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Force detection of magnetic resonance is now able to attain extremely high spin sensitivity. In these setups, microcantilevers were usually used as a sensitive force sensor and, in most cases, have been applied to solid-state samples such as paramagnetic impurities in solids. On the other hand, there are now growing demands for their applications to liquid-state samples in the research areas of life science because many proteins and enzymes are biofunctionally active only in solutions, where they interact with the surrounding water molecules. In this letter, we present an electron paramagnetic resonance (EPR) technique for solution samples using a SiNx nanomembrane and report high-frequency EPR spectroscopy of a microliter-volume frozen solution sample of hemin and myoglobin at multiple frequencies up to 350 GHz. This technique would be particularly useful to obtain more detailed insight into the electronic structure of metalloproteins/metalloenzymes under biologically active conditions. [ABSTRACT FROM AUTHOR]

Defect structure of MgB2 bulk and ultrafine particles, synthesized by solid state reaction route, have been investigated mainly by the aid of X-band electron paramagnetic resonance spectrometer. Two different amorphous Boron (B) precursors were used for the synthesis of MgB2, namely, boron 95 (purity 95%-97%, <1.5 µm) and nanoboron (purity >98.5%, <250 nm), which revealed bulk and nanosized MgB2, respectively. Scanning and transmission electron microscopy analysis demonstrate uniform and ultrafine morphology for nanosized MgB2 in comparison with bulk MgB2. Powder X-ray diffraction data show that the concentration of the by-product MgO is significantly reduced when nanoboron is employed as precursor. It is observed that a significant average particle size reduction for MgB2 can be achieved only by using B particles of micron or nano size. The origin and the role of defect centers were also investigated and the results proved that at nanoscale MgB2 material contains Mg vacancies. Such vacancies influence the connectivity and the conductivity properties which are crucial for the superconductivity applications. [ABSTRACT FROM AUTHOR]

The Z1/2 center in n-type 4H-SiC epilayers-a dominant deep level limiting the carrier lifetime-has been investigated. Using capacitance versus voltage (C-V) measurements and deep level transient spectroscopy (DLTS), we show that the Z1/2 center is responsible for the carrier compensation in n-type 4H-SiC epilayers irradiated by low-energy (250 keV) electrons. The concentration of the Z1/2 defect obtained by C-V and DLTS correlates well with that of the carbon vacancy (VC) determined by electron paramagnetic resonance, suggesting that the Z1/2 deep level originates from VC. [ABSTRACT FROM AUTHOR]

The amphoteric nature of Si/SiO2 interface states in submicron sized metal-oxide-silicon-field-effect-transistors is observed using an enhanced spectroscopic charge pumping method. The method's simplicity and high sensitivity makes it a powerful tool for interrogating the true nature of electrically measured interface states in samples which exhibit extremely low defect densities. The spectroscopic results obtained clearly illustrate a signature 'double peak' density of states consistent with amphoteric Pb center data obtained from electron spin resonance measurements. Since the method is a hybrid of the commonly used charge pumping methodology, it should find widespread use in electronic device characterization. [ABSTRACT FROM AUTHOR]

Magnetodielectric coupling effects of single phase multiferroic Pb(Fe0.5Nb0.5)O3 ceramics have been studied using standard ferroelectric measurements and electron paramagnetic resonance (EPR). Changes in the electrical polarization behavior were observed in the paramagnetic to weakly magnetized antiferromagnetic transition near 103 K associated with a rhombohedral to monoclinic symmetry reduction. The analysis of changes in the EPR spectral parameters confirms the transition from paramagnetic to weakly magnetized antiferromagnetic and reveals noticeable anomalies in the high temperature region near the ferroelectric-paraelectric transition (383 K), which are correlated with the tetragonal-to-cubic symmetry change and the characteristic diffuse phase transition of this material. [ABSTRACT FROM AUTHOR]

The electronic energy band structure of a (100)Ge/GeO2 interface with a Ge3≡Ge• center (Ge dangling bond) is calculated using the density functional theory. The defect level associated with this dangling bond is found to lie near the middle of the Ge band gap. Consequently, the Ge dangling bond at this interface should be paramagnetic when the Fermi level is near the midgap, and it should thus be observed by electron spin resonance (ESR), which appears to be in contradiction with the results reported by [Afanas’ev et al., Appl. Phys. Lett. 87, 032107 (2005)]. We point out that the density of Ge3≡Ge• centers at the (100)Ge/GeO2 interface is possibly at/below the ESR detection limit due to the viscoelastic properties of GeO2, owing to a better stress relaxation at/near the interface, compared to its silicon counterpart. [ABSTRACT FROM AUTHOR]

The magnetic behavior of titanium dioxide nanobelts has been investigated with and without Co doping. Room temperature ferromagnetism was observed when the Co-doped anatase TiO2 nanobelts were prepared via vacuum annealing of 2.5 at. % Co-doped titanate nanobelts, while annealing them in air resulted in paramagnetic ordering. Interestingly, by vacuum annealing the undoped titanate nanobelts under the same conditions, superparamagnetic ordering was observed in the resulting anatase TiO2 nanobelts. The electron paramagnetic resonance of this latter sample shows a strong symmetrical signal at g=2.003 suggesting some sort of exchange interactions among the localized electrons’ spin moments from single electron trapped in oxygen vacancies. [ABSTRACT FROM AUTHOR]

Needlelike CsBr:Eu x-ray storage phosphor plates exhibit an excellent sensitivity as expressed by their photostimulated luminescence (PSL) intensity and have ever growing applications in medical radiography. An earlier electron paramagnetic resonance (EPR) study revealed spectra due to a Eu2+ center with axial <100> symmetry. In this work, its EPR intensity is shown to exhibit a linear correlation with the PSL intensity and the sensitivity of the plates. It can thus be expected that the structural information retrieved from EPR and related techniques may substantially contribute to the understanding of the physics behind the writing and reading processes in the phosphor. [ABSTRACT FROM AUTHOR]

A combination of capacitance-voltage and lifetime decay measurements is used to show that corona biasing of silicon oxidized samples results in the generation of additional interface defects and an increase in surface recombination. The onset of interface degradation occurs at relatively low electric fields, estimated to be less than ∼+/-1.2 MV/cm. The majority of the defects generated by corona biasing can be removed by a short annealing at 400 °C. The results are consistent with the hypothesis that atomic hydrogen is chiefly responsible for the observed degradation. Corona biasing, even at low electric fields, cannot be relied on as a noninvasive characterization tool. [ABSTRACT FROM AUTHOR]

Zinc oxide crystals grown by the seeded chemical vapor transport method have been annealed in zinc vapor at 1100 °C for 30 min. These thermochemical reduction treatments produce a deep red coloration in the crystals and increase their n-type electrical conductivity. Electron paramagnetic resonance (EPR), optical absorption, and Hall measurements were used to monitor changes in the crystals. After an anneal, an intense optical absorption band is present that extends from the band edge out to approximately 550 nm, and the EPR signal near g=1.96 (due to shallow donors and/or conduction-band electrons), the free-carrier absorption, and the Hall electron concentration are all larger. Hydrogen was not present during these anneals, thus leaving oxygen vacancies and zinc interstitials as candidates for the added donors. Neutral oxygen vacancies are produced at high temperature by the additive-coloration mechanism, and are responsible for the broad near-edge absorption band. The observed increase in the number of free carriers is a result of either (1) the formation of zinc interstitials or (2) having the ground state of the neutral oxygen vacancy near the conduction band. [ABSTRACT FROM AUTHOR]

Scanning tunneling microscopy and spectroscopy were used to investigate a variation of resonant electron tunneling peaks of C60 molecules placed on oxidized Si(100) surfaces that had different impurity profiles. C60-derived resonance peak energy systematically varied depending on the position in the depletion region of lateral Si p-n junctions, indicating that the peak energy can be used for carrier density profiling. The peak energy was determined for uniformly doped substrates with a wide range of phosphorus and boron concentrations. The results were supported by a simple calculation of a one-dimensional tunnel diode. [ABSTRACT FROM AUTHOR]

We report millimeter-wave magneto-optical measurements on the high-spin molecule, Cr10(OMe)20(O2CCMe3)10. The dependence of the electron paramagnetic resonance as a function of orientation and temperature demonstrates that this compound behaves as a single molecule magnet, and exhibits one of the smallest zero-field splittings (D=-0.045±0.004 K) yet reported for such a system. [ABSTRACT FROM AUTHOR]

A three-dimensional (3D) electron spin resonance (ESR) microimaging system, operating in pulse mode at 9 GHz is presented. This microscope enables the acquisition of spatially resolved magnetic resonance signals of free-radicals in solid or liquid samples with a resolution of up to ∼3.5×7×11.4 μm in 20 min of acquisition. The detection sensitivity at room temperature is ∼1.2×109 spins/[Square_Root]Hz, which enables the measurement of ∼2×107 spins in each voxel after 60 min of acquisition. The resolution and detection sensitivity are the best obtained so far for ESR at ambient conditions of temperature and pressure. This ESR microscope can be employed in the investigation of a variety of samples in the fields of botany, life sciences, and materials science. [ABSTRACT FROM AUTHOR]

Electron spin resonance (ESR) measurements on (100)Si/SiOx/ZrO2 and (100)Si/Al2O3/ZrO2 stacks with nm-thick dielectric layers reveal, upon postdeposition oxidation (PDO) in the range of 650–800 °C, the appearance of various SiO2-characteristic defects, including E′ and EX centers and a 95-G doublet. These defects generally grow during PDO treatment, attesting to significant modification of the SiOx interlayer, and/or additional SiOx interlayer growth. The ESR results on E′ indicate that the SiOx interlayer formed in (100)Si/SiOx/ZrO2 is drastically inferior to standard thermal (100)Si/SiO2, exhibiting over one order of magnitude more O-deficiency centers. The (100)Si/Al2O3 system appears more robust in terms of SiOx interlayer growth, and has better interlayer properties. [ABSTRACT FROM AUTHOR]

Microcrystalline Ga[sub 1-x]Mn[sub x]N samples with Mn content up to x=0.005 were grown by an ammonothermal method and were studied using various techniques. X-ray diffraction showed characteristic diffraction lines for hexagonal GaN phase mixed with a small contribution (<5%) from the Mn[sub 3]N[sub 2] phase. Raman spectra exhibited characteristic peaks of pure GaN and modes that could be associated with Mn-induced lattice disorder. Electron spin resonance and magnetization measurements were consistent with the dominant Mn[sup 2+](d[sup 5]) configuration of spin S=5/2 which is responsible for the observed paramagnetic behavior of the GaMnN material. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Room-temperature stable paramagnetic defects have been induced in hydrogenated amorphous silicon nitride films by exposure to sub-band-gap ultraviolet light. These defects are almost certainly trivalent silicon centers which can be completely annealed at temperatures higher than 250 °C. These defects seem similar in chemical origin to light-induced centers in hydrogenated amorphous silicon and defects in irradiated metal-oxide-semiconductor field-effect transistors. [ABSTRACT FROM AUTHOR]

Pure fused low-OH silica (Tetrasil SE) has been studied by electron spin resonance (ESR) after it had been irradiated by 50 MeV/amu oxygen and 43 MeV/amu krypton ions at the GANIL accelerator. Paramagnetic defects have been observed which are closely related to intrinsic defects formed by γ-ray irradiation in amorphous SiO2, such as the E’ center and the peroxy radical. ESR signatures of defects formed by heavy ions exhibit, however, specific features in comparison with those formed by other types of irradiation (γ/x rays, electrons, or neutrons). The density of defects increases faster than the energy loss, so that the production of defects by heavy ion irradiation cannot be described by the total energy deposit alone. This is consistent with previous studies of latent ion tracks in insulating minerals using small angle x-ray scattering and track etching techniques. [ABSTRACT FROM AUTHOR]