Generating intense electric fields in 2D materials by dual ionic gating

Abstract

The application of an electric field through two-dimensional materials (2DMs) modifies their properties. For example, a bandgap opens in semimetallic bilayer graphene while the bandgap shrinks in few-layer 2D semiconductors. The maximum electric field strength achievable in conventional devices is limited to ≤0.3 V/nm by the dielectric breakdown of gate dielectrics. Here, we overcome this limit by suspending a 2DM between two volumes of ionic liquid (IL) with independently controlled potentials. The potential difference between the ILs falls across an ultrathin layer consisting of the 2DM and the electrical double layers above and below it, producing an intense electric field larger than 4 V/nm. This field is strong enough to close the bandgap of few-layer WSe2, thereby driving a semiconductor-to-metal transition. The ability to apply fields an order of magnitude higher than what is possible in dielectric-gated devices grants access to previously-inaccessible phenomena occurring in intense electric fields.

Strong gate-tunability of flat bands in bilayer graphene due to moiré encapsulation between hBN monolayers

“…Most recently, ref. 36 and 37 reported realizations of an electric field up to 3.5 V nm −1 across a WSe 2 bilayer using ionic liquid gates, one order of magnitude higher than required in this work. In Fig.…”

Pyridinic Dominance N-Doped Graphene: A Potential Material for SO2 Gas Detection

“…The sensor's response is noted as a variation in drain current when an electric field is applied usually, investigated using field-effect transistors (FETs). 67 In this section, we analyzed the modulated sensitivity of PNG toward SO 2 detection by examining the impact of the external electric field. The electric field along the z-direction (perpendicular to the surface) and intensity of −0.4 to +0.4 V/ Å are taken into consideration.…”

“…Many prior studies suggested that using an external electric field to modify the performance of 2D materials as a gas sensor is an effective method. , Electric fields cause changes in the carrier density ( E -field causes polarization of charge density) produced in a material by the field at its surface, which further alters the response of the sensor toward the adsorbate. The sensor’s response is noted as a variation in drain current when an electric field is applied usually, investigated using field-effect transistors (FETs) …”

Full control of solid-state electrolytes for electrostatic gating

“…[2][3][4] In transistors, the large capacitance leads to unrivaled performance in low-voltage operation [10][11][12] and sub-threshold swing. 5,12,13 It also enables the observation of physical phenomena, such as gate-induced superconductivity (at carrier densities ∼ 10 14 cm 2 ), 4,[14][15][16][17][18][19][20][21][22][23][24][25][26] the quenching of the band gap of two-dimensional (2D) semiconductors, 27,28 or the possibility to perform precise spectroscopic measurements of semiconducting band gaps (ionic-gate spectroscopy). 5,9,[29][30][31][32][33][34][35][36][37] These results have been enabled by liquid electrolytes, either ionic liquids and ionic solutions (ions dissolved in liquid electrolytes), or ion gels, i.e., ionic liquids or ions dispersed in a polymer matrix (such as polyethylene oxide), ideal for gating applications 4 because of their high electrochemical stability [2][3][4] and relatively large ionic conductivity.…”

“…39,40 Electrolyte back-gated devices would drastically expand the range of carrier density, and allow phenomena such as gate-induced superconductivity to be studied by ARPES (or, similarly, by scanning tunneling spectroscopy). Ionic double gated devices -which enable the applications of electric fields in excess of 3 V/nm perpendicular to 2D semiconductors to quench their gap-provide another pertinent and timely example, 27,28 since they require combining an top and back ionic-gate electrodes. These and other types of experiments cannot be performed using exclusively top ionic-gate electrodes, and to make them possible it is necessary to find solid-state electrolytes (SSE) [41][42][43][44] that can be employed reliably in a back-gate configuration, with performance comparable to that of top ionic gates.…”