Analysis of high-index Si(001) surfaces by reflectance difference spectroscopy

Abstract

We report surface-induced optical anisotropy spectra of high-index Si(115), (114), and (113) surfaces obtained using reflectance difference spectroscopy. Air-oxidized surfaces show sharp derivative-type features that are step-induced and located near the critical point energies of bulk Si, consistent with those of lower-index Si(001) surfaces. Clean reconstructed surfaces are characterized by a broad feature near 3 eV that tends to decrease in amplitude upon H exposure and a step-induced structure near the (E0′,E1) transition of bulk Si. In contrast, H exposure of Ge-covered surfaces tends to sharpen and enhance lower-energy structures. The derivative-type features located near the bulk critical point energies of Si can be described in terms of electronic states localized by the finite penetration depth of light.

Optical and Electronic Anisotropy of a π-Conjugated Molecular Monolayer on the Silicon(001) Surface

“…Previous studies have likewise observed the 4.2 eV peak, and have shown that it inverts in sign with increasing miscut angle. 23 Our data indicates that although this feature is mildly positive on the clean surface, it is strongly negative after dosing with either of the molecules investigated here. It appears that this feature may be more pronounced on our chemically modifed samples than on the previously studied high-index samples.…”

“…18,22,28 There are a number of bulk and surface effects that contribute to the spectrum, and the relative importance of these has been subject of some debate. 12-14, [16][17][18][21][22][23][24][25][28][29][30]58,59 The most pronounced features are usually seen near the bulk critical point energies associated with transitions between valence and conduction bands within the bulk crystal. For silicon, the (E o ′,E 1 ) and E 2 critical point energies are located at 3.4 and 4.3 eV.…”

“…Our spectra, such as in Figure 3, are very similar to those reported previously by other groups. 11, 16,18,23,28,29,31,58 In all cases, the clean surface gives rise to a negative peak at 3.0 eV, a small derivative-like structure near 3.4 eV, and a positive peak at ∼4.2 eV. Since the sign of the peaks is indicative of orientation at the surface, the broad negative feature at 3.0 eV indicates lower reflectivity along the [11 h0] crystallographic direction, parallel to both the dimer bond and the step edge.…”

“…9,10 Since bulk silicon is symmetric, measurement of the optical properties using polarized light can then be used to characterize the optical response of the near-surface region. 11,12 While this method has been applied previously to characterize the changes in optical properties of different surface reconstructions and the effects of atomic adsorbates, [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31] it has not been widely used to characterize the optical properties of organic molecules. [32][33][34][35][36] To use polarization spectroscopy on organic films, it is necessary to have organic layers that have a preferred orientation in the surface plane.…”

SiO 2 / Si interfaces on high-index surfaces: Re-evaluation of trap densities and characterization of bonding structures

“…It should also be pointed out that the data for the ͑110͒-just and ͑111͒just surfaces were missing in Ref. 5,[7][8][9][10][11] In addition, wet oxidation on the high-index surfaces has hardly been investigated, although wet oxidation is an effective method for fabricating nanowire MOS structures with little stress. More recently, detailed temperature dependence of D it for ͑001͒, ͑110͒, ͑111͒, and ͑115͒ surfaces were investigated by Vitkavage et al 6 Our literature survey indicated that very little is known about oxidation on ͑1n0͒-class surfaces.…”