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Nanohole array is particularly advantageous for light field manipulation. Here, we report a strategy to mimic the function of x-ray transmission gratings with free-standing quasiperiodic nanohole array. An analytical description is developed to reveal the physical mechanism of the free-standing quasiperiodic nanohole array that reduces higher-order contamination, and is verified by rigorous numerical simulations. An x-ray free-standing quasiperiodic nanohole array consisting of 1.6×109 nanoholes over an active area of 10 mm × 10 mm was fabricated. Experimental results of nearcomplete suppression of higher-order diffractions were obtained in the x-ray region. The capability to separate multiple overlapping orders makes this kind of nanohole array attractive for future development and application of high-resolution spectroscopy. [ABSTRACT FROM AUTHOR]

We have performed comparative depth-dependent x-ray excited optical luminescence (XEOL) and depth resolved cathodoluminescence spectroscopy measurements in order to understand the native point defect distribution in three SrTiO3 samples. Both techniques found surface segregation of Ti3+ defects, but apparent differences in the oxygen vacancy distribution. Due to the lower excitation flux densities employed in XEOL, there is a delayed onset ('dead layer') revealed in the oxygen defect depth distribution, which results from band bending near the surface. By modeling the data, we are able to estimate the Ti3+ depth distribution and the depletion layer width. [ABSTRACT FROM AUTHOR]

Bipolar resistive switching (RS) behavior was observed in epitaxially deposited TiO2-δ/La2/3Sr1/3MnO3 stacks. An intermediate initial state of this device demonstrated that the original resistive state would switch to either the higher or the lower state, depending only on the electrical polarity of the initial measurement. As the analogue intermediate states were obtained by device fabrication, the direct observation of these switching states was possible, knowing the microscopic physical origin of the RS effect. Based on x-ray photoelectron spectroscopy analysis, an understanding of this interesting phenomenon was proposed, well supporting the oxygen vacancy formation and recombination mechanism. [ABSTRACT FROM AUTHOR]

We demonstrate both theoretically and experimentally that edge-enhancement effects are produced when objects, in contact with the x-ray detector, are imaged by using very broad x-ray spectra. Radiographs of thin Al objects have been obtained with a table-top synchrotron source which generates x-rays in the energy range from a few kilo-electron-volts up to 6 MeV. Edge-enhancement effects arise from the combination of x-ray absorption (kilo-electron-volt part of the spectrum) and secondary particle emission (mega-electron-volt part of the spectrum) within the sample. The exact contribution of absorption and emission profiles in the edge-enhanced images has been calculated via Monte Carlo simulation. [ABSTRACT FROM AUTHOR]

The x-ray excited luminescence spectra of different quality CuI crystals were measured. The prevailing blue luminescence and the unusual red luminescence were found at the same time. The relative intensity of these two luminescence peaks was different because of the change of defect concentration in crystals. By comparing the spectra of CuI crystals before and after annealing in vacuum, air or iodine vapors, the origin of the red luminescence in the as-grown crystals was ascribed to the presence of iodine vacancy, as confirmed by the energy dispersive x-ray analysis. [ABSTRACT FROM AUTHOR]

Transmission electron microscopy (TEM), high-resolution TEM, and x-ray energy dispersive spectroscopy results showed that Zn metallic nanocrystals and ZnSiO3 insulating nanocrytals embedded in a SiO2 matrix were created from the ZnO thin films deposited on n-Si (001) substrates due to rapid thermal annealing. The formed Zn metallic nanocrystals were transformed into monoclinic ZnSiO3 insulating nanocrystals with increasing number of Zn atoms resulting from an increase in the annealing time up to 10 min. The transformation mechanisms from metallic Zn nanocrystals to insulating ZnSiO3 nanocrystals in a SiO2 matrix due to rapid thermal annealing are described on the basis of the experimental results. [ABSTRACT FROM AUTHOR]

The electronic structure of Zn1-xMgxO alloy thin films was determined by hard x-ray photoemission spectroscopy (HX-PES) and optical transmittance measurements. HX-PES measurements revealed that the binding energies of valence band, Zn 2p, and O 1s levels increased with increasing MgO fraction. The energy shift correlated with a widening of the band gap and change in ionicity of chemical bonds by alloying. The Fermi level in the alloy compounds was found to be close to the bottom of conduction band regardless of the MgO fraction. [ABSTRACT FROM AUTHOR]

We demonstrate a low series resistance contact of gold (anode)/zinc-phthalocyznine in a reverse organic photovoltaic device aided by oxygen plasma treatment. The power conversion efficiency appreciated from 0.2% to 2.13%, post O2 plasma treatment, predominantly due to the reduction in the series resistance of the device. A depth profile of zinc from x-ray photoelectron spectroscopy study revealed a gold layer with graded zinc composition, instead of pure gold, to be an efficient hole-collector from the organic interface. The zinc alloying of the gold layer has clearly been promoted by the oxygen plasma treatment. [ABSTRACT FROM AUTHOR]

We have investigated the dissolution of a natural oxide layer on a Nb(110) surface upon heating, combining x-ray reflectivity, grazing incidence diffuse scattering, and core-level spectroscopy. The natural oxide reduces after heating to 145 °C partially from Nb2O5 to NbO2, and an enrichment in subsurface interstitial oxygen by ∼70% in a depth of 100 Å is observed. After heating to 300 °C, the oxide reduces to NbO and the surplus subsurface oxygen gets dissolved into the bulk. Our approach can be applied for further investigation of the effect of subsurface interstitial oxygen on the performance of niobium rf cavities. [ABSTRACT FROM AUTHOR]

We element specifically studied the electronic and magnetic states of epitaxially grown full-Heusler alloy Co2MnSi (CMS) 1.1 nm (4 ML) thick ultrathin films facing an epitaxial MgO(001) tunnel barrier by means of x-ray absorption spectroscopy (XAS) and x-ray magnetic circular dichroism (XMCD). In situ reflection high-energy electron-diffraction observations indicated that the CMS films grew into the L21 structure. The observed XAS and XMCD spectra revealed that the CMS ultrathin film was not oxidized. The ratio of Mn and Co spin magnetic moments obtained by applying the sum rules was about 2.7, close to a theoretical value of 2.8 for CMS with the L21 structure. [ABSTRACT FROM AUTHOR]

The electronic and structural characteristics of xenon implanted in amorphous silicon are investigated. A different implantation approach, in which xenon atoms are implanted during the film deposition, was developed. Up to about 5 at. % of xenon were implanted at energy as low as 100 eV. X-ray absorption spectroscopy reveals that xenon atoms are dispersed in the amorphous Si network. The xenon 3d5/2 binding energy, from x-ray photoelectron spectroscopy, as well as the initial state contribution and relaxation energy, from x-ray excited Auger electron spectroscopy, depend on the implantation energy and indicate that the xenon atoms are trapped in voids of different sizes. [ABSTRACT FROM AUTHOR]

HfAl2O5 gate dielectric film with an O-gettering Ti capping layer treated with rapid thermal annealing process and its interfacial structure and electrical properties were reported. X-ray reflectivity measurements and x-ray photoelectron spectroscopy suggested that the interfacial layers were composed of a 0.5 nm HfAlSiO layer and a 1.5 nm Six(SiO2)1-x (x<1) layer for the as-deposited film. However, for the annealed film, HfAlSiO layer was not found and the 1.5 nm Six(SiO2)1-x transformed to a 1 nm SiO2. The electrical measurements indicated that the equivalent oxide thickness decreased to 2.9 nm, and the leakage current was only 70 μA/cm2 at the gate bias of 10 MV/cm for the annealed film. [ABSTRACT FROM AUTHOR]

The authors have fabricated germanium (Ge) metal-insulator-semiconductor (MIS) structures with a 7-nm-thick tantalum pentaoxide (Ta2O5)/2-nm-thick germanium nitride (GeNx) gate insulator stack by electron-cyclotron-resonance plasma nitridation and sputtering deposition. They found that pure GeNx ultrathin layers can be formed by the direct plasma nitridation of the Ge surface without substrate heating. X-ray photoelectron spectroscopy revealed no oxidation of the GeNx layer after the Ta2O5 sputtering deposition. The fabricated MIS capacitor with a capacitance equivalent thickness of 4.3 nm showed excellent leakage current characteristics. The interface trap density obtained by the modified conductance method was 4×1011 cm-2 eV-1 at the midgap. [ABSTRACT FROM AUTHOR]

Plasma immersion ion nitridation is used to produce thin HfO2 films with improved thermal and electrical properties. The film composition is investigated by examining the chemical shifts of the Hf 4f, Si 2p, and N 1s core-level spectra using x-ray photoelectron spectroscopy. The improved thermal stability and interfacial microstructure are further confirmed by high-resolution cross-sectional transmission electron microscopy. Electrical studies show an equivalent oxide thickness of about 1.25 nm, a negligible hysteresis of about 5 mV, and a low fixed charge density. [ABSTRACT FROM AUTHOR]

Plasma immersion ion nitridation is used to produce thin HfO2 films with improved thermal and electrical properties. The film composition is investigated by examining the chemical shifts of the Hf 4f, Si 2p, and N 1s core-level spectra using x-ray photoelectron spectroscopy. The improved thermal stability and interfacial microstructure are further confirmed by high-resolution cross-sectional transmission electron microscopy. Electrical studies show an equivalent oxide thickness of about 1.25 nm, a negligible hysteresis of about 5 mV, and a low fixed charge density. [ABSTRACT FROM AUTHOR]

The authors report the preparation of silica nanotubes by a simple two-stage thermal evaporation of ZnSe and SiO powders. Firstly, nanocables with single crystalline ZnSe nanowire cores and amorphous SiO2 shells were formed by a combined vapor-liquid-solid and SiO-assisted growth process. The ZnSe cores were then evaporated at high temperatures leaving behind SiO2 nanotubes. As-fabricated SiO2 nanotubes were studied with scanning electron microscopy, transmission electron microscopy, energy-dispersive x-ray spectroscopic analysis, and photoluminescence measurement. The SiO2 nanotubes were found to be amorphous, diameter uniform, smooth, and rigid. This method can be used to prepare other materials and morphology-controlled nanotubes. [ABSTRACT FROM AUTHOR]

Nanofocused x rays are indispensable because they can provide high spatial resolution and high sensitivity for x-ray nanoscopy/spectroscopy. A focusing system using total reflection mirrors is one of the most promising methods for producing nanofocused x rays due to its high efficiency and energy-tunable focusing. The authors have developed a fabrication system for hard x-ray mirrors by developing elastic emission machining, microstitching interferometry, and relative angle determinable stitching interferometry. By using an ultraprecisely figured mirror, they realized hard x-ray line focusing with a beam width of 25 nm at 15 keV. The focusing test was performed at the 1-km-long beamline of SPring-8. [ABSTRACT FROM AUTHOR]

A composite system comprised of polyaniline nanofibers bonded with gold nanoparticles is shown to possess a memory effect via a charge transfer mechanism. The charge transfer occurs between the imine nitrogen in the polyaniline and the gold nanoparticles as confirmed by x-ray photoelectron spectroscopy and Raman spectroscopy. This charge transfer enables a bistable electrical conductivity, allowing the material system to be used as a digital memory device. The charge transfer is further confirmed by the elimination of the conductance switching when the fully reduced form of polyaniline, leucoemeraldine, which possesses no imine nitrogens, is used in place of the emeraldine form. [ABSTRACT FROM AUTHOR]

All existing x-ray dispersive devices including crystals, multilayers and diffraction gratings generate spectra in multiple orders. In this letter the authors describe how an axis symmetrically distributed sinusoidal-shaped aperture with binary transmittance values can be used to disperse x rays and with a superior diffraction pattern where, along its symmetry axis, all higher-order diffractions can be effectively suppressed. Hence this sophisticated dispersive element generates pure soft x-ray spectra in the first diffraction order, free from interference from higher diffraction orders. [ABSTRACT FROM AUTHOR]

In situ potassium (K)-doped single-walled carbon nanotube (SWCNT) was synthesized using a hydrogen arc-discharge method. X-ray photoelectron spectroscopy analysis showed that the K-doped SWCNTs consisted of 0.12% K mass composition. The K-doped SWCNTs showed the lower turn-on electric field of 2.0 V/μm at a current density of 10-9 A/cm2 and the higher emission current density of 3.0 mA/cm2 at an applied field of 4.6 V/μm compared with the undoped SWCNTs. The improved field emission performance of K-doped SWCNTs was mainly attributed to the decreased work function and the increased density of state near the Fermi energy. [ABSTRACT FROM AUTHOR]

Carbon nanotubes-supported Pt nanoparticles were loaded using a microwave oven on the defective carbon nanotubes generated by an additional oxidant during acid treatment. The authors’ Raman spectra and x-ray diffraction analysis demonstrated that defects created during oxidation and microwave treatment acted as nucleation seeds for Pt adsorption. The generated Pt nanoparticles had the size distributions of 2–3 nm and were uniformly distributed on the defects of carbon nanotubes. The authors’ density functional calculations showed that the adsorption of Pt atom on the vacancy of nanotube was significantly stronger by s-p hybridization with carbon atoms near the defect site. [ABSTRACT FROM AUTHOR]

The O K-edge pre-edge structure in the x-ray absorption spectra of high quality La2/3Ca1/3MnO3 epitaxial thin films grown on top of (001) SrTiO3 and NdGaO3 substrates is analyzed as a function of structural strain and temperature. A clear correlation between temperature dependent spectral changes and the structural strain, induced by the film/substrate mismatch, is found. [ABSTRACT FROM AUTHOR]

The Er3+ doped transparent oxyfluoride glass ceramics containing Sr2GdF7 nanocrystals were prepared and their spectroscopic properties were discussed. The formation of Sr2GdF7 nanocrystals in the glass ceramics was confirmed by x-ray diffraction. The split peaks of the upconversion and near infrared emission bands of the Er3+ doped glass ceramics can be observed. The upconversion luminescence intensity of Er3+ in the glass ceramics increased significantly with the increasing heat treated temperature. The luminescence decay curves and time-resolved spectra indicated that the lifetime of the ´S3/2 state of Er3+ in the glass ceramic was longer than that in the glass. [ABSTRACT FROM AUTHOR]

Energy-dispersive x-ray spectroscopy was used to analyze quantum well intermixing between an InGaAs quantum well (QW) and InGaAsP barriers grown on GaAs induced by a low temperature, molecular beam epitaxy grown, InGaP cap. This cap layer produces an enhanced blueshift of the photoluminescence (PL) wavelength following postgrowth annealing, and degradation of the PL signal. Cross-sectional transmission electron microscopy reveals modification of the whole structure, with formation of arsenic precipitates, broadening, and subsequent disappearance of the QWs in the capped structure. Uncapped samples are relatively unchanged. Increased phosphorus observed in the QW for capped structures confirms the diffusion of phosphorus from the P-rich cap. [ABSTRACT FROM AUTHOR]

The extreme ultraviolet emission characteristics of laser-produced lithium plasma are experimentally and theoretically investigated. Taking into account the target oxidation, the ion fractional populations are analyzed and the averaged plasma parameters are obtained. Theoretical results show an insignificant influence of oxygen on the temperature dependence of the lithium ion fractional number. A comparison between the theoretical spectrum for stationary and homogenous plasma and experiments shows a reasonable agreement. [ABSTRACT FROM AUTHOR]

The interface between the conjugated polymer poly(3-hexylthiophene) (P3HT) and Au was investigated using photoemission spectroscopy. Electrospray thin film deposition was used to deposit P3HT on a polycrystalline Au thin film in several steps without breaking the vacuum. In between deposition steps, x-ray photoemission spectroscopy and ultraviolet photoemission spectroscopy measurements were carried out. The resulting series of spectra allowed the determination of the orbital lineup at the interface. The results indicate that the P3HT interface has a smaller hole injection barrier (0.59 eV) than comparably structured oligothiophene contacts. [ABSTRACT FROM AUTHOR]

Core-hole clock spectroscopy and near-edge x-ray-absorption fine structure measurements have been used to investigate the ultrafast electron transfer dynamics at the Copper(II) phthalocyanine (CuPc)/Au(111) interface. It was found that the strong electronic coupling between the first layer of CuPc molecules and Au(111) substrate favors ultrafast electron transfer from the lowest unoccupied molecular orbital of the CuPc molecules to the conduction band of Au(111) in the time scale of ∼6 fs. In contrast, the intermolecular electron transfer within multilayers of CuPc molecules via the weak van der Waals interaction was much slower. [ABSTRACT FROM AUTHOR]

X-ray photoelectron spectroscopy was used to measure the energy discontinuity in the valence band (ΔEv) of Zn0.95Cd0.05O/ZnO heterostructures grown by rf plasma-enhanced molecular-beam epitaxy. A value of ΔEv=0.17±0.03 eV was obtained by using the Zn 2p energy level as a reference. Given the experimental band gap of 2.9 eV for the Zn0.95Cd0.05O, this would indicate a conduction band offset ΔEC of 0.30 eV in this system. [ABSTRACT FROM AUTHOR]

We present a method to measure continuous-wave ferromagnetic resonance (FMR) spectra based on the core-level absorption of circularly polarized x rays. The technique is demonstrated by using a monochromatic x-ray beam incident on an yttrium–iron–garnet sample excited by a microwave field at 2.47 GHz. FMR spectra are obtained by monitoring the x-ray absorption intensity at the photon energy corresponding to the maximum of the magnetic circular dichroism effect at the iron L2,3 edges as a function of applied magnetic field. The x-ray FMR signal is shown to be energy dependent, which makes the technique element sensitive and opens up new possibilities to perform element-resolved FMR in magnetic alloys and multilayers. [ABSTRACT FROM AUTHOR]

The electronic structure and x-ray photoelectron spectra of silicon with octahedral B6 clusters are investigated using first-principles calculations. It is found that the B6 clusters act as double acceptors in silicon and that the simulated chemical shift of the B 1s orbital signals of the B6 clusters in x-ray photoelectron spectra coincides with the chemical shift of B 1s experimentally observed in as-implanted silicon at an extremely high dose of boron. These results reveal that the B6 clusters are the origin of hole carriers. We propose a mechanism of hole generation and a model of B6 cluster formation at implantation-induced divacancy sites. [ABSTRACT FROM AUTHOR]

A photoelectron-yield soft x-ray standing wave (SW) technique with the scanned-energy mode has been applied to the vertical height determination of the atoms of specific elements involved in an organic monolayer prepared by the Langmuir–Blodgett method on a W/C superlattice substrate (d=30.9 Å) that serves as a SW generator. The vertical positions of two different-element atoms were determined from the SW profiles. This kind of information is complementary to the molecular-orientation estimation by the polarized x-ray absorption spectroscopy and the combination of these techniques will be a powerful tool to understand the structures of organic monolayers. [ABSTRACT FROM AUTHOR]

We describe the passivation of InAs(001) surfaces with thioacetamide (CH3CSNH2 or TAM) as an alternative to the standard sulfur passivation using inorganic sulfide (NH4)2Sx. Quantitative comparison using x-ray photoelectron spectroscopy (XPS) demonstrates that TAM passivation dramatically improves the stability against reoxidation in air compared with the inorganic sulfide, with little to no etching during the treatment. We find that TAM passivation preserves the intrinsic surface charge accumulation layer, as directly confirmed with laser-induced photoemission. Overall, TAM appears to provide superior passivation for electronic device and sensing applications. [ABSTRACT FROM AUTHOR]

Thin films of thermochromic VO2, V1-xWxO2 and V1-x-yWxTiyO2 (x=0.014, and y=0.12) were synthesized onto quartz substrates using a reactive pulsed laser deposition technique. The films were then characterized by x-ray diffraction and x-ray photoelectron spectroscopy. The W and Ti dopant effects on the semiconductor-to-metal phase transition of VO2 were investigated by measuring the temperature dependence of their electrical resistivity and their infrared transmittance. Remarkably strong effects of Ti–W codoping were observed on both the optical and electrical properties of V1-x-yWxTiyO2 films. The IR transmittance was improved, while the transition temperature could be varied from 36°C for W-doped VO2 film to 60°C for Ti–W codoped VO2 film. In addition, at room temperature, a higher temperature coefficient of resistance of 5.12%/°C is achieved. Finally, both optical and electrical hysteresis are completely suppressed by Ti–W codoping the VO2 films. [ABSTRACT FROM AUTHOR]

High-energy bremsstrahlung and K x rays were used to produce nearly background-free K x-ray spectra of up to 87 keV (Pb) via x-ray fluorescence. The fluorescing radiation was produced by electron accelerators, consisting of heated and cooled cylindrical LiTaO3 and LiNbO3 crystals at mTorr pressures. The process of gas amplification whereby the ambient gas pressure is optimized to maximize the electron energy was used to produce energetic electrons which when incident on a W/Bi target, gave rise to a radiation field consisting of high-energy bremsstrahlung as well as W and Bi K x rays. These photons were used to fluoresce Ta and Pb K x rays. [ABSTRACT FROM AUTHOR]

We report on the 55Fe x-ray pulse height spectrum of an annular superconducting tunnel junction (STJ) collected without an external magnetic field. An energy resolution of 100 eV was obtained for the Kα line of the top electrode. The Josephson critical current and Fiske resonances were suppressed by the presence of trapped magnetic flux quanta which created a persistent current and self-generated magnetic field. The obtained energy resolution and the stability of the trapped magnetic flux under irradiation demonstrate the capability of an annular STJ device with trapped flux quanta to detect radiation without using the external magnetic field that is required in the conventional detection scheme. [ABSTRACT FROM AUTHOR]

High-quality Zn–Ni solid solution(8 nm)/Au(8 nm) ohmic contacts on p-GaN (5×1017 cm-3) have been investigated by means of current–voltage (I–V) measurements and x-ray photoemission spectroscopy. The as-deposited contact shows nonlinear I–V characteristics. However, oxidizing the contacts at 530 °C for 1 min in air ambient gives rise to considerable improvement in their I–V behaviors, yielding a specific contact resistance of 5.2×10-5 Ω cm2. The light transmittance of the annealed Zn–Ni solid solution/Au contacts is measured to be better than 74% at a wavelength of 470 nm. Green light-emitting diodes (LEDs) fabricated with the annealed Zn–Ni solid solution/Au contacts give a forward-bias voltage of 3.39 V at an injection current of 20 mA, which is better than that of the LEDs with the oxidized Ni/Au contacts. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Subpicosecond time-resolved differential transmission spectroscopy has been used to investigate the carrier density and temperature dependence of the quantum well electron capture time of blue-emitting InGaN/GaN multiple quantum well structures. It is found that the capture time varies significantly with both temperature and carrier density, the latter effect being consistent with carrier-induced band bending or increased carrier–carrier scattering. At room temperature, the electron capture time is in the range 0.4–0.8 ps for carrier densities ≤5×1018 cm-3. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We apply near-edge x-ray absorption fine structure spectroscopy, at the N K edge, in order to identify the signature of implantation-induced defects in the partial density of empty states in GaN implanted with O, Mg, and Si ions. The dose range was 10[sup 14]-10[sup 18] cm[sup -2]. It is found that two of the implantation-induced defects introduce characteristic resonances (hereafter called RL1 and RL2) in the near-edge x-ray absorption fine structure spectra. RL1 appears 1.7 eV below the absorption edge, its formation is independent of the projectile and the implantation dose, and is attributed to nitrogen interstitials. RL2, which appears at about 1.0 eV above the absorption edge, is generated when the dose exceeds 10[sup 16] cm[sup -2] and is attributed to nitrogen dangling bonds. [ABSTRACT FROM AUTHOR]

Soft x-ray spectra emitted by laser-produced plasmas in the wavelength range 10 Å<λ<250 Å were absolutely measured with a transmission grating and calibrated Kodak 101-01 film. Laser pulses with a length of 3 ns and a wavelength of 0.53 μm were focused at an intensity of 3×1013 W/cm2 on planar targets of various elements with atomic numbers ranging from 4 to 82. The overall conversion of incident laser energy into x-ray energy increases from 2% for Be to nearly 50% for the heaviest elements. [ABSTRACT FROM AUTHOR]

The Zn0.97-xCr0.03GaxO (0 ≤ x ≤ 0.03) films have been prepared by inductively coupled plasma enhanced physical vapor deposition and investigated by soft x-ray absorption spectroscopy. The soft x-ray absorption spectroscopy results indicate Ga doping can substantially transform Cr3+ to Cr2+ and improve the average magnetic moment of Cr ions. The strong localization of carriers suggests the bound magnetic polarons scenario, wherein the reduced localization radius of variable range hopping by the enhancement of high valence state Cr ions can suppress the hopping probability of carriers and stabilize the bound magnetic polarons, leading to a monotonic increase in saturation magnetization. [ABSTRACT FROM AUTHOR]