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Both amorphous and liquid As2Se3 exhibit fast decrease of optical transmittance under a nanosecond pulsed laser excitation. This light-induced effect is called fast photodarkening (PD). After the cessation of excitation (one shot), the PD recovers within 0.1 s, but remains in a wide time domain from 10–7 to 10–2 s. Dynamic responses of the PD-recovery are studied through the autocorrelation function (ACF) in time domain and the power spectrum (PS) in frequency domain. The first zero-crossing time in the ACF, τ0, a measure of decay time in the relaxation process, is scaled with the time interval of the original measured data, tm, with the relationship, τ0 ∝ tmγ (γ ~ 1.0) in both the amorphous and liquid states. The PS is described by 1/fα (α = 0.8–0.9). Both the ACF and PS results indicate that the structural relaxation of the As–Se network occurs with similar decay processes in "any" time region, which can be inferred to have fractal nature in time domain. [ABSTRACT FROM AUTHOR]

The frequency-dependent electrical conductivity of sputtered and glow-discharge amorphous silicon-nitrogen alloy films was investigated. The results showed that the introduction of hydrogen into the material resulted in decreased ac loss, indicating that hydrogenation reduces ac-loss centers. In glow discharge films, superlinear frequency dependent conductivity decreased with the temperature.

The dependence of impedance spectra on temperature and sample thickness are analyzed for AgAsS2 as a case example. Using the scaling properties of complex conductivity with thickness and temperature, we discuss the bulk and interfacial properties of the materials. Important physical parameters such as the number of mobile ions, diffusion coefficient in the bulk, and interface are deduced. The influence of the thickness of the sample on conductivity behavior is also discussed. A significant electrode polarization effect is observed even for a low number of localized (accumulated) ions (≈2×1017 cm-3) near the interface, which is significantly lower than the number of mobile ions (≈8×1021 cm-3) in this test material. The presented analytical method can be widely applied to potentially important ionic conducting systems. [ABSTRACT FROM AUTHOR]

The article discusses the dynamics of photoinduced defect creations (PDC) in amorphous chalcogenides, which is described by the stretched exponential function (SEF), while the well known photodarkening (PD) and photoinduced volume expansion (PVE) are governed only by the exponential function. It is shown that the exponential distribution of the thermal activation barrier produces the SEF in PDC, suggesting that thermal energy, as well as photon energy, is incorporated in PDC mechanisms. The differences in dynamics among three major photoinduced effects (PD, PVE, and PDC) in amorphous chalcogenides are now well understood. [ABSTRACT FROM AUTHOR]

Analysis of impedance spectra by a random-walk approach is proposed for the study of ionic-transport materials with a silver-containing chalcogenide glass as a case example. Through a full analysis of complex impedance spectra including the electrode polarization effect, some important physical parameters, such as the number of mobile ions in bulk and interface regions, the diffusion coefficient, etc., are extracted without using the conventional equivalent electric circuit analysis. A detailed discussion on electrode polarization, which is highly dependent on signal amplitude, is also presented. [ABSTRACT FROM AUTHOR]

The origin of a power-law correlation between ionic conductivity and cation-contents, found commonly in oxide and chalcogenide glasses, is discussed using the concept of configuration entropy. It is suggested that power-law dependence is primarily attributed to an increase in configuration entropy with mixing cation components into glasses. This effect reduces the potential barrier height to be surmounted by mobile ions, which results in a higher diffusion coefficient (and hence conductivity). The origin of anomalous pre-exponential factors of diffusion coefficient and conductivity can be interpreted in terms of the present context. [ABSTRACT FROM AUTHOR]

Hartree–Fock ab initio Raman spectra calculations and Raman spectroscopic measurements were carried out on amorphous selenium in order to identify the characteristic vibrational mode due to sigma bonds. Variations in measured peak intensity were observed as a consequence of band gap light illumination. Based on our previous theoretical investigations we originate these intensity variations from photoinduced covalent bond breaking. [ABSTRACT FROM AUTHOR]

Presents information on a study which described the frequency-dependent conductivity of amorphous silicon nitride films. Methods; Results; Discussion.