SrTiO3(001)−(5×5)−R26.6°reconstruction: A surface resulting from phase

Abstract

Scanning tunneling microscopy ͑STM͒ was used to produce atomic resolution images of the Nb-doped SrTiO 3 ͑001͒-͑ ͱ 5 ϫ ͱ 5͒-R26.6°reconstruction and its precursor surfaces. Low-energy electron diffraction was used to identify the surface structure in combination with the STM imaging. The ͑ ͱ 5 ϫ ͱ 5͒-R26.6°reconstruction was observed growing as an adlayer on top of the underlying terraces. The formation of this structure could routinely be detected by an increase in the crystal's electrical conductivity during ultrahigh vacuum ͑UHV͒ annealing at 1300°C. This rise in conductivity occurs due to significant reduction of the crystal. Scanning electron microscopy ͑SEM͒ 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 SEM images are TiO crystals, as reported by S. B. Lee et al. ͓Ultramicroscopy 104, 30 ͑2005͔͒. The flat regions between the islands are composed of a Sr adlayer on the surface that is consistent with the ͑ ͱ 5 ϫ ͱ 5͒-R26.6°adatom model of Kubo and Nazoye ͓Phys. Rev. Lett. 86, 1801 ͑2001͔͒. We propose that the TiO islands and the ͑ ͱ 5 ϫ ͱ 5͒-R26.6°Sr adlayer reconstruction form due to phase separation in the surface region of the crystal. This phase separation is driven by oxygen depletion which occurs during high-temperature UHV annealing of the sample.

Surface phase, morphology, and charge distribution transitions on vacuum and ambient annealedSrTiO3(100)

“…Transformations from one reconstruction to another are mainly governed by three parameters: temperature, annealing time, and the amount of oxygen offered during heating. [22,44,47,49] Understanding the possible phase trajectories is crucial to shed light on the thermodynamics and kinetics of these transformations.…”

Surface of Sputtered and Annealed Polar SrTiO3(111): TiOx-Rich (n × n) Reconstructions

“…This change in shape of the spectrum between 406 and 426 eV is due to varying oxidation states of the Ti. It has previously been shown that the characteristic peak shape of a Ti 4+ Auger peak has a main peak at 413 eV and a shoulder at 419 eV, 7,16 whereas the signature of a Ti 2+ species is an Auger spectrum with a main peak at 419 eV and a shoulder at 413 eV. Hence, the (6 × 6) surface contains Ti 4+ as its dominant species, and the TiO (111)-(2 × 2) nanophase contains Ti 2+ in greatest concentration.…”

Morphological and Interfacial Studies of Fe Clusters on SrTiO₃(001) Surfaces

“…Depending on preparation methods and conditions, various surface reconstructions are known to be formed on STO (001) [22][23][24][25][26][27][28][29]. The influential factors are annealing temperature, ambient atmosphere particularly partial pressure of oxygen, surface sputtering condition before annealing, and so on.…”