Preparation and passivation ofGaAs(001) surfaces for growing organic molecules

Abstract

Growth of ordered organic films of 3, 4, 9, 10-perylene-tetracarboxylic-dianhydride (PTCDA), on inorganicsubstrates of GaAs(001) is investigated by means of low-energy electrondiffraction, scanning tunnelling microscopy andatomic force microscopy. The passivation of the samplecan be achieved by exposing the substrate to sulphur (the SnS2compound) or wet-chemical etching using an S-containing etchant(S2Cl2). The sulphur-treated surfaces are less reactiveand are suitable as substrates for the growth of epitaxialfilms. In this work we have compared the growth of organicmolecules on substrates prepared by two different methods. Thesamples prepared by molecular beam epitaxy (MBE) presentsmoother surfaces compared with chemically treated samples. Therefore, an improvement of the PTCDA molecular order isobserved for the MBE samples, which exhibit the formation ofcrystals.