Molecular level investigation of 2,2,6,6-tetramethyl-3,5-heptanedione on Si(1 0 0)-2 × 1: Spectroscopic and computational studies

The molecular level chemistry of 2,2,6,6-tetramethyl-3,5-heptanedione (dpmH) has been investigated on a Si(1 0 0)-2 × 1 surface. The dpmH compound is a β-diketone, whose deprotonated form is used as a ligand in chemical precursors for metal-organic chemical vapor deposition (MOCVD). A combination of multiple internal reflection Fourier-transform infrared spectroscopy (MIR-FTIR), temperature programmed desorption (TPD), Auger electron spectroscopy (AES) and density functional theory (DFT) were employed to analytically detect and monitor surface species under different thermal conditions. Upon adsorption at cryogenic temperatures dpmH was shown to be present in the enolic form, while primarily OH dissociation and [2 + 2] carbonyl cycloaddition were revealed at room temperature. Upon heating from room temperature to 900 K, isobutene evolution into the gas phase was found to be a minor reaction pathway. The remainder of dpmH decomposes on the surface to release hydrogen into the gas phase.