Fast Scan Spectrometer For Monitoring Of Thin Film Optical Properties
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One of the most interesting techniques for in situ measurement of thin film optical properties and control of the coating deposition process is the wide wavelength band optical monitoring. This system allows the real time measurement of transmittance or reflectance of a sample during the film growth. In this paper a photometric monitoring system operating in the extended visible range (0.35- 1.1 μm) and connected to a r.f. sputtering apparatus is proposed. Real-time performances we-'e obtained by the use of 1K-diode array sensor positioned on the exit port of a grating monochromator. Optical fibers were used to obtain the required optical path inside the sputtering vacuum chamber. The instrument is computer controlled and the sample reflectance curve is displayed on a graphic monitor. An automatic control of the deposition process is obtained comparing this curve with expected reflectance values by the aid of a properly defined merit function. In the present configuration the monitoring equipment can be employed for single and multilayer dielectric coatings on transparent substrates.