Determination of conduction band edge and electron affinity in surface potential measurements of BaO

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Abstract
A technique is described which utilizes low‐energy electron reflections (LEER) to determine the electron affinity and to simultaneously locate the position of the conduction band edge with respect to the Fermi level at the surface. The method involves the use of very‐low‐energy incident electrons (<10 V) and subsequent analysis of relections using a kinematical approximation for the interference phenomena. The good agreement between the LEER analysis for thin epitaxial films of BaO and low‐energy electron diffraction (LEED) lattice spacings indicates the validity of the kinematic approximation for this case. An electron affinity of ∼0.6 eV is obtained which is also in good agreement with previously assumed values. Examples of changes in LEER patterns due to changes in electron affinity are correlated with changes in surface stoichiometry from Auger spectroscopy results, while changes in conduction band edge are found to result from changing the temperature or altering the donor density. Because of the depth resolution which is in the range of five to six atomic layers, LEER can be a suitable complementary surface analysis technique to Auger and LEED studies.