Stacking change in MoS$_{2}$ bilayers induced by interstitial Mo impurities

TL;DR

This study uses theoretical methods to show how interstitial Mo impurities can alter the stacking order and electronic properties of MoS₂ bilayers, with implications for material control and applications.

Contribution

It reveals that Mo impurities can reverse the stability order of bilayer stacking and modify electronic levels, providing new insights into impurity effects in layered materials.

Findings

Mo impurities reverse bilayer stability from AA' to AB stacking

Impurities create split electronic levels in the energy gap

Impurities enable potential applications like exciton trapping

Abstract

We use a theoretical approach to reveal the electronic and structural properties of molybdenum impurities between MoS$_{2}$ bilayers. We find that interstitial Mo impurities are able to reverse the well-known stability order of the pristine bilayer, because the most stable form of stacking changes from AA' (undoped) into AB (doped). The occurrence of Mo impurities in different positions shows their split electronic levels in the energy gap, following octahedral and tetrahedral crystal fields. The energy stability is related to the accommodation of Mo impurities compacted in hollow sites between layers. Other less stable configurations for Mo dopants have larger interlayer distances and band gaps than those for the most stable stacking. Our findings suggest possible applications such as exciton trapping in layers around impurities, and the control of bilayer stacking by Mo impurities in the growth process.