Nanostructured Nd 0.45 Sr 0.55 MnO 3 films grown on SrTiO 3 (110)
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To explore the relationships between microstructure and growth direction, metallic A-type antiferromagnetic and anisotropic magnetoresistant Nd0.45Sr0.55MnO3 (NSMO) thin films were grown on SrTiO3(110) by pulsed laser deposition method and characterized by (scanning) transmission electron microscopy. The interface between NSMO and SrTiO3 (110) is flat and sharp. The NSMO thin films exhibit a two-layered structure: a continuous perovskite layer epitaxially grown on the substrate followed by an epitaxially grown columnar nanostructure [Fig. 1(a)]. High-density stacking faults were found in the nanostructured layer with an in-plane translational displacement of 1/2a,111., accompanied by 1/2a[001] partial dislocations or (110) antiphase boundaries (APBs). These stacking faults terminate either at pores or in the grain matrix to eliminate (110) APBs. The formation mechanisms of the nanostructured NSMO films and the relevant stacking faults are discussed from the viewpoint of both film growth and specific substrate direction.
I. INTRODUCTION
Unconventional crystallographic orientations of perovskite substrates have garnered much attention recently for their potentially new functional interfaces.1 An exciting topological insulator originating from complex orbital order in transition metal perovskite oxide (111) heterostructures has been theoretically confirmed.2 It has also been found that [110]-oriented manganite epitaxial films are more promising to make magnetic tunnel junctions because of their resistance against electronic phase separation,3–5 which makes us more desirous to discover more intriguing effects as well as their corresponding crucial challenges.1 At present, perovskite oxide films grown on [001]-oriented substrates are controllable and becoming increasingly routine.1,6 However, for the potentially functional [110]- and [111]-oriented films, corresponding growth exploration is greatly lacking. Many challenges and/or unknown factors could affect the film growth, or some novel properties could be obtained for unanticipated device applications.1 For example, the polar state of different substrate surfaces may be different, and thus, the perovskite oxide film systems could be driven to form different types of functional interfaces.1,7 Meanwhile, the sharpness of the interface could be destroyed by these surface polar discontinuities.8 Moreover, the surface energy of (110) and (111) perovskite oxides is always higher than (001) perovskite oxides,9,10 and their surface reconstructions are fairly complex,11,12 which means that the growth mechanisms of perovskite films on (110) and (111) substrates could be relatively complicated. a)
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2012.416 1692
J. Mater. Res., Vol. 28, No. 13, Jul 14, 2013
http://journals.cambridge.org
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For colossal magnetoresistant Nd1xSrxMnO3/SrTiO3 films, the corresponding phase composition and physical properties are unusual when grown on SrTiO3(110). Bulklike behaviors were only observed in
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