| Mechanism to explain why the device with one-layer MoS2 generates more photocurrent than the seven-layer MoS2 one. (top) In the one-layer device MoS2 (right), the electron (red circle) has a higher probability to tunnel from the MoS2 layer to the GrT because the energy barrier (white arch) is smaller in that junction. In the seven-layers MoS2 device (left) instead, the energy barrier between MoS2/GrT and MoS2/GrB is the same so electrons do not have a preferred direction flow. More energy is generated in the one-layer MoS2 device because more electrons flow in the same direction. (bottom) Imagine that people want to cross a mountain without too much effort. If the mountains have different height (right), more people choose to climb (or better, to tunnel) the small mountain, while if the mountains have the same height (left), they do not have a preferred route. Image: IBS. |
