Historical remarks on surface Raman scattering
This chapter provides the recent developments using surface Raman scattering for the investigation of reconstructed surfaces.
Up to date, clean reconstructed surfaces of Si(111), Ge(001), and InP(110) have been investigated and surface phonon modes recorded by Raman spectroscopy. All these examples consider prototype semiconductor surfaces which have been investigated extensively in the 1980s and 1990s with respect to their atomic, electronic, and vibronic structures. Raman spectroscopy on surface phonons was firstly demonstrated at the end of 1990s on InP(110) [97H, 98H1, 98H2].
As far as adsorbate-terminated semiconductor surfaces are concerned, Raman data up to date have been recorded on Sb monolayer-terminated III–V(110) and metal adsorbate structures on Si and Ge surfaces. These structures represent examples for nonreactive metal–semiconductor interfaces, which form atomically sharp interfaces. The Sb/III–V(110) interface has been studied extensively in the 1980s and 1990s as a model system to understand interface structure and Schottky barrier on metal–semiconductor interfaces [96S]. The Sb monolayer forms a very well-ordered p(1x1) structure on III–V(110) and, due to its defined atomic structure, has been regarded as model interface structure and been intensively investigated by various experimental and theoretical methods.
More recently, metal adsorbates like In, Au, Pb, Sn, and Ag on Si and Ge have been attracting quite a lot of interest [01H1]. Metallic adlayers on semiconducting templates allow one to study electronic properties of low-dimensional systems, e.g., spin density waves and Peierls-driven metal insulator transitions [10W1]. In particular for those metal adsorbates which terminate the surface without inducing a strong chemical disruption of the semiconductor substrates, the surface structure is modified by the metal adsorbates, and metal nanolayers or metal nanowires are formed. Those systems exhibit interesting physical phenomena due to the reduction of dimensionality, (i.e., spin and charge density waves, Peierls transition, Luttinger liquid) and are under investigation as model systems for low-dimensional physical effects.