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The nitrogen vacancy (NV) center in diamond is fascinating and has a long spin coherence time. It is applied to magnetic sensors with high sensitivity (∼fT). To achieve a high sensitivity, an aligned NV ensemble is required. This paper presents a new methodology for the fabrication of two-dimensional (2D) aligned NV ensembles by using nitrogen-terminated (111) surface. To realize this, pure diamond growth and high nitrogen coverage on (111) surface were performed. As a result, we have succeeded in producing 2D NV ensembles, with 1 × 109 cm−2. Coherence time T2 was 2.45 μs. Also, Using dynamical decoupling, the decoherence sources were revealed. The alignment ratio along [111] axis was archived 60%. Thermal annealing of the nitrogen termination was introduced to improve the alignment ratio. After that, the alignment rate was up to 73%. This report shows that the aligned 2D NV ensemble has possibility to be applied for multiple quantum devices.

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.

The nitrogen-vacancy (NV) center in diamond is the most promising candidate for quantum sensing because of its beneficial properties. For quantum-sensing applications, a shallow NV center is critic...

The sheet resistance ( R sk ) underneath ohmic Au-electrodes on hydrogen-terminated surface-conductive diamond (001) surfaces was examined by a special current-voltage measurement. It has been found that R sk is about ~ 200 times larger than the sheet resistance, R sh , in the open areas without Au-electrodes. The specific contact resistance, R C , of ohmic Au-electrodes on H-terminated surface-conductive diamonds as determined by linear transmission line models must be corrected accordingly. As the results of this, R C is suggested to be of the order of 1 × 10 − 3 – 1 × 10 − 4 Ωcm 2 .

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.

A carbon film composed of graphite sticks as field emission (FE) points is studied using field/photoemission electron microscopy (F/PEEM) and scanning electron microscopy (SEM). The film is termed an ND/CNW film since nano-crystalline diamond is grown over a carbon nano-wall layer in the film. It was found that about 8% of graphite sticks present on the ND/CNW film work as field emitters. The sizes and postures of three representative graphite sticks that work as field emitters are determined by SEM observations. The time dependence of the FE current of the single emission sites was measured by FEEM at a field of 1.0 V/μm. The average FE current from a single emission site for the field of 1.0 V/μm is found to be 10-100 nA. This time dependence of the FE current was compared with those of FE currents of other carbon nano-materials. The results suggest that the cause of FE fluctuation is adsorption and desorption of molecules on the emission site, indicating the reason for the prolonged FE lifetime of the graphite sticks on the ND/NCW films. [DOI: 10.1380/ejssnt.2011.176]

The properties of surface conductivity (SC) of impurity-non-doped CVD diamond (001) samples were studied by various methods of sheet-resistance (RS) measurement, Hall-effect measurement, XPS, UPS, SES, SR-PES, PEEM and 1D band simulation taking into account special emphases on deriving the information about the surface band diagram (SBD). The RS values in UHV conditions were determined after no-annealing or 200 ∼ 300 °C annealing in UHV. C 1 s XPS profiles were measured in detail in bulk-sensitive and surface-sensitive modes of photoelectron detection. The energy positions of valence band top (EV) relative to the Fermi level (EF) in UHV conditions after no-annealing or 200 ∼ 300 °C annealing in UHV were determined. One of the samples was subjected to SR-PES, PEEM measurements. The SBDs were simulated by a band simulator from the determined RS and EV − EF values for three samples based on the two models of surface conductivity, namely, so-called surface transfer doping (STD) model and downward band bending with shallow acceptor (DBB/SA) model. For the DBB/SA model, there appeared downward bends of SBDs toward the surface at a depth range of ∼ 1 nm. C 1 s XPS profiles were then simulated from the simulated SBDs. Comparison of simulated C 1 s XPS profiles to the experimental ones showed that DBB/SA model reproduces the C 1 s XPS profiles properly. PEEM observation of a sample can be explained by the SBD based on the DBB/SA model. Mechanism of SC of CVD diamonds is discussed on the basis of these findings. It is suggested that the STD model combined with SBD of DBB/SA model explains the surface conductivity change due to environmental changes in actual cases of CVD diamond SC with the presence of surface EF controlling defects.

The characteristic energy band values such as the Fermi-level position with respect to valence band top for a boron-doped p-type hydrogen-terminated chemical-vapor-deposition (CVD) diamond (0 0 1)2 × 1 surface and for a clean CVD diamond (0 0 1)2 × 1 surface have been determined by a new method with an accuracy of ±0.02 eV. The electron attenuation length for the clean diamond (0 0 1)2 × 1 surface for the electron kinetic energy of C 1s X-ray photoemission peak by Mg Kα excitation is experimentally determined to be 2.1–2.2 nm. These values are compared and discussed with the previously reported experimental and simulation values.

A diamond pn-junction diode electron emitter was examined in an emission spectro-microscope. An electron emission efficiency of ∼10-2 to the diode current was confirmed at a forward diode current larger than ∼40 μA. Measured electron emission images showed that electron emission indeed occurs at the terrace and up to the terrace boundary of p-type diamond electrode. Measured energy distribution curves of emitted electrons showed that electrons are indeed injected to the conduction band of p-type diamond electrode and emitted from a negative electron affinity surface of p-type diamond. [DOI: 10.1380/ejssnt.2009.660]

Phosphorous (P)-doped CVD diamonds are expected to be good n-type semiconductor diamonds. However, the resistivity of P-doped intrinsic diamonds is very high due to a large ionization energy of impurity phosphorus. When phosphorus is doped in a large amount (≥∼1020cm−3), the resistivity reduces with a pseudo-n-type conductivity at temperatures above 400 K. These intrinsic n-type and pseudo-n-type P-doped diamond single crystal surfaces have been studied recently by electron spectroscopic methods. The surface electronic energy states of both intrinsic n-type and pseudo-n-type diamond surfaces have been examined by electron spectroscopic methods. The mechanism of field emission from the pseudo-n-type diamond surface has been elucidated.

A new magnetic nanodot (MND) memory with FePt nanodots was proposed. The FePt nanodots dispersed in SiO2 insulating film was successfully fabricated by self-assembled nanodot deposition (SAND). The size of the FePt nanodot can be controlled by SAND with a different target area ratio of the FePt pellets area in the SiO2 target. Thermal annealing converts the magnetic properties of the FePt nanodots from antiferromagnetic into high coercivity ferromagnetic without thermal agglomeration. An L10 face-centered tetragonal (fct) FePt MND film was successfully formed which acted as a charge retention layer. Furthermore, the fundamental characteristics of the MND memory were investigated using magnetic metal oxide semiconductor (MOS) capacitor devices.

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.

The surface energy band diagrams and the electron affinity of hydrogen-terminated and oxygen-terminated highly phosphorous-doped single crystal diamond (111) surfaces have been studied by ultraviolet photoelectron spectroscopy, secondary electron spectroscopy, X-ray photoelectron spectroscopy and photoemission electron micro-spectroscopy. A hydrogen-terminated boron-doped diamond (001) surface was used as a reference of surface energy band diagram. The electron affinity of the H-terminated heavily P-doped diamond was determined to be 0.2 ± 0.15 eV, thus close to zero. The electron affinity of the O-terminated highly P-doped diamond was determined to be 0.0 ± 0.15 eV, thus can be negative. However, the surface energy bands for the two highly P-doped samples were found to have large amounts (3 eV) of upward bending toward surface. [DOI: 10.1380/ejssnt.2007.33]

The mechanism of field emission from a highly P-doped diamond (111) surface has been studied by field/photo emission electron micro-spectroscopy. It was found that field emission peaks were located at -3 to -6 eV with respect to the substrate Fermi level (EF) and that photoemission peaks were located at -1 to +2 eV with respect to the substrate EF. Comparing this with the knowledge of work function and electron affinity of the sample, the mechanism of field emission has been elucidated. Namely, field emitted electrons are tunnel-emitted from states around the surface EF and there is a large amount of resistive potential drop at the emission site.

The usefulness of fully performed constant-momentum-transfer-averaging (CMTA) in low-energy electron diffraction (LEED) has been demonstrated for a single-domain Si(111)4×1-In surface. In the fully performed CMTA, thousands of I(V) curves were measured for the single-domain Si(111)4×1-In surface and CMTA intensity profiles were obtained for more than three hundred reciprocal rods in order to directly reconstruct three dimensional (3D) atomic positions of the surface. In the direct reconstruction, the minimum function method, a standard method in X-ray crystallography of the Patterson function analysis, was used. The 3D Si positions so obtained were in excellent agreement with the known heavily-reconstructed surface Si positions of 4×1. Indium atoms were not ‘ visible’ in the present case due to large thermal vibration amplitude of indium atoms for the room-temperature sample, which is not an inherent shortcoming of the fully performed CMTA method. [DOI: 10.1380/ejssnt.2006.661]

We have studied the chemisorption of benzene and pyrazine on Si(001)-2×1 at room temperature using photoelectron diffraction (PED). For benzene, comparison between the experimental and simulated PED patterns with R-factor analysis leads to the conclusion that a di-σ-bonded configuration is mainly formed at the saturation coverage. For pyrazine, the PED results show that the double dimer bridging configuration is formed, in which pyrazine molecule forms a bridging between the dimer rows with the two Si-N bonds.

The atomic structure of the Ca induced Si(111)-(3×2) surface at 300 K has been investigated using X-ray photoelectron diffraction (XPD). After confirming the quality of the single-domain (3×2) surface by LEED, in which weak ×2 streaks were observed likewise the patterns reported in the literature, we have measured the Ca 2p core-level spectra within an azimuthal angle range of ±66°, where 0° corresponds to the direction perpendicular to the Ca chain, and at takeoff angles from 9° to 15° using the Mg Kα line. The experimental XPD patterns showed good agreement with the simulated XPD patterns of the T4 site model, while the simulated XPD patterns of the H3 model do not agree with the experimental results. Taking these results into account, we conclude that Ca atoms are adsorbed on the T4 site at 300 K and thus that the weak ×2 streaks do not result from the presence of two adsorption sites as proposed in the literature. [DOI: 10.1380/ejssnt.2006.166]

Three diamond (001) samples were made by CVD growth on synthetic diamond substrates in a same batch of growth, for which sheet resistance in atmospheric environment was confirmed. A simple two-point probe method has been applied to the samples to measure sheet resistance in UHV of 0.2–50 MΩ/square. Soft X-ray-induced secondary electron spectroscopy has been used to determine the Fermi level position in UHV of the samples for which in-UHV sheet resistance values were known. The Fermi level as measured turned out to be 1.1±0.2 eV above the valence band top and stayed at the same position within ∼0.1 eV with the sheet resistance change of an order of 2. On the basis of these findings, a plausible model of surface conductivity of CVD diamond is suggested.

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.

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].

Chemisorption of thiophene on a Si(0 0 1) surface has been studied by synchrotron radiation induced photoelectron spectroscopy (SRPES). Two adsorption-related components in Si 2p and S 2p spectra are observed after exposure of thiophene. It is suggested that the two components of Si 2p are ascribed to silicon bonded to hydrocarbon and sulfur. The core-level shift resolved photoelectron diffraction (PED) result indicates that the low-kinetic-energy component of S 2p can be ascribed to 2,5-dihydrothiophehe (DHT)-like species. Another S 2p component could be assigned to dissociated sulfur based on the results of PED and time evolution of the spectrum under irradiation. These assignments are consistent with the core-level shift of S 2p.

The structural properties of the subsaturation coverage of 1,4-cyclohexadiene (C 6 H 8 ) on single domain Si(0 0 1)-2 × 1 surface have been investigated by using photoelectron diffraction (PD) at the C1s core level and at the photon energy of 330 eV. The high resolution core level study allows to determine the presence of a shifted replica of +0.9 eV in kinetic energy. The structural properties of adsorbed molecules are discussed at the light of ab initio multiple scattering calculations on several adsorption models with about the same least total energy. This quantitative experimental determination timely follows the many qualitative assessments present in literature for this important prototypical case of functional Si substrate and aims to fill the gaps between several experiments reported.

The authors review the correlated thermal diffuse scattering (CTDS) as a semi-direct tool for surface structure analysis. The strong vibrational correlation between very near-neighbor atoms induces broad features in the thermal diffuse scattering of diffraction. The broad features, which were paid little attention in crystallography, are the subject of CTDS. Only the short-range arrangement of neighbor atoms is reflected in CTDS so that one can treat CTDS as a kinematical diffraction, even with surface-sensitive electron diffraction. Thus the surface structure is semi-directly obtained by means of the kinematical analysis based on the Fourier transformation.

Field emission properties from diamond particles (DPs) are studied. The DPs with thin chemically vapor deposited (CVD) diamond overcoat, dispersed onto metal substrate, essentially exhibit negative electron affinity (NEA). Field emission, approximately 1 mA/cm 2 under a macroscopic electric field of 3.5 kV/mm are observed. Microscopic electrical properties were studied by scanning tunneling microscopy/spectroscopy. Most parts of the DP surface exhibit narrow gap and p-type characteristics. The localized regions, which have wide gap like bulk diamond properties, are randomly distributed near the top of DP. The field emission current distribution depicted by scanning field emission microscopy (SFEM) show that the electron emission is originating from a localized region on the selected DPs. We found, through SFEM measurement, some favorable field emission spots (“hot spots”) where measured emission current is several orders higher than that of the other DPs (“normal spots”). Field emission spectroscopy (FES) results suggest that a poorly conducting layer is present along the electron path from the metal electrode to vacuum. We propose two models for field emission from “hot spots”, which involve two main mechanisms. One is electron injection from the metal substrate to the DP, which is attributed to the electric field enhancement at intrinsic non-doped diamond (i-diamond) layer sandwiched between the metal substrate and the surface conductive layer (p-diamond) of the CVD diamond overcoat on the DP. The other is electron emission at the top site of NEA DP through the local i-diamond region or the depletion region of the p-diamond, which is caused by the applied electric field.

The structure of benzene adsorbed on a Si(001)(2 × 1) surface up to saturation at room temperature (RT) has been studied by C 1s photoelectron diffraction (PED). Experimental C 1s PED patterns were measured for two regimes of photoelectron kinetic energies at ~ 100 eV and ~ 1000 eV. Simulation of PED patterns was made for three possible structural models predicted so far. Comparison of actual PED patterns and R-factor analysis leads to the conclusion that the so-called standard butterfly (SB) configuration of benzene is present and stable at the saturation coverage at RT. The present PED patterns were not very sensitive to geometrical parameters of absorbed benzene except for the bond length between the topmost carbons in the SB configuration.

A chemical vapor deposition as-grown diamond (0 0 1) single-domain 2 × 1 surface was studied by electron-spectroscopy and electron-diffraction in ultrahigh vacuum (UHV). In order to change the surface conductivity (SC) of the diamond in UHV, three annealing stages were used; without annealing, annealing at 300 °C and annealing at 550 °C. From low energy electron diffraction and X-ray photoelectron spectroscopic (XPS) studies, an existence of SC was suggested for the first two stages of annealing and an absence of SC was suggested for the last stage of annealing. Changes in C KVV Auger electron spectroscopic spectra, C KVV Auger electron diffraction (AED) patterns and C 1s XPS peak positions were noticed between the annealing stages at 300 and 550 °C. These changes are interpreted as such that the state of hydrogen involvement in a subsurface of diamond (0 0 1)2 × 1 changes as SC changes. In particular, the presence of local disorder in diamond configuration in SC subsurface is pointed out from C KVV AED. From C 1s XPS peak shifts, a lower bound for the Fermi-level for SC layers from the valence band top is presented to be ∼0.5 eV.

The author witnessed the dawn of X-ray photoelectron diffraction with Chuck Fadley and has applied photoelectron diffraction to solid surfaces, particularly Si surfaces and submonolayer interfaces with it. In this article, the author reviews mainly his own photoelectron diffraction studies of silicon surfaces in an attempt to define the characteristics, roles and prospects of photoelectron diffraction, Auger electron diffraction and related diffraction techniques in general.

Atomistic morphology and structure of Si(0 0 1) surface exposed to ethylene at room temperature have been studied by scanning tunneling microscopy (STM) and photoelectron diffraction (PED). At an ethylene coverage ( θ C ) of ∼0.5 monolayer (ML, carbon atom/surface Si-atom), both p(2×2) and c(4×2) structures were clearly resolved in atomistic STM images. The alignments of chemisorbed ethylene of p(2×2) and c(4×2) were confirmed by PED and further shown is that the local structure around chemisorbed ethylene at θ C ≅0.5 ML is identical to that at the saturation coverage of 1 ML.

The atomic origin of the photoemission Si 2p core level, shifted at 0.35 eV higher binding energy, at the As/Si(0 0 1)-2×1 surface, is investigated. The study is based on the determination of the surface structure by means of multiple scattering analysis of As 3d azimuth photoelectron diffraction (PD) patterns. The obtained structure is used to assign the atomic origin of the Si 2p component by surface core level shift PD. We find that a single atom contributes to the core level, while, on the basis of final state calculations, a contribution from two different atoms would be expected.

A nitridation process of a diamond surface with nitrogen radical exposure far from the radio-frequency plasma for the stabilization of a negatively charged nitrogen-vacancy (NV−) centers near the surface is presented. At a nitrogen coverage of as high as 0.9 monolayers, high average Rabi contrasts of 0.40 ± 0.06 and 0.46 ± 0.03 have been obtained for single NV− centers formed by shallow nitrogen implantation with acceleration voltages of 1 and 2 keV, respectively. This indicates that nitrogen termination by a radical exposure process produces an electric charge state suitable for single NV− centers near the surface compared with the states obtained for alternatively terminated surfaces.

Here, we report a novel method for micropatterning oligonucleotides on the diamond surface via forming amine groups on the diamond surface by nitrogen/hydrogen radical treatment. The covalent bonding of the supporting oligonucleotide and characterization of an immobilized hybridized oligonucleotide with Cy5 modification were investigated by fluorescence microscopy. To investigate the effectiveness of nitrogen/hydrogen radical treatment for amine termination, two types of radical treatment were used: hydrogen/nitrogen radical treatment and pure nitrogen radical treatment. From the results, hydrogen/nitrogen radical treatment produces amine (NH2) termination on the diamond surface. The effect of amine termination was investigated by immobilization of single-stranded DNA via amide bonding between surface NH2 groups and COOH groups terminating the DNA. The immobilized single-stranded DNA (supporting DNA), which has a complementary relationship with the adenosine triphosphate (ATP) aptamer (DNA), hybridizes with the aptamer with attached fluorescence dye. When ATP molecules approach the double-stranded DNA, the aptamer forms a close relationship with the supporting DNA and combines with ATP. ATP detection was effectively carried out by reduction of fluorescence.

Structural parameters of the Si(0 0 1)(1×2)-Sb surface were optimized by photoelectron diffraction (PED) of Sb 4d peaks. The optimized parameters are 3.17±0.1 A for Sb-dimer bond length and 1.78±0.1 A for the layer spacing between Sb and the first layer Si. The main origin of a surface-core-level-shifted (SCLS) component in Si 2p core-level spectra is identified by SCLS-PED to be the first layer Si atoms connected to Sb dimers. Another SCLS component reported previously was not observed, which indicates that this SCLS component is related to some defects on the (1×2)-Sb surface.

The electronic and structural properties of diamond particles chemical vapor deposition (CVD)-grown on Si(001) surfaces were studied using a scanning probe μ-electron beam with SEM, RHEED, secondary-electron spectroscopy (SES) and Auger-electron spectroscopy in ultra-high-vacuum (UHV) conditions. The CVD grown diamond particles studied were made with a source gas of either CO/H 2 (sample A) or CH 4 /H 2 (sample B) on Si(001). The UHV-SEM images showed that sample A was composed of diamond particles with well-determined low-index surfaces while those for sample B with poorly determined surfaces. μ-RHEED patterns from diamond single-crystallites for sample A showed well-developed Kikuchi-bands together with surface spots indicating a good order of diamond framework near the surface. The diamond crystallites of sample A showed varieties of SES spectra and only a small fraction of them had negative electron affinity (NEA) although no differences are found in RHEED. The SES spectra for sample B showed that essentially all the diamond particles are NEA. It is found that the Fermi-level is located at ∼1.0 eV above the valence band maximum for NEA diamond particles and ∼1.5 eV for PEA ones. The change in electron affinity and the origin of surface conductive layers present on as-grown CVD diamonds are discussed in terms of the Fermi-level positions found presently.

A simple oscillatory intensity variation in medium-energy electron diffraction found recently [Abukawa et al., Phys. Rev. Lett. 82, 335 (1999)] was termed correlated thermal diffuse scattering (CTDS). The potential of CTDS as a direct surface structural tool has been fully explored for the $\mathrm{Si}(001)2\ifmmode\times\else\texttimes\fi{}1$ surface at 300 K in a very-grazing-incidence condition. Nearly $2\ensuremath{\pi}$ solid-angle, three-dimensional (3D) CTDS patterns were measured for an energy range of $500\char21{}2000$ eV. The 3D Patterson functions obtained by Fourier inversion of the measured CTDS patterns clearly revealed the building blocks of the $\mathrm{Si}(001)2\ifmmode\times\else\texttimes\fi{}1$ surface, i.e., the bond orientations and lengths of the buckled Si dimers, within an accuracy of 1\ifmmode^\circ\else\textdegree\fi{} and 0.1 \AA{}, respectively.

Correlated thermal diffuse scattering (CTDS), a direct structural technique using a simple oscillatory intensity variation in the medium energy electron diffraction, has been applied to the biatomic surface system of [Formula: see text]. A problem with the application of CTDS to multicomposition systems arises from the element-specific atomic scattering factors. The difference in atomic scattering factors disturbs the diffraction phase originating from the path length difference and causes the shift from the true atomic position in Patterson analysis. In order to recover the true atomic position, a numerical calibration method has been introduced. With the aid of the calibration, structural parameters for the topmost three layers of the [Formula: see text] surface have been determined with 0.1 Å accuracy. This shows that CTDS is applicable to multicomposition surface systems.

The structure of an $\mathrm{InAs}(111)A\ensuremath{-}(2\ifmmode\times\else\texttimes\fi{}2)S$ surface has been studied by using scanning tunneling microscopy (STM), synchrotron radiation photoemission spectroscopy (SRPES), and x-ray photoelectron diffraction (XPD). Honeycomblike images are observed by STM measured at a bias voltage of -1.4 V. Similar images are also observed at +1.5 V, although the intensity of the alternative corner of a hexagon is depressed, resulting in a threefold symmetry. $\mathrm{S}2s$ and $\mathrm{As}3d$ XPD patterns show that sulfur atoms rarely exchange the fourfold arsenic sites. Three surface components are found in the $\mathrm{In}4d$ spectra. On the other hand, no surface components are found in the $\mathrm{As}3d$ spectra. Based on the STM, SRPES, and XPD results, a probable structure model for the $(2\ifmmode\times\else\texttimes\fi{}2)S$ surface is proposed. The experimental XPD patterns are in good agreement with the calculated ones.

Valence electronic states for an InAs(111)A-(2×2)S surface are investigated by using synchrotron radiation angle-resolved photoemission spectroscopy (SRARPES). Three bands at 1.0–1.2, 3.3, and 4.6–4.7 eV below the Fermi level are found outside the projection of bulk bands along the M–Γ–M′ and Γ–K–M azimuths. A band at 2.8 eV below the Fermi level is found in the normal emission spectra for the (2×2)S surface. This band is located within the projection of bulk bands and independent of the momentum component normal to the surface, k ⊥ . The four bands are ascribed to surface states or surface resonances for the (2×2)S surface. The origin of the surface bands is discussed.

Structures of the ‘nanowire’ and 2× n phase of the submonolayer system of Bi/Si(001) have been studied by X-ray photoelectron diffraction (XPD). The general features of Bi 4d XPD patterns show that Bi atoms exist only at the topmost layer for the two phases. Single-scattering cluster simulations were performed for several structural models, including those for the ‘nanowire’ [Miki et al., Phys. Rev. B 59 (1999) 14 868] and for the 2× n phase [Hanada et al., Surf. Sci. 242 (1991) 137], to find they are very feasible.

X-ray photoelectron diffraction (XPD) patterns of In 3d core levels have been measured for the Si(001)-(4×3)-In surface. An R factor analysis with single-scattering and multiple-scattering simulations of In 3d XPD patterns was performed for three structural models proposed so far. Only the model proposed by surface X-ray diffraction [Appl. Surf. Sci.123/124, 104 (1998)] appeared to give a reasonably small R factor when the geometric parameters were modified from the original ones.

Surface core-level shift energy scan photoelectron diffraction (PED) was used to distinguish the two structural models of the C-terminated β-SiC(001)-c(2 × 2) surface under debate. An experimental PED curve of the surface C Is component is in good agreement only with the simulated curve of the unusual bridge dimer model denying the conventional dimer model. The optimized structural parameters of this bridge dimer model are 1.22, 1.84 and 2.7 A for the C-C, C-Si and Si-Si bond lengths, respectively, in agreement with recent theoretical calculations.

The formation of single-domain Si(001)4×3-In surfaces with several degrees of domain ratio is reported. A single-domain Si(001)2×1 surface was used as a substrate. A single-domain Si(001)3×4-In surface with a good domain ratio is found, the directional relationship of which is such that the threefold direction of 3×4-In corresponds to the twofold direction of substrate. Two other 4×3-In surfaces with poor domain ratios are found, the directional relationship of which is such that the fourfold direction corresponds to the twofold direction of substrate. The formation of these 4×3-In surfaces is explained by the electromigration of surface Si, the amount of which is dependent on the temperature of direct current annealing.

The atomic structure of the c(2[times]2) reconstruction of the C -terminated 3C-SiC(001) surface was unambiguously determined by scanning tunneling microscopy and surface-core-level-resolved photoelectron diffraction studies. This surface is found to uniquely and uniformly consist of anomalous bridge-bonded C dimers with a C-C bond length of 1.22thinspthinsp[Angstrom]. Furthermore, an extensive angle-resolved photoemission study clearly identifies two occupied [pi] state bands due to the surface-normal and -parallel [pi] orbitals of the [ital triple-bonded] C dimers. This provides an electronic explanation of the stability of this unique surface reconstruction. [copyright] [ital 1999] [ital The American Physical Society]