13:30 〜 15:30
▲ [25p-P03-3] Clarification of Co adsorbed on Si(111)-7×7 structure using QUANTUM ESPRESSO
キーワード：Si(111), DFT, Co
[Background] The adsorption of metal nanoclusters on Si surfaces has been widely investigated for several decades but the model of Co adsorbed on Si(111)-7×7 surface and the process of Co diffusion on Si surface are still uncertain [1]. Meanwhile, density functional theory (DFT) methods represent one of the most successful theoretical methods in the investigation of the structure and properties of solids in various fields of material research [2,3]. In this work, based on the ring-like Co clusters experiment results, the one/three Co adsorbed on Si(111)-7×7 models are calculated with QUANTUM ESPRESSO.
[Method] Ab initio simulations of Co adsorption on Si(111)-7×7 surface was performed using DFT within a planewave/pseudopotential framework as implemented within the QUANTUM ESPRESSO code. The standard Perdew-Burke-Ernzerhof generalized gradient approximation (PBE-GGA) for the exchange correlation energy was adopted. Wave functions were expanded in plane-waves with a kinetic energy cutoff of 300 Ry.
[Results and discussion] The ring-like Co cluster adsorbed on Si(111)-7×7 surfaces was observed in Fig.1 (a) with AFM/KPFM. The Co cluster was adsorbed on an off-center site in HUC, two center Si adatoms were missing, and it shows a ring-like shape. Therefore the one/three Co adsorbed on Si(111)-7×7 models are calculated, three Co adsorbed model shown in fig.1(b). The adsorption energy of one/three Co adsorbed models are -27.46 eV and -136.54 eV, respectively. So, these structures will be more stable than the initial state. However, in Fig1. (c) and (d) are DFT-calculated charge distributions of three Co adsorbed model. Compared with one Co adsorbed result, the charge distribution of three Co adsorbed model in the center of the ring-like structure is lower than outside which is a better explanation for the KPFM image.
[Method] Ab initio simulations of Co adsorption on Si(111)-7×7 surface was performed using DFT within a planewave/pseudopotential framework as implemented within the QUANTUM ESPRESSO code. The standard Perdew-Burke-Ernzerhof generalized gradient approximation (PBE-GGA) for the exchange correlation energy was adopted. Wave functions were expanded in plane-waves with a kinetic energy cutoff of 300 Ry.
[Results and discussion] The ring-like Co cluster adsorbed on Si(111)-7×7 surfaces was observed in Fig.1 (a) with AFM/KPFM. The Co cluster was adsorbed on an off-center site in HUC, two center Si adatoms were missing, and it shows a ring-like shape. Therefore the one/three Co adsorbed on Si(111)-7×7 models are calculated, three Co adsorbed model shown in fig.1(b). The adsorption energy of one/three Co adsorbed models are -27.46 eV and -136.54 eV, respectively. So, these structures will be more stable than the initial state. However, in Fig1. (c) and (d) are DFT-calculated charge distributions of three Co adsorbed model. Compared with one Co adsorbed result, the charge distribution of three Co adsorbed model in the center of the ring-like structure is lower than outside which is a better explanation for the KPFM image.