Ga doped ZnO thin films deposited by RF sputtering for NO2 sensing

International audienceGa doped ZnO thin films have been deposited by Radio-Frequency (RF) magnetron sputtering on fused silica substrates. The structural analysis of the n-type sensitive material showed a preferential orientation in the [00l] direction. The microstructure of the thin film indicated an increasing grain size with the increase of the thicknesses. The micro sensor platforms have been fabricated with ZnO:Ga thin film deposited using a reliable stencil mask onto interdigitated electrodes containing micro-hotplates. The as fabricated micro sensor allows to sense sub-ppm concentration (500 ppb) of nitric dioxide. This system reveals promising sensing performance with a sensitivity Rg/Ra up to 75 at low temperature (50 °C)

Sub-ppm NO2 sensing in temperature cycled mode with Ga doped ZnO thin films deposited by RF sputtering

International audienceIn this work Ga doped ZnO thin films have been deposited by RF magnetron sputtering onto a silicon micro-hotplate and their structural, microstructural and gas sensing properties have been studied. ZnO:Ga thin film with a thickness of 90 nm has been deposited onto a silicon based micro-hotplates without any photolithography process thanks to a low cost and reliable stencil mask process. Sub-ppm sensing (500 ppb) of NO2 gas at low temperature (50 °C) has been obtained with promising responses R/R0 up to 18. Micro-hotplates have been prepared using photolithographic process. The system is composed by a heating element and sensing electrodes. They are both integrated in membrane in order to have a localized heating and sensing spot onto which the sensitive thin film is deposited. The microhotplates can operate with low consumption and can heat up to 500 °C with a good stability. This system has been already published in [1]. The use of lift-off process to restrict the deposition of the thin film onto central electrodes can lead to the dissolution and/or contamination of the sensitive layer. That's why the photolithographic method was avoided and a stencil mask process was used

Thermoelectric Oxide Thin Films with Hopping Transport

In this chapter, we firstly show the interest of thermoelectric oxide thin films with hopping transport in terms of thermoelectric properties. Thermoelectric and electrical properties of hopping oxides will be presented with some examples of oxide materials and we will discuss about the interest of the development of thermoelectric thin films, more specifically in the case of hopping oxide semiconductor thin films. A second part devoted to make accurate measurements of the Seebeck coefficient of the thermoelectric thin films will then be showed. Then, we will expose in a last part the transport properties of one hopping oxide semiconductor deposited with the Mg doped CuCrO2 compound. A description of the optimization of the annealing temperature and the film thickness will be made in the aim to optimize the transport properties. At the end, we will expose the case of a three-strip Mg doped CuCrO2 thermoelectric thin film module which generates a power of 11 nW with a thermal gradient of 225 °C and we will discuss about their possible applications