GaN evaporation and enhanced diffusion of Ar during high-temperature ion implantation

GaN films were implanted with 150 keV Ar+ at temperatures up to 1100 °C to a dose of 3×1015 cm-2. Concentration profiles of Ar were measured by secondary ion mass spectroscopy and depth distributions of ion-induced damage were estimated from Rutherford backscattering/channeling spectra. No redistribution of Ar atoms was detected up to 700 °C. At 1000 °C a deep penetrating diffusion tail and a shift of the Ar peak to the surface were observed. At temperatures higher than 800 °C shift of the damage peak to the surface was also observed. We attributed the shift of the Ar peak and the damage peaks to evaporation of thin layer of GaN during high-temperature implantation and estimated its temperature dependence

Effect of nitrogen ion irradiation parameters on properties of nitrogen-containing carbon coatings prepared by pulsed vacuum arc deposition method

Studies of the effect of nitrogen ion irradiation on the structure and properties of nitrogenated amorphous carbon coatings prepared on polished sitall and silicon substrates by the pulsed vacuum arc deposition method are presented. The techniques used in the investigations were electron energy loss spectroscopy, Raman spectroscopy, and atomic force microscop

Electron transport in Tb- and Pr-based metallic glasses

Electrical resistivity measurements are reported on several metallic glasses based on Pr and Tb, and Ga and various transition metals as the glass formers. In general negative temperature coefficients were observed and these are discussed in terms of the extended Ziman theory and the tunneling or localization theory. Low temperature structure in the resistivity can be understood with the coherent exchange scattering model of Asomoza et al. Journal of Applied Physics is copyrighted by The American Institute of Physics

Approximating Mexican highways with slime mould

Plasmodium of Physarum polycephalum is a single cell visible by unaided eye. During its foraging behavior the cell spans spatially distributed sources of nutrients with a protoplasmic network. Geometrical structure of the protoplasmic networks allows the plasmodium to optimize transport of nutrients between remote parts of its body. Assuming major Mexican cities are sources of nutrients how much structure of Physarum protoplasmic network correspond to structure of Mexican Federal highway network? To find an answer undertook a series of laboratory experiments with living Physarum polycephalum. We represent geographical locations of major cities by oat flakes, place a piece of plasmodium in Mexico city area, record the plasmodium's foraging behavior and extract topology of nutrient transport networks. Results of our experiments show that the protoplasmic network formed by Physarum is isomorphic, subject to limitations imposed, to a network of principle highways. Ideas and results of the paper may contribute towards future developments in bio-inspired road planning

Silicon-Germanium Films Deposited by Low Frequency PE CVD: Effect of H2 and Ar Dilution

We have studied structure and electrical properties of Si{sub 1-Y}Ge{sub Y}:H films deposited by low frequency PE CVD over the entire composition range from Y=0 to Y=1. The deposition rate of the films and their structural and electrical properties were measured for various ratios of the germane/silane feed gases and with and without dilution by Ar and by H{sub 2}. Structure and composition was studied by Auger electron spectroscopy (AES), secondary ion mass spectroscopy (SIMS) and Fourier transform infrared (FTIR) spectroscopy. Surface morphology was characterized by atomic force microscopy (AFM). We found: (1) The deposition rate increased with Y maximizing at Y=1 without dilution. (2) The relative rate of Ge and Si incorporation is affected by dilution. (3) Hydrogen preferentially bonds to silicon. (4) Hydrogen content decreases for increasing Y. In addition, optical measurements showed that as Y goes for 0 to 1, the Fermi level moves from mid gap to the conduction band edge, i.e. the films become more n-type. No correlation was found between the pre-exponential and the activation energy of conductivity. The behavior of the conductivity {gamma}-factor suggests a local minimum in the density of states at E {approx} 0.33 eV for the films grown with or without H-dilution and E {approx} 0.25 eV for the films with Ar dilution

Quinine doped hybrid sol-gel coatings for wave guiding and optical applications

Pure and quinine doped silica coatings have been prepared over sodalime glasses. The coatings were consolidated at low temperature (range 60-180 A degrees C) preserving optical activity of quinine molecule. We designed a device to test the guiding properties of the coatings. We confirmed with this device that light injected in pure silica coatings is guided over distances of meters while quinine presence induces isotropic photoluminescence. With the combined use of both type of coatings, it is possible to design light guiding devices and illuminate regions in glass elements without electronic circuits

ON THE GROWTH FROM THE AMORPHOUS PHASE IN SEMICONDUCTORS

On développe un modèle de croissance d'une phase ordonnée basé sur la diffusion des lacunes thermiques produites à l'interface avec l'amorphe. Il fournit pour Ge et Si la dépendance exacte du taux de croissance pour les couches évaporées et les couches implantées avec la température, l'état de l'orientation cristallin, le dopage, l'ionisation et la nature des ions implantés.A model of growth based on the diffusion of thermally generated vacancies to the interface is developed which provides the exact dependence of the growth rate with temperature, crystalline orientation, doping, ionisation and nature of implanted ions in evaporated as well as implanted layers, for both Ge and Si

Transport properties of amorphous rare-earth alloys

Nous discutons divers aspects des propriétés de transport des alliages amorphes de terres rares : contributions de l'ordre magnétique à la résistivité, magnétorésistance et son anisotropie, anomalies logarithmiques de résistivité à basse température, effet Hall extraordinaire.We discuss several aspects of the transport properties of RE amorphous alloys : contributions from magnetic ordering to the resistivity, magnetoresistance and its anisotropy, low temperature resistivity anomalies, extraordinary Hall effect