Arrhenius Plot Method Research Articles

Determination of parameters of deep level defects from numerical fit of deep level transient spectroscopy spectra: Analysis of accuracy and sensitivity to noise

The numerical fit of deep level transient spectroscopy (DLTS) spectra, used primarily to analyze complex DLTS spectra, is evaluated in terms of the accuracy of measuring deep levels and the sensitivity to noise. It is shown that by using numerical fit of DLTS spectra, the uncertainties in the emission activation energy and the capture cross section of deep level defects can be improved by three to four times over the standard Arrhenius plot method. Two modifications of the fitting procedure are tested: a fit of a DLTS spectrum using one rate window, and a simultaneous fit using five different rate windows. It is shown that simultaneous fit of spectra using different rate windows is significantly more accurate, has noticeably larger convergence radius for the initial values of parameters, and is less sensitive to noise. The advantages of the fitting routine are demonstrated on experimentally obtained noisy DLTS spectra.

A kinetic study of coal reject-derived char activation with CO 2, H 2O, and air

Activation reactions of coal reject-derived char (CRC) with CO 2, H 2O, and air are experimentally studied using a TGA technique. The experimental kinetic data are treated via kinetic data unification based on the half-time, and the intrinsic rate constants are extracted by the modified Arrhenius plot method. The effect of structural evolution on the overall rate changes is modelled with a modified random pore model and percolation model taking into account the ash content of the coal reject char. It is found that the relative reaction rates for the reaction pairs CO 2—CRC, H 2O—CRC and air-CRC are at an increasing order of sequence at a given temperature. The effect of gaseous pressure on the reaction rate is shown to be significant for CO 2—CRC and H 2O—CRC reactions. It has shown that both models can predict well the maximum rate and the conversion at which the maximum rate occurs. The agreement between the data and model predictions are generally good for H 2O—CRC and CO 2—CRC reactions, but not satisfactory for air oxidation. The model fitting also showed that the percolation model, taking into account the closed pore evolution, predicts the initial rate better than the modified random pore model.

A new method of analysis of DLTS-spectra

We propose a new algorithm to obtain the energy and the capture cross section of a deep trap in the band gap of a semiconductor from deep-level transient spectroscopy (DLTS) measurements. This numerical method requires only a single temperature cycle with a fixed rate window for data acquisition. It is capable to resolve DLTS signals with a shoulder, generated by two trap levels. Experiments with Schottky barrier diodes onn-GaAs demonstrate the contribution of a second trap to the EL6 level in GaAs and the superior reliability in cases of non-negligible resistivity of the back-contacts compared to conventional Arrhenius plot method.

Departures from linearity in Arrhenius plots of vacancy concentration

Relations between intrinsic thermodynamic functions of lattice vacancies are derived and are shown to parallel the standard thermodynamic identities valid for reversible changes of a closed, one-component phase. The straight-line Arrhenius plot method of determining enthalpies and entropies of formation is critically examined. For gold, silver and copper the inaccuracy introduced by this procedure is shown to be somewhat less than present experimental errors. Estimates are made of ( ∂ 2g ∂T 2 ) P and ( ∂ 2g ∂P 2 ) T where g is the Gibbs free energy of formation of a lattice vacancy. The maximum expected temperature and pressure variations of the enthalpy of formation are also estimated.