Optical EngineeringAnalysis of characteristic parameters of a plasma ion source and of ion-assisted deposited optical thin films
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It is well known that ion-assisted deposition (IAD) using a plasma source improves the optical and physical characteristics of optical thin films. A broad-beam cold-cathode plasma source was used in this study. The versatile ion source selected can easily be retrofitted into existing deposition chambers or new installations. This paper discusses characterization of the ions produced by the plasma source and analyzes the properties of thin films produced using the plasma source for IAD. Ion energy measurements were made using an ion energy analyzer for the determination of ion energy distribution functions (IEDFs). IEDFs were measured for three gases; argon, oxygen, and nitrogen. The ion characteristics in oxygen are focused on. The effect of pressure and drive current on the IEDFs of oxygen ions is discussed. Mean ion energies of oxygen as a function of pressure, drive voltage, and drive current were calculated. Since the density and quality of films are related to the ion current density during deposition, the effects of drive voltage, pressure, and the pumping speed of the system are discussed. Characteristics of TiO2 and Ta2O5 films deposited on silicon wafers and microscope slides were investigated. The conditions for moisture stability of these films were analyzed.