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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.

Single-crystalline MgO is used as a substrate for the deposition of various functional thin films. The present study focused on the development of a complete sequence of fabricating atomic step-terrace structures on the MgO substrate via a method that includes grinding, precise mechanical polishing, chemical mechanical polishing (CMP), and high-temperature annealing. The effect of a damage-free surface pretreatment on the subsequent high-temperature annealing was investigated. An atomically smooth and damage-free MgO substrate surface with an average surface roughness of 0.05 nm was obtained via a CMP process using a colloidal silica slurry. Atomic step-terrace structures were formed on the substrate after the high-temperature annealing process at 1000 °C for 20 h under atmospheric air. The obtained step height was 0.20 nm, which corresponds to one-half the unit cell of an MgO crystal (0.21 nm). By contrast, when a mechanically damaged MgO substrate was subjected to the annealing process, Ca segregation was observed on the annealed surface, without the formation of an atomic step-terrace structure. CMP was found to be necessary prior to high-temperature annealing to attain atomic step-terrace structures and to avoid the out-diffusion of impurities in the MgO bulk crystals.

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.

In-situ reflectance interferometry was utilized in this study to understand the characteristics of the reflectance profile for the growth of heteroepitaxial diamonds. We observed the time-resolved Fabry-Perot oscillation of the growing heteroepitaxial diamond. Oscillations in the reflectance profile provided information on the grown thickness and provided the growth rate in real-time. The obtained in-situ profile was experimentally compared with the actual growth status via ex-situ observations and the strong correlation between the in-situ profile and the actual growth status was suggested. The analysis of the profiles provided a reasonable prediction to whether there would be any unexpected growth behavior in real-time for heteroepitaxial diamond growth.

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 reusability of Ir(111)/α-Al2O3(0001) substrates for graphene CVD in multiple cycles was studied. Better reusability was obtained by using Ir layers prepared at a high growth temperature, 1150 °C, which had a stable surface morphology in the multiple CVD cycles. Multilayer graphene islands were observed in the graphene films grown in the multiple CVD cycles, which was attributed to the carbon atoms dissolved during the previous CVD cycle. A method combining annealing, quenching, and oxygen plasma etching was proposed to remove the residual carbon atoms in the Ir layers. We succeeded in growing uniform monolayer graphene films in the multiple CVD cycles using the same Ir(111)/α-Al2O3(0001) substrate.

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.

The structural properties of optically thin (15 nm) silver (Ag) films deposited on SiO2/Si(100) substrates with a germanium (Ge) nucleation layer were studied. The morphological and crystallographical characteristics of Ag thin films with different Ge nucleation layer thicknesses were assessed by cross-sectional transmission electron microscopy (XTEM), reflection high-energy electron diffraction (RHEED), X-ray diffractometry (XRD), grazing incidence X-ray diffractometry (GIXRD), X-ray reflection (XRR), and Fourier transform infrared spectroscopy (FTIR). The surface roughness of Ag thin films was found to decrease significantly by inserting a Ge nucleation layer with a thickness in the range of 1 to 2 nm (i.e., smoothing mode). However, as the Ge nucleation layer thickness increased beyond 2 nm, the surface roughness increased concomitantly (i.e., roughing mode). For the smoothing mode, the role of the Ge nucleation layer in the Ag film deposition is discussed by invoking the surface energy of Ge, the bond dissociation energy of Ag-Ge, and the deposition mechanisms of Ag thin films on a given characteristic Ge nucleation layer. Additionally, Ge island formation, the precipitation of Ge from Ag-Ge alloys, and the penetration of Ge into SiO2 are suggested for the roughing mode. This demonstration of ultrasmooth Ag thin films would offer an advantageous material platform with scalability for applications such as optics, plasmonics, and photonics.

Diamond thin film has outstanding physical and chemical properties. Diamond-on-iridium configurations have been prepared by several methods, such as microwave enhanced plasma CVD, direct currency plasma CVD, and hot filament CVD. In this study, an Ir interlayer was deposited on single crystal sapphires (Al 2 O 3 ) with A-planes {1120} by an RF magnetron sputtering method after annealing samples. In addition, a diamond thin film was deposited by a microwave enhanced plasma chemical vapor deposition (MPCVD) method using a mixture of hydrogen and methane gases after a bias enhanced nucleation (BEN) procedure. Ir (001) was grown on the A-plane of sapphire by X-ray pole figure measurement. Diamond thin films were synthesized on each Ir/sapphire substrate and characterized by SEM, Raman spectroscopy. D {100} faces were exhibited in substantial areas of diamond films, and a flat D {100} plane was partially obtained. It is considered that diamond thin films on Ir {100} were mainly grown towards the direction and were epitaxially grown in part.

The effect of bias-treatment (BT) on Ir(001)/MgO(001) substrates in a newly invented planar-diode DC-plasma system has been characterized in-situ and ex-situ by X-ray photoelectron diffraction (XPD), XPS, LEED and SEM. Features of XPD patterns of C 1s core levels were in good agreement with those of three-electrode BT [Diamond Relat. Mater. 13 (2004) 2081], although the degrees of anisotropy of C 1s XPD were smaller. Thicknesses of carbon films estimated from intensity ratios of C 1s/Ir 4d 5/2 (or 4f) XPS peaks were about 2 times larger than those of three-electrode BT. LEED patterns showed no diffraction spots after BT. As a result, we conclude that epitaxial diamond crystallites with the size of a few nm or so are embedded in a non-oriented carbon layer. In the cases where no finite anisotropy of C 1s XPD was observed, no epitaxial diamond grains were grown in post-CVD as revealed by ex-situ SEM. Thus, it is concluded that the anisotropy of C 1s XPD can be a useful measure of diamond nucleation by BT on Ir(001) substrates.

Three elastic stiffness coefficients of nanometer grain-size polycrystalline CVD diamond (NCD) films and micrometer grain-size diamond (MCD) film were measured by resonant-ultrasound spectroscopy coupled with laser-Doppler interferometry (RUS/Laser method). The diagonal stiffness coefficients C 11 and C 44 of the NCD films are found to be smaller than those of bulk polycrystalline diamond and MCD film, and decrease as the film thickness decreases. The off-diagonal coefficient C 12 of the NCD films was much larger than those of the bulk diamond and MCD films. Large C 12 was consistently explained by the micromechanics model with random-oriented pancake-shape graphite plates at the grain boundaries. This indicates that the NCD films consist of sp 3 -bonded diamond grains and sp 2 -bonded grain boundaries. Raman spectra showed two peaks due to the D-band and G-band of sp 2 -bonded graphite phase. These peaks increased with an increase of C 12 . Thus, the coefficient of C 12 can predict the grain boundary chemistry or structure of the CVD polycrystalline diamond film.

We have evaluated the absolute adhesive strength against the Mode-I decohesion of 78-μm-thick polycrystalline CVD diamond (CVDD) film deposited on a sintered SiC substrate by pulse laser spallation. Strong tensile stress wave, impinging on the film/substrate interface, was produced by confined silicone grease breakdown to induce the spallation. The spallation was observed at the laser energies above 46 mJ when the laser focusing diameter and grease thickness are 1.0 mm and 20 μm, respectively. The threshold laser energy to cause the spallation changed from 46 to 69 mJ depending on the test position, and interfacial strength was estimated to be larger than 222 MPa by measuring the particle velocity of stress wave at the interface. Next we attempted to determine the spallation initiation utilizing acoustic emission (AE) and laser ultrasonics. An AE sensor detected the high frequency waves of 13–15 MHz besides the component of the main resonant frequency (5 MHz) of the AE sensor. Amplitude of this high frequency component drastically decreased for small spallation of 0.6 mm in diameter. We also observed a distinguishable decrease of 0.42% in the Rayleigh wave velocity through the delaminated part of CVDD/SiC surface.

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.

A novel microfabrication method for heteroepitaxial diamond was developed. Substrates used in present work were heteroepitaxial Ir(001) films deposited on MgO(001) by sputtering method. The Ir surfaces were treated with ion irradiation of CH 4 /H 2 gas by dc discharge using planar diode. Resist masks were patterned on the ion irradiated Ir surface by electron-beam lithography. The mask patterned Ir surface was etched by Ar ion to remove the irradiated surface at non-patterned area using an ion beam etching system. Then, diamond was grown on the substrate by dc plasma CVD method. As a result, we have successfully fabricated the heteroepitaxial diamond on the patterned areas of the substrate in submicron scale.

The effect of bias treatment (BT) on direct-current plasma CVD diamond growth has been studied in situ by X-ray photoelectron diffraction (XPD) together with LEED and XPS. It was found that C 1s XPD patterns from the sample after BT are similar to those of diamond (001). Coverage of carbon after BT is several tens of ML when BT is very successful. However, LEED shows no diamond (001) spots for the sample after BT. These apparently contradictory findings are explained by the sizes of the diamond (001) crystallites, which, after BT, are large enough to produce C 1s XPD patterns of diamond, but too small to have coherent interference spots in LEED. It is concluded from this and other information that BT in a DC plasma creates hetero-epitaxial diamond crystallites a few nm or less. These diamond crystallites may be related to the atomically abrupt diamond/Ir interfaces of DC plasma CVD-grown samples revealed by TEM [A. Sawabe, H. Fukuda, T. Suzuki, Y. Ikuhara, T. Suzuki, Surf. Sci. 467 (2000) L845].

We succeeded hydrogenated amorphous carbon passivation of diamond surface conductive layer. Hydrogenated amorphous carbon thin films were formed by r.f. plasma chemical vapor deposition (CVD) on diamond surface conductive layer. It is found that there is no major difference in resistance of diamond surface conductive layer between before and after amorphous carbon formation on the grounded electrode. The thermal stability up to 200 °C in air of diamond surface conductive layer was improved by the hydrogenated amorphous carbon formation.

We have developed a novel microfabrication method by combining a microwave plasma treatment with a reactive ion etching (RIE) method. First, the RIE system was used for fabricating whiskers of single crystalline diamond. Then, the whiskers were exposed to microwave plasma of hydrogen gas. As a result, we have successfully fabricated a nano-scale diamond rod of the single crystal, which has the crystalline facets. The sizes of the ‘nano-rods’ were 50–200 nm in thickness and several microns in height. Morphology of the nano-rods could be controlled by changing the crystal orientation of the diamond substrate.

Heavily nitrogen (N)-doped polycrystalline diamond is reported to have excellent electron emission properties although its emission sites are limited. This report describes the fabrication processes, characterisation and electron emission properties of N-doped heteroepitaxial diamond which posses high potential as broad area emitter devices. We have obtained epitaxial diamond films on iridium (Ir) substrates by hot filament CVD using urea [(NH 2 ) 2 CO] as a dopant for N. The Ir substrates are bias treated via direct current plasma CVD (d.c. plasma CVD) method prior to the growth. Surface of the deposited films is smooth and continuous in scanning electron microscopy (SEM) observation. The epitaxial diamond growth is confirmed from reflective high energy electron diffraction (RHEED) pattern. It is found that the electron emission from heteroepitaxial diamond film is dominated by standard Fowler-Nordheim type emission due to the existence of strong electric field in the vacuum with the value of 26 V/μm.

Electron spin resonance (ESR) measurements on free-standing monocrystalline CVD diamond samples allowed us to deduce the symmetry of the previously reported KUL1 and KUL3 centers as trigonal and monoclinic-I, respectively. Based on the correlation between the intensities of the KUL3 ESR signals and of the 1.68 eV Si-related luminescence peak, and on the analysis of the observed hyperfine interaction structure, the KUL3 center is suggested to involve one Si and one hydrogen atom. Two previously undocumented centers, labeled as KUL16 and KUL17, have been characterized and attributed to two 〈100〉-oriented surface defects, each involving one hydrogen atom.

The electron emission properties of N-doped homoepitaxially grown diamond have been measured and discussed in order to clarify the electron emission mechanism by excluding the effects of polycrystallinity. As a result, N-doped homoepitaxially grown diamond exhibits extremely low threshold electron emission even from extremely flat smooth surfaces without grain boundaries. This result strongly implies that the low threshold electron emission from N-doped diamond should be caused by the resistance of the film rather than by high β whatever the underlying mechanism is.

Electron emission from both the hydrogenated and the oxidized boron-doped heteroepitaxial diamond with smooth surface is studied in order to understand the effect of adsorption on electron emission. B-doped heteroepitaxial diamond is grown on iridium (Ir) by direct current plasma chemical vapor deposition (CVD). A relatively smooth surface is obtained. The Cls peaks in X-ray photoelectron spectroscopy (XPS) for the hydrogenated and oxidized diamond surfaces are 284.1 and 285.6 eV, respectively. The threshold voltage of the hydrogenated diamond surface in the electron emission is lower than that of the oxidized diamond surface. The emission barrier height ratio of the hydrogenated diamond surface to the oxidized diamond surface is estimated to be 2.6 from the slopes of Fowler–Nordheim (F–N) plots. The change in the emission properties might be examined by the surface dipole formed on diamond surface from the XPS results and the F–N plots.

Although we had reported the remarkable low threshold emission from polycrystalline diamond heavily doped with nitrogen (N) [Nature 381 (1996) 140], the problems caused by polycrystallinity still remain for understanding the electron emission mechanism. This paper describes the growth of N-doped homoepitaxial diamond film {100}, {111} and {110}, and their electron emission properties. N-doped homoepitaxial diamond is grown on synthetic diamond by hot filament chemical vapor deposition. Urea [(NH2)2CO] is used as a dopant for N. Atomic force microscope (AFM) observations indicate that the relatively smooth surface morphologies are obtained for all the films. The epitaxial growth of all the film is confirmed using reflective high energy electron diffraction (RHEED) patterns. Reflective electron energy loss spectra (REELS) indicate that the very surfaces of {100} and {111} are diamond while {110} is graphite rather than diamond. Raman spectra suggest that the bulk of the obtained films are diamond. The resistivities of the films are found to be much higher than the detection limit of the system. The relatively low threshold emission was observed even from the smooth surface and the threshold voltage is confirmed to depend on the crystal orientation. It is speculated from the film characterizations and the electron emission properties that the low threshold emission is due to high resistance rather than rough surface and/or grain boundaries.

We obtained an epitaxially grown free-standing diamond platelet utilizing epitaxial diamond film formed on a {100} iridium surface using a d.c. plasma CVD process. Iridium was selected as a suitable substrate material for the heteroepitaxy of diamond based on original criteria. Confocal Raman spectroscopy revealed that the diamond platelet contained little or no non-diamond carbon. The obtained diamond platelet is transparent to visible light and cleavable along the 〈110〉 direction on the surface. The angles between the top surface and the cross-sectional surfaces are approximately 55°, almost equal to the theoretical angle of 54.74° between {100} and {111} planes in cubic crystals. Therefore, the cross-sectional surfaces would be {111} planes of a typical facet for single-crystalline diamond. This means that the diamond platelet we have formed has relatively good crystallinity.

sp 3 and sp 2 -rich nitrogen (N)-doped diamond electron emitters are prepared by modifying the substrate temperature. Their electron emission properties have been measured in order to examine the effect of the sp 2 /sp 3 ratio on the electron emission from N-doped diamond. The obtained electron emitters have been characterized by reflective high energy electron diffraction, X-ray diffraction and Raman spectroscopy. The electrical resistivities of the sp 3 -rich diamond is 100 G Ω cm or higher while that of the sp 2 -rich diamond is 100 Ω cm. In electron emission characteristics, the threshold voltage of the sp 3 -rich emitter is found to be lower than that of the sp 2 -rich emitter. From the threshold voltage versus the anode-diamond spacing characteristics, it has been found that most of the anode voltage drops in the bulk of the sp 3 -rich emitter and almost no voltage drop takes place in the sp 2 -rich emitter. The difference in electron emission properties should be explained by the resistivity of the N-doped diamond bulk.

Surface oxidation of an iridium film and the possibility of epitaxial growth of PZT spin-coated film on sputtered iridium were investigated. The free surface on the iridium film oxidized over 400 °C with random orientation. Nevertheless, both the PZT(111)/Ir(111) and PZT(100)/Ir(100) interfaces were realized using the highly oriented iridium layer. These results suggest that PZT nucleation has priority over iridium surface oxidation.

Electron emission from boron (B)- and nitrogen (N)-doped diamond electron emitter with silver (Ag)-loaded conductive epoxy, titanium (Ti)/gold (Au), aluminum (Al) and amorphous carbon contacts are studied. Both Ti/Au and amorphous carbon contacts on B-doped diamond electron emitters lead to lower turn-on voltage compared to other contacts, while the turn-on voltage of N-doped diamond electron emitter is independent on the backcontacts.

An Ir layer was epitaxially grown on a MgO(100) substrate by radio frequency magnetron sputtering, and was used as the substrate for the epitaxial growth of diamond by microwave plasma-assisted chemical vapor deposition (MPCVD) using CH4–H2 systems. The Ir(100) layer was then bias-treated under a wide variety of conditions. Thus, a bias voltage of −150 V, a methane concentration of 3%, and a continuation of 15 min, were determined to be the optimum conditions. In the subsequent diamond growth step, oriented diamond particles, 100–250 nm in size with pyramidal structures, were formed at a population density of (0.15–1.5)×108 cm−2. It is noteworthy that the fraction of oriented particles was nearly unity. Tilted or rotated diamond particles were seldom observed. Substrate erosion and graphitic carbon formation, also often observed in the case of Ni and Pt substrates, were not found during the diamond deposition on the Ir(100) substrate.

Giant magnetoresistance (GMR) Δϱ ϱ of about 10% was observed in bulk-MnAu 2 at 300 K in a field of 70 kOe. MnAu 2 is a tetragonal material with a spiral spin structure of Mn and shows a metamagnetic transition from a spiral to a ferromagnetic structure at an applied field of about 10 kOe at 300 K. Significant GMR was observed simultaneously with the metamagnetic transition.

n -Type semiconducting diamond thin films were successfully grown by microwave plasma CVD using phosphine (PH 3 ) as a dopant source. The addition of PH 3 in the gas ambient strongly influences the optimal growth condition for diamond. The {111} surface of diamond was found to be the best surface as a substrate for the growth of phosphorous (P) doped diamond. At a methane to hydrogen ratio of 0.15% and a substrate temperature of 950 °C, smooth {111} oriented homoepitaxial diamond thin films are obtained even with the addition of PH 3 up to 1000 ppm to CH 4 . The epitaxial films grown with PH 3 /CH 4 : 600–20 000 ppm have shown clear n -type conduction by Hall effect measurements over a wide temperature range. An activation energy of electron of 0.46 eV was deduced from the temperature dependence of the carrier concentration. For the best (600 ppm) sample, the Hall mobility of 28 cm 2 /V-s has been obtained at a temperature range around 400–600 K.

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 authors propose a novel structured magnetic thin film inductor using rotation magnetization only. The thin film inductor has a sandwich structure, which consists of a double-rectangular spiral coil between top and bottom CoZrNb amorphous thin films. The sputtered CoZrNb amorphous magnetic thin films have uniaxial magnetic anisotropy induced by direct current field annealing. The easy magnetization axis is directed to the main axis of the rectangular spiral coil. Hence, only the rotation magnetization process dominates in this device. The typical specifications are as follows; 3.5/spl times/5.5 mm in size, inductance of 1 /spl mu/H constant up to 10 MHz, and a quality factor of 10 at 10 MHz. A MHz switching chopper dc-dc converter has been developed by using this thin film inductor, bare-chip semiconductor devices (a power MOSFET and a Schottky barrier diode), and a multilayer ceramic capacitor. This converter with a 0.1 cc volume has an output power over 1 W at 5 MHz switching, and the power density exceeds 10 W/cc (160 W/in/sup 3/). >

Co90Fe10/Cu spin-valve structures were prepared by the RF and DC magnetron sputtering methods. X-ray diffraction data showed that the spin-valves on a sapphire substrate exhibited good fcc (111) preferred orientations. The maximum value of Δρ/ρ0 was 11%, which was larger than that obtained for Co/Cu spin-valve structures.

Pb(Zr0.5Ti0.5)O3 (PZT) thin film was heteroepitaxially grown on an iridium/magnesium oxide (Ir/MgO) (001) substrate using the metalo-organic decomposition method, and its crystal orientation and ferroelectric properties were investigated. The Ir film by rf-magnetron sputtering on a MgO single crystal showed high crystallinity with the full width at half maximum of 0.2°. The obtained PZT film has a tetragonal structure. Reciprocal space mapping revealed that it consisted of only c-axis orientation. The Ir/PZT/Ir capacitor showed the remanent polarization of 45 μ C/cm2 and a coercive force of 100 kV/cm. These large values were derived from 100% 180° domain switching, which state is difficult to realize in bulky single crystal and ceramics because of piezostress relaxation.

This letter presents a clear explanation of the electron emission mechanism of the high-resistivity N-doped diamond cathode. Due to the very low barrier to emission of electrons from the N-doped diamond conduction band into vacuum, electrons in the conduction band of diamond can establish an appreciable leakage current at very low anode voltage. When such a current starts to flow, there is a field which is developed across the diamond bulk. This field is observed as an increase in the electric field at the back contact, causing the injected tunneling current increases exponentially. This process leads to the low threshold emission from the high resistivity N-doped diamond cathode.

A nitrogen (N)-doped diamond-based electron emitter has been fabricated by the sintering technique prior to the chemical vapor deposition process in order to improve the uniformity. There are no spatial differences in reflective electron energy loss spectra (REELS) from the diamond-based electron emitter, suggesting that uniform surface conditions are obtained. The uniform electron emission from the obtained electron emitter is confirmed through emission current vs anode voltage characteristics measurements. It seems that the uniformity of the emitter surface results in uniform electron emission from the diamond electron emitter.

The voltage drop of vacuum and boron (B)-doped diamond electron emitter bulk has been discussed in order to understand the electron emission mechanism of B-doped diamond. It is confirmed that the electron emission from B-doped diamond depends on its film thickness and the localized electron pass/channel is formed in the film. From the results of the threshold voltage versus anode-diamond spacing characteristics, it is found that most of the anode voltage is applied in vacuum, and the high electric field near the B-doped diamond surface is required for the electron emission from B-doped diamond regardless of the film thickness.

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.