Structural properties of thin Zn0.62Cu0.19In0.19S alloy films grown on Si(111) substrates by pulsed laser deposition

Alloys of Zn2-2xCuxInxS2 (ZCIS) have been grown on Si(lll) substrates by pu lsed laser deposition (PLD). The thin films grew epitaxially on chemically treated Si(lll) regardless of an about 2-5 nm thick interfacial amorphous l ayer between the ZCIS and the Si substrate. The particular Zn0.62Cu0.19In0. 19S layers under investigation consist of column-like grains propagating fr om the interface to the layer surface. Despite of the existence of the amor phous layer in the interfacial region each ZCIS grain is precisely oriented to the structure of the underlying silicon substrate and to the neighborin g ZCIS grains without any azimuthal misorientation. Each individual column- like grain contains many twin lamellae of various thickness that lie parall el to the interface and, therefore, coherent Sigma 3{111} twin boundaries o ccur. Sigma 3{112} grain boundaries are formed perpendicular to the interfa ce during the intergrowth of the individual columns. Perfect dislocations w ith their lines parallel to the interface envelop the columns and finally, a dislocation network like a honeycomb can be observed during TEM plane-vie w observation. However, polycrystalline ZCIS layers exhibiting a distinct [ 111] texture have been formed on untreated Si(lll) substrates, where the 2- 2.5 nm thick intermediate native layer consists of amorphous SiOx. The indi vidual ZCIS grains were found to be polysynthetically twinned too. Amorphis ized regions have always been produced inside the chemically treated Si sub strates due to the outdiffusion of copper from the layer into the Si substr ate: that seems to be favored against that of Zn. However, the amorphous na tive SiOx layer which covers the untreated silicon substrates prevents subs tantially the out-diffusion of metal atoms from the layer into the substrat e and, therefore, no diffusion-induced defects have been generated inside t he untreated Si substrate. (C) 2000 Elsevier Science S.A. All rights reserv ed.