期刊
ACS NANO
卷 12, 期 2, 页码 1306-1312出版社
AMER CHEMICAL SOC
DOI: 10.1021/acsnano.7b07539
关键词
functional oxides; molecular beam epitaxy; SrTiO3 thin films; oxide electronics; ferroelectrics; strain engineering
类别
资金
- Department of Energy [DE-SC0012375]
- Penn State MRSEC Program [DMR-1420620]
- National Science Foundation [DMR-1352502]
- Division Of Materials Research
- Direct For Mathematical & Physical Scien [1352502] Funding Source: National Science Foundation
Strain engineering of thin films is a conventionally employed approach to enhance material properties and to energetically prefer ground states that would otherwise not be attainable. Controlling strain states in perovskite oxide thin films is usually accomplished through coherent epitaxy by using lattice-mismatched substrates with similar crystal structures. However, the limited choice of suitable oxide substrates makes certain strain states experimentally inaccessible and a continuous tuning impossible. Here, we report a strategy to continuously tune epitaxial strains in perovskite films grown on Si(001) by utilizing the large difference of thermal expansion coefficients between the film and the substrate. By establishing an adsorption-controlled growth window for SrTiO3 thin films on Si using hybrid molecular beam epitaxy, the magnitude of strain can be solely attributed to thermal expansion mismatch, which only depends on the difference between growth and room temperature. Second-harmonic generation measurements revealed that structure properties of SrTiO3 films could be tuned by this method using films with different strain states. Our work provides a strategy to generate continuous strain states in oxide/semiconductor pseudomorphic buffer structures that could help achieve desired material functionalities.
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