Zinc oxide as an ozone sensor

Abstract

This work presents a study of intrinsic zinc oxide thin film as ozone sensor based on the ultraviolet ͑UV͒ photoreduction and subsequent ozone re oxidation of zinc oxide as a fully reversible process performed at room temperature. The films analyzed were produced by spray pyrolysis, dc and rf magnetron sputtering. The dc resistivity of the films produced by rf magnetron sputtering and constituted by nanocrystallites changes more than eight orders of magnitude when exposed to an UV dose of 4 mW/ cm 2 . On the other hand, porous and textured zinc oxide films produced by spray pyrolysis at low substrate temperature exhibit an excellent ac impedance response where the reactance changes by more than seven orders of magnitude when exposed to the same UV dose, with a response frequency above 15 kHz, thus showing improved ozone ac sensing discrimination.

Fabrication of fully transparent nanowire transistors for transparent and flexible electronics

“…Ozone is also expected to increase the density of oxygen vacancies near the nanowire surface. Because oxygen vacancies act as donor states 31,32 , this should increase nanowire conductivity. Although the ITO and IZO microstructures and chemical bonding states are more complex, the basic crystal structures are sufficiently similar to those of In 2 O 3 and ZnO to reasonably expect that the In 2 O 3 and ZnO nanowire work functions will increase similarly upon ozone treatment 30,33 .…”

Effect of oxygen on the threshold voltage of a-IGZO TFT

“…Specifically, it can effectively enhance the switching behavior and threshold voltage (V th ) of TFTs through proper semiconductor resistance path adjustment [2,15]. The properties of a-IGZO TFTs are highly dependent on their oxygen content, but in an interactive way; this is because oxygen vacancies provide the needed free carriers for electrical conduction [3]. In fact, oxygen vacancy can be easily generated in the oxides.…”

“…In the semiconductor study for TFTs, various research groups have focused on amorphous oxide semiconductors based on the adoption of metal cation species [1][2][3][4][5][6][7]. The primary demands for such oxide-based semiconductors are: high optical band gap (>3.5 eV), biocompatibility, nontoxicity, good tailored electrical conductivity, high optical transparency (>80% in VIS-IR), good ability for etching; lithography process compatibility, surface uniformity, and high thermal and chemical stability in various environments [8][9][10].…”

Oxide semiconductors: Order within the disorder

“…Nowadays these active oxides are key components in a wide range of device applications like sensors [29] and thin-film transistors (TFTs), where it has been demonstrated that they can present high electronic performance even when disordered ionic oxides are used [30][31][32][33][34][35][36]. Concerning p-type oxide semiconductors, this activity has been also pursued in the last years [37][38][39][40][41][42][43][44][45].…”

“…The ndoping effect in oxide semiconductors is essentially related to the existence of oxygen vacancies (meaning that the films are non stoichiometric and so there are not enough anions to compensate the existing cations), which work as a source for electrons. Their control depends on the oxidation state of the cation, which leads to changes in the film composition, as opposed to the substitutional doping in covalent semiconductors [18,29]. For p-type oxides, a passivation of vacancies and deep defects is also necessary prior to the introduction of the correct impurities in the host matrix [39].…”