Hydrogen gas sensing negative differential resistance device based on phase transformation of metal hydride

Negative differential resistance (NDR) devices receive broad attentions due to their applicability to neuromorphic computing. Previously, we have proposed a novel mechanism for inducing NDR, namely phase transformation-based NDR. In the present study, gas sensing ability of such NDR devices is demonstrated. Because dehydrogenation reaction of metal hydride is employed as the phase transformation, hydrogen gas (H2) partial pressure has a significant impact on the NDR properties. Indeed, the critical input power to induce NDR is found to be almost proportional to H2 partial pressure and, therefore, H2 pressure can be estimated from the NDR properties. Detailed discussion revealed that H2 pressure affects the NDR properties in two ways: one is a direct thermodynamic impact and another is a secondary impact due to higher thermal conductivity at higher H2 pressure. We believe that the phase transformation-based NDR devices are suitable for sensors, as the phase transformation of the material is governed simply by the environment in which the material is located.