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Title: Dual-Gate Modulation of Carrier Density and Disorder in an Oxide Two-Dimensional Electron System

Abstract

Carrier density and disorder are two crucial parameters that control the properties of correlated two-dimensional electron systems. Furthermore, in order to disentangle their individual contributions to quantum phenomena, independent tuning of these two parameters is required. By utilizing a hybrid liquid/solid electric dual-gate geometry acting on the conducting LaAlO 3/SrTiO 3 heterointerface, we obtain an additional degree of freedom to strongly modify the electron confinement profile and thus the strength of interfacial scattering, independent from the carrier density. A dual-gate controlled nonlinear Hall effect is a direct manifestation of this profile, which can be quantitatively understood by a Poisson–Schrödinger sub-band model. In particular, the large nonlinear dielectric response of SrTiO 3 enables a very wide range of tunable density and disorder, far beyond that for conventional semiconductors. This study provides a broad framework for understanding various reported phenomena at the LaAlO 3/SrTiO 3 interface.

Authors:
 [1];  [2];  [2];  [1];  [1];  [3];  [3];  [2]
  1. Stanford Univ., CA (United States). Geballe Lab. for Advanced Materials
  2. Stanford Univ., CA (United States). Geballe Lab. for Advanced Materials; SLAC National Accelerator Lab., Menlo Park, CA (United States). Stanford Inst. for Materials and Energy Sciences
  3. SLAC National Accelerator Lab., Menlo Park, CA (United States). Stanford Inst. for Materials and Energy Sciences
Publication Date:
Research Org.:
SLAC National Accelerator Lab., Menlo Park, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1348871
Grant/Contract Number:
AC02-76SF00515; N00014-12-1-0976
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Nano Letters
Additional Journal Information:
Journal Volume: 16; Journal Issue: 10; Journal ID: ISSN 1530-6984
Publisher:
American Chemical Society
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; disorder; ionic liquid gating; nonlinear Hall effect; oxide interface; quantum confinement; SrTiO3 dielectric constant

Citation Formats

Chen, Zhuoyu, Yuan, Hongtao, Xie, Yanwu, Lu, Di, Inoue, Hisashi, Hikita, Yasuyuki, Bell, Christopher, and Hwang, Harold Y. Dual-Gate Modulation of Carrier Density and Disorder in an Oxide Two-Dimensional Electron System. United States: N. p., 2016. Web. doi:10.1021/acs.nanolett.6b02348.
Chen, Zhuoyu, Yuan, Hongtao, Xie, Yanwu, Lu, Di, Inoue, Hisashi, Hikita, Yasuyuki, Bell, Christopher, & Hwang, Harold Y. Dual-Gate Modulation of Carrier Density and Disorder in an Oxide Two-Dimensional Electron System. United States. doi:10.1021/acs.nanolett.6b02348.
Chen, Zhuoyu, Yuan, Hongtao, Xie, Yanwu, Lu, Di, Inoue, Hisashi, Hikita, Yasuyuki, Bell, Christopher, and Hwang, Harold Y. 2016. "Dual-Gate Modulation of Carrier Density and Disorder in an Oxide Two-Dimensional Electron System". United States. doi:10.1021/acs.nanolett.6b02348. https://www.osti.gov/servlets/purl/1348871.
@article{osti_1348871,
title = {Dual-Gate Modulation of Carrier Density and Disorder in an Oxide Two-Dimensional Electron System},
author = {Chen, Zhuoyu and Yuan, Hongtao and Xie, Yanwu and Lu, Di and Inoue, Hisashi and Hikita, Yasuyuki and Bell, Christopher and Hwang, Harold Y.},
abstractNote = {Carrier density and disorder are two crucial parameters that control the properties of correlated two-dimensional electron systems. Furthermore, in order to disentangle their individual contributions to quantum phenomena, independent tuning of these two parameters is required. By utilizing a hybrid liquid/solid electric dual-gate geometry acting on the conducting LaAlO3/SrTiO3 heterointerface, we obtain an additional degree of freedom to strongly modify the electron confinement profile and thus the strength of interfacial scattering, independent from the carrier density. A dual-gate controlled nonlinear Hall effect is a direct manifestation of this profile, which can be quantitatively understood by a Poisson–Schrödinger sub-band model. In particular, the large nonlinear dielectric response of SrTiO3 enables a very wide range of tunable density and disorder, far beyond that for conventional semiconductors. This study provides a broad framework for understanding various reported phenomena at the LaAlO3/SrTiO3 interface.},
doi = {10.1021/acs.nanolett.6b02348},
journal = {Nano Letters},
number = 10,
volume = 16,
place = {United States},
year = 2016,
month = 9
}

Journal Article:
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Cited by: 2works
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  • The two-dimensional electron gas (2DEG) formed at the perovskite oxides heterostructures is of great interest because of its potential applications in oxides electronics and nanoscale multifunctional devices. A canonical example is the 2DEG at the interface between a polar oxide LaAlO{sub 3} (LAO) and non-polar SrTiO{sub 3} (STO). Here, the LAO polar oxide can be regarded as the modulating or doping layer and is expected to define the electronic properties of 2DEG at the LAO/STO interface. However, to practically implement the 2DEG in electronics and device design, desired properties such as tunable 2D carrier density are necessary. Here, we reportmore » the tuning of conductivity threshold, carrier density and electronic properties of 2DEG in LAO/STO heterostructures by insertion of a La{sub 0.5}Sr{sub 0.5}TiO{sub 3} (LSTO) layer of varying thicknesses, and thus modulating the amount of polarization of the oxide over layers. Our experimental result shows an enhancement of carrier density up to a value of about five times higher than that observed at the LAO/STO interface. A complete thickness dependent metal-insulator phase diagram is obtained by varying the thickness of LAO and LSTO providing an estimate for the critical thickness needed for the metallic phase. The observations are discussed in terms of electronic reconstruction induced by polar oxides.« less
  • The electron density, n{sub e}, modulation is measured experimentally using a resonance hairpin probe in a pulsed, dual-frequency (2/13.56 MHz), dual-antenna, inductively coupled plasma discharge produced in argon-C{sub 4}F{sub 8} (90–10) gas mixtures. The 2 MHz power is pulsed at a frequency of 1 kHz, whereas 13.56 MHz power is applied in continuous wave mode. The discharge is operated at a range of conditions covering 3–50 mTorr, 100–600 W 13.56 MHz power level, 300–600 W 2 MHz peak power level, and duty ratio of 10%–90%. The experimental results reveal that the quasisteady state n{sub e} is greatly affected by the 2 MHz power levels and slightly affected by 13.56 MHzmore » power levels. It is observed that the electron density increases by a factor of 2–2.5 on increasing 2 MHz power level from 300 to 600 W, whereas n{sub e} increases by only ∼20% for 13.56 MHz power levels of 100–600 W. The rise time and decay time constant of n{sub e} monotonically decrease with an increase in either 2 or 13.56 MHz power level. This effect is stronger at low values of 2 MHz power level. For all the operating conditions, it is observed that the n{sub e} overshoots at the beginning of the on-phase before relaxing to a quasisteady state value. The relative overshoot density (in percent) depends on 2 and 13.56 MHz power levels. On increasing gas pressure, the n{sub e} at first increases, reaching to a maximum value, and then decreases with a further increase in gas pressure. The decay time constant of n{sub e} increases monotonically with pressure, increasing rapidly up to 10 mTorr gas pressure and at a slower rate of rise to 50 mTorr. At a fixed 2/13.56 MHz power level and 10 mTorr gas pressure, the quasisteady state n{sub e} shows maximum for 30%–40% duty ratio and decreases with a further increase in duty ratio.« less
  • We have studied the effect of top gate bias (V{sub TG}) on the generation of photocurrent and the decay of photocurrent for back channel etched inverted staggered dual gate structure amorphous indium-gallium-zinc-oxide (a-IGZO) thin-film-transistors. Upon 5 min of exposure of 365 nm wavelength and 0.7 mW/cm{sup 2} intensity light with negative bottom gate bias, the maximum photocurrent increases from 3.29 to 322 pA with increasing the V{sub TG} from −15 to +15 V. By changing V{sub TG} from negative to positive, the Fermi level (E{sub F}) shifts toward conduction band edge (E{sub C}), which substantially controls the conversion of neutral vacancy to charged one (V{submore » O} → V{sub O}{sup +}/V{sub O}{sup 2+} + e{sup −}/2e{sup −}), peroxide (O{sub 2}{sup 2−}) formation or conversion of ionized interstitial (O{sub i}{sup 2−}) to neutral interstitial (O{sub i}), thus electron concentration at conduction band. With increasing the exposure time, more carriers are generated, and thus, maximum photocurrent increases until being saturated. After negative bias illumination stress, the transfer curve shows −2.7 V shift at V{sub TG} = −15 V, which gradually decreases to −0.42 V shift at V{sub TG} = +15 V. It clearly reveals that the position of electron quasi-Fermi level controls the formation of donor defects (V{sub O}{sup +}/V{sub O}{sup 2+}/O{sub 2}{sup 2−}/O{sub i}) and/or hole trapping in the a-IGZO /interfaces.« less
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