Size dependent 2p3/2 binding-energy shift of Ni nanoclusters on SiO2 support: Skin-depth local strain and quantum trapping

An in situ X-ray photoelectron emission investigation revealed that the size trend of the 2p_3/2 binding-energy shift (BES) of Ni nanoclusters grown on SiO₂ substrate follows the prediction of the bond order-length-strength (BOLS) correlation theory [30]. Theoretical reproduction of the measurements turns out that the 2p_3/2 binding energy of an isolated Ni atom is 850.51 eV and its intrinsic bulk shift is 2.70 eV. Findings confirmed that the skin-depth local strain and potential well quantum trapping induced by the shorter and stronger bonds between under-coordinated surface atoms provide perturbation to the Hamiltonian and hence dominate the size dependent BES.