Inter-row Adsorption Configuration and Stability of Threonine Adsorbed on the Ge(100) Surfaces

Abstract

E-mail: easyscan@sookmyung.ac.krReceived December 7, 2012, Accepted January 8, 2013The adsorption structures of threonine on the Ge(100) surface were investigated using core-level photoemissionspectroscopy (CLPES) in conjunction with density functional theory (DFT) calculations. CLPES measurementswere performed to identify the experimentally preferred adsorption structure. The preferred structure indicatedthe relative reactivities of the carboxyl and hydroxymethyl groups as electron donors to the Ge(100) surfaceduring adsorption. The core-level C 1s, N 1s, and O 1s CLPES spectra indicated that the carboxyl oxygencompeted more strongly with the hydroxymethyl oxygen during the adsorption reaction. Three among sixpossible adsorption structures were identified as energetically favorable using DFT calculation methods thatconsidered the inter- and intra-bonding configurations upon adsorption onto the Ge(100) surface. Thesestructures were O-H dissociated N dative inter bonding, O-H dissociated N dative intra bonding, O-H dissociationbonding. One of the adsorption structures: O-H dissociated N dative inter bonding was predicted to be stablein light of the transition state energies. We thus confirmed that the most favorable adsorption structure is theO-H dissociated N dative-inter bonding structure using CLPES and DFT calculation.Key Words : Threonine, Ge(100), Inter-row adsorption configuration, DFT calculation, CLPESIntroductionStudies of the reactions between organic molecules andsemiconductor surfaces have become increasingly importantover the past few years. Technologies that rely on interactionsbetween organic materials and semiconductor technologiesare being developed for molecular electronics, biosensor,and nanotechnology applications.