Investigation of MgO Seed Layer Crystallinity and Morphology-Dependent Characteristics of NO₂ Gas Sensors Using In₂O₃ Nanorods Grown by Hydrothermal Synthesis Method

This study investigated the effects and influences of MgO seed layer and morphology on the characteristics of NO<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> gas sensors fabricated using the In<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> nanorod sensing membranes grown by the hydrothermal synthesis method. The morphologies of In(OH)<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> nanorods were modified using different MgO seed layers and different precursor solutions of indium chloric tetrahydrate and urea. The In(OH)<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> nanorods were converted into In<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> nanorods in a hydrogen ambience at 300 oC for 10 min. Using the hydrothermal synthesis method with indium chloric tetrahydrate of 65 mM and urea of 1.42 M, the optimal response of the NO<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> gas sensors was 219.1 by using the In(OH)<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> nanorods grown on 100-nm-thick MgO seed layers sputtered with RF power of 100 W and annealed in oxygen ambience at 500 oC for 2 hours. The response time and recovery time of the resulting NO<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> gas sensors were 42 sec and 82 sec, respectively.