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Printed Schottky diode based on ZnO and carbon nanotube applied as UV sensor

Grant number: 19/24430-0
Support type:Scholarships in Brazil - Scientific Initiation
Effective date (Start): February 01, 2020
Effective date (End): December 31, 2020
Field of knowledge:Engineering - Materials and Metallurgical Engineering
Principal researcher:Neri Alves
Grantee:Luis Henrique Tigre Bertoldo
Home Institution: Faculdade de Ciências e Tecnologia (FCT). Universidade Estadual Paulista (UNESP). Campus de Presidente Prudente. Presidente Prudente , SP, Brazil

Abstract

Ultraviolet radiation (UVR) is beneficial for people's health, however, if the exposure is excessive it can cause diseases as, for instance, skin cancer. Brazil is one of the countries with the biggest skin cancer incidence in the world. For this reason, UVR sensor devices, printed on personal adornments or in clothing is very important. Zinc oxide (ZnO) is a semiconductor material widely used for UVR detection, just because due to its wide energy bandgap the incident light produces pairs electrons-hole, increasing the charge carrier number and, consequently the conductivity. This project is proposed to develop a printed diode based on ZnO to be applied as a UVR sensor. ZnO thin films heavily doped with aluminum (AZO) and carbon nanotube (CNT) are used as ohmic contact and Schottky barrier, respectively. AZO thin films are produced in-situ by ZnO spray pyrolysis deposition onto a thin aluminum layer, of ~10 nm by vacuum thermal evaporation. In the same sequence, the ZnO thin film is deposited and, to accomplish the device, a layer of MWCNT is deposited by spray on the top of the set. AZO electrodes show transparence bigger than 90% and sheet resistance lower than 100 &/¡, while MWCNT needs to be thicker to show low resistance, and therefore they are is not transparent. The performance of diode with architecture CNT/AZO/CNT, as a radiation sensor, will be compared to one of the photoresistor devices with architecture CNT/AZO/CNT. For the photoresistor will be evaluated mainly on the ratio between the UVR current and dark current, the rise time and decay time. The Schottky diode will be evaluated, under URV and in dark, the rectification ration, the Schottky barrier height, the ideality factors, and others. Also, will be studied the real feasibility of these devices as UVR sensors. (AU)