Chemical bonding and nanomolecular length effects on work function at Au-organophosphonate-HfO2 interfaces

We demonstrate that introducing a thiol-terminated organophosphonate nanomolecular layer (NML) can increase the effective work function at Au-HfO2 interfaces by up to ΔΦeff = 0.55 ± 0.05 eV. Capacitance measurements of Au-NML-HfO2-SiO2-Si stacks and ultraviolet photoelectron spectroscopy of Au-NML-HfO2 structures, and parts thereof, reveal that Φeff shifts are primarily determined by the length of the molecules comprising the NML, while Au-NML and NML-oxide bonding dipole contributions tend to counteract each other. Our findings provide insights into tailoring the electronic properties of metal-oxide heterointerfaces for applications by harmonizing the effects of interfacial bonding and NML morphology.