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Doping mechanisms able to populate low-dimensional systems by introducing a negligible defect concentration are essential for developing novel devices. In this context, Surface Transfer Doping (STD) offers promising perspectives because it promotes the inhomogeneous doping of a semiconductor by exchange carrier with dopants. These dopands ensure carriers, which are confined at the semiconductor surface due to the electrostatic potential established by charge separation with a minimal surface perturbation. This unconventional kind of doping seems to be the method of choice for manipulating conductivity of typical nano-materials as nanotubes (1-2) and a large diversity of pioneering systems in nanotechnology that exhibit still unexplored common features.
In comparison with high-speed electronic devices, 2D STD systems would be expected to suffer from an enhancement of long-range Coulomb interactions at similar carrier densities due to the absence of spacer layer. Consequently, their conducting behavior would critically depend on the balance between the disorder potential felt by carriers (3) and its screening(4), in a way that may exceed the frame of the standard screening theory of 2D systems.
The Si(111)V3xV3-Ag system arises here as an ideal candidate to test the strength of competing mechanisms. Bare Si(111)V3xV3-Ag interface is intrinsically semiconducting with an unoccupied surface state, which can be densely populated by STD with small amount of extra Ag atoms deposited on top, without perturbing its isotropic 2D conducting nature. Hence, the general aim of this work is to establish a basic frame to face further studies on the conducting properties of more sophisticated STD systems. In this presentation, we will analyze the origin and character of the mechanisms controlling the metallicity onset of Si(111)V3xV3-Ag as a function of doping, where the analytical calculations of the conductivity versus doping have been evaluated using recently published experimental angular resolved photoemission data.
1.- J. Kong et al., Science (287), 622 (2000).
2.- P. G. Collins et al. Science (287), 1801 (2000).
3.- A. Lewalle et al. PHys. Rev. B (66), 075324 (2002).
4.- S. Das Sarma and E. H. Hwang, PHys. Rev. B (69),195305 (2004).
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