H CU(110) - KINETICS OF RECONSTRUCTION AND DE-RECONSTRUCTION/

The adsorption of atomic H on Cu(110) was studied with LEED, thermal d esorption spectroscopy (TDS) and work function change measurements (DE LTAphi) in the temperature range of 90-400 K. For the production of at omic H, molecular hydrogen was dosed through a resistivily heated Ta t ube onto the Cu(110) surface. At a source temperature of 1325 K the H- 2 dissociation rate was > 80%. LEED as well as TDS experiments were pe rformed to calibrate the coverage theta(H). From the same experiments the sticking coefficient S0 at 90 K was deduced to be 0.05 +/- 0.04. T he kinetics of the reconstruction reaction (1 X 3)H --> (1 X 2)H at co nstant theta(H) and temperatures between 100-200 K and the de-reconstr uction (1 x 2)H --> (1 X 1) above 250 K with the simultaneous desorpti on of H-2 were determined from isothermal DELTAphi measurements. For t he (I X 2)H --> (1 X 1) de-reconstruction at constant T between 257 an d 283 K the experimental data can be fitted assuming a constant Avrami exponent of n = 1.27 and an activation energy of 1.02 +/- 0.07 eV. Th e reconstruction (1 X 3)H --> (1 X 2), at low temperatures (115-140 K) is found to be much more complex.