Contreras, J., R. Martins, P. Wojcik, S. Filonovich, H. Águas, L. Gomes, E. Fortunato, and I. Ferreira,
"Color sensing ability of an amorphous silicon position sensitive detector array system",
Sensor Actuat. A-Phys., vol. 205, pp. 26-37, 2014.
AbstractThe color sensing ability of a data acquisition prototype system integrating a 32 linear array of 1D amorphous silicon position sensitive detectors (PSD) was analyzed. Besides being used to reproduce a 3D profile of highly reflective surfaces, here we show that it can also differentiate primary red, green, blue (RGB) and derived colors. This was realized by using an incident beam with a RGB color combination and adequate integration times taking into account that a color surface mostly reflects its corresponding color. A mean colorimetric error of 25.7 was obtained. Overall, we show that color detection is possible via the use of this sensor array system, composed by a simpler amorphous silicon pin junction.
Loureiro, J., J. R. Santos, A. Nogueira, F. Wyczisk, L. Divay, S. Reparaz, F. Alzina, C. M. S. Torres, J. Cuffe, F. Montemor, R. Martins, and I. Ferreira,
"Nanostructured p-type Cr/V2O5 thin films with boosted thermoelectric properties",
J. Mater. Chem. A, vol. 2, issue 18, pp. 6456-6462, 2014.
AbstractThe urgent need for non-toxic and abundant thermoelectric materials has become a significant motivation to improve the figures of merit of metal oxides in order to remove the barrier towards their widespread use for thermoelectric applications. Here we show the influence of a Cr layer in boosting the thermoelectric properties of vanadium pentoxide (V2O5) thin films, deposited by thermal evaporation and annealed at 500 °C. The Cr to V2O5 thickness ratio controls the morphological and thermoelectric properties of the thin films produced. The optimized Seebeck coefficient and power factor values at room temperature are +50 μV K−1 and 7.9 × 10−4 W m−1 K−2, respectively. The nanograin structure of the films is responsible for an improvement in the electrical conductivity up to 3 × 105 (Ω m)−1 with a typical thermal conductivity of 1.5 W m−1 K−1. These results combine to yield promising p-type thermoeletric CrV2O5 thin films with a ZT of 0.16 at room temperature.
Loureiro, J., N. Neves, R. Barros, T. Mateus, R. Santos, S. Filonovich, S. Reparaz, C. M. S. Torres, F. Wyczisk, L. Divay, R. Martins, and I. Ferreira,
"Transparent aluminium zinc oxide thin films with enhanced thermoelectric properties",
J. Mater. Chem. A, vol. 2, issue 18, pp. 6649-6655, 2014.
AbstractImproved thermoelectric properties of Aluminum Zinc Oxide (AZO) thin films deposited by radio frequency (RF) and pulsed Direct Current (DC) magnetron sputtering at room temperature are reported. In both techniques films were deposited using sintered and non-sintered targets produced from nano-powders. It is confirmed that both the Al doping concentration and film thickness control the thermoelectric, optical and structural properties of these films. Seebeck coefficients up to −134 μV K−1 and electrical conductivities up to 4 × 104 (Ω m)−1 lead to power factors up to 4 × 10−4 W mK−2, which is above the state-of-the-art for similar materials, almost by a factor of three. The thermoelectric I–V response of an optimized AZO element with a planar geometry was measured and a maximum power output of 2.3 nW, for a temperature gradient of 20 K near room temperature, was obtained. Moreover, the low thermal conductivity (<1.19 W mK−1) yields a ZT value above 0.1. This is an important result as it is at least three times higher than the ZT found in the literature for AZO, at room temperature, opening new doors for applications of this inexpensive, abundant and environmental friendly material, in a new era of thermoelectric devices.