Photoemission study of size selected InP nanocrystals: the relationship between luminescence yield and surface structure
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The surfaces of luminescent InP nanocrystals were investigated by photoelectron spectroscopy (PES) technique with synchrotron radiation. Semiconductor samples were prepared by an organometallic approach using trioctylphosphine (TOP) and trioctylphosphine oxide (TOPO) as stabilizing and size regulating agents. As prepared, InP nanocrystals exhibit poor photoluminescence (PL) yield, usually less than 1%. However the yield can be drastically enhanced to about 20-30% by photoetching of the nanoparticle surface with fluorine compounds. High resolution In 3d and P 2p core level spectra of etched and non-etched particles taken at different excitation energy reveal changes of the nanocrystal surface. Three different InP samples are analyzed and a simple model for the etching process is discussed.