VAN-DER-WAALS EPITAXY OF THE LAYERED SEMICONDUCTORS SNSE2 AND SNS2 - MORPHOLOGY AND GROWTH MODES

The recent development of so-called van der Waals epitaxy offers a who le new variety of material combinations for semiconductor heterojuncti ons. In this paper we investigate the morphology and the growth modes of the layered semiconductors SnSe2 (E-g = 1.03 eV) and SnS2 (E-g = 2. 18 eV) on a variety of layered single crystalline substrate materials (highly oriented pyrolytic graphite, MoTe2, MoS2, WSe2, GaSe, SnS2 and SnSe2). The growth modes were investigated by low energy electron dif fraction, photoemission spectroscopy and scanning tunnelling microscop y. We found that both of the materials grow in a two-dimensional layer -by-layer fashion with three-dimensional nucleation. However, despite the strong similarities of both of the materials the results indicate that SnS2 grows in a more ideal layer-by-layer mode than SnSe2. This i s attributed to different surface diffusion rates due to different gro wth temperatures. The difference in empirically determined optimized g rowth temperatures are explained by the different thermal stabilities of the materials. (C) 1997 Elsevier Science B.V.