Exploiting the properties of TiO2 thin films as a sensing layer on (MEMS)-based sensors for radiation dosimetry applications

In this work, we investigate the potential of exploiting TiO2 thin films as sensing layers on silicon micro-electromechanical systems for the detection of gamma radiations. All samples are exposed to gamma rays produced by 60Co, with different doses ranging from 0 kGy to 40 kGy. Properties of silicon coated with a 200-nm-thick layer of TiO2 grown at 200 °C by atomic layer deposition are studied before and after its gamma irradiation using x-ray diffraction (XRD), scanning electron microscopy, and spectroscopic ellipsometry. Atomic force microscopy (AFM) is carried out on functionalized microcantilevers to measure the resonance frequency shift (Δf 0) resulting from irradiation of the TiO2 thin film. XRD results show a change in the films from a mixture of rutile and anatase phases to an anatase phase upon irradiation. Spectroscopic ellipsometry results show a change with a fixed pattern in the film thickness, roughness, void, and optical constants with different irradiation doses. This pattern appears as Δf 0 in AFM, where the response of sensors to doses between 0 kGy and 20 kGy was linear. The values of Δf 0 are convenient to control parameters for the proposed dosimeter, which is characterized by the reproducibility and sensitivity of measurements. The maximum detectable linear effect of the proposed dosimeter was found at a dose of 20 kGy. This makes a 200-nm thin layer of TiO2 coated on a microcantilever surface, a possible candidate for dosimetry for the range lower than 20 kGy applications, such as in personal dosimeters.