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

Restructuring of hex-Pt(100) under CO gas environments: formation of 2-D nanoclusters

The atomic-scale restructuring of hex-Pt(100) induced by carbon monoxide with a wide pressure range was studied with a newly designed chamber-in-chamber high-pressure STM and theoretical calculations. Both experimental and DFT calculation results show that CO molecules are bound to Pt nanoclusters through a tilted on-top configuration with a separation of {approx}3.7-4.1 {angstrom}. The phenomenon of restructuring of metal catalyst surfaces induced by adsorption, and in particular the formation of small metallic clusters suggests the importance of studying structures of catalyst surfaces under high pressure conditions for understanding catalytic mechanisms

Thin-film transistors based on poly, (3,3 '''-dialkyl-quarterthiophene) and zinc oxide nanowires with improved ambient stability

The ambient stability of thin-film transistors (TFTs) based on zinc oxide (ZnO) nanowires embedded in poly (3,3'''-dialkyl-quarterthiophene) was monitored through time dependence of electrical characteristics over a period of 16 months. The hybrid-based TFT showed an initial hole mobility in the linear regime of 4.2 x 10(-4) cm(2)/V s. After 16 months storage in ambient conditions (exposed to air, moisture, and light) the mobility decreased to 2.3 x 10(-5) cm(2)/V s. Comparatively the organic-based TFT lost total carrier mobility after one month storage making the hybrid-based TFTs more suitable for transistor applications when improved stability combined with structural flexibility are required. (C) 2011 American Institute of Physics. [doi:10.1063/1.3560982