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The LaAlO3/SrTiO3 interface has been one of the topics studied most during the past few years due to its many intriguing properties such as the two-dimensional electron gas, transient photoconductivity (PC), persistent photoconductivity (PPC), and the coexistence of the PC and PPC. Of them, the PPC effect is the most interesting because of its potential application in exploring the photoelectric memory devices. Until now, tuning of the PPC of the LaAlO3/SrTiO3 interface under the external stimuli, such as electric or magnetic field is less addressed, while the relevant knowledge is of great value for exploring the memory devices with multifunctionality. In this paper, we report on an electric field control of the persistent PPC at the LaAlO3/SrTiO3 interface. Our LaAlO3/SrTiO3 heterojunction is fabricated by growing the LaAlO3 film on the SrTiO3 substrates through using pulsed laser deposition. The substrate temperature is kept at 750 ℃ and the partial pressure of oxygen is maintained at 3.3 × 10–5 Torr (1 Torr = 1.33322 × 102 Pa) during the deposition. The thickness of LaAlO3 film is controlled to be about 2 nm by setting an appropriate deposition time. The X-ray diffraction experiment confirms that the LAO film is well epitaxial and of single phase. To guarantee the good electric contacts, Al electrodes are soldered at the LaAlO3/SrTiO3 interface and the back side of the SrTiO3 respectively by ultrasonic welding. We find that the PPC at the LaAlO3/SrTiO3 interface can be significantly reinforced and modulated by the light-enhanced gating effects: that is, after a negative back gate voltage processing combined with a simultaneous light illumination, the LaAlO3/SrTiO3 interface can exhibit a notable PPC effect. And the PPC effect increases as the negative gate voltage increases, and then attains a maximum at a back gate voltage of about –70 V. Further increase of the negative gate voltage can cause the PPC to decrease. Additionally, the PPC is also found to increase monotonically with increasing the gating time. The present result can be understood in terms of the migration of the oxygen vacancies under the influence of photoelectric synergetic effect. This field enhanced PPC effects at the LaAlO3/SrTiO3 interface may find their applications in designing the photoelectric memory devices with electric tunability.
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Keywords:
- LaAlO3/SrTiO3 interface /
- persistent photoconductivity /
- illumination /
- gating effect
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图 1 LAO/STO测量接线示意图
Figure 1. Sketch of the experimental setup of the LAO/STO device.
图 2 LAO/STO样品的界面R-T特性曲线
Figure 2. R-T curve measured at LAO/STO interface.
图 3 LAO/STO界面电阻R与门电压Vgate随时间t的变化 (a)在不同光照下R随t的变化; (b)Vgate随t的变化
Figure 3. Time dependence of resistance R and gate voltage Vgate of LAO/STO: (a) Time dependence of R under different light illumination; (b) time dependence of gate voltage.
图 4 光照对LAO/STO界面电阻R的影响, 图中“on”和“off”分别代表光照的开和关
Figure 4. Effect of light illumination on the LAO/STO resistance. “on” and “off” represent the switch on and off of the illumination, respectively.
图 5 LAO/STO界面R随t的变化, 其中测量期间, 门电压或光照来回“开”和“关”; 图中, “L”代表加光照, “U”代表加电压; “on”和“off”分别代表门电压或光照的开和关; 内插图为830—1460 s区间的放大图
Figure 5. R of the LAO/STO interface as a function of response time while the gate voltage (marked by “U”) and light illumination (marked by “L”) is switched on and off. Inset is a close view of the R-time curve between 830 s and 1460 s.
图 6 LAO/STO界面R分别经不同栅压处理后的随t变化, 其中测量期间, 门电压或光照来回“开”和“关” (图中, “L”代表加光照, “U”代表加电压; “on”和“off”分别代表门电压或光照的开和关) (a) –40 V; (b) –60 V; (c) –70 V; (d) –80 V
Figure 6. Time dependences of R of the LAO/STO interface after the processing of various gate voltages while the gate voltages (marked by “U”) and light illumination (marked by “L”) are switched on and off: (a) –40 V; (b) –60 V; (c) –70 V; (d) –80 V.
图 7 PPC值随Vgate的变化, 其中内插图为Rn随Vgate的变化
Figure 7. Relationship between the PPC value and gate voltage (Vgate). Inset is the dependence of Rn on Vgate.
图 8 门电压的处理时间td对PPC值的影响关系, 插图为Rn随td的变化关系
Figure 8. The PPC value as a function of gating time td. Inset is the dependence of Rn on td.
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[1] Ohtomoa A, Hwang H Y 2004 Nature 427 423
Google Scholar
[2] Reyren N, Thiel S, Caviglia A D, Kourkoutis L F, Hammerl G, Richter C, Schneider C W, Kopp T, Ruetschi A S, Jaccard D, Gabay M, Muller D A, Triscone J M, Mannhart J 2007 Science 317 1196
Google Scholar
[3] Richter C, Boschker H, Dietsche W, Fillis-Tsirakis E, Jany R, Loder F, Kourkoutis L F, Muller D A, Kirtley J R, Schneider C W, Mannhart J 2013 Nature 502 528
Google Scholar
[4] Dikin D A, Mehta M, Bark C W, Folkman C M, Eom C B, Chandrasekhar V 2011 Phys. Rev. Lett. 107 056802
Google Scholar
[5] Caviglia A D, Gariglio S, Cancellieri C, Sacépé B, Fête A, Reyren N, Gabay M, Morpurgo A F, Triscone J M 2010 Phys. Rev. Lett. 105 236802
Google Scholar
[6] Liu Z Q, Li C J, Lu W M, Huang X H, Huang Z, Zeng S W, Qiu X P, Huang L S, Annadi A, Chen J S, Coey J M D, Venkatesan T, Ariando 2013 Phys. Rev. B 87 201102(R)
Google Scholar
[7] Herranz G, Basletić M, Bibes M, Carrétéro C, Tafra E, Jacquet E, Bouzehouane K, Deranlot C, Hamzić A, Broto J M, Barthélémy A, Fert A 2007 Phys. Rev. Lett. 98 216803
Google Scholar
[8] Kalabukhov A, Gunnarsson R, Börjesson J, Olsson E, Claeson T, Winkler D 2007 Phys. Rev. B 75 121404
Google Scholar
[9] Siemons W, Koster G, Yamamoto H, Harrison W A, Lucovsky G, Geballe T H, Blank D H A, Beasley M R 2007 Phys. Rev. Lett. 98 196802
Google Scholar
[10] Zhang H R, Zhang Y, Zhang H, Zhang J, Shen X, Guan X X, Chen Y Z, Yu R C, Pryds N, Chen Y S, Shen B G , Sun J R 2017 Phys. Rev. B 96 195167
Google Scholar
[11] Guduru V K, Granados del Aguila A, Wenderich S, Kruize M K, McCollam A, Christianen P C M, Zeitler U, Brinkman A, Rijnders G, Hilgenkamp H, Maan J C 2013 Appl. Phys. Lett. 102 051604
Google Scholar
[12] Lu H L, Liao Z M, Zhang L, Yuan W T, Wang Y, Ma X M, Yu D P 2013 Sci. Rep. 3 2870
Google Scholar
[13] Tarun M C, Selim F A, McCluskey M D 2013 Phys. Rev. Lett. 111 187403
Google Scholar
[14] Tebano A, Fabbri E, Pergolesi D, Balestrino G, Traversa E 2012 ACS Nano 6 1278
Google Scholar
[15] Ristic Z, di Capua R, Chiarella F, de Luca G M, Maggio-Aprile I, Radovic M, Salluzzo M 2012 Phys. Rev. B 86 045127
Google Scholar
[16] Rastogi A, Pulikkotil J J, Budhani R C 2014 Phys. Rev. B 89 125127
Google Scholar
[17] Jin K X, Lin W, Luo B C, Wu T 2012 Sci. Rep. 5 8778
Google Scholar
[18] Lei Y, Li Y, Chen Y Z, Xie Y W, Chen Y S, Wang S H, Wang J, Shen B G, Pryds N, Hwang H Y, Sun J R 2014 Nat. Commun. 5 5554
Google Scholar
[19] Ravikumar V, Wolf D, Dravid V P 1995 Phys. Rev. Lett. 74 960
Google Scholar
[20] Haeni J H, Irvin P, Chang W, Uecker R, Reiche P, Li Y L, Choudhury S, Tian W, Hawley M E, Craigo B, Tagantsev A K, Pan X Q, Streiffer S K, Chen L Q, Kirchoefer S W, Levy J, Schlom D G 2004 Nature 430 758
Google Scholar
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