Our colleagues Ana Senkić (currently a postdoctoral researcher at the University of Münster), Marko Kralj, and Nataša Vujičić have recently published a paper on tungsten-doped molybdenum disulfide (MoS2), the most prominent member of the family of transition metal dichalcogenides (TMDs). The research was carried out in collaboration with colleagues from the University of Pennsylvania and Penn State University and originated during Dr. Senkić’s doctoral studies, which focused on the synthesis of alloys as well as vertical and lateral heterostructures.
In this work, the authors investigate how the properties of bilayer MoS2 can be modified and controlled through doping, i.e., by introducing very small amounts of foreign atoms into the material. In this case, an isoelectronic tungsten atom was incorporated into the MoS2 crystal lattice. The materials were synthesized by chemical vapor deposition (CVD) under carefully controlled growth conditions.
In bilayer TMDs, different layer stacking arrangements strongly influence crystal symmetry and interlayer interactions. These differences can be identified using optical spectroscopic techniques such as Raman spectroscopy and second-harmonic generation (SHG). The results demonstrate that even extremely low tungsten concentrations (0.03–0.13%) can induce a transition from one semiconducting crystal phase to another. This transition manifests itself through changes in the energies of interlayer vibrational modes and a reduction of the nonlinear SHG signal caused by modifications in crystal symmetry.
Using scanning transmission electron microscopy (STEM), the researchers confirmed the presence of tungsten atoms within the MoS2 crystal matrix and directly observed structural changes at the atomic scale. A particularly noteworthy aspect of this study is that the weak doping induces a transition between different semiconducting crystal structures, rather than the more commonly studied semiconductor-to-metal phase transition. The findings further demonstrate that the structure and properties of 2D materials can be precisely engineered using only minute amounts of dopants, opening new opportunities for the design of advanced materials, heterostructures, and single-photon emitters (SPEs).
The paper was published in npj 2D Materials and Applications and was largely carried out at the Institute of Physics, with contributions from the group of Prof. Marija Drndić at the University of Pennsylvania and theoretical support provided by Prof. Vincent Meunier at Penn State University. We would also like to extend our special thanks to our student Petra Ivatović for her long-standing collaboration and invaluable assistance in the development and implementation of the nonlinear microscopy experimental setup.
The full publication is available here: doi.org/10.1038/s41699-026-00707-z
