In this investigation thin films of NiO doped with cobalt of 90 nm of thickness have been prepared, these were deposited by spinning coating on borosilicate glass substrates of 12mm x 12 mm x 1mm, through the sol-gel method, the same ones that are evaluated the effect of the molar percentage (3, 5 and 7%) of dopant and the annealing temperature of (250,300 and 350 ° C) that influencing the electrical, optical properties and in the same way there being a relationship with the crystalline structure. X-ray diffraction measurements (u.a) and intensity patterns of the UV-Vis absorption bands (u.a) show that with the method used thin films of NiO have an FCC structure (figures 3.8 - 3.10), As the annealing temperature increases, its crystal sizes increase, however the cobalt dopant decreases it, the size details and network parameters in each temperature and percentage (table 3.2). The percen...