In this presentation we show how individual atomic defects and linear mirror twin boundaries in 2- D MoSe 2 , identified with super resolution atomic force microscopy, alter the electronic wave function, imaged via Scanning Tunneling Spectroscopic mapping, leading along mirror twin boundaries to charge density waves and solitons.

Hierarchically ordered defects or adsorbents in two dimensional transition metal dichalcogenides modify the local electronic states in terms of energy and geometry of the electronic wave functions at length scales of individual wave functions, inducing novel functionality. Due to their 2-D nature, 2-D TMDs are an excellent model system to directly access, visualize and determine the effects of defect mediated electronic wave function tuning using high resolution AFM and differential conductance mapping.

We focused on studying various defect classes in 2-D MoSe2. We identified individual Se vacancies – on both, the SPM facing and the substrate facing surface. Both result in particular electronic wave function related to states localized at the atomic defect [1]. These defect states form atomically sharp type 1 hetero junctions with the surrounding pristine MoSe2, and form an excellent test bed to study catalytic activity with atomic precision.

We also identified hierarchically ordered defects in from of Mirror Twin Boundaries (MTB) in MoSe2, which form truly 1-D metal channels embedded in the surrounding semiconductor. At low temperatures these 1-D metallic states open a band gap at the Fermi level of 100meV. The new band gap frontier states exhibit a spatial modulation along the channels with a periodicity of three times the lattice constant. Density Functional Theory calculation confirm that the observed charge modulation is a result of the formation of a charge density wave [2]. Charging up the charge density wave we observe the creation of solitons – a self-reinforcing wave - and are able to measure its’ energetic dispersion [3].

These results demonstrate how defects can not only modify the local electronic wave function, but directly alter the material properties and opens up a large playground to study the effects of linear defects, hierarchically ordered defects or adsorbents.

1 Maps of Electronic Wave functions associated with various atomic defects in MoSe2, S. Barja, S. Wickenburg, , A.Weber-Bargioni et al. submitted

2 Charge density wave order in 1D mirror twin boundaries of single-layer MoSe2, S. Barja, S. Wickenburg, A.Weber-Bargioni et al. accepted in nature physics