Paper Title
Influence of As-Se Based Chalcogenide Glasses’ Electrical Conductivity on The Direction of Photo-Induced Mass Transport

Amplitude-phase optical reliefs can be directly recorded as holograms or other photonic elements in amorphous chalcogenide glasses. Recording efficiency depends on illumination intensity, polarization, photon energy and also on the glass, amorphous layer composition, which are usually p-type semiconductors. Basically, the recording consists of charge generation by band-gap illumination interconnected with excitons, charged defect and structure reconstructions within amorphous phase towards more or less ordered or even towards crystallization. At the presence of illumination gradients by polarized laser beams mass transport effects appear and result deep geometrical surface reliefs [1-3]. It was established that the direction of mass-transport (from illuminated region to the dark or reverse) changes near the transition from pure a-Se (which may be considered as n-type) to p-type AsxSe1-x, where x~0.01 [4]. We demonstrated it by preparing special co-deposited samples with different composition and recording surface holograms or simply illuminating the layers through the mesh and recording diffraction pictures at the boundary. These results indicate, that the direction of the mass-transport is dependent on the amorphous semiconductors conduction type. Continuing this direction, we have combined the results of charge transport time of flight measurements in Se, with different content of dopants, as well as the influence of applied electric field in the samples on the direction of mass transport, either through a transparent electrode method or comb-like patterned electrical contacts. Results show the increasing efficiency of recording under applied electric field, gave us additional data and support to the previously developed model [3] of light-stimulated mass transport in such materials. These may be applied for the development of electric field driven optical data recording. Keywords- chalcogenides, mass transport, holography, conduction type