Electronic structure of electron doped<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">SrTiO</mml:mi></mml:mrow><mml:mrow><mml:mn>3</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>:<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">SrTiO</mml:mi></mml:mrow><mml:mrow><mml:mn>3</mml:mn><mml:mi>−</mml:mi><mml:mi>δ</mml:mi></mml:mrow></mml:msu

Shanthi, N.; Sarma, D. D.

doi:10.1103/physrevb.57.2153

Cited by 208 publications

(126 citation statements)

References 19 publications

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“…38 Although, we do note that recent theoretical models of the LaAlO 3 /SrTiO 3 system point to the possibility of ferroelectric-like distortions in the LaAlO 3 layer as well. 2,39,40 In accord with previous observations however, 38 we suspect an interface dipole in SrTiO 3 , which in turn suggests that the electron gas lies not exactly at the interface, but burried one or a few monolayers within the SrTiO 3 . We thus speculate that the large influx of charge carriers into the potential well at the onset of Zener tunneling changes the local electric field and modifies the dipole strength, causing the observed hysteretic behaviour in CV .…”

supporting

confidence: 76%

“…1 shows a sketch of the expected band gaps and Fermi level E f of each component of the tunnel junction as measured in bulk. [1][2][3][4][5] The Fermi level for SrTiO 3 is drawn at 0.3 eV below the conduction band rather than the midgap to account for oxygen vacancy doping in real substrates. 2 We note that for LaAlO 3 thin films grown on SrTiO 3 , a bandgap of 6.5 eV has also been measured 6 and will be compared with the 5.6 eV bulk gap 4,5 (depicted in Supplementary Fig.…”

Section: Competing Financial Interestsmentioning

confidence: 99%

“…2 For instance, a layer of trapped screening charge forms the two dimensional electron gas that compensates a polarization mismatch at gallium nitride 3 and zinc oxide 4 based heterostructure interfaces. In insulating oxides, charge accumulation was observed at the interface between SrTiO 3 substrates with atomically precise surfaces and polar LaAlO 3 films.…”

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Built-in and induced polarization across LaAlO3/SrTiO3 heterojunctions

et al. 2010

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Ionic crystals terminated at oppositely charged polar surfaces are inherently unstable and expected to undergo surface reconstructions to maintain electrostatic stability. Essentially, an electric field that arises between oppositely charged atomic planes gives rise to a built-in potential that diverges with thickness. Here we present evidence of such a built-in potential across polar LaAlO3 thin films grown on SrTiO3 substrates, a system well known for the electron gas that forms at the interface. By performing tunneling measurements between the electron gas and metallic electrodes on LaAlO3 we measure a built-in electric field across LaAlO3 of 80.1 meV/Å. Additionally, capacitance measurements reveal the presence of an induced dipole moment across the heterostructure. We forsee use of the ionic built-in potential as an additional tuning parameter in both existing and novel device architectures, especially as atomic control of oxide interfaces gains widespread momentum.As dictated by Maxwell's equations, the accumulation of screening charges at the boundary between dissimilar materials is one means 1 of ensuring a continuous electric displacement at the interface. 2 For instance, a layer of trapped screening charge forms the two dimensional electron gas that compensates a polarization mismatch at gallium nitride 3 and zinc oxide 4 based heterostructure interfaces. In insulating oxides, charge accumulation was observed at the interface between SrTiO 3 substrates with atomically precise surfaces and polar LaAlO 3 films. 5 LaAlO 3 thin films grown on singly terminated SrTiO 3 surfaces 6 comprise negatively charged AlO 2 and positively charged LaO end planes and are polar in the ionic limit. 1,7,8 When at least four unit cells (u.c.) of LaAlO 3 are deposited on TiO 2 terminated SrTiO 3 , an electron gas forms near the interface in SrTiO 3 . 5,9,10 It is often hypothesized that at a thickness of four u.c. the potential across LaAlO 3 exceeds the band gap of SrTiO 3 and electrons tunnel from the valence band of LaAlO 3 to the SrTiO 3 potential well, completely diminishing the potential across LaAlO 3 . 11 Thus within this picture, in the presence of an electron gas no field would be expected across the LaAlO 3 . However, if all the charge carriers do not lie precisely at the interface or have an extrinsic (oxygen vacancies 12 or cation doping 13 ) origin, the LaAlO 3 potential will not be fully screened and can thus be probed. 14 Alternatively, the precise band alignment between the LaAlO 3 and SrTiO 3 will also determine the strength of the residual fields in the LaAlO 3 . 15 Addressing this issue by determining the existence of an uncompensated built-in potential in LaAlO 3 is central to understanding the true nature of the polar LaAlO 3 /SrTiO 3 interface.We probe the potential landscape across the LaAlO 3 and the interface region in SrTiO 3 by employing a typical metal-insulator-metal capacitor geometry such that the LaAlO 3 thin films form the dielectric layer sandwiched between evaporated metallic electrodes an...

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confidence: 76%

Section: Competing Financial Interestsmentioning

confidence: 99%

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Built-in and induced polarization across LaAlO3/SrTiO3 heterojunctions

et al. 2010

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“…In this limit, the transport is dominated by the oxygen vacancies, which ionize partially by localizing some of the electrons. Particularly, clusters of oxygen vacancies can act as localizing sites for such itinerant electrons 25,26 and clustering of vacancies is a common feature in PLD grown STO thin films grown under low pressures. 27 In the case of samples containing 15% La, the low temperature resistivity is best described by ρ ∼ sinh 2 ( 1 T ), characteristic of small polaron conduction.…”

Section: B Optical Spectroscopymentioning

confidence: 99%

Tuning the electronic effective mass in double-dopedSrTiO3

et al. 2011

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We elucidate the relationship between effective mass and carrier concentration in an oxide semiconductor controlled by a double doping mechanism. In this model oxide system, Sr1−xLaxTiO 3−δ , we can tune the effective mass ranging from 6-20me as a function of filling (carrier concentration) and the scattering mechanism, which are dependent on the chosen lanthanum and oxygen vacancy concentrations. The effective mass values were calculated from the Boltzmann transport equation using the measured transport properties of thin films of Sr1−xLaxTiO 3−δ . We show that the effective mass decreases with carrier concentration in this large band gap, low mobility oxide and this behavior is contrary to the tradional high mobility, small effective mass semiconductors.

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“…This is also supported by the work of Shanti and Sharma. 5 Unless authors fit lineshapes, linewidths, and especially temperature dependences to a polaron model, it remains speculative in our opinion to identify these features as due to polarons. In thin films, they may be entirely instrumental (contrary to the views in the Comment, the work of Kafadaryan cited and also of Ref.…”

mentioning

confidence: 99%