Review on fabrication methods of SrTiO3-based two

Eur. Phys. J. Appl. Phys. 93, 21302 (2021)© EDP Sciences, 2021https://doi.org/10.1051/epjap/2021200326

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Review on fabrication methods of SrTiO3-based two dimensionalconductive interfacesMing Li, Shuanhu Wang, Yang Zhao, and Kexin Jin*

Shaanxi Key Laboratory of Condensed Matter Structures and Properties and MOE Key Laboratory of Materials Physics andChemistry under Extraordinary Conditions, School of Physical Science and Technology, Northwestern Polytechnical University,Xi’an 710072, P.R. China

* e-mail: j

Received: 13 October 2020 / Received in final form: 21 December 2020 / Accepted: 8 January 2021

Abstract. The SrTiO3-based two dimensional conductive interfaces have attracted considerable attention inthe last decade owing to the emergence of novel physical phenomena. These heterointerfaces are generallyformed by depositing the films on SrTiO3 substrates. Particularly, the controllable and precise characteristicsof pulsed laser deposition (PLD) allow the deposition of an atomically flat oxide films and control the growthlayer-by-layer. Recently, the deposition methods of atomic layer deposition (ALD) and spin coating haveexhibited an excellent practicability and many interesting results are obtained by analyzing the chemicalreaction pathway. In addition, the surface treatment methods (such as high vacuum annealing, Ar+ ionirradiation and photoirradiation etc.) can also obtain the two dimensional conductive SrTiO3 effectively.Furthermore, owing to the difference of fabrication method, the SrTiO3-based two dimensional conductiveinterfaces significantly show different performances of the same oxides. Thus, this review compares thecharacteristics of different methods in preparing the SrTiO3-based interfaces. The appropriate method andprocess is the precondition to obtain high-quality oxide films and establish the foundation for the developmentof oxide and interface electronics.

1 Introduction

Two dimensional electron gas (2DEG) is a system, wherelow-density electrons are limited to the free movement intwo directions. For conventional GaAs-based 2DEGs, theconducting electrons are s or p electrons, only exhibitingthe charge property due to the lack of interaction betweenelectrons. However, since Ohtomo et al. [1] have reportedoxide 2DEG at the interface between LaAlO3 (LAO) andSrTiO3 (STO), the oxide 2DEG has attracted manyresearchers’ attention. Because of the strong correlationbetween 3d electrons, the oxide 2DEG displays magnetism,ferroelectric, spin polar or spin orbit coupling character-istics [2–8]. Moreover, owing to the strong interactionbetween the spin, charge, lattice and orbital etc., the STO-based two dimensional conductive interface has exhibitedfascinating physical properties, including a high electronmobility, two dimensional superconductivity and ferro-magnetism [9]. Many emerging properties have beenextensively reviewed in other venues, for examples,Christensen et al. [9], Mannhart and Schlom [10], Hwanget al. [11], Pai et al. [12], Chen Yunzhong et al. [13,14],Huang et al. [15] and Yan et al. [16].

In oxide 2DEGs, the STO is the workhorse in oxide-electronics as Si in microelectronics. At room temperature,

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the STO crystal is a cubic Pm3m space group and its latticeparameter is 3.905 Å, which is similar to that of many otherperovskite oxides and thus commonly used as theirsubstrates. Especially, the lattice parameter of Si closelymatches with the STO and the lattice mismatch of STO/Siis less than 2% [17]. It is hopeful that STO will become acandidate in transistor devices. Moreover, the STO withfavorable stability hardly reacts with other materials,contributing to the formation of epitaxial heterointerfaceswith various oxides (CaZrO3, EuO, GdTiO3, NdGaO3, andso on) [18–24]. In addition, the STO has been extensivelyapplied in the fields of ferroelectric memory, pyroelectricand microwave-controlled devices etc. [25–28]. Theapplications of these devices are mostly based on theirhigh permittivity (300 F/m), low dielectric loss and highcritical breakdown field. Furthermore, the STO has thelarge bandgap (the indirect bandgap width is 3.25 eV andthe direct bandgap width is 3.75 eV), meaning that it is agood insulator [29,30]. Because the bottom of conductionband is mainly composed of the Ti 3d electronic orbit [31],the STO-based conductive material can be formed by ntype [32–34] or p type [35–37] doping. It can display delectronic characteristics by the filling of different d orbits.Thus, the STO-based 2DEG has a great potential in theapplication of oxide electronic devices. In this review, wesummarized the recent progress about the fabricationmethods of two dimensional conductive STO-basedinterfaces.

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Fig. 1. The diagram for the routine to obtain STO-based twodimensional conductive interface.

Fig. 2. Schematic diagram of PLD equipment.

2 M. Li et al.: Eur. Phys. J. Appl. Phys. 93, 21302 (2021)

2 Fabrication methods of STO-based twodimensional conductive interfaces

As shown in Figure 1, the fabrication methods can bedivided into two categories: (1) the epitaxy growth ofheterointerface, (2) the surface treatment. The epitaxygrowth includes the physical vapor deposition (PVD) andthe chemical deposition (CD), such as PLD, the molecularbeam epitaxy (MBE), the ALD and the spin coating et al.The surface treatments involve high vacuum annealing,Ar+ ion irradiation, ion doping and laser irradiation et al.In the following sections, we will discuss the differentfabrication methods in details.

2.1 PLD method

PLD is one of the representative PVD technologies. Withthe invention of high-energy excimer laser, Dijkkamp et al.[38] firstly prepared the thin films of Y-Ba-Cu-O super-conductors, thus causing the rapid development of PLDtechnology and gradually becoming one of the most widelyapplied deposition in the field. The basic process includesthe bombardment of high-energy pulsed laser and theablation of ceramic target. Ceramic target can be gasifiedinto the plasma rapidly, and then the thin film is formed atthe surface of single crystal substrates with the directionalexpansion of plume. The schematic diagram is shown inFigure 2.

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In oxide heterointerfaces, Ohmoto and Hwang firstlyreported a high-mobility electron gas at LAO/STOheterointerfaces by the PLD technology [1,39]. The PLDcan atomically control the heteroepitaxial growth and formpolarity discontinuities at interfaces. Then, the PLDtechnology has become a preferable method to preparethe oxide heterointerfaces. Many groups have fabricated aseries of oxide heterointerfaces to reveal the two dimen-sional conductive behavior. For examples, Chen et al. havefabricated a high-mobility 2DEG at the g-Al2O3/STOinterface by PLD, and the mobility reaches to 1.4� 105

cm2V�1s�1 [13,40,41]. Moreover, various (NdGaO3/STO,CaZrO3/STO, LaVO3/STO, Al2O3/STO and amorphousLAO/STO etc. [42–46]) and multifunctional (ferromagne-tism, superconductivity or their coexistence [47–55]) oxideheterointerfaces have been prepared by the PLD technolo-gy. Meanwhile, Yan et al. have obtained the LAO/STOand (La0.3Sr0.7)(Al0.65Ta0.35)O3/SrTiO3 (LSAT/STO)heterointerfaces with different thicknesses and strains[56] (as shown in Fig. 3), and further found that thephotoinduced resistance changes of LAO/STO interfacespresented a roughly greater value than that of strain-relaxed LSAT/STO due to the larger lattice mismatch.The PLD advantages are as following: 1. the PLDtechnology can prepare multicomponent complex filmswith the same stoichiometric ratio of target; 2. the high-energy pulsed laser can grow the film of high-melting-pointmaterials; 3. it can precisely control the growing rate layer-by-layer; 4. it can flexibly adjust atmosphere, temperature,energy or other parameters.

2.2 MBE method

MBE is another PVD technique to produce high-qualityepitaxial films. For traditional MBE, firstly, the sourcematerial is heated in the ultra-high vacuum (∼10�10 Torr).Secondly, the evaporated atoms or molecules are ejected tothe surface of substrate. Finally, the epitaxial growth ofmaterial is realized through the surface adsorption,migration and nucleation. The schematic diagram is shownin Figure 4. Compared with the PLD, the main difference isthe heating method of source materials (thermal evapora-tion). The generated steady-state beam typically has thelow energy of 1.0 eV or less [57], which successfully avoidsthe extrinsic defects in the substrate and is beneficial to theformation of a sharp heterointerface. Moreover, the ultra-high vacuum environment and low growing rate contributeto the growth of high-purity and high-crystallinity films.Furthermore, combined with the Reflection High EnergyElectron Diffraction (RHEED), Mass Spectrometer (MS)and Auger Electron Spectrometer (AES), the MBEtechnique can not only monitor the molecular beam fluxand the surface structure of film, but also fabricateepitaxial films with precise atomic control layer-by-layer.

Since Cho et al. [58,59] proposed the MBE technique inthe 1960s, it has been widely applied to fabricate thevarious multilayer superlattice [60], quantumwell [61], twodimensional conductive material [62,63], especially in thepreparation of oxide two-dimensional electron liquid(2DEL). As shown in Figure 5, Warusawithana et al.[64] prepared perfect LAO/STO interfaces without

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Fig. 3. (a–c) Temperature dependence of the sheet resistance, carrier density (n) and electron mobility (m) for LAO/STOheterointerfaces with different thicknesses in dark, respectively. (d–f) Temperature dependence of sheet resistance, carrier density (n)and mobility (m) for LSAT/STO heterointerfaces with different thicknesses in dark, respectively [56].

Fig. 4. Schematic diagram of MBE equipment.

M. Li et al.: Eur. Phys. J. Appl. Phys. 93, 21302 (2021) 3

extrinsic defects including the absence of oxygen deficien-cy. Moreover, by controlling the shutter-open times of Lasource and Al source, different stoichiometric LAO filmsare deposited on STO substrates. The results revealed thatthe cation stoichiometry of LAO filmwas a critical factor toform 2DEL. Through first principle calculations, theyindicated that the origin of 2DEL was the intrinsicelectronic reconstruction. Besides, due to the manageable,flawless, slow-growing advantages, Tsai et al. [65] also haveprepared a series of high quality LAO films with differentLa/Al ratios and thicknesses by MBE technique. They

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showed that the control of La/Al ratio was an effectivemethod to tune the carrier concentration of 2DEL.

2.3 ALD method

ALD technique is a special chemical deposition technique,which can achieve the sequential, self-limiting and self-saturating reaction at surface and is suitable for complexsubstrates [66,67]. The major process of ALD is a gas-solidchemisorption reaction, as shown in Figure 6, the reactionpathway consists of four primitive steps: 1. the pulsedadsorption reaction of precursor A (trimethylaluminum,Me3Al); 2. the purgation of redundant reactants andby-products via noble gas; 3. the pulsed adsorption reactionof precursor B (H2O); 4. the secondary purgation ofredundant reactants and by-products via noble gas. Then,the film grows layer-by-layer on the substrate by the cycleof above reaction [68]. Based on the reaction mechanism,choosing a proper chemical reaction is the key issue in theALD method, such as the need of precursor with excellentthermostability, reactivity and volatility etc. Therefore,only a small number of proper chemical reactions have beenutilized in ALD process, limiting the application of ALDtechnique [69,70].

With the continual improvement of chip’s integrationlevel, the ALD technique exhibits considerable potentialapplications in the preparation of small-scale and complexdevices. For examples, in the field of transistor, Bent et al.[71] have deposited the Al2O3 insulation layer via theparticularity of chemisorption reaction. In the field ofenergy storage devices, Kozen et al. [72] have fabricated

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Fig. 5. Flux gradients and interfacial conductivity of mosaic samples. (a) Mosaic arrangement of substrates for each growth.(b) Temperature dependence of resistance of the 2DEL is plotted for a representative set of conducting samples from the mosaicgrowths. The samples are labelled with the mosaic number followed by substrate number—for example, 2–1D indicates mosaic 2, pieceD of substrate 1. (c) A representative low-temperature resistance versus temperature plot shows the 2-DEL is superconducting. Thescaling between the resistance and the sheet resistance is approximate [64].


Al2O3 layer to protect the Li electrode due to the large-areauniformity property of ALD technique. Moreover, a fewgroups also have launched the profound and systematicalresearch on the oxide 2DEG. For example, Lee et al. [73–75]have prepared a series of amorphous oxide layers (LaAlO3,YAlO3, Al2O3, Y2O3, La2O3) at STO substrates by ALD.They found that only the LaAlO3, YAlO3 or Al2O3 layerscould produce the 2DEG. The key factor is the oxidation ofMe3Al precursor because the Me3Al can be oxidized by theTiO2 of STO termination in ALD process. The possibledetailed reactions are the following:

2AlðCH3Þ3 þ 8TiO2 ¼ Al2O3 þ 4Ti2O3 þ 3CH4ðgÞ

þ 3

2C2H4ðgÞ þ 1

2O2ðgÞ

DGr;573K ¼ �947:156 kJ=mol ð1Þ

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or

2AlðCH3Þ3 þ 10TiO2 ¼ Al2O3 þ 5Ti2O3 þ 3CH4ðgÞþ C2H4ðgÞ þ CO2ðgÞ þH2ðgÞDGr;573K ¼ �1062:726 kJ=mol: ð2Þ

The reactions show that the change of Gibbs freeenergies (DGr) is negative at 573K. The reaction pathway(1) or (2) is dependent on the stronger Al-O bond under thereduction of STO substrate by Me3Al. Furthermore, asshown in Figure 7, the amorphous Al2O3 layer has thecritical thickness, meaning that the activation energy canbe overcome by the enough thermal energy when thethickness of Al2O3 film is larger than the critical value atthe appropriate thermodynamic condition.

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Fig. 6. Schematic diagram of ALD technique.

Fig. 7. (a) A schematic of creation mechanism of 2DEG by the diffused-out oxygen atoms from STO surface through the grownamorphous Al2O3 layer by ALD. (b) The variation in the electron densities at Al2O3/STO heterostructures depending on the Al2O3

film thickness. (c) A transmission rate of oxygen atoms through the Al2O3 layer as a function of Al2O3 thickness using the value of2.5� 1010 oxygen atoms per cm2 per s at a 1 nm thickness (d) the number of total oxygen atoms transmitted during Al2O3 ALD wascalculated using equation (1), and the experimental curve is obtained by dividing the number of electrons in (b) by 2 (assuming that oneoxygen vacancy generates two free electrons) [74].


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Fig. 8. Schematic diagram for preparing the YAlO3/STO heterointerfaces by the spin coating method [75].


2.4 Spin coating method

As one of the different methods, the spin coating is animportant and widely-used processing technique. Thetypical process is mainly divided into two steps:precursor solution dropping, high speed rotation andcrystallization. Firstly, a drop of precursor solution isplaced on a spinning flat substrate. Then the liquidspreads outward and forms a quite thin, uniform andmulticomponent coating by the centrifugal force [76].This scenario is depicted in Figure 8, taking YAlO3/STOheterointerfaces as an example [77]. The film is easilycontrolled by the spin speed, the viscosity of solution, thecomposition of precursor liquid and the annealingtemperature et al. So, the spin coating method has beenwidely applied in the semiconductors, solar cells, diodeand transistors devices [78–82].

The spin coating technique has drawn more and moreattentions due to its obvious advantages of mild processconditions, simple facilities, easy operation and control,etc. Specifically, the spin coating technique has beensuccessfully applied to prepare the oxide 2DEG. Recently,the obtained 2DEGs at the (001), (011) and (111)-orientedLAO/STO interfaces not only exhibited excellent metallicconductive behavior but also had a high carrier mobility[8,83]. Meanwhile, we also have prepared a series of oxide2DEGs by the spin coating method (such as g-Al2O3,YAlO3 and Y2O3). As shown in Figure 9, the TEM resultsexhibited that the prepared g-Al2O3 layer had highcrystallinity and grew epitaxially along the (001) orienta-tion of STO. The abrupt interface reflected no cationinterdiffusion according to EDS analysis [84]. Moreover,through preparing YAlO3/STO heterointerfaces withdifferent thicknesses and stoichiometry ratios, we revealedthat the origin of metallicity was attributed to oxygenvacancies from the redox reaction between yttriumaluminum oxides film and STO substrates [77]. The resultsshow that the spin coating technique has an enormouspotential in the fabrication of oxide 2DEGs. Comparedwith the PLD, MBE and ALD, this technique needs nosophisticated facility and rigorous chemical reaction,avoiding the laser bombardment. However, the drawbackis that it is hard to fabricate ultrathin film and preciselycontrol the thickness by spin coating method.

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2.5 High-vacuum annealing

Generally, the fabrication methods of STO-based twodimensional conductive interface are focused on variousepitaxial growth techniques. Based on the deposition ofheterointerfaces between different oxides and STO sub-strates, the metallic-like conductive interfaces are formed.The main conductive mechanisms were attributed to thepolar catastrophe, oxygen vacancy, and so on. However,there are many other ways to generate the two dimensionalconductive surface at STO. For example, the high-vacuumannealing can form oxygen defects and electron doping atSTO surface [85,86]. Thereby, the quasi-two dimensionalconductive layer can be generated at STO by the surfacetreatment. Based on this technique, we have prepared self-doped STO by the thermal annealing in high vacuum(∼10�6mbar) at 550, 650, 750, and 850 °C [87]. As shown inFigure 10, the results reveal that the samples with highannealing temperature (≥650 °C) exhibits an excellentmetal-like conductive behavior, and the conductivities aremonotonously increased with the increase of annealingtemperature. The Hall effect measurement (20K) showsthat the electron density is 1.2� 1017 cm�2 and the carriermobility is 5700 cm2 ·V�1 · s�1 for the sample annealed at750 °C. Moreover, the annealing can effectively tune theelectronic transport properties of STO and the resistanceunder irradiation is changed by the twelve orders ofmagnitude at 20K. In addition, the oxygen-deficient oxidesstill exhibited many peculiar physical properties as same asthe 2DEG at LAO/STO interfaces, such as persistentphotoconductivity [88,89], magnetism [90] or their coexis-tence [91].

2.6 Ar+ ion irradiation

The low-energy Ar+ ion beam irradiation is anothermethod to generate oxygen vacancy at STO surfaces. Theconductive mechanism is consistent with that of the highvacuum annealing. When the Ar+ ion bombards the STOsurface, the O atoms have the faster diffusion [92]. Then, acertain amount of oxygen vacancies is generated at STOsurfaces, that is, the quasi-two dimensional conductivesurface is formed by the Ar+ ion irradiation. Moreover, theirradiation time and energy of Ar+ ion can directly

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Fig. 9. (a) and (b) TEM images of Al2O3/STO heterointerfaces annealed at 800 °C. (c) and (d) Selected-area electron diffractionpatterns of square in (b); weak spots (yellow spots) originate from g-Al2O3. (e) The HAADF image of the Al2O3/STO heterointerfaceannealed at 800 °C. (f)–(i) EDS maps of the Al, Sr, Ti, and O concentration corresponding to (e) [84].

Fig. 10. (a) Temperature dependent sheet resistance data measured on STO single crystals annealed in vacuum at temperatures of550 °C (S55), 650 °C (S65), 750 °C (S75), and 850 °C (S85). The resistance of the as-received STO substrate exceeds the measurementlimit. The corresponding optical images of the reduced STO substrates are shown in the insets. Also illustrated is the atomic perovskitestructure of STO, where the green, blue and red balls represent Sr, Ti andO atoms, respectively. (b) Semi-logarithmic plots of the roomtemperature current-voltage characteristics measured in various reduced STO samples both in the dark (dashed lines) and under UVlight illumination. Inset shows the schematic of the Pt/STO/Al device [87].


influence the conductive property and the thickness ofconductive layer [93–97]. As shown in Figure 11, Reagoret al. [96] have made a series of samples with differentenergy levels. Firstly, the metallic-like conductive behavior

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is found in the samples at the energy of above 200 eV.Secondly, the residual resistance ratio is up to about 100 forthe sample formed by the beam energy of nearly 300 eV.The high residual resistance ratio indicated a highly

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ordered conduction channel was produced at the surface.Thirdly, the resistivity vs. temperature relationshipimplied that the conduction mechanism was a commonlyelectron-doped conduction behavior. In addition, the Ar+

ion-irradiated samples still show other physical phenome-na, such as, anisotropic magnetotransport [98], spin-orbitcoupling [94,99], blue-light emission [100], persistentphotoconductivity [93,101] and so on. Overall, comparedwith high vacuum annealing, the Ar+ ion irradiation hastwo advantages: 1. the spatial distribution of oxygenvacancies is localized because the depth of oxygen vacancystrongly depends on the penetration depth of Ar+ ion. 2.the conductive domain can be easily controlled.

Fig. 11. Four-probe resistivity versus temperature for severalsamples. The ion-bombarded samples at the lowest energies had acontact dresistance that diverged at low temperatures, and onlythe high-temperature data are shown [96].

Fig. 12. (a) Temperature dependence of the sheet resistance in air aenergy density of 500mJ/cm2. (b) The sheet resistance of irradiatedthe partial pressure of 5� 10�4 Pa [102].

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2.7 Others

According to the results mentioned above, it is likely to findthat the fabrication methods can significantly manipulatethe conductive properties of STO-based interfaces.Therefore, a number of researchers are engaged in theexploration of novel preparation methods. And many othermethods have also exhibited a potential to fabricate STO-based two dimensional conductive interfaces, such as laserirradiation [102], photoirradiation [103] and ion doping[104,105] etc. As shown in Figure 12, Zhang et al. [102] haverealized the metal-like STO surface via KrF laserirradiation, which strongly depends on the vacuum andlaser energy density. Like as Ar+ ion irradiation, theconductive mechanism was caused by oxygen vacancy dueto the laser ablation. Besides, the UV light of 300 nm andthe Cr, Nb, La ion doping can also induce insulator-metalphase transition of bare STO single crystals [33,103–106].

2.8 Comparison of different methods

Finally, we summarize the characteristics of differentmethods, the merits and demerits are shown in Table 1.The results would provide a favorable reference for thepreparation of STO-based two dimensional conductiveinterfaces. For examples, the chemical deposition of ALDcan be used to grow a large-area film on the complexsubstrate and the conductive mechanism can be illustratedfrom an aspect of redox reaction. In addition, the high-melting-point materials can apply the PLD. And the MBEor spin coating is favorable to the fabrication ofmulticomponent and doped film, and so on.

3 Conclusion and perspectives

Although the achievements are obtained over recentyears, many challenges of all-oxide interfaces are stillremained. For examples, the origin of oxide-2DEG is

nd the partial pressure of ∼5, 5� 10�2 and 5� 10�4 Pa at the laserSTO as a function of temperature at different energy densities in

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Tab

le1.

Com

parisonof

differentmetho

ds.

Structure

Adv

antages

Disad

vantages

PLD

Heterointerface

Highest

quality

precisecontrolof

film

thickn

essan

dcompo

sition

,grow

high

-melting

-point

thin

film

Mostdifficultto

grow

largearea

film

need

high

-energypu

lsed

laser,

soph

isticatedfacilities

MBE

Heterointerface

Mostprecise

high

quality,

precisecontrol

offilm

thickn

essan

dcompo

sition

,easy

doping

Low

estgrow

thrate

high

cost,complex

processes,

soph

isticatedfacilities

ALD

Heterointerface

Highqu

ality,

self-lim

iting,

low

grow

thtemperature,

unifo

rm,largearea

grow

th

App

ropriate

reaction

andrecycletime,

soph

isticatedfacilities,

low

grow

thrate

Spin

coating

Heterointerface

Easiest

andlatest

metho

dlow

cost,mild

cond

ition,

easy

doping

,largearea

grow

th,simplefacilities

Mostdifficultto

fabricateultrathin

film

andpreciselycontrolthe

thickn

ess

Ann

ealin

gSu

rface

Easiest

metho

deasy

operation,

simplefacilities

Hardto

preciselycontrolthe

spatialdistribu

tion

ofox

ygen

vacanciesan

dcond

uctive

domain

Ionor

laser

irradiation

Surface

Easily

controlthespatialdistribu

tion

ofox

ygen

vacanciesan

dcond

uctive

domain,

simplefacilities

Depends

ontheenergy

andtime

ofirradiation


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still controversial, and the defects (such as oxygen defects,nonstoichiometries, cation intermixing, and nonhomoge-neities) are inevitable in the heterointerfaces [107,108].In addition, the mobilities can be influenced by the qualityof sample, the composition of capping layer and thealtering of sample structure. And it is not even clear howthese properties are limited. Therefore, in order to revealthese problems, the modified techniques and other novelfabrication methods need to be proposed to realize moreperfect heterointerfaces.

Moreover, with the development of multifunctional andcomplicated oxide electronic devices, the combination ofthe situ monitoring RHEED and the advanced characteri-zation techniques (such as MS, AES, X-ray photoelectronspectroscopy and nondestructive resonant X-ray reflectiv-ity et al.) has more significance in improving the quality ofheterointerfaces. Meanwhile, the assisting of externalstimuli also can reduce the defects in the preparation.Inspired by these, the next challenge is to explore theproper oxides and fabrication methods, design an excellentmicrostructure, apply a single or multiple external stimulito product multifunctional complex oxide devices (such asquantum devices, tunneling junctions or superconductingqubits). We hope that the review paves a way for the realapplication of oxide electronics and electronic devices.

Project supported by the National Natural Science Foundation ofChina (Nos. 51572222 and 61471301) and the FundamentalResearch Funds for the Central Universities (Grant No.3102017jc01001).

Author contribution statement

Ming Li contributed to the data analysis, interpretationand writing of the manuscript. Prof. Shuanhu Wang andProf. Yang Zhao contributed to the concept design. Prof.Kexin Jin contributed to the concept design and revisingthe manuscript. All authors discussed the results andcommented on the manuscript. The authors declare nocompeting financial interests.

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Cite this article as: Ming Li, Shuanhu Wang, Yang Zhao, Kexin Jin, Review on fabrication methods of SrTiO3-based twodimensional conductive interfaces†, Eur. Phys. J. Appl. Phys. 93, 21302 (2021)

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Review on fabrication methods of SrTiO3-based two