Epitaxial strontium titanate films grown by atomic layer deposition on SrTiO{sub 3}-buffered Si(001) substrates

Journal Article · Tue Jan 15 00:00:00 EST 2013 · Journal of Vacuum Science and Technology. A, Vacuum, Surfaces and Films

DOI:https://doi.org/10.1116/1.4770291· OSTI ID:22099155

McDaniel, Martin D.; Posadas, Agham; Ngo, Thong Q.; Dhamdhere, Ajit; Smith, David J.; Demkov, Alexander A.; Ekerdt, John G. ^[1]

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1. Department of Chemical Engineering, University of Texas at Austin, 1 University Station C0400, Austin, Texas 78712 (United States)

Epitaxial strontium titanate (STO) films have been grown by atomic layer deposition (ALD) on Si(001) substrates with a thin STO buffer layer grown by molecular beam epitaxy (MBE). Four unit cells of STO grown by MBE serve as the surface template for ALD growth. The STO films grown by ALD are crystalline as-deposited with minimal, if any, amorphous SiO{sub x} layer at the STO-Si interface. The growth of STO was achieved using bis(triisopropylcyclopentadienyl)-strontium, titanium tetraisopropoxide, and water as the coreactants at a substrate temperature of 250 Degree-Sign C. In situ x-ray photoelectron spectroscopy (XPS) analysis revealed that the ALD process did not induce additional Si-O bonding at the STO-Si interface. Postdeposition XPS analysis also revealed sporadic carbon incorporation in the as-deposited films. However, annealing at a temperature of 250 Degree-Sign C for 30 min in moderate to high vacuum (10{sup -6}-10{sup -9} Torr) removed the carbon species. Higher annealing temperatures (>275 Degree-Sign C) gave rise to a small increase in Si-O bonding, as indicated by XPS, but no reduced Ti species were observed. X-ray diffraction revealed that the as-deposited STO films were c-axis oriented and fully crystalline. A rocking curve around the STO(002) reflection gave a full width at half maximum of 0.30 Degree-Sign {+-} 0.06 Degree-Sign for film thicknesses ranging from 5 to 25 nm. Cross-sectional transmission electron microscopy revealed that the STO films were continuous with conformal growth to the substrate and smooth interfaces between the ALD- and MBE-grown STO. Overall, the results indicate that thick, crystalline STO can be grown on Si(001) substrates by ALD with minimal formation of an amorphous SiO{sub x} layer using a four-unit-cell STO buffer layer grown by MBE to serve as the surface template.

• OSTI ID: 22099155
• Journal Information: Journal of Vacuum Science and Technology. A, Vacuum, Surfaces and Films, Vol. 31, Issue 1; Other Information: (c) 2013 American Vacuum Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 0734-2101
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ANNEALING
CHEMICAL BONDS
CRYSTAL GROWTH
DEPOSITION
MOLECULAR BEAM EPITAXY
ORGANIC COMPOUNDS
SILICON
SILICON OXIDES
STRONTIUM TITANATES
THICKNESS
THIN FILMS
TITANIUM COMPOUNDS
TRANSMISSION ELECTRON MICROSCOPY
WATER
X-RAY DIFFRACTION
X-RAY PHOTOELECTRON SPECTROSCOPY