The n-p tunable room-temperature hydrogen response of SnO2-modified MoS2 thin films and its in-situ SKPM study

The development of high-performance hydrogen sensors is considered of great significance for the safety of hydrogen energy and related industries. The two-dimensional (2D) MoS2 nanomaterials have exhibited great superiority in building fast and reliable room-temperature hydrogen sensors. However, their poor sensitivity and selectivity issues still limit their wide exploitation. In this work, nano-SnO2-modified MoS2 thin films with structure-dependent n-p tunable hydrogen response behaviours were reported. The in-situ scanning Kelvin probe microscopy (SKPM) study on the hydrogen response of the SnO2/MoS2 systems revealed the different reductions in the surface potential of SnO2 (0.38 eV) and MoS2 (0.26 eV) in a hydrogen environment, which results in different variations in the interface potential barrier with the increasing surface coverage of SnO2. As a result, the contribution from the interface effect to the n-type hydrogen response was changed from the positive enhancement to the negative compensation. The sensor exhibited a fast, enhanced, and selective n-type hydrogen response with the SnO2 coverage down to 6.4%, while a p-type sensor response was achieved when the SnO2 coverage increased to 95.6%. Such structure-dependent n-p tunable hydrogen sensing behaviour can not only be utilized for the sensitization of the sensing layers but may also provide a simple and cost-effective way for the modulation of the response type of the sensor composed of the MoS2-based 2D materials.