Precise Layer Control and Electronic State Modulation of a Transition Metal Dichalcogenide via Phase-Transition-Induced Growth

Wafer-scale growth of transition metal dichalcogenides with precise control over the number of layers, and hence the electronic state is an essential technology for expanding the practical application of 2D materials. Herein, a new growth method, phase-transition-induced growth (PTG), is proposed for the precisely controlled growth of molybdenum disulfide (MoS2) films consisting of one to eleven layers with spatial uniformity on a 2 in. wafer. In this method, an energetically unstable amorphous MoSxOy (a-MoSxOy) phase is effectively converted to a thermodynamically stable crystalline MoS2 film. The number of MoS2 layers is readily controlled layer-by-layer by controlling the amount of Mo atoms in a-MoSxOy, which is also applicable for the growth of heteroatom-inserted MoS2. The electronic states of intrinsic and Nb-inserted MoS2 with one and four layers grown by PTGare are analyzed based on their work functions. The work function of monolayer MoS2 effectively increases with the substitution of Nb for Mo. As the number of layers increases to four, charge screening becomes weaker, dopant ionization becomes easier, and ultimately the work function increases further. Thus, better electronic state modulation is achieved in a thicker layer, and in this respect, PTG has the advantage of enabling precise control over the film thickness.

Automated summary

The phase-transition-induced growth (PTG) method successfully achieved the growth of one to eleven layers of MoS2 films on 2-inch wafers, with the ability to precisely control the number of layers and apply to heteroatom-inserted MoS2. Furthermore, analysis based on work functions revealed that the work function of MoS2 increases with the number of layers, with better electronic state modulation observed in thicker layers.