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LaAlO3/SrTiO3异质结界面体系具有新奇的二维自由电子气现象、暂态光电导效应、持续光电导效应等丰富的光电性质, 是近年来科学界研究的热点之一. 本文研究了场效应对LaAlO3/SrTiO3界面光电导效应的调控, 发现光电协同增强的场效应可以使得LaAlO3/SrTiO3界面产生显著的持续光电导效应, 进一步研究发现: 在光电协同效应的影响下, 随着负的背栅门电压的增加, 持续光电导的数值增大, 在–70 V附近达到极值; 随着负的背栅门电压处理时间的增加, 持续光电导的数值单调增加. LaAlO3/SrTiO3异质结中这种场增强的持续光电导效应可为多参数可调的光电子记忆器件的研发提供参考依据.
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关键词:
- LaAlO3/SrTiO3界面 /
- 持续光电导 /
- 光照 /
- 场效应
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.-
Keywords:
- LaAlO3/SrTiO3 interface /
- persistent photoconductivity /
- illumination /
- gating effect
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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
Fig. 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
Fig. 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
Fig. 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
Fig. 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
Fig. 7. Relationship between the PPC value and gate voltage (Vgate). Inset is the dependence of Rn on Vgate.
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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)
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Google Scholar
[8] Kalabukhov A, Gunnarsson R, Börjesson J, Olsson E, Claeson T, Winkler D 2007 Phys. Rev. B 75 121404
Google Scholar
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Google Scholar
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Google Scholar
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[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
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Google Scholar
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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
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Google Scholar
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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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