the SBHs determined for the thin-metal samples are the average SBHs on the measured surface and that the SBHs determined for the thick-metal samples are the highest SBHs within the measured µm-size metal islands. The presently determined SBHs were compared with previously reported SBHs and reasonable agreement was found. Photoemission electron microscopy (PEEM) images were observed for the thick-Ag Schottky sample and the "low barrier" islands were identified. The methodologies of XPS, XPS imaging, and PEEM used for the thick-metal samples can be applied to any Schottky junction on diamond.

A phosphorus (P)-doped n-type heteroepitaxial diamond (001) sample was grown in a DC-plasma chemical-vapor-deposition chamber. The crystalline properties of incorporated phosphorus were examined by cathode luminescence. Hall-effect measurement of the sample was performed for the temperature range of 293–870 K. The results of these measurements showed that the bulk properties of the n-type sample are comparable to those of previously reported homoepitaxial P-doped n-type diamond (001) samples. The work function of the heteroepitaxial sample was measured by photoemission electron microspectroscopy. The Fermi-level positions at the surface and at a Au Schottky junction of the sample were determined by X-ray photoelectron spectroscopy. Knowing the bulk properties and the critical values of the energy band structure, the whole energy band diagrams at the surface and at the Schottky junction of the sample were evaluated by solving the Poisson equation. The resulting surface electronic structure of the sample was qualitatively different from those of the previously reported H-terminated P-doped n-type diamond (111) surface and heavily P-doped H- and O-terminated diamond (111) surfaces. The presence of ∼0.02 ML of Sn impurity is tentatively ascribed to the peculiarity of the surface electronic structure of the heteroepitaxial sample. The Schottky barrier height of ∼4.2 eV determined for the present sample was consistent with those of previously reported n-type diamond (111) and (001) samples. It is noted that the Schottky barrier height may be determined by the Fermi-level pinning states at the junctions irrespective of the type of dopant to diamond.

not Available.

The method of electron-beam-induced current (EBIC) was used to visualize the defect sites on a p-type (boron-doped) diamond (001) film. For this purpose, an Ag-Schottky layer (~ 2 mm × ~ 2 mm × ~ 50 nm) was deposited on the oxygen-terminated p-type diamond (001) film and used as a source of EBIC signal. The signal current of EBIC image appeared to be as large as ~ 1200 times that of the incident electron-beam current and the difference range in image intensity was also large (1–1200). The observed EBIC images showed many kinds of signatures that are possible ‘killer’ defects for Schottky devices. In order to identify ‘killer’ defects in the EBIC image, an array of Ag-dots (~ 40 × ~ 50 μm 2 ) was deposited on an oxygen-terminated p-type diamond (001) film and I–V characteristics were measured on 53 Ag-dots. The resulting I–V characteristics showed that 21 Ag-dots reside on ‘killer’ defects. Comparison between the EBIC image and the positions of Ag-dots residing on ‘killer’ defects showed that large dark dots in EBIC image correspond to the position of ‘killer’ defects. The number density of the large dark dots (i.e., ‘killer’ defects) was ~ 10 4 /cm 2 in the present sample. It is suggested that a high yield Schottky-junction device may be fabricated by avoiding these ‘killer’ defects by the use of EBIC.