CALIBRATION OF AN OFF-AXIS QUARTZ-CRYSTAL THICKNESS MONITOR FOR A PULSED-LASER DEPOSITION SYSTEM USING A HIGH-RESOLUTION SCANNING ELECTRON-MICROSCOPE

The deposition rate in a pulsed laser deposition system is known to depend on a variety of system parameters including wavelength, energy density, target material, target exposure, geometry and repetition rate. In an attempt to dynamically monitor the progress during deposition of tribological thin films, an off-axis quartz crystal monitor was used to determine the thickness of the growing film. A Hitachi S-900 high resolution, field emission scanning electron microscope was used to determine the thickness of films for various laser parameters. Consecutive depositions of MoS2 using the same crystal over several days showed that the calibration factor was constant. The calibration factor did not change appreciably when films of NbSe2 totaling approximately 3.8 mu m were deposited between two groups of MoS2 depositions. It increased significantly when approximately 1.1 mu m of WS2 films were deposited. Decreasing the energy density by changing the focus of the laser was also shown to decrease the calibration factor. Suggestions for the calibration of the off-axis quartz crystal monitor when the same crystal is to be used for different targets are presented.