INTERACTION OF BORAZINE WITH A Re(OOO1) SURFACE, STUDIED BY LEED, TDS, AES AND ELS

The interaction of borazine (NsB,H,) with a Re(0001) surface has been studied by low energy electron diffraction (LEED), thermal desorption spectroscopy (TDS), Auger electron spectroscopy (AES) and electron energy loss spectroscopy (ELS). Two LEED patterns have been observed following borazine adsorption and annealing. One is the 2 X 2 structure, assigned to arise from atomic nitrogen. The other is the 3 ‘/* x 21’/* pattern and is related to boron. The appearance of the two patterns indicates that borazine dissociates at 570 K. With a high exposure (> 6 L) of borazine and a subsequent annealing, only the well-formed 3”* x 21”* pattern is observed. Completion of this boron structure depends on both the surface boron coverage and the annealing temperature. Thermal desorption spectra show three states for borazine (a, p, and fi2) and three states for hydrogen (a, PI, /I,). The a state in the borazine desorption spectrum is due to desorption of multilayers of borazine. The /I state hydrogen is shown to correspond primarily to decomposition of borazine on Re(OOO1). Two desorption states of nitrogen are observed at T > 1300 K and also arise from the decomposition of borazine. AE data show that borazine decomposes to a boron-nitrogen compound when irradiated with a 2 keV e--beam. Chemisorbed borazine, on the other hand, without e--beam irradiation, dissociates into atomic nitrogen and boron upon annealing to T > 450 K. ELS results corroborate the LEED, TDS, and AES data that borazine adsorbs on Re(OOO1) non-dissociatively at 115 K and dissociates into N and B upon annealing to 600 K.