A new compact low-temperature hydrogen ion beam apparatus has been developed for in situ physical property measurements. Introduction of hydrogen can significantly alter the physical properties of materials. Conventional methods such as exposure to H2 gas are limited to materials having hydrogen sorption. The present method is, in principle, applicable to any material of interest. Our setup provides a facile way to conduct both low-temperature hydrogen ion beam irradiation and in situ electrical resistivity measurements, which enables observation of novel physical properties induced by the low-temperature irradiation. The lowest temperature of 3.8 K was achieved by utilizing a newly designed rotatable radiation shield and a closed-cycle cryostat, which is advantageous for long-time low-temperature experiments for heavy hydrogen doping and in situ analysis. It was found that the resistivity of ZnO largely decreased by hydrogen ion beam irradiation at 50 K. Furthermore, the in situ measurements revealed an unforeseen irreversible thermal hysteresis for resistivity.
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