Observation of Electrically-Inactive Interstitials in Nb-Doped SrTiO sub(3)

Despite rapid recent progress, controlled dopant incorporation and attainment of high mobility in thin films of the prototypical complex oxide semiconductor SrTiO sub(3) remain problematic. Here, analytical scanning transmission electron microscopy is used to study the local atomic and electronic st...

Full description

Saved in:
Bibliographic Details
Published in:ACS nano 2013-05, Vol.7 (5), p.4487-4494-4487-4494
Main Authors: Jeong, Jong Seok, Ambwani, Palak, Jalan, Bharat, Leighton, Chris, Mkhoyan, KAndre
Format: Article
Language:English
Subjects:
Electronic structure
Electronics
Interstitials
Nanostructure
Niobium
Semiconductors
Single crystals
Strontium titanates
Thin films
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:Despite rapid recent progress, controlled dopant incorporation and attainment of high mobility in thin films of the prototypical complex oxide semiconductor SrTiO sub(3) remain problematic. Here, analytical scanning transmission electron microscopy is used to study the local atomic and electronic structure of Nb-doped SrTiO sub(3) both in ideally substitutionally doped bulk single crystals and epitaxial thin films. The films are deposited under conditions that would yield highly stoichiometric undoped SrTiO sub(3), but are nevertheless insulating. The Nb incorporation in such films was found to be highly inhomogeneous on nanoscopic length-scales, with large quantities of what we deduce to be interstitial Nb. Electron energy loss spectroscopy reveals changes in the electronic density of states in Nb-doped SrTiO sub(3) films compared to undoped SrTiO sub(3), but without the clear shift in the Fermi edge seen in bulk single crystal Nb-doped SrTiO sub(3). Analysis of atomic-resolution annular dark-field images allows us to conclude that the interstitial Nb is in the Nb super(0) state, confirming that it is electrically inactive. We argue that this approach should enable future work establishing the vitally needed relationships between synthesis/processing conditions and electronic properties of Nb-doped SrTiO sub(3) thin films.
ISSN:1936-0851
1936-086X
DOI:10.1021/nn401101y