Dresden 2006 – wissenschaftliches Programm
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MM: Metall- und Materialphysik
MM 29: Poster Session (SYNW)
MM 29.5: Poster
Donnerstag, 30. März 2006, 10:00–11:00, P4
Quantum size effects and phase transitions in bismuth nanowires — •R. Lovrincic1, T. W. Cornelius2, M. E. Toimil Molares2, S. Karim2, R. Neumann2, A. Pucci1, and G. Fahsold1 — 1Kirchhoff-Institut für Physik, Universität Heidelberg, INF 227, 69120 Heidelberg — 2Gesellschaft für Schwerionenforschung, Planckstr. 1, 64291 Darmstadt
We investigate the IR-optical properties of bismuth nanowires (Bi-NW). The wires were prepared at the GSI in Darmstadt by template directed growth of Bi in etched ion tracks [1] and then dispersed on silicon wafers for IR-spectroscopic measurements under UHV-conditions. When the wire diameter is in the same range as the de Broglie wavelength of the conduction electrons, quantum size effects (QSE) occur and the energy bands split into subbands. As the electrons in Bi have a Fermi wavelenght of 40nm, the energy change due to QSE in Bi-NW is measurable for relatively thick wires [2]. We report on a shift of an absorption edge that is proportional to 1/d^2 while varying the diameter from 300 to 40nm. This blueshift is attributed to an increasing direct band gap. In addition we studied the thermal stability of these NW. During heating up, a strong jump in IR-transmission occurred which can clearly be attributed to the semimetal-metal transition at the melting point of bismuth. While cooling down, this jump occurred at a 100K lower temperature which can be explained within nucleation theory.
References
[1] T. W. Cornelius et al., Nanotechnology 16 (2005), 246. [2]Y.-M Lin et al., Phys. Rev. B. 62 (2000), 4610