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Printed hybrid devices for UV photodetectors and gas sensors.


ZnO thin films produced by the pyrolysis of zinc acetate dihydrate, sprayed on heated substrates, are naturally n-doped due to structural defects like oxygen vacancy, interstitial zinc, and others. Since the ZnO band gap is about 3.3 eV, ultraviolet radiation (UVR) photons can generate electron-hole pairs, increasing the number of electrons in the conduction band. These photo-generated electrons interact with the adsorbed oxygen, at the defects, in a reversible reaction [O2(g)+e-ÌO2(ad)], releasing it to the atmosphere. Thus, ZnO-based devices may have their conductivity changed when exposed to the atmosphere and UVR, which is an undesirable effect under the device's stability viewpoint. However, such characteristic is fundamental to apply the ZnO as the active material in sensor devices. The excessive exposure to UVR can cause serious diseases, including skin cancer. It's worth to emphasizes that Brazil is one of the countries with the highest incidence of skin cancer, corresponding to almost one-third of malignant tumors, with 90% of them related to the excessive exposure to UVR. A cheap sensor, printed onto cards or personal adornments, can be an important ally to avoid the harmful effects of UVR and maximize the beneficial effects. In this context, our main goal is to develop and characterize a printed UVR photodetector and gas sensor, based on ZnO, prepared by spray pyrolysis technique. Aiming the sensor's development will be studied the performance and stability of ZnO based devices, such as photoresistors, Schoktty diodes, p-n diodes, transistors, and MIS (metal-insulator-semiconductor) capacitors. (AU)

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Scientific publications
(References retrieved automatically from Web of Science and SciELO through information on FAPESP grants and their corresponding numbers as mentioned in the publications by the authors)
VIEIRA, DOUGLAS HENRIQUE; OZORIO, MAIZA DA SILVA; NOGUEIRA, GABRIEL LEONARDO; FUGIKAWA-SANTOS, LUCAS; ALVES, NERI. UV-photocurrent response of zinc oxide based devices: Application to ZnO/PEDOT:PSS hydrid Schottky diodes. MATERIALS SCIENCE IN SEMICONDUCTOR PROCESSING, v. 121, . (18/04169-3, 19/01671-2, 19/08019-9)
GOMES, TIAGO C.; KUMAR, DINESH; ALVES, NERI; KETTLE, JEFF; FUGIKAWA-SANTOS, LUCAS. The Effect of Anodization Parameters on the Aluminum Oxide Dielectric Layer of Thin-Film Transistors. JOVE-JOURNAL OF VISUALIZED EXPERIMENTS, n. 159, . (19/08019-9, 14/13904-8, 16/03484-7, 19/05620-3, 19/01671-2)

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