Surface chemistry of the linear chromium chain complex on GaN(0001)

Abstract

Better understanding about the chemistry of the organometallic chain complexes reacting on the solid surface can foster concepts of nanowire fabrication which are central to the continued advance of the electronic and optoelectronic industries. In this study, the adsorption and thermal reactivity of a trinuclear chromium chain complex, tetrakis (2,2′-dipyridylamino)chromium(VI) chloride, on the GaN(0001) surface were investigated using x-ray photoelectron spectroscopy, temperature-programmed desorption, and static secondary ion mass spectrometry in order to obtain some insight into the bonding changes involved in the reaction of the linear metal chain complex on the compound semiconductor surface. One of the two terminal Cr–Cl bonds of the complex may be cleaved upon adsorption at 110K, leading to the formation of the Ga–Cl bonds on the surface, although some complexes remained intact upon adsorption and bonded strongly to the surface. No ligand was dissociated from the chromium chain complex during the adsorption. The Cl-cleaved complex residue preserved its original chemical configuration. Both the Cl-cleaved and the intact complexes in the first layer were stable on the surface in the substrate temperature range between 110 and 260K. A partial decomposition in which some ligands were dissociated from the adsorbed complex took place before the substrate temperature reaching 400K. Additional Cr–Cl bonds were disrupted, resulting in a larger population of Ga–Cl bonds on the surface. Further thermal reaction at higher temperatures led to the dominance of the Ga–Cl bonding for the Cl presence on the surface. Surface etching of Ga by the dissociated Cl atoms started at a substrate temperature of ∼525K and the etching rate reached its maximum at ∼590K.