Dopant based electron beam lithography in CuxTiSe2

A method for creating a patterned array of sub-micron crystals on the surface of a doped layered dichalcogenide using a scanning electron microscope has been developed. Exposing the surface of copper doped TiSe2 to iodine vapor induces sub-micron CuI crystals to form upon the surface. The copper ions diffuse to the surface from within the crystal to react with the iodine vapor, with larger crystals forming at higher temperatures. The amount and size of the crystals formed in a given area could be controlled by first exposing of portions of the surface to electron radiation within the microscope. Increasing the radiation exposure results in the formation of fewer and smaller CuI crystallites, and it is possible to completely prevent their formation using large exposures. It appears that the electron beam creates a thin barrier that limits the diffusion of copper ions to the surface. The system is sufficiently inert that exposing the surface to air for a few hours has no significant effect. The resultant surface features can be arranged with a lateral resolution limited mainly by the size of the features themselves.