酸化ニッケルスパッタ膜の多孔性評価とNO_2検出特性

摘要

ガスセンサに用いられる酸化物半導体の多くはn型であrnるが，NiOは数少ないp型ガスセンサ材料の一つとして研rn究されてきた．その薄膜についても構造とガス検出特性の検rn討がなされている．例えば，STAMATAKI等及びrnFASAKI等はパルスレーザ蒸着によって堆積されたNiO薄rn膜の伝導タイプは蒸着中の酸素圧に依存すること，またH_2rnに対して高い感度を示すとことを報告している．Hotovyrn等はスパッタ膜の作製においてガス流量やアルゴンと酸素のrn混合比および熱処理温度を変えてNiO膜を作製し，その構rn造とNO_2やCOに対する感度を報告した．%NiO films were deposited by DC magnetron sputtering under various pressures from 0.12 to 12 Pa. The structure of the films was investigated using X-ray diffraction, scanning electron microscopy, and measurement of density and surface area. The films generally consisted of columnar grains. In the as-deposited films, as the pressure increased, voids developed between columnar grains and the density decreased with an abrupt increase in surface area. The surface area of a film with a low density considerably decreased after annealing at 400℃. The sensitivity of annealed films to NO_2 at a concentration of 1 ppm in dry air was also investigated. The highest sensitivity, 3.0, was obtained at 200℃ for the sensor made of a film with the lowest density deposited at 12 Pa.