Temperature dependent EXAFS of InN

Abstract

The effect of temperature on the bonding environment of indium in an InN epilayer is studied using X‐ray absorption fine structure (EXAFS) spectroscopy. Shell‐by‐shell fitting of the EXAFS spectra reveals that, in the temperature range 80‐245 K, the change in the nearest neighbour distances is smaller than the uncertainty of the measurement. The Debye–Waller factor of the second neighbouring shell (In–In pair) shows strong temperature dependence. Fitting using the Einstein model yields an Einstein temperature equal to 193 K ± 5%. An alternative way of extracting information on the vibrational properties of the lattice is the simulation using the equation of motion method for the determination of the Debye–Waller factors. The used values of 120 N/m and 50 N/m of the force constants for In–N and In–In bond stretching, respectively, simulate satisfactory the spectra measured at five different temperatures in the range 80– 245 K. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Extended X-ray absorption fine structure study of the Er bonding in AlNO:Erx films with x ≤ 3.6%

“…21,22,23 For the point defects (Er substituting for Al or located in voids) the Debye temperature of AlN (835 K) was used. 24 Although the use of the Debye model works well for crystalline semiconductors, 25 it is not expected to be very accurate for the case of point defects.Therefore, only the positions of Fourier transform maxima can be used for comparison with the experimental data. It should be mentioned that the peak positions are not corrected for phase shifts, in either the theoretical or experimental spectra.…”

Bond thermal expansion and effective pair potential in crystals: the case of cadmium selenide

“…In the last two to three decades, extended x-ray absorption finestructure (EXAFS) spectroscopy has provided the possibility of obtaining original information on the local lattice dynamics of crystals, in particular thanks to accurate temperaturedependent EXAFS measurements [1][2][3][4][5][6]. The EXAFS signal of one coordination shell, in fact, samples a one-dimensional distribution ρ(r ) of interatomic distances which can be parameterized in terms of its cumulants, in which the first cumulant (C * 1 ) corresponds to the average value of the distribution, the second cumulant (C * 2 ) to the variance, the third cumulant (C * 3 ) measures the asymmetry and the fourth cumulant (C * 4 ) the flatness [7,8].…”

On the neglecting of higher-order cumulants in EXAFS data analysis

“…The importance of including higher-order cumulants in EXAFS analysis has been recognized in many works (Yokoyama et al, 1997;Soldo et al, 1998;Bus et al, 2006;Vaccari et al, 2007;Ahmed et al, 2009). Other groups recognized the asymmetry in the distance distribution, but did not use the cumulants beyond the second order (Diaz-Moreno et al, 1997;Berlier et al, 2002;Katsikini et al, 2008;Chu et al, 2009), with the consequence that the resulting errors in the fit parameters may have drastic effects on the EXAFS structural parameters. In some specific cases, the errors owing to the use of a Gaussian pair distribution have been estimated (Mobilio & Incoccia, 1984;Wei et al, 2000), with the result that it produces a significant error for the distance and coordination number.…”