STM study of the reactivity of niobium diselenide in air and N

STM has been used to investigate the variety of processes taking place in the surface of NbSe2in air and N2. Induced surface layer by layer etching and formation and evolution of surface reaction sites both in air and N2, are discussed. Residues removed and transported by the tip were found in N2 but they seemed to get dissolved in air. Rests of chemicals andror surface defects.have been observed to be left in the edges of pre-existing terrace steps in N2, providing a preferential place for the formation of new reaction sites when air was re-introduced. In places where apparently no defects were present, the tip induced etching process was not possible, but focusing in a pre-existing small depression, the etching proceeded fast not only in that layer but also in the layers beneath. We propose that the processes taking place at the surface of NbSe2 are due to mechanical and chemical interactions that unsaturated bonds which are present in surface defects and step edges have with the environment and the tip. q1998 Elsevier Science B.V. All rights reserved