Fluorine-Terminated Polycrystalline Diamond Solution-Gate Field-Effect Transistor Sensor with Smaller Amount of Unexpectedly Generated Fluorocarbon Film Fabricated by Fluorine Gas Treatment

In this study, a partially fluorine-terminated solution-gate field-effect transistor sensor with a smaller amount of unexpectedly generated fluorohydrocarbon film on a polycrystalline diamond channel is described. A conventional method utilizing inductively coupled plasma with fluorocarbon gas leads the hydrogen-terminated diamond to transfer to a partially fluorine-terminated diamond (C-F diamond); an unexpected fluorohydrocarbon film is formed on the surface of the diamond. To overcome this issue, we newly applied fluorine gas for the fluoridation of the diamond. Analytical results of X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry suggest that the fluorocarbon film does not exist or only a smaller amount of fluorocarbon film exists on the diamond surface. Conversely, the C-F diamond fabricated by the conventional method of inductively coupled plasma with a perfluoropropane gas (C F gas) source possesses a certain amount of fluorocarbon film on its surface. The C-F diamond with a smaller amount of unexpectedly generated fluorohydrocarbon film possesses nearly ideal drain-source-voltage vs. gate-source-current characteristics, corresponding to metal-oxide-silicon semiconductor field-effect transistor theory. The results indicate that the fluorine gas (F gas) treatment proposed in this study effectively fabricates a C-F diamond sensor without unexpected semiconductor damage.