This research is presenting a study of optical and structural properties of (Fe2O3)1-x(MgO)x composites synthesized as thin film that can be used as a gas sensor. Pulsed laser deposition technique was used to prepare thin films of (Fe2O3)1-x(MgO)x. The pattern of X-ray diffraction of the composites powder showed the consistency of iron oxide (α-Fe2O3) hematite phase along with the planes (104) and (110) as preferred planes for crystal growth where the intensities of which varied with MgO content. The crystal size of the thin film material was varied in between (26.8-35.1) nm. The diffraction pattern of the pulsed laser deposited thin films was absent from any diffraction peaks. The maximum transparency obtained of hematite– magnesium oxide thin films was about 60% in the visible region, with an energy gap in the range (3.5-4.1) eV for direct allowed transition. The optical constants were determined and were found greatly affected by the MgO content. The gas sensor cells from (Fe2O3)1-x(MgO)x/c-Si showed maximum sensitivity approximately of 73.3% for NH3 gas for MgO content x=0.3 at temperature of 343 K.
