Linear Metal Atom Chain on GaN(0001) by Chemical Vapor Deposition
Resource
The Journal of Physical Chemistry B 108 (44): 17206-17215
Journal
The Journal of Physical Chemistry B
Journal Volume
108
Journal Issue
44
Pages
17206-17215
Date Issued
2004
Date
2004
Author(s)
Abstract
The adsorption, reaction, growth, and the bonding configuration of a trinuclear linear metal atom chain complex, tetrakis(2,2‘-dipyridylamino)chromium(VI) chloride (DPCC, Cr3(μ3-dpa)4Cl2), on the GaN(0001) surface at 110 K were studied using synchrotron-induced X-ray photoelectron spectroscopy (XPS) and static secondary ion mass spectrometry (SIMS). XPS studies revealed three Cr chemical states of equal surface population present on the sample surface exposed to DPCC of low doses. The SIMS spectra showed main signals contributed from the sputter desorption of pyridine and the dipyridylamino ligand. Studies on small model molecules, such as pyridine and dipyridylamine (Hdpa), exposed to the sample surface showed that upon adsorption at 110 K, these small molecules were present on the sample surface in the molecular form only. They yielded the molecule-Ga adducts formed during SIMS detection. The absence of these adduct signals in the SIMS spectra taken from the DPCC-exposed surface indicated that DPCC chelates were not disintegrated upon adsorption. Instead, DPCC chelates of low doses reacted with the surface via bond rupture of one of the two terminal Cr−Cl bonds on their central Cr atom chains, leaving the Cl atom separated from DPCC to bond on the Ga site of the surface. The resulting chemisorbed DPCC chelate bonded to the surface via the terminal Cr atom of its trinuclear metal chain, resulting in one end of the chain anchored to the surface and the other oriented away from it. There was a change in the DPCC adsorption behavior as the exposure was increased to high doses. The DPCC layer grew molecularly by physisorption at high exposures and the chelates were present on the surface in an inclined configuration. The chelate effect from the presence of four chelating groups in DPCC may provide the chelate its large stability and chemical inertness.
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