TY - JOUR
T1 - Epitaxial strontium titanate films grown by atomic layer deposition on SrTiO3-buffered Si(001) substrates
AU - McDaniel, Martin D.
AU - Posadas, Agham
AU - Ngo, Thong Q.
AU - Dhamdhere, Ajit
AU - Smith, David
AU - Demkov, Alexander A.
AU - Ekerdt, John G.
N1 - Funding Information:
This work was supported by the National Science Foundation (Award DMR-1006725) and Office of Naval Research (Grant N000 14-10-1-0489). The authors acknowledge use of the facilities in the John M. Cowley Center for High Resolution Electron Microscopy at Arizona State University.
PY - 2013/1
Y1 - 2013/1
N2 - 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 SiOx 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 °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 °C for 30 min in moderate to high vacuum (10-6-10-9 Torr) removed the carbon species. Higher annealing temperatures (>275 °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° ± 0.06° 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 SiOx layer using a four-unit-cell STO buffer layer grown by MBE to serve as the surface template.
AB - 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 SiOx 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 °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 °C for 30 min in moderate to high vacuum (10-6-10-9 Torr) removed the carbon species. Higher annealing temperatures (>275 °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° ± 0.06° 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 SiOx layer using a four-unit-cell STO buffer layer grown by MBE to serve as the surface template.
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U2 - 10.1116/1.4770291
DO - 10.1116/1.4770291
M3 - Article
AN - SCOPUS:84871916064
SN - 0734-2101
VL - 31
JO - Journal of Vacuum Science and Technology A: Vacuum, Surfaces and Films
JF - Journal of Vacuum Science and Technology A: Vacuum, Surfaces and Films
IS - 1
M1 - 01A136
ER -