Recent studies of oxide-semiconductor heterostructures using aberration-corrected scanning transmission electron microsc
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HsinWei Wu and Sirong Lu School of Engineering for Matter, Transport and Energy, Arizona State University, Tempe, AZ 85287-6106, USA
Toshihiro Aoki LeRoy Eyring Center for Solid State Science, Arizona State University, Tempe, AZ 85287-1704, USA
Patrick Ponath and Kurt Fredrickson Department of Physics, The University of Texas at Austin, Austin, TX 78712, USA
Martin D. McDaniel and Edward Lin Department of Chemical Engineering, The University of Texas at Austin, Austin, TX 78712, USA
Agham B. Posadas and Alexander A. Demkov Department of Physics, The University of Texas at Austin, Austin, TX 78712, USA
John Ekerdt Department of Chemical Engineering, The University of Texas at Austin, Austin, TX 78712, USA
Martha R. McCartney Department of Physics, Arizona State University, Tempe, AZ 85287-1504, USA (Received 25 April 2016; accepted 6 July 2016)
The integration of dissimilar materials is highly desirable for many different types of device applications but often challenging to achieve in practice. The unrivalled imaging capabilities of the aberration-corrected electron microscope enable enhanced insights to be gained into the atomic arrangements across heterostructured interfaces. This paper provides an overview of our recent observations of oxide-semiconductor heterostructures using aberration-corrected high-angle annular-dark-field and large-angle bright-field imaging modes. The perovskite oxides studied include strontium titanate, barium titanate, and strontium hafnate, which were grown on Si(001) and/or Ge(001) substrates using the techniques of molecular-beam epitaxy or atomic-layer deposition. The oxide layers displayed excellent crystallinity and sharp, abrupt interfaces were observed with no sign of any amorphous interfacial layers. The Ge(001) substrate surfaces invariably showed both 1 and 2 periodicity consistent with preservation of the 2 1 surface reconstruction following oxide growth. Overall, the results augur well for the future development of functional oxide-based devices integrated on semiconductor substrates. I. INTRODUCTION
The perovskite oxides have conductivities that vary from metallic to semiconducting to insulating, and they possess an extremely diverse range of optical, electronic, and magnetic properties that include ferroelectricity, ferromagnetism, piezoelectricity, and superconductivity.1,2 Integration of these oxides with semiconductors could open up many opportunities for novel device functionalities.3 These intriguing possibilities have garnered considerable attention during the past decade, especially given the relatively simple perovskite cubic structure and the
Contributing Editor: Thomas Walther a) Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2016.273
close in-plane lattice-matching with common semiconductors such as Si, Ge, and GaAs. However, perovskite oxides cannot be easily deposited directly onto semiconductor surfaces, mostly because of differences in the bonding of the two types of material. Moreover, oxidation of semic
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