For the deposition of nickel oxide (NiO) a molecular beam deposition process in an ozone atmosphere was developed. Purl gaseous ozone is received from a cooling system, which stores only O-3 at -78 degrees C from a O-2/O-3 gas mixture stream, created with an ozone generator. The ozone is released by heating up the system to room temperature. For the deposition process nickel is evaporated while a constant ozone partial pressure is adjusted in the growth chamber. The reactive species of ozone reacts on the substrate surface with the impinging metal atoms to form the compound. This process was carried out in an ultra high vacuum (UHV) chamber to create pure nickel oxide films at room temperature and to study the fundamental layer properties for sensor applications. These films were characterized with respect to their stoichiometric and optical properties by Auger Electron spectroscopy and ellipsometry. The gas sensitivity of the films (as deposited and annealed) on various gases (H-2, NH3, NO2, SO2, CO) was investigated by work function measurements.