Notes: We analyzed the permeability measurement error of a low permeance thin film. We clarified that the noise voltage was excited by a current loop which is composed of the coaxial cable and the ground plane. The current loop should be removed for high sensitivity of the permeameter. The permeability of a high electrical resistivity film (CoFeHfO) has been demonstrated 1 MHz–3.5 GHz. © 1999 American Institute of Physics.

Notes: The electronic structure of YCo5 was calculated self-consistently by the scalar-relativistic linear muffin–tin orbital method using an atomic sphere approximation within the framework of the local spin density approximation. Using the spin–orbit interaction (SO) and orbital polarization term (OP), magnetocrystalline anisotropy energy due to 3d-electrons (3d-MAE) was calculated as a function of bandfilling q [Ea(q)]. At the Fermi level, the calculated Ea(q), including SO and OP, depended greatly on whether an f basis was used for Co. Just below the Fermi level, however, Ea(q) showed a large and c-axial 3d-MAE comparable with the experimental data. This behavior of Ea(q) is closely related to the calculated anisotropy of orbital magnetic moments and the shape of density of states of the 3d band. © 1996 American Institute of Physics.

Notes: Arsenic precipitation from a thin, 100-nm surface layer of GaAs grown at low temperature (LT) by molecular beam epitaxy is investigated. The precipitate depth distribution is examined for different rapid thermal annealing cycles. It is found that the precipitate distribution can tail a long distance into the underlying stoichiometric GaAs layer, depending on the peak annealing temperature. The distribution for an 800 °C anneal is virtually unaffected by a prior low temperature "soak'' at 600 °C, thus showing that the precipitation is insensitive to the initial point defect concentrations in this temperature range. The relevance of these results to the precipitation process and to the use of thin LT layers in device applications is discussed. © 1996 American Institute of Physics.

Notes: We have carried out an investigation of n+–p–p+ silicon diodes after irradiation with 1 MeV electrons and 10 MeV protons and subsequently after annealing. The effects upon the material and device parameters of samples irradiated with different particles are compared by expressing the particle fluence in terms of an effective absorbed dose of 1 MeV electrons. Although the spectrum of defects (observed by deep-level transient spectroscopy) introduced by 1 MeV electrons and 10 MeV protons was slightly different, the total defect introduction rate per effective 1 MeV electron dose was similar, as was the effect upon the device parameters. After irradiation with high fluences of electrons or protons, the effective carrier concentration in the base of the diodes was reduced dramatically, an effect referred to as "carrier removal." The effects of carrier removal upon the device parameters, in particular, the series resistance and saturation current, are discussed in detail. In addition, the relative importance of different radiation-induced defects is compared. © 1998 American Institute of Physics.

Notes: This paper discusses two new kinds of micromagnetoelastic devices made on silicon wafer whose function is to control the permeability of magnetostrictive soft magnetic thin films by voltage-controlled elastic strain. One is piezoelectric type and the other is electrostatic type. Structure, fabrication process, characteristics, and maximum possible output are discussed. The feasibility of these devices has been clarified although the rate of obtained permeability change was less than 1%. These device characteristics could be improved to 11% for piezoelectric type and to 80% for electrostatic type by the optimization of device dimensions and reduction of process damage to the magnetic film. © 1998 American Institute of Physics.

Notes: We have carried out modeling of the evolution of silicon solar cell performance following irradiation with high energy protons and electrons. Using the traditional semiempirical expression the solar cell output parameters of a given cell structure could be predicted for various particle energies by expressing the particle fluence as a displacement damage dose. We discuss the extent to which the evolution of different silicon solar cell structures in a radiation environment can be predicted using the software package PC-1D by taking account of the degradation of the minority carrier lifetime and majority carrier concentration in the cell. © 1997 American Institute of Physics.

Notes: We present a detailed study of n+(backward-slash)p(backward-slash)p+ silicon diodes irradiated with fluences of 1 MeV electrons high enough to cause device failure due to majority carrier removal. Capacitance–voltage (C–V) measurements were used to monitor the change in the carrier concentration of the base of the device as a function of radiation fluence. These were compared to the defect spectra in the same region obtained by deep level transient spectroscopy, and to the current–voltage characteristics of the device, both before and after annealing. We observed the expected deep levels with activation energies of 0.18 and 0.36 eV, but the C–V results imply that other trap levels must play a more important role in the carrier removal process. © 1997 American Institute of Physics.

Notes: We present a new method to evaluate the photo-oxidative activity of sunscreening agents based on the photodynamic oxidation of uric acid. Uric acid was selected as the oxidant probe for its high reactivity to singlet oxygen and oxygen radicals, high sensitivity of detection using electrochemical (EC) techniques, low light absorptivity and high photochemical stability in the UVA/B region of interest, and stability to autoxidation. The method is demonstrated by the photodynamic oxidation of uric acid on co-irradiation with Rose Bengal, a highly efficient photosensitizing dye for the production of singlet oxygen (1O2). Using this assay we found that the relative photodynamic oxidation rates of UVB-absorbing sunscreens in 80% methanol on irradiation with 〉290 nm light decreased in the order 2-ethylhexyl 4-dimethylaminobenzoate (DMABA-2EH) ≫ 2-ethylhexyl 4-methoxycinnamate (MCA-2EH) and the experimental sunscreens, 1-(1,1-dimethylethyl)-3-octanoyl-4,4-dimethyl- 1,4,5,6,-tetrahydropyridine (ICI-319) and 1-(2-methylpropyl)-3-propionyl-4,4-dimethyl-1,4,5,6-tetrahydropyridine (ICI-855). The relative photodynamic oxidation rates of UVA-absorbing sunscreens decreased in the order 4-tert-butyl-4'-methoxydibenzoylmethane (BMDBM) and 4-(2-propyl)benzophenone (PB) 〉 2-hydroxy-4'-methoxy-benzophenone (HMB) and 2,2'-dihydroxy-4-methoxybenzophenone (DHMB). We have confirmed the photodynamic activity of DMABA-2EH for the production of singlet oxygen (1O2) using electron paramagnetic resonance (EPR) spectroscopy and the reagent 2,2,6,6-tetramethyl-4-piperidone (4-oxo-TEMP). We failed to detect the photodynamic production of the oxyradicals, superoxide (O2.-) and hydroxyl radical (HO.) using N-tert-butyl-a-phenylnitrone (PBN) and 5,5-dimethyl-1-pyrrolidine-1-oxide (DMPO) as a result of photochemical interference caused by these spin-trapping reagents. The uric acid photo-oxidation assay was also used to compare the photodynamic reactivity of light-reflective, microfine oxides TiO2, ZnO and ZrO2 suspended in aqueous 80% methanol. All of the microfine oxides (uncoated) showed greater photodynamic reactivity in equimolar dispersion than did any of the organic UVA- and UVB-absorbing sunscreens in homogeneous solution. In this assay the photodynamic oxidation rates for the microfine oxides decreased in the order ZnO ≫ TiO2 (anatase) 〉 ZrO2 〉 TiO2 (rutile). Resume Nous presentons un nouveau procede d'evaluation de l'activite photooxydante d'agents pour ecrans solaires base sur l'oxydation photodynamique de l'acide urique. L'acide urique a ete choisi comme test a l'oxydation en raison de sa forte reactivite a l'oxygene singulet et aux radicaux oxygene, sa haute sensibilite a la detection par les techniques electrochimiques (EC), sa faible capacite d'absorption de la lumiere, sa stabilite photochimique elevee dans le domaine UVA/UVB concerne, et sa stabilite a l'autooxydation. La demonstration du procede est effectuee au travers de l'oxydation photodynamique de l'acide urique co-irradie avec du Rose du Bengale, colorant phosensibilisateur tres efficace pour generer de l'oxygene singulet (1O2). En mettant ce test en oeuvre nous avons trouve que les vitesses relatives d'oxydation photodynamique d'ecrans solaires aux UVB dans due methanol a 80%, irradies avec une lumiere 〉 290nm, diminuent dans l'ordre: 2-ethylhexyl 4-dimethylamino-benzoate (DMABA-2EH) ≫ 2-ethylhexyl 4-methoxycinnamate (MCA-2EH) et les ecrans a l'essai: la 1-(1,1-dimethylethyl)-3-octanoyl-4,4-dimethyl-1,4,5,6-tetrahydopyridine (ICI-319) et la 1-(2-methylpropyl)-3-propionyl-4,4-dimethyl-1,4,5,6-tetrahydropyridine (ICI-855). les vitesses relatives d'oxydation photodynamique d'ecrans solaires aux UVA diminuent dans l'ordre: 4-tert-butyl-4'-methoxydibenzoylmethane (BMDBM) et 4-(2-propyl) benzophenone (PB) 〉 2-hydroxy-4'-methoxybenzophenone (HMB) et 2'2'-dihydroxy-4-methoxybenzophenone (DHMB). Nous avons confirme l'activite photdynamique du DMABA-2EH pour la production d'oxygene singulet (1O2) en utilisant la spectroscopie par resonance paramagnetique electronique et le reactif 2,2,6,6-tetramethyl-4-piperidone (4-oxo-TEMP). Nous n'avons pas pu detecter la production photodynamique des oxyradicaux du superoxyde (O2.) et du radical hydroxyle (HO.) a l'aide de la N-ter-butyl-a- phenylnitrone (PBN) en raison d'interferences photochimiques causees par ces reactifs spin-Bloquants. Le test de photooxydation de l'acide urique a aussi ete utilise pour comparer la reactivite photodynamique d'oxydes microfins reflechisseurs de lumiere TiO2, ZnO et ZrO2 en suspension dans du methanol aqueux a 80%. Tous ces oxydes microfins (non enrobes) ont montre une meilleure reactivite photodynamique en dispersion equimolaire que ne l'a fait aucun des ecrans solaires aux UVA et UVB en solution homogene. Lors de ce test les vitesses d'oxydation photodynamique des oxydes microfins ont diminue dans l'ordre ZnO ≫ TiO2 (anatase) 〉 ZrO2 〉 TiO2 (rutile).

Notes: Lateral patterning of arsenic precipitates in GaAs is reported. The positions of near-surface precipitates in a GaAs layer grown by molecular beam epitaxy at low temperature are controlled by InGaAs stressors 45 nm in width covered by a SiO2 film. The stressors form a surface grating which governs the precipitate position by modulating the strain in the GaAs near the surface. Electron microscopy clearly reveals the formation of precipitates about 15 nm in diameter aligned with the stressors at a depth of ∼50 nm. It is suggested that this capability to control the position of nanometer-size metallic particles within a semiconductor could open up new possibilities for novel devices. © 1995 American Institute of Physics.

Notes: A process for the patterned self-assembly of nanometer-scale particles within a solid is described. The process uses crystal strain and composition to guide the formation of arsenic precipitates in GaAs-based epitaxial layers grown at low temperature by molecular beam epitaxy. The lateral particle position is controlled by the strain produced by a surface stress structure while the vertical position is controlled by the epitaxial layer composition. Arsenic particles ∼16-nm in diameter are fabricated in one-dimensional arrays with a 23-nm edge-to-edge particle spacing at a depth of 45 nm below stressors 200 nm in width, thereby demonstrating this technique. © 1996 American Institute of Physics.