Surface confined quantum well state in MoS₂(0001) thin film

Surface confined quantum well state (scQWS) is a QWS confined around the surface of a thin film whose electronic energy is smaller than the work function of the film. The scQWS is rather rare in most thin films. Here, we show the existence of scQWS in thin films of transition metal dichalcogenides, MoS₂. Signatures of scQWS are identified as the overall downward band dispersion in the bulk gap of 2 H-MoS₂ thin film at larger binding energy range. These scQWSs are also characterized with a Shockley-type surface state having an inverse parabolic decay into the film and a symmetric (asymmetric) distribution of projected charge density at the two surfaces of odd-layer (even-layer) films. Our findings of scQWS in MoS₂ shed some light on understanding the electronic properties of 2D materials with implications in future 2D electronic devices.