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First-principles study of X/Bi2Te3(0001) surface (X = Ag, Ni, Ti)

Kaczkowski J, Jezierski A

Materials Science Poland

2008

Vol. 26, No. 4

939--845

The influence of Ag, Ni and Ti on the electronic properties of Bi2Te3 has been analysed. The relaxation of clean Bi2Te3(0001) surface and relaxation of silver, nickel and titanium on clean Bi2Te3(0001) surface have been studied using ab-initio density-functional techniques. STM images of surface, the total density of states and the band structure of bismuth telluride were determined by using the QuantumEspresso ab-initio simulation package based on pseudopotential method. The relaxation was performed on a 8×8×1 k-point mesh, whereas in the calculations of the density of states the 12×12×1 k-point mesh was used.

Use of vibronic phenomena in adsorption phase for developing of semiconductor gas sensors

Zaitsev V., Kebbecus B.

Materials Science

2002

Vol. 20, No. 3

29-36

Semiconductor sensor selectivity is of the most importance for environment monitoring. The surfach modifications and multi-sensor systems are widely used for the selectivity increasing in commercial sensors. The work presented is an experimental study aimed to show the use of fine vibrational phenomena on the semiconductor surface for the increase of the sensor selectivity. Our experiments showed that resonant vibrational energy transfer from the photoexcited adsorbed dye may occur if gas molecules have correspondent vibrational modes. This energy transfer controls both the luminescent signal from the dye and electrical response of the semiconductor substrate. The sensor selectivity in this case is due to the overlapping of rich vibrational spectra of the molecules. We have shown that isotopes can be distinguished from each other in this way since they have different vibrational frequencies. This could not be done with traditional 'chemiresistors'. Selective sensors for specific gas molecules could be produced in this way by depositing organic dye molecules on the semiconductor surface with vibrational modes 'tuned' to the vibrations of those gas molecules.