The secondary electron yield of TiZr and TiZrV non-evaporable getter thin ®lm coatings

The secondary electron yield (SEY) of two different non-evaporable getter (NEG) samples has been measured `as receivedʹ and after thermal treatment. The investigated NEGs are TiZr and TiZrV thin ®lm coatings of 1 mm thickness, which are sputter deposited onto copper substrates. The maximum SEY dmax of the air exposed TiZr and TiZrV coating decreases from above 2.0 to below 1.1 during a 2 h heat treatment at 250 and 2008C, respectively. Saturating an activated TiZrV surface under vacuum with the gases typically present in ultra-high vacuum systems increases dmax by about 0.1. Changes in elemental surface composition during the applied heat treatments were monitored by Auger electron spectroscopy (AES). After activation carbon, oxygen and chlorine were detected on the NEG surfaces. The potential of AES for detecting the surface modi®cations which cause the reduction of SE emission during the applied heat treatments is critically discussed. # 2001 Elsevier Science B.V. All rights reserved.