Carrier Density Modulation over an Exceptional Voltage Window in BaSnO$_{\mathrm{3}}$ Films \textit{via} Ion Gel Gating

BaSnO$_{\mathrm{3}}$ has drawn interest recently due to its outstanding room temperature mobility and potential applications in oxide transistors, transparent conductors, \textit{etc}. Here we report effective control of the electronic transport properties of sputtered oxygen-vacancy-doped~BaSnO$_{\mathrm{3}}$~(BaSnO$_{\mathrm{3-\delta }})$ films \textit{via} ion gel gating in electric double layer transistor structures. The electron densities of the starting films is tuned by thickness, from 4 $\times$ 10$^{\mathrm{19}}$ cm$^{\mathrm{-3}}$ at 13 nm to much lower densities at lower thickness. The response to gate voltage is found to be notably robust, with largely reversible response (even in vacuum) over an exceptionally wide window from -4 to $+$4 V, even at 300 K. The data support predominantly electrostatic response, unlike many other oxides, which we ascribe to Sn redox stability. In this manner the sheet resistance of 13-nm-thick BaSnO$_{\mathrm{3}}$ films can be modulated by a factor of 50 at 300 K, increasing to almost 10$^{\mathrm{3}}$ at low temperatures. Similar measurements at lower thickness/electron density will also be discussed.