Surface pattering of Ge-As-Se thin films by electric charge accumulation

We deposited electric charge in periodic manner in form of square lattices of points in Ge-As-Se chalcogenide semiconductor films by electron beam. Various types of surface reliefs are observed as a result of interaction of electron beam with the semiconductor thin films. For the films where charge removal is facilitated by conducting gold underlayer shape of surface relief is similar for all deposited doses per point. For the films with no gold underlayer, where charge removal is hindered, the shape of local relief depends on the dose per point and at higher doses also on the lattice period. When the lattice period is larger than interaction volume of electron in the material the identical surface reliefs consisting of spire and crater are formed during each charge deposition. When the lattice period is smaller than the interaction volume of the electron identical surface reliefs are formed only in every second charge deposition event. As a result highly organized checkerboard-like lattices are formed. We suggest that a reason for the appearance of such complex periodic structures is charge accumulation in these films. When the ratio between the size of space charge region and lattice period is small enough there would be influence of already deposited charge on the charge deposition in the next step. This opens possibility to fabricate structures on the surface of these materials by combining charge already accumulated in the material with charge deposited in consecutive step. We also show that it is possible to experimentally define the size of space charge region in chalcogenide thin films.