The structural, morphological, optical and gas-sensing properties of Mn3O4 thin films grown by successive ionic layer adsorption and reaction technique

In this study, Mn 3 O 4 thin films were grown by Successive Ionic Layer Adsorption and Reaction Technique (SILAR) with 20 and 50 cycles.The effect of the number of cycles on the structural and morphological properties were determined from X-ray diffraction (XRD), scanning electron microscopy (SEM) measurements and RAMAN spectroscopy. The XRD results indicated that the structures are formed as amorphous. For both Mn 3 O 4 thin films, distribution of the films was observed, as seen in SEM analysis, but some voids were seen and which is in line with the XRD results. The various optical parameters such as absorption ( A ), transmission (% T ), reflection (% R ), absorption coefficient ( α ) and extinction coefficient ( k ) of the Mn 3 O 4 films with different deposition cycle were calculated. The absorption coefficient values are more than 10 4 cm −1 and quite near to the reported values. The optical absorption measurements showed that the Mn 3 O 4 film exhibit direct optical band gap energy and increase from 2.30 to 2.50 eV depending on the increasing number of SILAR cycles. The refractive index ( n ) of the examined films was determined by three different methods depending on the band gap energy and reflection. A fairly good agreement was obtained between the refractive index calculated using different models. The refractive index decreased when the band gap increased. The RT gas-sensing performance of p-type Mn 3 O 4 thin films with different SILAR cycle number have been reported and the responses at room temperature were calculated 14% and 43% for Mn 3 O 4 sensors which are 50- and 20-cycle, respectively. The deposited films which properties can be controlled by the number of SILAR cycles have the potential application in optoelectronic and sensor industries due to their band gap values, high refractive index and high sensitivity to CO gas.