Low-dimensional electron gas at semiconductor surfaces
I. Barkea, R. Bennewitza, J.N. Craina, S.C. Erwinb, A. Kirakosiana, J.L. McChesneya and F.J. Himpsela, , 1,
aDepartment of Physics, UW-Madison, 1150 University Ave., Madison, WI 53706, United States bNaval Research Laboratory, Washington DC 20375, United States Received 27 March 2007; accepted 8 April 2007. by E. Burstein. Available online 20 April 2007.
In recent years, it has become possible to create well-ordered semiconductor surfaces with metallic surface states by using self-assembly of metal atoms. Since these states lie in the band gap of the semiconductor, they completely decouple from the substrate. In addition to two-dimensional structures it is possible to obtain arrays of one-dimensional atomic chains, which may be viewed as the ultimate nanowires. The dimensionality can be varied systematically by using vicinal surfaces with variable step spacing. Angle-resolved photoemission and scanning tunnelling spectroscopy reveal surprising features, such as a fractional band filling, nanoscale phase separation into doped and undoped chain segments, and a spin-splitting at a non-magnetic surface. Prospects for one-dimensional electron gas physics in atomic chains are discussed.
Keywords: A. Semiconductors; B. Surfaces and interfaces; C. Scanning tunnelling microscopy; D. Photoelectron spectroscopy