Surface-induced optical anisotropy of Si and Ge

Abstract

We compare surface-induced optical anisotropy spectra measured by reflectance difference/ anisotropy spectroscopy of Si and Ge. Our previous work on Si has shown that we can roughly distinguish two types of contributions to the optical response of surfaces: direct contributions involving surface state transitions and indirect contributions in which the surface modifies the bulk response. We demonstrate here that this view is valid for Ge as well. For Si the indirect surface contributions exhibit three extreme, basic line shapes, which are all related to the bulk dielectric function ⑀ b or nanostructured material. We demonstrate that this line shape analysis can also be applied to Ge.

In situ study of Ge(100) surfaces with tertiarybutylphosphine supply in vapor phase epitaxy ambient

“…While the shape of the spectrum is similar, the characteristic features at 1.9 eV and 3 eV present lower intensities and are slightly shifted towards lower energies. The spectrum is similar to RA spectra of UHV prepared vicinal Ge(100) surfaces [17,20], thus indicating a H-free surface. After exposure to TBP as described above, the RA spectrum of the Ge(100) surface at RT (Fig.…”

“…In crystals with cubic symmetry, the bulk does not contribute to the signal, so that RAS may be applied as a surface sensitive in situ monitoring tool [16]. Regarding Ge(100) surfaces, the clean [17] and monohydride terminated [5] vicinal Ge(100) surfaces exhibit characteristic RA spectra.…”

Si(100) versus Ge(100): Watching the interface formation for the growth of III-V-based solar cells on abundant substrates

“…The spectrum shows local maxima around the critical point energies of Ge(100) E1 and E1+Δ1 around 2.2 eV and E2 at 4.3 eV, and also two negative features, a narrow structure at 1.9 eV and a broad structure around 3 eV. The spectrum agrees very well to spectra of clean vicinal Ge(100) prepared in UHV [9], [10]. For Si(100) it was shown in [3] that the surface is terminated with monohydrides after processing in a H2 MOVPE-ambient, and it exhibits the characteristic RA spectrum related to a monohydride termination.…”

“…lower panel, red) taken at 168 eV show pronounced spot splitting along the [011] direction resulting from step edges at terraces of regular width. Half-ordered spots parallel to [0][1][2][3][4][5][6][7][8][9][10][11] originate in the (2×1)-like dimerized surface reconstruction and indicate a single-domain respectively highly preferential domain surface. In comparison, the LEED images do not reveal any differences in surface quality regarding domain ratio or spot intensities.…”

Optical in situ monitoring of hydrogen desorption from Ge(100) surfaces

“…1, we include the RA spectrum (dash-dotted thin gray line) of a UHV-prepared Ge(100) surface with 6 offcut for comparison. 27 If we shift and apply a scaling factor of 0.6 to the RA spectrum obtained after annealing in N 2 , the spectrum (dotted black line in Fig. 1) largely overlaps with the RA spectrum of the clean UHV-prepared Ge(100) surface.…”