ELECTROCHEMICAL-CELL FOR IN-SITU X-RAY-DIFFRACTION UNDER ULTRAPURE CONDITIONS

An electrochemical cell has been developed for in situ x-ray diffracti on from a working electrode under clean conditions equivalent to ultra high vacuum conditions of 5 x 10(-10) mbar. The substrate crystals can be prepared ex situ and transferred into the cell under protection of ultrapure water within a few seconds. The oxygen level in the electro lyte is reduced by continuous N-2 flow to less than 0.2% compared to t hat of a fresh electrolyte. This can be done while rotating the cell b y 360 degrees about the surface normal. The electrode potential is acc urately measured at the position of the crystal using a Luggin capilla ry and a standard reference electrode. We demonstrate the performance of our cell by in situ synchrotron x-ray diffraction measurements on u ltrathin Co layers electrodeposited on Cu(001) in an aqueous H2SO4/CoS O4 solution. (C) 1998 American Institute of Physics.