GROWTH OF CRYSTALLINE WSE2 AND WS2 FILMS ON AMORPHOUS SUBSTRATE BY REACTIVE (VAN-DER-WAALS) RHEOTAXY

Thin films of metal dichalcogenide compounds with a layered structure, such as MoS2 (WSe2), play an important role in a number of technologi es, like solid lubrication, experimental photovoltaic cells, etc. Such films usually adopt a type-I texture, in which case the c-axis of the crystallites is parallel to the substrate plane. However, for the afo rementioned applications, type-II texture, where the c-axis of the cry stallite is perpendicular to the substrate, is required. We have recen tly demonstrated a novel growth technique (Van der Waals rheotaxy, VdW R) which yields a crystalline film having exclusively type-II texture on amorphous (quartz) substrate. In the present work superior crystall ine, optical and electronic properties of the overlying WSe2 (WS2) fil m together with an improved adhesion of the film to the quartz substra te are obtained by replacing the ultra thin Ni film with a Ni/Cr film.