After ex situ etching with various solutions of hydrofluoric acid (HF) and ammonium fluoride (NH4F) Si(111) samples are transferred into ultrahigh vacuum with an ultrafast load‐lock and characterized by scanning tunneling microscopy (STM): Concentrated HF selectively removes any surface oxide and, thus chemically prepares the initially burried, isotropically rough Si/SiO2 interface while highly buffered HF (i.e., NH4F) attacks bulk silicon anisotropically. After a rapid homogenization of the chemical surface termination (HF: various hydrides, fluorine, ...) towards a perfect, unreconstructed monohydride phase, Si(111)‐(1×1):H, NH4F etching leads to a time‐dependent transformation of isotropic roughness into a pattern of triangular etch defects with monohydride steps perpendicular to <211≳ due to a preferential removal of lower‐coordinated atomic defect sites. A predominant atomic step structure due to sample miscut (vicinal surfaces with azimuth ≠<211≳) can oppose the anisotropic NH4F etching: At low st...

Anisotropic etching versus interaction of atomic steps: Scanning tunneling microscopy observations on HF/NH4F‐treated Si(111)

Defect analysis at surfaces with LEED or RHEED have so far been essentially restricted to steps or superstructure domains. Even if there are no superstructures, variations of the scattering factor influence the spot profile. With the now available high-resolution instruments more details of the spot profile may be observed. Therefore it will be discussed how a careful study of the spot profile at different energies may be used to analyze a surface with simultaneous steps and inhomogeneities. It will be shown how the asperity height is obtained without fitting parameters and how inhomogeneities are analyzed with respect to coverage and size distribution.

Electron diffraction at stepped homogeneous and inhomogeneous surfaces

http://w0.rz-berlin.mpg.de/hjfdb/pdf/184e.pdf

Metal deposition in adsorbate atmosphere: growth and decomposition of a palladium carbonyl-like species

The density of interfacial [111]Pb centers, i.e., 0Si≡Si3 defects with unpaired bond along [111], has been accurately determined by K‐band electron spin resonance at 4.3 K on (111)Si/SiO2 structures using various oxidation conditions. Reversible defect depassivation (dehydrogenation) has been monitored by post‐oxidation vacuum annealing in the temperature range 752–835 °C. It was found that the density of both ESR active and passivated Pb defects is (11.4±0.6)×1012 cm−2 on all (111)Si/SiO2 interfaces prepared by oxidation in dry O2 at 920–1000 °C. This number appears to be a natural constant predominantly set by the oxidation temperature; variations in oxidation oxygen pressure (1.5×10−5–840 Torr) and time have little influence. The Pb’s are found to account for all the fast interface states.

Maximum density of Pb centers at the (111) Si/SiO2 interface after vacuum anneal

http://w0.rz-berlin.mpg.de/hjfdb/pdf/160e.pdf

J. Wollschläger

Papers

Defects at the Si(111)/ SiO 2 interface investigated with low-energy electron diffraction