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Published byJoelle Cordingley Modified over 2 years ago

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Quantum System “ Ion flux fraction measurement system

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Talk Outline Theory of Operation What is a Quartz Crystal Oscillator Calibration

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A quartz crystal oscillator mounted at the bottom of the RFEA grid stack enables deposition rates of ions and neutrals to be determined Theory of Operation

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Quartz is a piezoelectric material which changes shape when subjected to electric fields What is a Quartz Crystal Oscillator The industrial standard is 14mm in diameter and 0.2mm thick and has a resonant frequency at 6MHz When material is deposited on the crystal the resonant frequency changes and the change is proportional to the thickness of the deposited layer Governed by Sauerbrey’s Equation f C f m

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The aspect ratio of the structure determines the amount of ion / neutral loss to the walls Given the aspect ratio of our system the deposition rate due to neutrals can be underestimated by about 30% Therefore the system uses a second “calibration sensor” without any grids (only crystal) to calibrate the gridded sensor Calibration

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