ADSORPTION AND DECOMPOSITION OF HYDRAZINE ON RU(001)

The adsorption and decomposition of hydrazine on Ru(001) have been investigated in the temperature range 150-1000 K utilizing HREELS, thermal desorption and reaction spectroscopy, LEED and DELTAPHI measurements. N2H4 multilayers desorb in one peak at almost-equal-to 190 K. After desorption of these multilayers, a chemisorption layer consisting mainly of molecular hydrazine remains. Decomposition of monolayer hydrazine starts approximately at 220 K. The thermal evolution of this reactive chemisorption layer has been investigated in detail. N-N bond and N-H bond scission proceed essentially in parallel, with the first being complete at lower T. In monolayer TPD, the desorption products N2, NH3 and H-2, but not N2H4, are observed. In the course of the complex N2H4 thermal decomposition, several intermediate species can be identified in different temperature ranges, among them surface NH2 (220 ... 280 K) and surface NH (280 ... almost-equal-to 480 K). The latter is the last intermediate containing an N-H bond. The final decomposition product on the surface is atomic N for T>480 K which desorbs recombinatively between 570 and 1000 K. The decomposition routes and reaction mechanisms leading to these intermediate and final products are discussed.