Abstract
The matrix assisted pulsed laser evaporation (MAPLE) technique has been used for the deposition of metal dioxide (TiO2, SnO2) nanoparticle thin films for gas sensor applications. For this purpose, colloidal metal dioxide nanoparticles were diluted in volatile solvents, the solution was frozen at the liquid nitrogen temperature and irradiated with a pulsed excimer laser. The dioxide nanoparticles were deposited on Si and Al2O3 substrates. A rather uniform distribution of TiO2 nanoparticles with an average size of about 10 nm and of SnO2 nanoparticles with an average size of about 3 nm was obtained, as demonstrated by high resolution scanning electron microscopy (SEM-FEG) inspections. Gas-sensing devices based on the resistive transduction mechanism were fabricated by depositing the nanoparticle thin films onto suitable rough alumina substrates equipped with interdigitated electrical contacts and heating elements. Electrical characterization measurements were carried out in controlled environment. The results of the gas-sensing tests towards low concentrations of ethanol and acetone vapors are reported. Typical gas sensor parameters (gas responses, response/recovery time, sensitivity, and low detection limit) towards ethanol and acetone are presented.
Highlights
The synthesis of nanoparticles of different materials and the study of their properties and possible applications are at present among the most active research areas
High resolution Scanning Electron Microscopy (SEM) images of the TiO2 nanoparticle films deposited on silicon substrates showed that the nanoparticles preserved the starting dimensions, a tendency to form aggregates can be noted
By a comparison with TiO2 nanoparticle films deposited by the spin coating technique, starting from a solution with the same TiO2 nanoparticle concentration (i.e. 0.2 wt %) used for the matrix assisted pulsed laser evaporation (MAPLE)-deposited films, a much more uniform coverage for the MAPLE deposited film was observed (Figure 2)
Summary
The synthesis of nanoparticles of different materials and the study of their properties and possible applications are at present among the most active research areas. Even if some obtained results are of interest, the problem of the large size distribution poses strong limits to the extensive use of PLD for nanoparticle film fabrication. Nanoparticles with well tailored size and low size dispersion were obtained by chemical growth techniques, which are relatively easy and cheap. These techniques can produce spherical colloidal nanoparticles of different materials [7,8]. The difficulty of realization of uniform close-packed nanoparticle thin films is a very strong limit to their possible applications This is why a versatile, fast deposition technique, like MAPLE, was considered as a very attractive alternative. A summary of the methodology and of the obtained results [12,13,16,17] is given here
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