Investigations of ultra thin Co/Cu(100)films by electrochemical method

• Main Authors: Y. H. Li, 李育鴻
• Other Authors: J. S. Tsay
• Format: Others
• Language: zh-TW
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/27170040678436141928

碩士 === 國立臺灣師範大學 === 物理學系 === 96 === The electrodeposition of Co on a Cu(100) electrode in diluted hydrochloric acid was investigated by means of cyclic voltammetry (CV), electrochemical scanning tunnelling microscopy (EC-STM) and electrochemical magneto-optic Kerr effect (EC-MOKE). In the pure supporting electrolyte (1 mM HCl), the typical current peak pair in the CV measurements for Cl de- and adsorption is missing because of the smooth Cu(100) surface. Cl adsorption occurs at E=-375 mV vs Ag/AgCl. Exchanging the electrolyte against a 1 mM CoCl2/1 mM HCl solution causes the peaks to shift to E=-325 mV vs Ag/AgCl. We assign these new peaks to the bulk deposition and desorption of Co. The Co electrodeposition at E=-800 mV and no under potential deposition (UPD) adsorption peak is found. The STM images show a well ordered c(2  2)-Cl structure for the adsorption of chloride anions from hydrochloric acid solutions. Desorption of chloride at negative potentials resulted in the rearrangement of atoms at the step edges. In cobalt containing solution, cobalt aggregate at the step edge and form smooth interface while no mono-atomic step was observed indicating no UPD. Magnetic response was observed for the potential smaller than -850 mV. As the Co thickness increases, both remanent Kerr intensity and coercivity increase rapidly within the first couple layers. This is due to the nucleation of Co islands to form large clusters. For thicker films, the surface morphology remains unchanged as revealed from EC-STM measurements and as a consequence coercivity keeps constant. After adding 0.005 mM PbCl2 into the electrolyte, hysteresis behavior occurs at E =-850 mV. However, the squareness of the hysteresis loops does not increase. Pb plays no positive role as a surfactant in this case.