Schottky Barrier Variable Heterostructure Hydrogen Gas Detector through Electron Transfer between Pd NPs and Graphene

Among future fuels that are in the spotlight, hydrogen has a dangerous side. The combustion rate and low flash point of hydrogen cause major explosion accidents. Therefore, leakage accidents are the most important issue in using hydrogen as a fuel. Therefore, a system that can detect hydrogen from very low concentrations is an essential problem.<br/>Palladium (Pd) has the property of decomposing and bonding hydrogen molecules when exposed to hydrogen atmosphere. At this time, the volume changes at the same time as the bonding, and the energy structure of Pd also changes. Research on a system for sensing hydrogen using these properties of Pd has been conducted. In this study, we propose a hydrogen sensor attached to the surface of graphene by fabricating such Pd in the form of naoparticles (NPs).<br/>In the case of Pd NPs, it has a larger surface area than that of Pd sheet, minimizing the effect of volume increase and maximizing the contact area with hydrogen molecules. Pd NPs were fabricated through the annealing process and were confirmed using electrical characterization and Scanning Electron Microscope (SEM). When Pd NPs are attached to graphene, electrons are moved between graphene and Pd NPs when the energy structure is changed as the Pd NPs adsorb hydrogen. This results in changes in the energy structure and surface conductivity of graphene. This change occurs with the concentration of hydrogen.<br/>We fabricated a device using a heterogeneous structure of Silicon (Si) and Graphene. The two materials have the characteristics of a semiconductor and a metalloid, forming a Schottky barrier. Then, Pd NPs are attached to the graphene surface of the device. When the device is exposed to hydrogen, the Pd NPs adsorb hydrogen, which changes the energy structure of graphene. As a result, the Schottky barrier between Si and graphene changes and the current flowing through the device changes.<br/>Using this principle, the reactivity to hydrogen is electrically detected with a Si/graphene heterostructure device. As a result of the detection, it was confirmed that it was possible to detect low-concentration hydrogen gas at a level of 250 ppm.