Very Large Capacitance Enhancement in a Two-Dimensional Electron System

Electron correlation effects at the interface of two metal oxides lead to a lower chemical potential and enhance capacitance. Increases in the gate capacitance of field-effect transistor structures allow the production of lower-power devices that are compatible with higher clock rates, driving the race for developing high-κ dielectrics. However, many-body effects in an electronic system can also enhance capacitance. Onto the electron system that forms at the LaAlO3/SrTiO3 interface, we fabricated top-gate electrodes that can fully deplete the interface of all mobile electrons. Near depletion, we found a greater than 40% enhancement of the gate capacitance. Using an electric-field penetration measurement method, we show that this capacitance originates from a negative compressibility of the interface electron system. Capacitance enhancement exists at room temperature and arises at low electron densities, in which disorder is strong and the in-plane conductance is much smaller than the quantum conductance.

[1]  Akira Ohtomo,et al.  A high-mobility electron gas at the LaAlO3/SrTiO3 heterointerface , 2004, Nature.

[2]  J. Mannhart,et al.  Tunable Quasi-Two-Dimensional Electron Gases in Oxide Heterostructures , 2006, Science.

[3]  B. Shklovskii,et al.  Anomalously large capacitance of an ionic liquid described by the restricted primitive model. , 2010, Physical review. E, Statistical, nonlinear, and soft matter physics.

[4]  B. Holländer,et al.  Electrical characterization of amorphous lanthanum aluminate thin films grown by molecular-beam deposition on silicon , 2006 .

[5]  R. H. Silsbee,et al.  The Landau level density of states as a function of Fermi energy in the two dimensional electron gas , 1992 .

[6]  E. A. Galaktionov,et al.  Thermodynamic density of states of two-dimensional GaAs systems near the apparent metal-insulator transition. , 2006, Physical review letters.

[7]  J. Mannhart,et al.  Oxide Interfaces—An Opportunity for Electronics , 2010, Science.

[8]  West,et al.  Compressibility of the two-dimensional electron gas: Measurements of the zero-field exchange energy and fractional quantum Hall gap. , 1994, Physical review. B, Condensed matter.

[9]  West,et al.  Negative compressibility of interacting two-dimensional electron and quasiparticle gases. , 1992, Physical review letters.

[10]  A. Millis,et al.  Two-Dimensional Electron Gases at Oxide Interfaces , 2008 .

[11]  D. Ceperley,et al.  Ground state of the two-dimensional electron gas. , 1989, Physical review. B, Condensed matter.

[12]  Kravchenko,et al.  Evidence for the influence of electron-electron interaction on the chemical potential of the two-dimensional electron gas. , 1990, Physical review. B, Condensed matter.

[13]  M. Bibes,et al.  Dynamical response and confinement of the electrons at the LaAlO3/SrTiO3 interface. , 2009, Physical review letters.

[14]  H. Jaffrès,et al.  Towards two-dimensional metallic behavior at LaAlO3/SrTiO3 interfaces. , 2009, Physical review letters.

[15]  Higgins,et al.  Capacitance measurements of a quantized two-dimensional electron gas in the regime of the quantum Hall effect. , 1985, Physical review. B, Condensed matter.

[16]  H. Hwang,et al.  Dominant mobility modulation by the electric field effect at the LaAlO3/SrTiO3 interface. , 2009, Physical review letters.

[17]  A. Millis,et al.  Lattice relaxation in oxide heterostructures: LaTiO3/SrTiO3 superlattices. , 2006, Physical review letters.

[18]  T. Kopp,et al.  Two-dimensional electron liquid state at LaAlO 3 -SrTiO 3 interfaces , 2009, 0907.1176.

[19]  K. Müller,et al.  SrTi O 3 : An intrinsic quantum paraelectric below 4 K , 1979 .

[20]  Jochen Mannhart,et al.  Calculation of the Capacitances of Conductors -- Perspectives for the Optimization of Electronic Devices , 2009, 0902.4673.

[21]  N. Reyren,et al.  Electric field control of the LaAlO3/SrTiO3 interface ground state , 2008, Nature.