Scanning tunnelling microscopy was used to produce atomic resolution images of the Nb-doped SrTiO3(001)-(√5 x √5)-R26.6° reconstruction and its precursor surfaces. Low-energy electron diffraction was used to identify the surface structure in combination with scanning tunnelling microscopic imaging. The (√5 x √5)-R26.6° reconstruction was observed to grow as an adlayer on top of the underlying terraces. The structure formation could be routinely detected by an increase in the crystal's electrical conductivity during ultra-high vacuum annealing at 1300C. This rise in conductivity occurred due to significant reduction of the crystal. Scanning electron microscopy on these samples showed small islands with a rectangular base separated by flat regions. Auger electron spectroscopy showed titanium enrichment, and strontium and oxygen depletion of the surface region. The islands seen in the scanning electron microscopic images were TiO crystals, as reported by Lee et alia (2005). The flat regions between the islands were composed of a Sr adlayer on the surface that was consistent with the (√5 x √5)-R26.6° adatom model of Kubo & Nazoye (2001). It was proposed that the TiO islands and the (√5 x √5)-R26.6° Sr adlayer reconstruction formed due to phase separation in the surface region of the crystal. This phase separation was driven by oxygen depletion which occurred during high-temperature ultra-high vacuum annealing of the sample.

SrTiO3(001)-(√5x√5)-R26.6° Reconstruction - a Surface Resulting from Phase Separation in a Reducing Environment. D.T.Newell, A.Harrison, F.Silly, M.R.Castell: Physical Review B, 2007, 75[20], 205429 (9pp)