Dresden 2006 – scientific programme
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O: Oberflächenphysik
O 21: Phase transitions
O 21.3: Talk
Tuesday, March 28, 2006, 11:45–12:00, WIL C207
Thermal switching due to a surface phase transition. — •Justin Wells, Jesper Kallehauge, and Philip Hofmann — Institute for Storage Ring Facilities and iNano center, University of Aarhus, Denmark.
Temperature induced surface phase transitions such as charge density waves (CDWs) have recently been studied extensively because of the interesting basic physics of these quasi two dimensional systems. Although changes in surface electronic structure due to such phase transitions have been well studied, a direct influence on the physical properties appears not to have been measured.
We report on the surface conductivity of Si(111)+Ag(√3 × √3) as it undergoes a surface phase transition. A temperature dependent switching of the surface conductivity between ≈ 10−6 Ω−1 and 10−3 Ω−1 can be seen. The transition temperature is around 200 K, but small changes in the surface preparation can shift the transition temperature by at least 20 K
Such a strong conductivity change due to a surface phase transition has applications as an ultimately small thermal switch, with a switching temperature that can be controlled by the surface preparation.
The measurements of surface conductivity have been made under UHV conditions in our newly developed micro 4 point probe. As a demonstration of the instrument, Si(111) 7×7 has also been studied, and the surface and bulk conductivities are clearly distinguishable. This is confirmed by observing the effect of changing the bulk properties (by changing the doping) and changing the surface properties (by the adsorption of silver).