Low-temperature growth of crystalline tungsten disulfide thin films by using organic liquid precursors

Abstract

A low-temperature growth method for crystalline thin films of transition metal dichalcogenides (TMDCs) is urgently required to use various materials as substrates. In this paper, we report the growth of crystalline tungsten disulfide (WS2) thin films at a low growth temperature of 400 °C by using organic liquid precursors: bis(tert-butylimido)bis(dimethylamido)tungsten(VI) [(t-BuN)2W(NMe2)2] and di-tert-butyl disulfide [(t-C4H9)2S2]. To achieve low-temperature growth, these precursors were introduced onto a substrate through pulse-controlled valves that are similar to the atomic layer deposition process. Furthermore, we determined that a crystalline WS2 film can be grown even at 350 °C on the entire surface of a SiO2/Si substrate by first depositing a catalytic metal film (W or Au) onto a limited area of the substrate, although almost no growth of the crystalline WS2 film was observed at 350 °C without pre-deposition of the metal film.