Quasi-two-dimensional electron gas at the interface of γ-Al2O3/SrTiO3 heterostructures grown by atomic layer deposition
- Univ. of Texas, Austin, TX (United States)
- Case Western Reserve Univ., Cleveland, OH (United States)
- Arizona State Univ., Tempe, AZ (United States)
- IBM T.J. Watson Research Center, Yorktown Heights, NY (United States)
We report the formation of a quasi-two-dimensional electron gas (2-DEG) at the interface of γ-Al2O3/TiO2-terminated SrTiO3 (STO) grown by atomic layer deposition (ALD). The ALD growth of Al2O3 on STO(001) single crystal substrates was performed at temperatures in the range of 200–345 °C. Trimethylaluminum and water were used as co-reactants. In situ reflection high energy electron diffraction, ex situ x-ray diffraction, and ex situ cross-sectional transmission electron microscopy were used to determine the crystallinity of the Al2O3 films. As-deposited Al2O3 films grown above 300 °C were crystalline with the γ-Al2O3 phase. In situ x-ray photoelectron spectroscopy was used to characterize the Al2O3/STO interface, indicating that a Ti3+ feature in the Ti 2p spectrum of STO was formed after 2–3 ALD cycles of Al2O3 at 345 °C and even after the exposure to trimethylaluminum alone at 300 and 345 °C. The interface quasi-2-DEG is metallic and exhibits mobility values of ~4 and 3000 cm2 V–1 s–1 at room temperature and 15 K, respectively. The interfacial conductivity depended on the thickness of the Al2O3 layer. In conclusion, the Ti3+ signal originated from the near-interfacial region and vanished after annealing in an oxygen environment.
- Research Organization:
- Brookhaven National Lab. (BNL), Upton, NY (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), Basic Energy Sciences (BES)
- Grant/Contract Number:
- SC00112704; N00014-10-10489; FA9550-12-10494; FA9550-12-1-0441; AC02-98CH10886
- OSTI ID:
- 1354507
- Report Number(s):
- BNL-113024-2016-JA
- Journal Information:
- Journal of Applied Physics, Vol. 118, Issue 11; ISSN 0021-8979
- Publisher:
- American Institute of Physics (AIP)Copyright Statement
- Country of Publication:
- United States
- Language:
- English
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