NO₂ gas sensing properties of amorphous InGaZnO₄ submicron-tubes prepared by polymeric fiber templating route

One-dimensional (1D) amorphous InGaZnO₄ (a-IGZO) submicron-tubes were synthesized in a method involving an electrospun polymeric fiber template and the direct RF-sputter-coating of a-IGZO films combined with subsequent calcination at 450°C. The a-IGZO hollow fibers with a diameter of 300nm and a shell thickness of 20–30nm showed an amorphous structure, as confirmed by XRD and HR-TEM analyses. Gas sensors using semiconducting a-IGZO tube networks exhibited n-type gas sensing characteristics and a 3.7-fold higher gas response (Rgₐₛ/Rₐᵢᵣ=109.5 at 2ppm NO₂) compared to (Rgₐₛ/Rₐᵢᵣ=29.4) planar a-IGZO thin films at an operating temperature of 300°C. The enhanced gas response of a-IGZO tubes is attributed to the greater space charge modulation depth associated with the thin shell structures and the porous networks which are readily accessible by gas.