Development of a SnS Film Process for Energy Device Applications

Abstract

Tin monosulfide (SnS) is a promising p-type semiconductor material for energy devices. To realize the device application of SnS, studies on process improvement and film characteristics of SnS is needed. Thus, we developed a new film process using atomic layer deposition (ALD) to produce SnS films with high quality and various film characteristics. First, a process for obtaining a thick SnS film was studied. An amorphous SnS2 (a-SnS2) film with a high growth rate was deposited by ALD, and a thick SnS film was obtained using phase transition of a-SnS2 film by vacuum annealing. Subsequently, we investigated the effect of seed layer on formation of SnS film to verify the applicability of SnS to various devices. Separately deposited crystalline SnS and SnS2 thin films were used as seed layer. The SnS film with a SnS seed showed small grain size and high film density from the low surface energy of the SnS seed. In the case of the SnS film using a SnS2 seed, volume expansion occurred by vertically grown SnS grains due to a lattice mismatch with the SnS2 seed. The obtained SnS film using the SnS2 seed exhibited a large reactive site suitable for ion exchange.