Electron mobility in oxide heterostructures

Trier, Felix; Christensen, Dennis Valbjørn; Pryds, Nini

doi:10.1088/1361-6463/aac9aa

Cited by 51 publications

(50 citation statements)

References 140 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…SrTiO 3 has been the object of immense attention for over half a century owing to its multifunctional nature and popularity as a template for epitaxial growth of artificial nanostructures such as heterostructures, superlattices, and vertically aligned nanostructures. It is a classic example where a seemingly simple material gives rise to a range of interesting properties such as superconductivity, high electron mobility, ferromagnetism and 2D electron gases . In the multitude of the properties exhibited by SrTiO 3 , pyroelectricity, ferroelectricity, and piezoelectricity are markedly absent as these properties are symmetry prohibited in centrosymmetric crystal lattices.…”

mentioning

confidence: 99%

Surface Pyroelectricity in Cubic SrTiO₃

et al. 2019

Self Cite

View full text Add to dashboard Cite

material gives rise to a range of interesting properties such as superconductivity, [1] high electron mobility, [2,3] ferromagnetism [4,5] and 2D electron gases. [6] In the multitude of the properties exhibited by SrTiO 3 , pyroelectricity, ferroelectricity, and piezoelectricity are markedly absent as these properties are symmetry prohibited in centrosymmetric crystal lattices. The polar phase required for exhibiting these properties can, however, be induced artificially by modification of the lattice. Large biaxial strain, [7] light pulses, [8,9] and elemental substitutions [10] can convert SrTiO 3 into a ferroelectric material, whereas strain gradients can induce a polarization via the flexoelectric effect [11,12] or oxygen vacancies migration. [13] Electron diffraction measurements furthermore show that the top TiO 2 surface layer of SrTiO 3 undergoes surface relaxation and oxygen ions move outward from the surface relative to the titanium ions, leading to a polarization of this layer. [14][15][16] This is supported by shell model and density functional theory calculations. However, the calculations also predict that the SrO layers underneath display a polarization opposite to that of the TiO 2 surface layer, [17][18][19] leaving the question of the predicted net polarization and a possible pyroelectricity at the surface wide open.Symmetry-imposed restrictions on the number of available pyroelectric and piezoelectric materials remain a major limitation as 22 out of 32 crystallographic material classes exhibit neither pyroelectricity nor piezoelectricity. Yet, by breaking the lattice symmetry it is possible to circumvent this limitation. Here, using a unique technique for measuring transient currents upon rapid heating, direct experimental evidence is provided that despite the fact that bulk SrTiO 3 is not pyroelectric, the (100) surface of TiO 2 -terminated SrTiO 3 is intrinsically pyroelectric at room temperature. The pyroelectric layer is found to be ≈1 nm thick and, surprisingly, its polarization is comparable with that of strongly polar materials such as BaTiO 3 . The pyroelectric effect can be tuned ON/OFF by the formation or removal of a nanometric SiO 2 layer. Using density functional theory, the pyroelectricity is found to be a result of polar surface relaxation, which can be suppressed by varying the lattice symmetry breaking using a SiO 2 capping layer. The observation of pyroelectricity emerging at the SrTiO 3 surface also implies that it is intrinsically piezoelectric. These findings may pave the way for observing and tailoring piezo-and pyroelectricity in any material through appropriate breaking of symmetry at surfaces and artificial nanostructures such as heterointerfaces and superlattices. PyroelectricitySrTiO 3 has been the object of immense attention for over half a century owing to its multifunctional nature and popularity as a template for epitaxial growth of artificial nanostructures such as heterostructures, superlattices, and vertically aligned nanostructures. It is a classic example whe...

show abstract

mentioning

confidence: 99%

Surface Pyroelectricity in Cubic SrTiO₃

et al. 2019

Self Cite

View full text Add to dashboard Cite

show abstract

“…Moreover, the dependence of electron mobility with back‐gate voltage was found to correlate positively with the carrier density modulation, i.e., with positive voltages applied resulting in larger electron mobilities as well as more charge carriers and vice versa. It is worth noting that this trend is opposite to the typical reciprocal relationship between electron mobility and charge carrier density in as‐grown STO‐based heterointerfaces, which may be explained by a stronger scattering at the interface due, e.g., broken lattice symmetry, STO vicinal steps, or preferential defect formation at the interface …”

Section: Electrostatic Potentialmentioning

confidence: 66%

“…Here, ω c and τ are the cyclotron frequency and scattering time, respectively. Many methods have been employed to achieve a high mobility in oxides as reviewed Trier et al For example, using surface treatments, Xie et al achieved a mobility higher than 20 000 cm 2 V −1 s −1 for the LAO/STO system . Huijben et al incorporated a thin layer of SrCuO 2 between the surface of a LAO/STO heterostructure and a capping layer of STO.…”

Section: Magnetic Fieldmentioning

confidence: 99%

Stimulating Oxide Heterostructures: A Review on Controlling SrTiO₃‐Based Heterointerfaces with External Stimuli

Christensen

Trier

Niu

et al. 2019

Adv Materials Inter

Self Cite

View full text Add to dashboard Cite

Oxides are an exciting class of electronic materials which share key properties with conventional semiconductors, but also bring new intrinsic functionalities that are not used in most current electronics: superconductivity, ferro-, pyro-, and piezoelectricity, ferromagnetism, and multiferrocity. Among the large number of oxides, strontium titanate (SrTiO 3 , STO) has been the center of attention in numerous studies for more than half a century. STO both serves as a popular template for epitaxial growth of oxide thin films as well as by itself exhibiting an attractive palettes of properties, including Numerous of the greatest inventions in modern society, such as solar cells, display panels, and transistors, rely on a simple concept: An external stimulus is applied to a material and the response is then utilized. Oxides often exhibit a colorful palette of responses to external stimuli due to the close coupling between lattice, spin, orbital, and charge degrees of freedom. In particular, oxide heterostructures where oxide thin films are deposited on SrTiO 3 have proven to be a fertile playground for material scientists, and a vast amount of interesting theoretical and experimental studies showcase the wide tunabilities of these heterostructures when subjected to external stimuli. Here, the authors review how the properties of SrTiO 3 -based heterostructures can be changed by external stimuli using electric fields, magnetic fields, light, stress, particle bombardment, liquids, gases, and temperature. The application of a single stimulus or several stimuli combined often leads to unexpected changes in properties which can open up for designing new devices as well as expanding the boundaries of our understanding within fundamental science. Hall of Fame Article is a research scientist at the Technical University of Denmark, Department of Energy Conversion and Storage. He received his B.Sc. (2009) and M.Sc. (2012) in nanoscience from the University of Copenhagen, followed by his Ph.D. (2017) and postdoc (2018) from the Technical University of Denmark. His work is currently focused on the physics of oxide materials and oxide devices for information technology and energy harvesting, including oxide electronics, memristors, internet of things, and thermoelectricity. Felix Trier is a postdoctoral researcher at CNRS/Thales, University Paris-Saclay. He obtained his B.Sc. (2009) and M.Sc. (2012) in nanoscience from the University of Copenhagen. Then he earned his Ph.D. degree (2016) from the Technical University of Denmark. His current research is focused on fabrication and characterization of metallic oxide heterointerface devices for the study of the spin-charge interconversion in 2D Rashba systems. His work concerns the LaAlO 3 /SrTiO 3 heterointerface 2D metal and its electrostatic tunability.Nini Pryds is a Professor and head of the research section "Functional Oxides" at the Department of Energy Conversion and Storage, Technical University of Denmark (DTU), where he is leading a group of researchers working in the field...

show abstract

“…This also extends to heterostructures (81,224,225) and is ascribed to strong scattering by phonons, which even triggers the formation of polarons (226). At liquid-helium temperatures, the mobility of SrTiO 3 -based heterostructures can rise to above 10 4 cm 2 /Vs (225). In these devices, we expect the mobility increase to be limited to about 1000 cm 2 /Vs because of the presence of the Au top electrode (see Chapter 4 for details).…”

Section: Transfer Characteristicsmentioning

confidence: 87%

“…We attribute this to the low room-temperature mobility of SrTiO 3 , even in bulk: ∼1 − 10 cm 2 /Vs (223), compared to ∼700 cm 2 /Vs (222). This also extends to heterostructures (81,224,225) and is ascribed to strong scattering by phonons, which even triggers the formation of polarons (226). At liquid-helium temperatures, the mobility of SrTiO 3 -based heterostructures can rise to above 10 4 cm 2 /Vs (225).…”

Section: Transfer Characteristicsmentioning

confidence: 88%

Manifold field effects at a complex oxide interface

Smink¹

View full text Add to dashboard Cite

Another driving force for the formation of distinctive electronic phases are interactions between electrons, or electronic correlations. Because the kinetic energy of d-orbital electrons is typically relatively small, they are particularly susceptible to the effects of these interactions (12). Prominent examples of correlated-electron effects are superconductivity, the Mott insulator state, and different types of magnetism. Field-effect control of such correlations may lead to the discovery of new physics, as well as to realizing new components for electronics (13). This applies in particular to the interfaces between complex oxides, where the mesoscopic physics of semiconductor interfaces can be combined with the electronic correlations found in oxides (14).

show abstract

Electron mobility in oxide heterostructures

Cited by 51 publications

References 140 publications

Surface Pyroelectricity in Cubic SrTiO₃

Surface Pyroelectricity in Cubic SrTiO₃

Stimulating Oxide Heterostructures: A Review on Controlling SrTiO₃‐Based Heterointerfaces with External Stimuli

Manifold field effects at a complex oxide interface

Contact Info

Product

Resources

About

Electron mobility in oxide heterostructures

Cited by 51 publications

References 140 publications

Surface Pyroelectricity in Cubic SrTiO3

Surface Pyroelectricity in Cubic SrTiO3

Stimulating Oxide Heterostructures: A Review on Controlling SrTiO3‐Based Heterointerfaces with External Stimuli

Manifold field effects at a complex oxide interface

Contact Info

Product

Resources

About

Surface Pyroelectricity in Cubic SrTiO₃

Surface Pyroelectricity in Cubic SrTiO₃

Stimulating Oxide Heterostructures: A Review on Controlling SrTiO₃‐Based Heterointerfaces with External Stimuli