Nanostructures on La-doped SrTiO3 surfaces

Abstract

SrTiO(3)(100) single crystals with high donor dopant concentrations (5 at% La) were annealed at 1000 degrees C for up to 150 h in ultrahigh vacuum (UHV). By applying scanning tunneling microscopy (STM) nanostructures are observed on top of the surface with typical diameters of 20 nm and typical heights of 8 nm. To characterize their electronic structure and chemical composition, the surface was analyzed by metastable impact electron spectroscopy (MIES), ultraviolet photoelectron spectroscopy (UPS), scanning tunneling spectroscopy (STS), and depth profiling Auger electron spectroscopy (AES). Investigations of the stoichiometry suggest that the secondary phases consist of LaTiO(3). We present a defect chemistry model which attempts to explain the observed effects.

Structural and Morphological Study of Ni Clusters Deposited on SrTiO₃ Surfaces Studied by UHV-TEM/STM

“…The concentration of oxygen vacancies are compensated either by an increase in dopant concentrations or by reducing the electron concentration in the form of Ti desorption. Bigger particles which are likely to be LaTiO x are found on that samples as has been reported before [19] which were accidentally annealed at higher temperatures.…”

“…Also, about 5 nm sized clusters are observed on STO surfaces during STM observation after annealing. Formation of small particles on annealed samples has been reported by many research groups [15][16][17][18][19]. The sizes and composition of these particles depend on substrate dopant types and concentrations, and annealing and quenching conditions.…”

Sr diffusion in undoped and La-doped SrTiO3single crystals under oxidizing conditions

“…Also, the formation of Ti 31 containing phases like Ti 2 O 3 or LaTiO 3 is observed. [22][23][24] Although the defect chemical model seems to be consistent, reliable experimental data for the crucial parameter of the system, the Sr diffusivity, is not yet available. Decades ago, an experimental study on Sr and Ti diffusion in undoped SrTiO 3 focussing on the dislocation dependence 25 was published, which was confined to a single temperature of 1875 1C and did also not address the dopant concentration dependency.…”

Strontium titanate surfaces

“…Various recipes for preparing a given surface are employed and each recipe depends on the system being used. Scanning tunnelling microscopy and LEED are invaluable tools in discovering new surface structures and morphologies (further examples include results in Refs [128][129][130]…”