Ultrahigh sensitivity and linearity humidity sensor base on vertical alignment of ZnO nanorods sensing layer

Abstract

Capacitive humidity sensor was fabricated on CMOS technology with multiple parallel metals coplanar (interdigitage electrodes, IDEs) by lithography process base on silicon bulk substrate and coated Nickel-gold onto IDEs by electroless method. This paper proposed the IDEs humidity sensor with vertical alignment of zinc oxide (ZnO) nanorods on thick seed layer by sputtering process (IDEs/ZnO nanorods) for high sensitivity. ZnO nanorods structure and morphology were obtained by scanning electron microscope (SEM) and X-Ray diffractometer (XRD), respectively. The humidity sensors were comparatively examined properties before/after sputtering process. We have observed sputtering time for 3.0h with 100 nm thick seed layer effected to optimal vertical alignment of ZnO nanorods (length 480 nm) which shown high sensitivity (up to 1913.83%). Moreover, the IDEs/ZnO nanorods significantly improved on wide ranges relative humidity (30-90 %RH), fast response (up to 42.39%) and a little recovery times (16sec), precise repeatability as well as low hysteresis (18.22%). Finally, it demonstrated long-term stability and also exhibited a temperature dependence.