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We report the change of surface electronic structure of indium–tin–oxide (ITO) as a function of ultraviolet (UV)–ozone treatment time. The voltage of organic light emitting diodes at a current density of 100 mA/cm[sup 2] was reduced as the surface treatment time using UV–ozone was lengthened. X-ray photoelectron spectroscopy results showed that the relative concentration of carbon atoms decreased, but oxygen concentration increased relatively with UV–ozone treatment. This led to the increase in the ITO work function via the reduction of operation voltage. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Thermally stable Schottky contacts on n-type 4H–SiC with high Schottky barrier height were demonstrated by annealing the rare earth metal contacts (Ir and Ru) under O[sub 2] ambient. The formation of rare earth metal oxides (IrO[sub 2] and RuO[sub 2]) after O[sub 2] annealing led to the increase of Schottky barrier height (>1.9 eV) and a low reverse leakage current (∼10[sup -9] A/cm[sup 2]). Synchrotron radiation photoemission spectroscopy showed that the work function of IrO[sub 2] is higher about 0.23 eV than that of Ir and the binding energies of Si 2p and C 1s shifted toward lower binding energies by 0.12 eV in both O[sub 2] and N[sub 2] annealed samples. The oxidation annealing caused predominant Si outdiffusion to the IrO[sub 2] (RuO[sub 2]), leaving Si vacancies behind, leading to the shift of surface Fermi level to the energy level of Si vacancy. Both the formation of oxide and the Fermi level movement played a role in forming the Schottky contact with high barrier height and excellent thermally stability. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We developed a kinetic model to predict the preferred orientation for the case of rock-salt MgO crystal by assuming random walk diffusion of the adatom between (111) and (100) planes during growth. This model suggests that the tendency of the (111) preferred orientation increases under high deposition rate and low activation energy for diffusion of the adatom between (111) and (100) grains because the adatoms on the (111) surface stick to the surface more strongly compared to those on the (100) plane. The theoretical model was confirmed experimentally by growing several polycrystalline MgO films using the electron beam evaporation method. We could easily control the flux and energy of MgO adatoms by modulating the emission current of the electron gun, substrate temperature, and extra energy source such as ion beam assisted deposition. Our experimental results show good qualitative agreement with the model for the various polycrystalline MgO films deposited at several growth conditions. [ABSTRACT FROM AUTHOR]

We report the growth mechanism of metal oxide nanostructures synthesized by electron beam evaporation. The condensed electron beam can easily decompose metal oxide sources that have a high melting point, thereby creating a self-catalytic metal nanodot for the vapor-liquid-solid process. The metal oxide nanostructures can be grown at a temperature just above the melting point of the self-catalyst by dissolving oxygen. The morphology of nanostructures, such as density and uniformity, strongly depends on the surface energy and surface migration energy of the substrate. The density of the self-catalytic metal nanodots increased with decreasing surface energies of the substrate due to the perfect wetting phenomenon of the catalytic materials on the high surface energy substrate. However, the surfaces with extremely low surface energy had difficulty producing the high density of self-catalyst nanodot, due to positive line tension, which increases the contact angle to>180°. Moreover, substrates with low surface migration energy, such as single layer graphene, make nanodots agglomerate to produce a less-uniform distribution compared to those produced on multi-layer graphene with high surface migration energy. [ABSTRACT FROM AUTHOR]

We developed a method to control the alignment and density of indium tin oxide (ITO) nanowires by using ion beam assisted deposition (IBAD). During electron beam evaporation, IBAD changed the randomly oriented branch type nanowires to aligned nanowires without branches. This is due to the energetic ion beams which play a role in nucleating tin containing indium nanodots at the initial stage of growth. The improved alignment of the ITO nanowires reduced the sensing time for ethanol gas. [ABSTRACT FROM AUTHOR]

We present the growth mechanism of MgO film on Si (100), specifically, epitaxial growth at the interface, strain relaxation at critical thickness, and preferred orientation formation after strain relaxation. We first focused on domain matching epitaxy (DME) between MgO and Si with a large lattice mismatch of 22.4%. MgO/Si (100) with 4/3 and 5/4 domain matching during growth of MgO on Si (100) are equally mixed to reduce domain mismatch. Two continuous 4/3 domains have domain mismatch of 0.1124 nm, but mixed 4/3 and 5/4 domains have mismatch of only 0.0093 nm. The experimental critical thickness for strain relaxation is ∼100 nm, and this result is supported by theoretical modeling of MgO film growth using an overall film energy model. We focus the anisotropic properties of MgO material to explain the preferred orientation in the (111) direction after strain relaxation. MgO with strong ionic bonding characteristic has a polar surface along particular orientations in which anions and cations are arranged alternately; this is the MgO (111) orientation. This orientation has strong sticking probability and tends to be preferred orientation by adsorbing adatom dominantly. [ABSTRACT FROM AUTHOR]

Abnormal behavior of contact resistance with annealing in Ohmic contacts to laser-irradiated n-GaN is investigated. Ti/Al contacts on as-grown n-GaN shows no change in contact resistivity with annealing at the temperature range of 100–400 °C. However, the annealing results in the significant increase in contact resistivity in the contacts on laser-irradiated n-GaN. Synchrotron radiation photoemission study reveals the reduction of the concentration of donor-like N vacancies near the surface by the annealing. These results suggest that preventing the annihilation of N vacancies in the laser-irradiated n-GaN is important in improving the performance of vertical-structure GaN-based light-emitting diodes fabricated by laser lift-off. [ABSTRACT FROM AUTHOR]

The interface dipole energies between 4,4′-bis[N-(1-naphtyl)-N-phenyl-amino]biphenyl and Ir interfacial layers with different thicknesses (2 and 20 nm) coated on indium tin oxides (ITOs) were measured in situ using synchrotron radiation photoemission spectroscopy. In 20 nm Ir coated ITO, the work function increment of 0.15 eV due to O2 plasma treatment was accompanied by an increase of interface dipole energy. In 2 nm Ir coated ITO, no change in the interface dipole energy was found. Thus, the work function increase (0.45 eV) in the 2 nm Ir by O2 plasma treatment reduced the hole injection barrier by about 0.45 eV. [ABSTRACT FROM AUTHOR]

We report the reduction of contact resistivity between Au and pentacene by O2 plasma treatment. Contact resistance dramatically reduced from 5.65 to 0.22 MΩ cm by the treatment. O2 plasma treatment transformed Au to AuOx, increasing the surface energy from 45.1 to 71.5 mJ/m2. Molecular adsorption geometry of pentacene on AuOx changed from a planar structure to an upright type, improving crystallinity and molecular packing. Thus, defects and traps at the interface were reduced, decreasing the contact resistance between Au and pentacene. [ABSTRACT FROM AUTHOR]

We report the enhancement of quantum efficiency using the Mg–Al alloy cathode and IrOx-coated indium tin oxide (ITO) anode in organic light emitting diodes (OLEDs). The external quantum efficiency at the current density of 64 mA/cm2 increased from 0.04% to 1.89% as the Al cathode and ITO anode changed to the Mg–Al cathode and IrOx-coated ITO anode, respectively. Synchrotron radiation photoelectron spectroscopy results show that the work function of IrOx-coated ITO is higher by 0.5 eV than that of the ITO and the work function of the Mg–Al alloy is lower by 0.2 eV than that of Al. Thus, both the hole and electron injection energy barriers were simultaneously lowered, reducing the turn-on voltage and increasing the quantum efficiency of OLEDs. [ABSTRACT FROM AUTHOR]

We report the enhancement of hole injection using an IrOx layer between indium tin oxide anodes and 4,4’-bis[N-(1-naphtyl)-N-phenyl-amino]biphenyl in organic light-emitting diodes (OLEDs). The turn-on voltage of OLEDs decreased from 7 V to 4 V and the maximum luminescence value increased from 1200 cd/m2 to 1800 cd/m2 as the Ir layer changed to IrOx by surface treatment using O2 plasma. Synchrotron radiation photoelectron spectroscopy results showed that the work function increased by 0.6 eV as the Ir layer transformed into IrOx. Thus, the hole injection energy barrier was lowered, reducing the turn-on voltage and increasing the quantum efficiency of OLEDs. [ABSTRACT FROM AUTHOR]

The mechanism for ohmic contact formation of Ni/Ag contacts on p-type GaN was investigated using synchrotron photoemission spectroscopy. A low contact resistivity of 6.6×10-5 Ω cm2 was obtained from Ni(50 Å)/Ag(1200 Å) contact after annealing at 500°C in O2 ambient. Ni out-diffused to form a NiO and Ag in-diffused into the contact interface during the oxidation annealing. Out-diffused Ga atoms from GaN could dissolve in the Ag layer to form Ag–Ga solid solutions, leaving Ga vacancies below the contact. Ga vacancies could increase the net hole concentration and reduce the surface band bending, resulting in the ohmic contact formation. [ABSTRACT FROM AUTHOR]

We report a metallization scheme of low-resistance, high-reflectance, and thermally-stable ohmic contact on p-type GaN. The specific contact resistivity as low as 5.2×10-5 Ω cm2 and the high reflectance of 91% were simultaneously obtained from Ni (50 Å)/Ag (1200 Å)/Ru (500 Å)/Ni (200 Å)/Au (500 Å) contact annealed at 500 °C in O2 ambient. The oxidation annealing promoted the outdiffusion of Ga atoms to dissolve in the Ag layer, leaving Ga vacancies below the contact. The Ru layer could act as a diffusion barrier for intermixing of the reflective Ag with upper layers of Ni and Au. Thus, suppression of the intermixing results in the high reflectance and good thermal stability of the contact. [ABSTRACT FROM AUTHOR]

Investigates the change of the Fermi energy level at the interface of Pd/p-type GaN by surface treatment using positron annihilation spectroscopy. Interpretation of the electrical properties of the contact; Changes in the positron parameters at the interface in the aqua regia-treated GaN.

Determines the energy levels of surface states at the surface of GaAs through capacitance deep-level transient spectroscopy of GaAs metal-semiconductor field-effect transistor with large gate periphery. Types of hole-like traps observed in the spectra.

Studies the effects of impurities Si and Be on the creation of Ga vacancies and Ga interstitials in GaAs grown by molecular beam epitaxy. Growth of the undoped and Si-doped GaAs layers on a Be-doped epilayer; Decrease in the concentration of V[sub Ga] created from the surface of the undoped GaAs during the annealing.

Discusses the application of slow positrons to the as-etched gallium arsenide (GaAs) and/or the (NH[sub 4])[sub 2] S[sub x]-treated GaAs semiconductors. Formation of a thin oxide film on the surface of as-etched GaAs as soon as the etched surface is exposed to air for several minutes before the measurement.

Investigates the palladium/germanium/titanium/gold ohmic contact to aluminum gallium arsenide/indium gallium arsenide pseudomorphic high electron mobility transistor. Cause of a decrease in contact resistivity; Factors responsible for good ohmic contact; Role of the compounds in the creation of group-III vacancies.

The effects of Au nanoparticles on the electronic properties of a GaN surface were investigated using synchrotron radiation photoelectron spectroscopy (SRPES). A 30-Å-thick Au film on GaN was transformed to nanoparticles by annealing at 300 °C. Ga 3d core level peak as well as Au 4f for p-GaN shifted towards higher binding energies with the formation of Au nanoparticles, while peak shifts in the SRPES spectra for n-GaN were negligible. Poor conductivity of the p-GaN substrate and high resistance between Au nanoparticles and the p-GaN led to positive charges being distributed on the p-GaN surface, suggesting that Au nanoparticles on p-GaN strongly affect the evaluation of surface band bending and the measurement of Schottky barrier heights by photoemission spectroscopy. [ABSTRACT FROM AUTHOR]

Presents a response to a commentary regarding the interpretation of Fermi level pinning on 4H-SiC using synchroton photoemission spectroscopy. Finding that Fermi level (Ef) pinning at the surface of p-type SiC originated from hole trap (H1); Claim that 4-A-thick Ni layer deposited on SiC was too thin to determine the barrier height; Use of a deep level transient spectroscopy measurement to obtain the depth information of the trap.

Presents a response to a comment on the article, 'Thermally stable Ir Schottky contact on AlGaN/GaN heterostructure,' published in a 1003 issue of the journal 'Applied Physics.' Changes in both work function and atomic composition of group-III elements using the synchrotron radiation photoemission spectroscopy; Measurement of the work function of UrO[sub 2].

Responds to the comments on the article "Enhancement of Schottky barrier height on AlGaN/GaN heterostructure by oxidation annealing" in the "Applied Physics Letters" journal. Recognition of the improvement in the barrier height due to oxidation annealing; Demonstration of the core level and valance band spectra shift with the aqua-regia treatment; Decrease of the electron affinity of AlGaN.

Serial femtosecond crystallography (SFX) enables the determination of roomtemperature crystal structures of macromolecules with minimized radiation damage and provides time-resolved molecular dynamics by pump--probe or mixand- inject experiments. In SFX, a variety of sample delivery methods with unique advantages have been developed and applied. The combination of existing sample delivery methods can enable a new approach to SFX data collection that combines the advantages of the individual methods. This study introduces a combined inject-and-transfer system (BITS) method for sample delivery in SFX experiments: a hybrid injection and fixed-target scanning method. BITS allows for solution samples to be reliably deposited on ultraviolet ozone (UVO)-treated polyimide films, at a minimum flow rate of 0.5 nl min-1, in both vertical and horizontal scanning modes. To utilize BITS in SFX experiments, lysozyme crystal samples were embedded in a viscous lard medium and injected at flow rates of 50-100 nl min-1 through a syringe needle onto a UVO-treated polyimide film, which was mounted on a fixed-target scan stage. The crystal samples deposited on the film were raster scanned with an X-ray free electron laser using a motion stage in both horizontal and vertical directions. Using the BITS method, the room-temperature structure of lysozyme was successfully determined at a resolution of 2.1 Å, and thus BITS could be utilized in future SFX experiments. [ABSTRACT FROM AUTHOR]

We reported the evidence of oxygen doping to copper-phthalocyanine (CuPc) by O2-plasma treatment to inverted top-emitting organic light-emitting diodes (ITOLEDs). In situ synchrotron-radiation photoelectron spectroscopy results showed that a new Cu–O bond appeared and the energy difference between the highest-occupied molecular orbital and EF is lowered by 0.15 eV after plasma treatment. The oxygen ions chemically interacted with Cu atoms and transferred charges to the CuPc. Thus the hole injection barrier was lowered, enhancing the electroluminescent property of ITOLEDs. [ABSTRACT FROM AUTHOR]

The mechanism for thermally stable Ag–Cu alloy Ohmic contact on p-type GaN was investigated. Ag–Cu contact showed lower contact resistivity as low as 8.6×10-6 Ω cm2, higher reflectance of 84% at 460 nm, and better thermal stability than Ag contact after annealing in air ambient. The formation of Ag–Ga solid solution lowered the contact resistivity. Additionally the formation of Cu oxide suppresses the Ag oxidation and increases the work function of the Ag–Cu contact via decreasing the Schottky barrier height for hole injection. Precipitation of Cu oxide at grain boundaries suppresses the Ag agglomeration, leading to enhanced light reflectance as well as thermal stability. [ABSTRACT FROM AUTHOR]

The effect of oxygen plasma treatment on enhancement of hole mobility was demonstrated using pentacene organic thin-film transistors (OTFTs) with bottom-contact Au electrodes. Linear field-effect mobility increased from 3.2×10-2 to 7.4×10-2 cm2/V s as the Au electrodes were treated with O2 plasma. Secondary electron emission spectra revealed that the work function of oxygen plasma-treated Au is 0.5 eV higher than that of untreated Au. This led to a reduced hole injection barrier at the interface of Au with pentacene, increasing the field-effect mobility of OTFTs. [ABSTRACT FROM AUTHOR]

We study degradation behaviors of luminance and voltage in organic light-emitting diodes. We find that normalized luminance and inverse normalized voltage with time, L(t) and V(t)-1, follow the stretched exponential decay. On this basis, we derive a general relation of luminance and voltage with time as L(t)=V(t)-δ(t), where δ(t) indicates a decay exponent, which is attributed to time-dependent space-charge limitation. Here the observation of higher δ(t) at higher initial luminance explains why luminance decay is faster at higher initial luminance. [ABSTRACT FROM AUTHOR]

A distributed Bragg reflector (DBR) is conducted as a bottom reflector in see-through organic photovoltaics (OPVs) with an active layer of poly(3-hexylthiophene) and phenyl-C61-butyric acid methyl ester (P3HT:PCBM). The DBR consists of alternative layers of the high- and low-refractive index materials of Ta2O5 (n = 2.16) and SiO2 (n = 1.46). The DBR selectively reflects the light within a specific wavelength region (490 nm-630 nm) where the absorbance of P3HT:PCBM is maximum. The see-through OPVs fabricated on DBR exhibit efficiency enhancement by 31% compared to the device without DBR. Additionally, the angle-dependent transmittance of DBR is analysed using optical simulation and verified by experimental results. As the incident angle of light increases, peak of reflectance shifts to shorter wavelength and the bandwidth gets narrower. This unique angle-dependent optical properties of DBR allows the facile color change of see-through OPVs. [ABSTRACT FROM AUTHOR]

Indium tin oxide (ITO) nanobranched structures with low reflectance have been designed for application to organic solar cells. The ITO nanobranches are deposited on the front surface of glass without damages to organic active layer by using an electron beam deposition. Through a finite-difference time-domain, we find that the field intensity in the glass region is enhanced with ITO nanobranches. Consequently, the number of incident photons induces strong absorption within the PTB7-PC70BM active layer, leading to the enhanced short circuit current density (Jsc). Compared with a flat device (power conversion efficiency (PCE)=6.53%, Jsc=13.3 mA/cm²), improved PCE of 7.09% is achieved in an antireflection coating, which is mainly due to the increased Jsc of 14.2 mA/cm². [ABSTRACT FROM AUTHOR]

The simple and cost-effective method to form vanadium oxides (VOx) with high density of gap-states and role of gap-states for organic electronics were investigated. The percentage of V2O5 decreased from 82.7% to 29.3% as the deposition rate increased from 0.1 to 1.0Å/s in thermal evaporation. Synchrotron radiation photo emission spectroscopy revealed that a number of gap states relating to oxygen vacancies was induced near the Fermi level, transporting charges and lowering the hole injection barrier from 0.92 to 0.67eV. As a result, the operation voltage at 1mA/cm2 was reduced from 8.3 to 5.2V [ABSTRACT FROM AUTHOR]

Graphene film grown by chemical vapor deposition using Cu substrate is promising for industrial applications. After etching the Cu substrate, which is essential step in graphene transfer process, the etchant solution must be chemically treated to prevent water pollution. Here we investigated that a method of reusing Cu etchant used to synthesize graphene, the synthesis of graphene on the resulting reused Cu films (R-G), and the application of R-G to organic light-emitting diodes (OLEDs) and organic photovoltaic cells (OPVs). The turn-on voltage of OLEDs based on the R-G electrode was 4.2 V, and the efficiencies of OPVs based on the R-G electrode were 5.9-5.95%, that are similar to or better than those of the indium-tin-oxide-based devices. These results suggest that the reusing of Cu foil by the electroplating method could reduce the cost of graphene synthesis, thus opening a wide range of applications in graphene electronics. [ABSTRACT FROM AUTHOR]

We demonstrated a novel contact structure of a silver (Ag) reflector that had an enhanced thermal stability at an elevated temperature. The Ag film was epitaxially grown on GaN by the insertion of an ultrathin Ni contact layer (∼10 Å). The Ag film in the Ni/Ag structure, which was tensilely strained due to the expansion of the lattice constant by oxidation of Ni (3.532 Å) to NiO (4.176 Å), could compensate for the thermal compressive stress of 0.83 GPa that developed at the interface of Ag with GaN at 500 °C. The tensile stress, as determined by high resolution X-ray diffraction, was 0.24 GPa for a single period of the Ni/Ag contact, but it increased to 0.65 GPa for triple periods of the Ni/Ag contact, resulting in further suppression of Ag agglomeration and improved long-term thermal stability. [ABSTRACT FROM AUTHOR]

The mechanism for thermally stable indium-containing silver [Ag(In)] Ohmic contact on p-type GaN has been investigated. The specific contact resistivity as low as 3.8×10-5 Ω cm2 and a high reflectance of 88.4% at a 460 nm wavelength were obtained by annealing Ag(0.5 wt % In) alloy contact at 450 °C in air ambient. The In atoms in Ag matrix made In–O chemical bonds, producing a tensile stress in the film. This compensated thermal compressive stress built in the Ag film. As a result, In atoms in Ag film play a role in preventing Ag contact from agglomeration, leading to high reflectance and good thermal stability. [ABSTRACT FROM AUTHOR]

We investigate effects of Ni cladding layers on suppression of Ag agglomeration in Ag contacts on p-GaN using high-resolution x-ray diffraction. In the annealed Ag contact, Ag (100) grains disappear and agglomerate to form a selectively epitaxial growth of Ag (111). An ultrathin Ni contact layer (10 Å) below Ag film plays a role to epitaxially grow (111) Ag films on GaN, leading to the suppression of Ag agglomeration. A 20-Å-thick Ni overlayer effectively acts as a passivation layer to prevent the surface diffusion of Ag atoms during annealing, leading to high light reflectance and low contact resistivity. [ABSTRACT FROM AUTHOR]

The local structure of Mn impurities in ferromagnetic (Ga,Mn)N nanowires was investigated using extended x-ray absorption fine structure (EXAFS). By N2 plasma treatment, the nitrogen concentration increased and the ferromagnetic signal also increased. The EXAFS results showed that the Mn concentration occupying Ga sites increased and interstitially doped Mn atoms significantly decreased due to the plasma treatment. As a result, the N vacancies reduced and crystalline quality improved, resulting in the enhancement of ferromagnetic properties. [ABSTRACT FROM AUTHOR]

With the aim of improving the electrical and adhesion properties of the indium–tin–oxide (ITO) electrode/organic interface, we tested Cl- and CF3-terminated self-assembled monolayers (SAMs), which react with the indium atoms of the electrode, and compared the results to those obtained using a CH3-terminated SAM. The contact resistance of the interface between the Cl-terminated surface and the ITO electrode (1.5 kΩ) was found to be much lower than that of the interface between the ITO and the CF3-terminated surface (21.3 kΩ), which can be attributed to the higher dipole moment of the In–Cl complex compared to the In–F complex. In the ITO films deposited on the CH3-terminated surface, the contact resistance (138.0 kΩ) was much higher than those of the reactive metal contacts because the ITO thin film deposited on the CH3-terminated surface does not react with the SAM. [ABSTRACT FROM AUTHOR]

We report the enhancement of the electron injection by inserting a 1-nm-thick magnesium oxide (MgO) buffer layer between Al cathode and tris (8-hydroxyquinoline) aluminum in an inverted top-emitting organic light-emitting diode (OLED). The turn-on voltage of OLEDs decreased from 10 to 6 V and the luminance increased about 61% as the MgO interfacial layer was employed. The MgO interfacial layer played a role in reducing the energy barrier of electron injection, leading to the reduction of the turn-on voltage and the enhancement of luminance. [ABSTRACT FROM AUTHOR]

The authors report the enhancement of hole injection using an RhOx layer between indium tin oxide anodes and 4,4′-bis[N-(1-naphtyl)-N-phenyl-amino]biphenyl in organic light-emitting diodes (OLEDs). The operation voltage of OLEDs at 700 cd/m2 decreased from 13 to 10 V as the Rh layer changed to RhOx by surface treatment using O2 plasma. Synchrotron radiation photoelectron spectroscopy results showed that the work function increased by 0.2 eV as the Rh layer transformed into RhOx. Thus, the hole injection energy barrier was lowered, reducing the turn-on voltage and increasing the quantum efficiency of OLEDs. [ABSTRACT FROM AUTHOR]

Ferromagnetic properties of (Ga,Mn)N nanowires were examined by treating with nitrogen plasma at 200 °C. Nanowires grown by chemical vapor deposition were n-type and no secondary phases were found. The magnetic moment increased and was maintained at room temperature by this treatment. Synchrotron radiation photoemission spectroscopy revealed that Ga vacancies significantly increased, but N vacancies decreased by plasma treatment, leading to a decrease of MnGa–VN complex and the enhancement of Mn activation. [ABSTRACT FROM AUTHOR]

N and Mn ions were co-implanted into p-type GaN and subsequently annealed at 700–900 °C. Compared with Mn-implanted sample, the (Mn+N)-implanted sample revealed a larger ferromagnetic signal. This was attributed to the increase of Ga–Mn magnetic phases. Mn–N compounds, such as Mn[sub 6]N[sub 2.58] and Mn[sub 3]N[sub 2], decreased and the resistivity significantly increased, meaning a reduction of N vacancies. It is suggested that enhancement in ferromagnetic properties in the (Mn+N)-implanted GaN originated from the reduction of N vacancies and the increase of Ga–Mn magnetic phases. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The microstructural evolution of Mn-implanted p-type GaN has been studied using cross-sectional transmission electron microscopy. As Mn[sub 3]Ga nanoclusters (3–7 nm) with a hexagonal structure were produced by annealing (<=800 °C), the weak ferromagnetic property emerged. Higher-temperature annealing (>=900 °C) reduced the ferromagnetic signal and produced antiferromagnetic Mn-nitride nanoclusters, such as Mn[sub 6]N[sub 2.58] and Mn[sub 3]N[sub 2]. This provides evidence that the ferromagnetic property was deeply related to microstructural changes of nanoclusters. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The article addresses a low spin injection efficiency issue for Alq3 and suggests a solution. It first notes that both problems may be simultaneously solved by using organic-based magnets. It modifies Alq3 itself and make it magnetic. The room-temperature ferromagnetism in Co-doped 8-hydroxy-quinoline aluminum synthesized by thermal coevaporation of pure Co metal and Alq3 powders is reported.

The structural evolution during heteroepitaxial growth of ZnO/sapphire(001) by radio-frequency magnetron sputtering has been studied using real-time synchrotron x-ray scattering. The two-dimensional (2D) ZnO(002) layers grown in the initial stage are highly strained and well aligned to the substrate having a mosaic distribution of 0.01° full width at half maximum (FWHM), in sharp contrast to the reported transition 2D layers grown by molecular-beam epitaxy. With increasing film thickness, the lattice strain is relieved and the poorly aligned (1.25° FWHM) three-dimensional (3D) islands are nucleated on the 2D layers. We attribute the 2D-3D transition to the release of the strain energy stored in the film due to the film/substrate lattice mismatch. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Field emission of diamond film was enhanced after surface treatment using boiling aqua-regia solution. The current generated by the emission of electrons was distinctly increased and the threshold field was reduced from 18.1 to 13.8 V/μm by the treatment. The amount of C-C bonds was decreased, but the O-C one was increased by the treatment. The Fermi level at the treated surface was increased by 2.2 eV. This provides evidence that the enhancement of electron emission originated from the reduction of the work function, caused by the chemisorption of oxygen atoms at the surface of diamond during the aqua regia treatment. Thus, the effective electron affinity changed from positive to negative, leading to the reduction of the potential barrier height and width for electron emission at the surface of diamond. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]