Electrical field induced growth of triangular nanometer structures on WSe2

We report on the conditions for the growth of triangular structures on WSe2 surfaces in scanning tunneling experiments with a vertical dimension of one layer (Se-W-Se) and up to 200 nm in horizontal direction. Experiments carried out in different atmospheres (ambient air, dry N-2, dry O-2) suggest that the growth is directly related to the presence of a thin physisorbed water layer on the surface of WSe2. Furthermore examinations under different scanning and bias conditions show that the electric field of the tip induces the growth of these nanometer structures.