Functionalization and characterization of InAs and InP surfaces with hemin

Chemical functionalization of hemin molecules onto InAs and InP is reported. X-ray photoelectron spectroscopy (XPS), atomic force microscopy, and spectroscopic ellipsometry (SE) analyses are used to characterize the III-V surfaces. One notable feature of the C 1s core level spectra is a peak at similar to 284 eV observed for the functionalization chemistries, which is attributed to C = N bonding within the porphyrin molecule. This is corroborated by the observation of N Is, Fe 2p, and other distinguishable chemical bonding peaks. For example, in the As 3d and P 2p core levels, -COOH bonding is observed to the As and P anion in the InAs and InP samples, respectively, which implies chemisorption of the functional groups to the material surfaces. Another result of the XPS analysis is the impact of the surface functional group on the electronic state of the surface causing upward band bending of the valence band maximum, indicating surface charge transfer as explored in previous work [Garcia et al., Appl. Phys. Lett. 88, 013506 (2006)]. SE analysis on the functionalization process provides data for the effect of hemin and benzoic acid solution concentrations. The authors discuss the dependence of the band bending, surface coverage, and hemin layer thickness as determined by XPS and SE