Modifying behaviour of Cu on the orientation of formate on ZnO(000(1)over-bar)-O

The orientation of formic acid (HCOOH) on ZnO(000 (1) over bar)-O and the e ffect of co-adsorbed Cu have been studied using polarisation dependent C K- edge near edge X-ray absorption fine structure. Formate created by exposure of the substrate to 20 L of HCOOH at 110 K and heating to 340 K is tilted by 55 +/- 5 degrees with respect to the surface normal. Pre-absorbing Cu to create 2D islands covering about half the substrate results in an apparent tilt angle of 32 +/- 5 degrees with respect to the surface normal. Since t his is dose to the magic angle, the apparent tilt could arise from a random orientation of the molecule, The origin of the apparent tilt is likely to be buckling of the Cu(110)-like islands. (C) 2001 Elsevier Science B.V. All rights reserved.