Thermal Desorption of Deuterium from GaN(0001)

Abstract

AbstractThe recombinative desorption of deuterium from GaN(0001) has been investigated using temperature programmed desorption (TPD) with variable heating rates. With a heating rate of 1°C/s, molecular deuterium desorption peaks at 410 C in agreement with related previous work. However, the shape of the curve indicates a secondary peak at around 280°C which is merged into the lower temperature shoulder of the dominant peak. By changing linear heating rate from 0.05 C/s to 8°C/s desorption peak temperatures from 380°C to 570°C were observed. Fitting to a pseudo-first-order desorption model results in a hydrogen desorption barrier, Ed, from surfaceof 1.1eV and a pre exponential factor, n, of 2 x 106s-1. Both are below expected values and are assumed to be due to a variation of desorption barrier heights. If a typical pre-exponential factor of 1 x 1013s-1is assumed, reanalysis of the desorption data produce a desorption barrier of 2.0 eV, in agreement with the existence of the surface adsorption barrier at room temperature.