Electron spin resonance signature of the oxygen vacancy in HfO 2

The oxygen vacancy has been inferred to be the critical defect in HfO 2, responsible for charge trapping, gate threshold voltage instability, and Fermi level pinning for high work function gates, but it has never been conclusively identified. Here, the electron spin resonance g tensor parameters of the oxygen vacancy are calculated, using methods that do not over-estimate the delocalization of the defect wave function, to be g xx = 1.918, g yy = 1.926, g zz = 1.944, and are consistent with an observed spectrum. The defect undergoes a symmetry lowering polaron distortion to be localized mainly on a single adjacent Hf ion. © 2012 American Institute of Physics.

Quantum trajectory analysis for electrical detection of single-electron spin resonance

A Monte Carlo simulation on the basis of quantum trajectory approach is carried out for the measurement dynamics of a single-electron spin resonance. The measured electron, which is confined in either a quantum dot or a defect trap, is tunnel coupled to a side reservoir and continuously monitored by a mesoscopic detector. The simulation not only recovers the observed telegraphic signal of detector current, but also predicts unique features in the output power spectrum which are associated with electron dynamics in different regimes.

Distinguishing the sources of Asian dust based on electron spin resonance signal intensity and crystallinity of quartz

IEECAS SKLLQG

Long lasting phosphorescence, thermoluminescence and electron spin resonance property of Mn2+ activated ZnO-Al2O3SiO2 ceramic

The long lasting phosphorescence (LLP) phenomenon in Mn2+-doped ceramic based on ZnO-Al2O3-SiO2 (ZASM) is observed. After irradiation by a UVP standard mercury lamp peaking at 254 nm with a power of 0.6 mW/cm(2) for 15 min, the ceramic sample emits a bright green light peaking at 519 nm, which can be seen in the dark even 15 h after the removal of UVP standard mercury lamp by the naked eyes whose limit of light perception is 0.32 mcd/m(2). The initial afterglow intensity reaches about 1900 mcd/m(2), and the color coordinate (X, Y) is (0.2280, 0.5767) at about 10 s after stopping irradiation. The thermoluminescence (TL) spectra show that there are at least three kinds of trap centers with different trap levels while electron spin resonance (ESR) spectra indicate that there are electron- and hole-trapping centers induced after irradiation by a UVP standard mercury lamp. Based on these measurements, the LLP is considered to be due to the recombination of electrons and holes at trapping centers with different levels, which are firstly thermally released back to Mn2+ and then give rise to the bright green LLP at room temperature.

Study on the modified electrode of conducting polymers .3. Electron spin resonance characteristic of polypyrrole film electrode doped with heteropolyanions

The ESR of PPy films doped with Co (W2O7)(6)(10-) and CuW12O406- ions were reported and discussed. Results show that heteropolyanions not only play the role of neutralizing electricity in the PPy film, but also interact with the PPy molecular chain to form some adducts. The adducts affect the electronic structure of the PPy film and are unstable at more positive or more negative potentials. Dysonian ESR lineshape was recorded for the dry PPy film with CuW12O406- for the first time.

Electron spin resonance study of puff-resolved free radical formation in mainstream cigarette smoke

Puff-by-puff resolved gas phase free radicals were measured in mainstream smoke from Kentucky 2R4F reference cigarettes using ESR spectroscopy. Three spin-trapping reagents were evaluated: PBN, DMPO and DEPMPO. Two procedures were used to collect gas phase smoke on a puff-resolved basis: i) the accumulative mode, in which all the gas phase smoke up to a particular puff was bubbled into the trap (i.e., the 5th puff corresponded to the total smoke from the 1st to 5th puffs). In this case, after a specified puff, an aliquot of the spin trap was taken and analysed; or, ii) the individual mode, in which the spin trap was analysed and then replaced after each puff. Spin concentrations were determined by double-integration of the first derivative of the ESR signal. This was compared with the integrals of known standards using the TEMPO free radical. The radicals trapped with PBN were mainly carbon-centred, whilst the oxygen-centred radicals were identified with DMPO and DEPMPO. With each spin trap, the puff-resolved radical concentrations showed a characteristic pattern as a function of the puff number. Based on the spin concentrations, the DMPO and DEPMPO spin traps showed better trapping efficiencies than PBN. The implication for gas phase free radical analysis is that a range of different spin traps should be used to probe complex free radical reactions in cigarette smoke.

Characterization, photoluminescence, thermally stimulated luminescence and electron spin resonance studies of Eu(3+) doped LaAlO(3) phosphor

Europium-doped lanthanum aluminate (LaAlO(3)) powder was prepared by using a combustion method. The crystallization, surface morphology, specific surface area and luminescence properties of the samples have been investigated. Photoluminescence studies of Eu doped LaAlO(3) showed orange-reddish emission due to Eu(3+) ions. LaAlO(3):Eu(3+) exhibits one thermally stimulated luminescence (TSL) peak around 400 degrees C. Room temperature electron spin resonance spectrum of irradiated phosphor appears to be a superposition of two centres. One of them (centre I) with principal g-value 2.017 is identified as an O(-) centre while centre II with an isotropic g-value 2.011 is assigned to an F(+) centre (singly ionized oxygen vacancy). An additional defect centre observed during thermal annealing around 300 degrees C grows with the annealing temperature. This centre (assigned to F(+) centre) originates from an F-centre (oxygen vacancy with two electrons) and the F-centre along with the associated F(+) centre appear to correlate with the observed TSL peak in LaAlO(3):Eu(3+) phosphor. The activation energy for this peak has been determined to be 1.54 eV from TSL data. (C) 2010 Elsevier Masson SAS. All rights reserved.

Electron spin resonance of Gd3+ in the antiferromagnetic heavy fermion CeIn3 and its reference compound LaIn3

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Asymmetrical penetration of microwave in a conducting media and determination of microwave conductivity for very thin samples using electron spin resonance

Dyson's theory of conduction electron spin resonance (CESR) has been used in the limit d less than or equal to delta (d being the thickness of the sample and delta the skin depth of the microwave field) to obtain the microwave conductivity from the (A/B) ratio of the CESR absorbed power derivative. In this work we calculate the CESR absorbed power derivative using Kaplan's approach and show that the (A/B) ratio can be enhanced if asymmetrical penetration of microwave is used, which means that the microwave field enters into the sample from one of the faces. Therefore, the determination of the microwave conductivity from the (A/B) ratio of the CESR line can be performed for thinner samples. Experimentally, asymmetrical penetration can be obtained if one of the sample's faces is covered with a thin gold layer. The determination of microwave conductivity in conducting polymers films is among the possible applications of this method. (C) 2001 Elsevier B.V. Ltd. All rights reserved.