Sputtering of chemisorbed nitrogen from the (100)--planes of tungsten and molybdenum: a comparison of computer simulation and experimental results.

Abstract

The Naval Postgraduate School simulation model, QDYN86, was used to examine sputtering of nitrogen from the (100) faces of single crystals of molybdenum and tungsten. The nitrogen placement was varied, and analyses were conducted on the sputtering cross sections of the nitrogen. The cases where the a da torn was directly hit by the incident ion, or if it was sputtered due to the collision cascade process, were analyzed separately. The simulations were conducted to compare the results with Winters' recent work, and to build upon the efforts of earlier studies completed at the Naval Postgraduate School. It was found that placement of nitrogen at 0.245 A from the surface of molybdenum resulted in cross sections similar to those found by Winters. The effect of the mass of the substrate was verified, in that a substrate of greater mass results in a higher sputtering cross section. This agreed with Winters' findings, and conflicted with earlier conclusions of past theses. The adatoms apparently reduce the momentum available to create collision cascades, reducing the sputter yield ratio of the substrate when the ions directly hit the adatoms.