Functional Dielectric Properties of Solution-Processed Lithium Indium Tin Oxide (LiInSnO₄) and Its Application as a Gate Insulator of a Low Voltage Thin Film Transistor

Abstract

The electrical conductivity of indium–tin oxide (In–Sn-O) arises from the conduction band electrons, which largely varies on the ratio of In and Sn. By exploiting this large variation of electrical conductivity, this material could be treated both as a semiconductor and a transparent conductor. Interestingly, incorporation of lithium (Li) ion can convert it to an effective insulator when the ratio of Li, In, and Sn becomes equal and could be successfully used as a gate dielectric of a thin-film transistor (TFT). In this work, LiInSnO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> (LITO) thin film has been deposited by a solution-processed technique, which shows high areal capacitance due to its mobile Li-ion. A low operating voltage (≤2 V) solution-processed zinc oxide (ZnO) TFT has been fabricated by using this LiInSnO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> thin film as a gate dielectric. The carrier mobility of this ZnO TFT has been enhanced by one order by the addition of one titanium oxide (TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ) gate interface due to the reduction of dielectric/semiconductor interface trap state. Our optimized ZnO TFT with TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> gate interface shows the carrier mobility of 5.66 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> / <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{V}\,\cdot $ </tex-math></inline-formula> ,s with an ON/ OFF ratio of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$10^{{4}}$ </tex-math></inline-formula> .