Enhancement Mode Flexible SnO<sub>2</sub>Thin Film Transistors Via a UV/Ozone-Assisted Sol-Gel Approach
Bongho Jang, Hongki Kang, Won‐Yong Lee, Jin‐Hyuk Bae, In Man Kang, Kwangeun Kim, Hyuk‐Jun Kwon, Jaewon Jang
Abstract
The effect of ultraviolet/Ozone (UV/O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> )-assisted annealing process on the structural, chemical, and electrical properties of sol-gel-processed SnO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> films is investigated in this study. Via the UV/O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> -assisted annealing processes, mixed-phase SnO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> films composed of amorphous SnO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> and polycrystalline SnO were obtained. Furthermore, the XPS spectra indicate an increase in the SnO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> /SnO ratio and a substantial decrease in the number of -OH groups (serving as trap sites). This results in an increase in the conductivity and field-effect mobility of the films. The field-effect mobility of the UV/Ozone-assisted 300 °C-annealed SnO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> thin film transistor (TFT) increases considerably (by ~500×), yielding a device with a field-effect mobility of 3.09 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> /Vs. In addition, flexible SnO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> TFTs with Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> insulator and Au gate on Polyimide substrate fabricated via gate electrode engineering shows a decreased conduction bandgap offset, compared to the SnO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> TFTs on SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> , and enhancement mode operation properties (normally off at zero gate voltage) with a field-effect mobility of 1.87 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> /Vs.