“…However their detecting mechanism is not fully yet established. Film parameters that are widely known to affect the sensing properties of a thin film are surface roughness, stoichiometry, grain size, structure (amorphous or polycrystalline), and porosity [1][2][3][4][5][6]. Furthermore depending on the preparation conditions of the sensing layers (physical vapor deposition, chemical vapor deposition, screen-printed and sintered materials) and also on the sensor design (nature and geometry of the electrodes), large differences of behavior concerning gas response and selectivity are observed [7][8][9].…”