Detection of heavy ions for cancer therapy using amorphous carbon nitride a-CN films prepared by a nitrogen radical sputter method

Abstract Secondary-electron (SE) yields from amorphous carbon nitride (a-CN X ) films on Al foil were measured by using fully-stripped and fixed-velocity (6 MeV/n) heavy ion beams, C 6+ . The purpose of our research is to study the characteristics of a-CN X films for the application to heavy particle detectors. a-CN X films were prepared by a nitrogen radical sputter method, and were deposited on one side of an Al foil. SE yields from both surfaces of forward and backward ( Q F , Q B ) by the impact of 6 MeV/n C 6+ ions were independently measured. When a-CN X film was on the backside of the Al foil in the beam direction, the SE yield ( Q B ) from a-CN X was significantly larger than Q F from the Al surface side. This was an unexpected result from the well-known knowledge. Comparing the SE yields between the Al surface side with the backward of a-CN X and the pure Al foil (without a-CN X ), Q B from a-CN X was significantly larger than Al, suggesting a promising possibility of a-CN X for the application of a new detector; meanwhile Q F from Al (with a-CN X ) was smaller than that from the pure Al by a factor of 3.4. We found the latter phenomenon can be explained by a decrease in a vacuum level of a-CN X film side.