Growth and properties of GdTiO3 films prepared by hybrid molecular beam epitaxy

Moetakef, Pouya; Ouellette, Daniel G.; Zhang, Jack; Cain, Tyler A.; Allen, S. J.; Stemmer, Susanne

doi:10.1016/j.jcrysgro.2012.06.052

Cited by 42 publications

(49 citation statements)

References 43 publications

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“…This raises the question of the origin of absorption with an onset around 0.7 eV observed in reflectivity measurements. [4][5][6] We attribute this onset to transitions between self-trapped holes and the LHB. 15 The presence of self-trapped holes in rare-earth titanates has been inferred from thermally activated ptype hopping conductivity.…”

Section: Discussionmentioning

confidence: 87%

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Determination of the Mott-Hubbard gap inGdTiO3

et al. 2015

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The band gaps of rare-earth titanates are commonly reported to be 0.2-0.7 eV. These values are based on optical reflectivity measurements, from which the onset of optical absorption is derived. Here we report experimental and theoretical results on GdTiO3 (GTO) indicating that the gap is significantly larger. Photoluminescence (PL) measurements show a strong peak near 1.8 eV, consistent with an observed onset in PL excitation (PLE) at about the same energy. First-principles calculations, based either on density functional theory (DFT) with a hybrid functional or on DFT+U , consistently show that the gap is close to 2 eV. We also propose an interpretation of the previously reported optical absorption spectra. Given the similarities in electronic structure between the rareearth titanates, our results for GTO have repercussions for the other members of the series. The results also affect the design of complex-oxide heterostructures involving these materials.

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Section: Discussionmentioning

confidence: 87%

“…Previous efforts to determine the Mott-Hubbard gap of GTO were based on optical absorption obtained by Kramers-Kronig analysis of reflectivity data on bulk crystals 4 or thin films grown on (LaAlO 3 ) 0.3 (Sr 2 AlTaO 6 ) 0.7 (LSAT), 5 and from transmission spectroscopy of films grown on SrLaGaO 4 .…”

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confidence: 99%

Determination of the Mott-Hubbard gap inGdTiO3

et al. 2015

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“…The STO/GTO system has been studied extensively [15][16][17][18][19][20][21][22][23][24][25][26], and the 2DEG here has been found to exhibit extremely high carrier densities and ferromagnetic effects, with both electrostatic and doping modulation being observed to change the carrier properties. The proposed explanation for the 2DEG creation can be found in a simple charge transfer picture [7,14,16].…”

Section: (Sto) and The Ferromagnetic Mott Insulator Gdtio 3 (Gto)mentioning

confidence: 99%

Energetic, spatial, and momentum character of the electronic structure at a buried interface: The two-dimensional electron gas between two metal oxides

Nemšák¹,

Conti²,

Gray³

et al. 2016

Phys. Rev. B

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The interfaces between two condensed phases often exhibit emergent physical properties that can lead to new physics and novel device applications and are the subject of intense study in many disciplines. We here apply experimental and theoretical techniques to the characterization of one such interesting interface system: the two-dimensional electron gas (2DEG) formed in multilayers consisting of SrTiO 3 (STO) and GdTiO 3 (GTO). This system has been the subject of multiple studies recently and shown to exhibit very high carrier charge densities and ferromagnetic effects, among other intriguing properties. We have studied a 2DEG-forming multilayer of the form [6 unit cells (u.c.) STO/3 u.c. of GTO] 20 using a unique array of photoemission techniques including soft and hard x-ray excitation, soft x-ray angle-resolved photoemission, core-level spectroscopy, resonant excitation, and standing-wave effects, as well as theoretical calculations of the electronic structure at several levels and of the actual photoemission process. Standing-wave measurements below and above a strong resonance have been exploited as a powerful method for studying the 2DEG depth distribution. We have thus characterized the spatial and momentum properties of this 2DEG in detail, determining via depth-distribution measurements that it is spread throughout the 6 u.c. layer of STO and measuring the momentum dispersion of its states. The experimental results are supported in several ways by theory, leading to a much more complete picture of the nature of this 2DEG and suggesting that oxygen vacancies are not the origin of it. Similar multitechnique photoemission studies of such states at buried interfaces, combined with comparable theory, will be a very fruitful future approach for exploring and modifying the fascinating world of buried-interface physics and chemistry.

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“…Coherently strained SrTiO 3 and GdTiO 3 layers were grown on (001) ðLa 0:3 Sr 0:7 ÞðAl 0:65 Ta 0:35 ÞO 3 (LSAT), as described elsewhere [21]. Figure 1(a) shows a schematic of the sample.…”

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confidence: 99%

“…The preferred orientation for GdTiO 3 on LSAT is ð110Þ o kð001Þ c , where the subscripts indicate the orthorhombic or cubic unit cells, respectively [21]. Orientation variants that are related by a 90 rotation about ½001 c are expected [25,26]; see Fig.…”

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confidence: 99%