PREPARATION OF Au-Pt NANOSTRUCTURES ON HIGHLY ORIENTED PYROLYTIC GRAPHITE SURFACES BY PULSED LASER DEPOSITION AND THEIR CHARACTERIZATION BY XPS AND AFM METHODS

Au-Pt nanostructures on highly oriented pyrolytic graphite (HOPG) were prepared by irradiating bimetallic target under ultrahigh vacuum with pulsed radiation of Nd:YAG laser. The deposited nanostructures were characterized by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). The measured spectra of Au (4f) and Pt (4f) photoelectrons of laser deposits were composed of two overlapping doublets. Analysis of images obtained from AFM revealed bimodal particle size distribution and presence of few large particles. In agreement with AFM images of the deposit we attributed a two doublet structure of Au (4f) and Pt (4f) spectra to bimodal nanoparticle size distribution. Carbon KLL Auger electron spectra revealed formation of defects in the superficial layers of HOPG by impinging metal ions accompanied by appearance of sp(3) hybridized carbon atoms. The dependence of Au (4f) and Pt (4f) core level binding energies on the amount of metals deposited and formation of bimetallic nanoparticles are discussed.