Donor-acceptor pair recombination in AgIn5S8 single crystals

Cataloged from PDF version of article.Photoluminescence (PL) spectra of AgIn5S8 single crystals were investigated in the 1.44-1.91 eV energy region and in the 10-170 K temperature range. The PL band was observed to be centered at 1.65 eV at 10 K and an excitation intensity of 0.97 W cm(-2). The redshift of this band with increasing temperature and with decreasing excitation intensity was observed. To explain the observed PL behavior, we propose that the emission is due to radiative recombination of a donor-acceptor pair, with an electron occupying a donor level located at 0.06 eV below the conduction band, and a hole occupying an acceptor level located at 0.32 eV above the valence band. (C) 1999 American Institute of Physics

Controlled damaging and repair of self-organized nanostructures by atom manipulation at room temperature

The possibility of controlled local demolition and repair of the recently discovered self-organized Pt nanowires on Ge(001) surfaces has been explored. These nanowires are composed of Pt dimers, which are found to be rather weakly bound to the underlying substrate. Using this property, we demonstrate the possibility of carrying the constituting dimers of the Pt nanowires from point to point with atomic precision at room temperature. Pt dimers can be picked-up in two configurations: (i) a horizontal configuration at the tip apex, resulting in double tip images and (ii) a configuration where the Pt dimer is attached to the side of the tip apex, resulting in well-defined atomically resolved images

Initial stages of Pt growth on Ge(001) studied by scanning tunneling microscopy and density functional theory

We have studied the initial stages of submonolayer Pt growth on the Ge(001). We have observed several stable and meta-stable adsorption configurations of Pt atoms at various temperatures. Calculations indicate relatively high binding energies of Pt atoms onto the Ge lattice, at different adsorption sites. Our results show that through-the-substrate bonding (concerted bonding) of two Pt atoms is more favored on Ge(001) surface then a direct Pt-Pt bond. Both our experiments and calculations indicate the breaking of Ge-Ge bonds on the surface in the vicinity of Pt adsorbates. We have also observed the spontaneous generation of 2 + 1 dimer vacancy defects at room temperature that cause the ejection of Ge atoms onto the surface. Finally we have studied the diffusion of Pt atoms into the bulk as a result of annealing and found out that they get trapped at subsurface sites

Temperature dependence of the step free energy

We have derived an expression for the step free energy that includes the usual thermally induced step meandering term and a vibrational entropy term related to the step edge atoms. The latter term results from the rèduced local coordination of the step atoms with respect to the terrace atoms and was introduced recently by Frenken and Stoltze as well as by Bonzel and Emundts. Additionally, we have added third and fourth terms that deal with the vibrational entropy contribution of the thermally generated step and kink atoms. At elevated temperatures the two latter vibrational entropy terms are of the same order of magnitude. Incorporation of these vibrational entropy terms results in a faster decrease of the step free energy with increasing temperature than anticipated previously. This enhanced temperature dependence of the step free energy results in a lower thermal roughening temperature of the facet