Using Au 198 und Ag 110m as tracers the diffusion of gold and silver is measured in bulk samples of glassy As2Se3. In doped arsenic selenide the temperature dependence of the diffusion coefficient D obeys the following Arrhenius equations: DAg = 3 exp (−0.89 eV/kT) cm2/s; DAu = 6 exp (−1.15 eV/kT) cm2/s. Doping with Ge remains DAu and DAg unchanged, Cu doping markedly decreases the diffusion. The results are discussed with respect to the diffusion mechanism.
The migration of gold in amorphous arsenic selenide, influenced by an electric field, is investigated in the range 130 to 180°C by means of radioactive tracers. In order to evaluate the electromigration profiles, the exact solution of the Fick equation with drift term under the initial condition of a thin layer on a semi‐infinite is derived and applied. The displacement of the concentration peak yields the mobility and the charge of the migrating gold atoms: at 180°C 2.9 × 10−11 cm2/Vs and 1e, respectively. The deviations of the experimental diffusion profiles from the theoretical ones are discussed.
The electromigration of silver in bulk As2Se3 samples is studied. It is found that, by the electric field, the silver is drawn to the negative electrode. Using a thin silver film as initial condition in experiments at 180 °C pronounced peaks in the concentration distribution are found. From their position the mobility is obtained (μ(180 °C) = 1 × 10−8 cm2/Vs) and from this the charge of the silver atoms during jumping is calculated (q = (1.2 ± 0.2) e). At 120 °C the peaks are broadened, which is attributed to an alteration of the field distribution due to the migrating silver ions. For the activation energy of the mobility a value 0.8 eV is found. Consequences for the diffusion mechanism are discussed.
By means of a precision radiotracer‐sectioning technique, diffusion and electrodiffusion profiles of copper in amorphous AS2Se3 are measured between 120 and 180 °C. Fickian diffusion behaviour is found. From the D(T)‐dependence an interstitial‐like mechanism is proposed. Using a δ‐like Cu source the electrodiffusion profiles (EDP) show at low electric fields of ≈ 102 V/cm nearly ideal Gaussian shape from which the diffusion coefficient D (being equal to the “field‐free” value) and the mobility μ could be determined with high accuracy. Via the Nernst‐Einstein relation, the charge q of the migrating Cu species could be determined to (+ 1.0 ± 0.1) e for the whole temperature range ascertaining that the experimental q's are true ones. At electric fields of ⪆ 103 V/cm strong asymmetries in the EDP's occur which still remain unexplained.
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