Photochemical attachment of amine linker molecules on hydrogen terminated diamond

摘要

The photochemical attachment of 10-amino-dec-l-ene molecules protected with trifluoro acetamide acid group ("TFAAD") on hydrogen terminated single crystalline CVD diamond, using a high-pressure mercury lamp with a peak emission around 250 nm, is described and characterized by XPS measurements. Angular resolved XPS experiments reveal oriented molecular bonding on diamond with protecting amide groups at the top. The time dependence of photoattachment follows an exponential law, with a time constant of only 1.7 h due to spin-coating of TFAAD. Based on total photoyield spectroscopy (TPYS) and spectrally resolved photoconductivity (SPC) data, measured on high quality single crystalline diamond, we introduce a model where valence-band electrons are optically excited with energies of 4.7 to 5.2 eV into empty states of TFAAD molecules. This transition is stimulated by the negative electron affinity of H-terminated diamond, which shifts the photochemical reaction window of diamond below its optical gap (5.47 eV) into a regime where commercially available UV light sources emit and organic molecules like TFAAD are still transparent.