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Retrieving the energy band of Cu thin films using quantum well states

Angle-resolved photoemission electron spectroscopy (ARPES) measurement was performed on epitaxially grown Cu/Co/Cu(001) films to observe the quantum well (QW) states due to the electron confinement inside the Cu film by the Cu/Co and Cu/vacuum interfaces. By studying the in-plane dispersion of the QW states, we find a nearly isotropic electronic structure in the neck region of the Fermi surface. Based on the quantization condition, we achieve a model-free method for obtaining the copper energy band and the energy contour near the Fermi energy. The result is in good agreement with theoretical calculations of the bulk copper energy band, showing that there is no significant difference in the energy bands between the bulk and thin film copper. This method can be generalized to measure energy bands of other metallic films using the QW states.