## 2 Materials and Methods  
The cleaning of a Cu(110) surface (\(10\times 10\times 1\) mm) was carried out using several cycles of Ar+ ion sputtering at 1 keV for 20 min per cycle at 700 K, followed by an additional annealing process at 1100 K for 20 min. The level of cleanliness of the Cu(110) surface was confirmed using low-energy electron diffraction measurements of pristine Cu(110) surface. L-leucine (Leu; C\({}_{3}\)H\({}_{7}\)NO\({}_{2}\), \(<\)99% purity; Sigma Aldrich, St. Louis, Missouri, United States) and L-tyrosine (Tyr; C\({}_{9}\)H\({}_{11}\)NO\({}_{3}\), \(<\)99% purity; Sigma Aldrich, St. Louis, Missouri, United States) were purchased and further purified by several sublimation cycles to remove contaminated impurity prior to the adsorption experiments.  
RAIRS spectra were obtained using a NICOLET 6700 FT-IR spectrometer (Thermo Scientific, US), which was equipped with liquid nitrogen (LN2)-cooled MCT (Mercury-Cadmium-Telluride). All RAIR spectra of the specimen were measured at less than \(1\times 10^{-10}\) Torr, referring to a background single-beam spectrum recorded on pristine Cu(110) surface. Each spectrum with a spectral range of 800-3200 cm\({}^{-1}\) was obtained at a resolution of 4 cm\({}^{-1}\) by averaging 500 scans.  
The C 1s, N 1s, and O 1s core-level spectra included in amino acids molecules were acquired using HRPES equipped at the Pohang Accelerator Laboratory (10D HRPES-I beamline) with photon energies of 340, 460, and 590 eV to increase the surface sensitivity factors. Their binding energies were corrected by that of the pure Au 4f core-level spectrum (84.0 eV) for the identical photon energy. The base pressure of the chamber was maintained under ultra-high vacuum condition (below 9.5 \(\times\) 10\({}^{-11}\) Torr). The three core-level spectra were carefully fitted with Voigt functions to analyze the bonding configurations [15]. The 1.0 ML of Leu and Tyr coverage was defined as the maximum density at which they can be deposited on a Cu(110) surface without yielding the N 1s core-level peak at 399.1 (\(\pm\)0.1) eV characteristic of multilayer formation.  
DFT calculations were also performed to predict the adsorption energies of Leu and Tyr on the Cu(110) surface. All DFT adsorption energy was calculated by using the JAGUAR 9.1 software package, which applied a hybrid density functional method and included [PERSON]'s three-parameter nonlocal exchange functional with Lee, Yang, and Parr nonlocal correlation functional (B3 LYP) [16]. In these calculations, we considered four-dimer (Cu35H32) cluster models. For the determination of the geometries corresponding to the important local minima on the potential energy surface, we applied a mixed basis set that uses the LACVP basis set to describe Cu atoms and the 6-31 G basis set to describe the remaining atoms developed by [PERSON] and [PERSON] [17]. In detail, the upper layer structure of Cu atoms allowed the atoms of the adsorbate to relax because the adsorption proceeded directly, and the optimization energy was calculated by fixing the lower layer of Cu atoms. Each calculated energy value was obtained with the minimum value and the geometry was chosen. We also verified the local minimum and transition states in each calculation.