UNSPECIFIED. (2004) Temperature dependence of secondary ion emission from tantalum produced by atomic and polyatomic gold projectiles. INTERNATIONAL JOURNAL OF MASS SPECTROMETRY, 237 (1). pp. 55-63. ISSN 1387-3806

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Abstract

Temperature dependencies have been measured within a wide range of target temperatures of 300 K less than or equal to T less than or equal to 2400 K for secondary ion yields of Ta-n(+), TanO(m)(+), TanNb+ and TanAu+(n = 1-14, m = 1-3) under the bombardment of tantalum target with 12 keV atomic Au- and 18 keV polyatomic Au-3(-) projectiles. It is demonstrated that yields of Ta-n(+) (n = 2-14) and TanNb+ ions increase with temperature for T less than or equal to 1700K and then tend to become temperature independent. On the contrary, the yields of TanOm+ and TanAu+ ions slightly increase with temperature reaching their maxima in the range of 1000K less than or equal to T less than or equal to 1500 K and then sharply decrease to zero at T approximate to 1700 and 2100K, respectively. These trends are interpreted to indicate the redistribution of the sputtered flux between these different emission channels while sputtering conditions change with the target temperature. Oxygen presence on the surface at lower temperatures limits the yield of Ta-n(+) clusters and stimulates that of TanOm+. Removing oxygen from the surface enhances the yield of Ta-n(+) clusters and the disappearance of TanOm+. After clean surfaces are established in the range of 1700 K less than or equal to T less than or equal to 2400 K, the yield of the Ta-n(+) and TanNb+ cluster ions becomes constant thus indicating that their ionization probability does not depend on the target temperature in this range. Some differences in the temperature dependencies obtained under the atomic and polyatomic ion bombardment are observed and interpreted as the indication of different efficiencies of the sputtering process since polyatomic projectiles sputter more material than atomic ones. This, in addition to better surface cleaning, enhances yields of cluster ions. For atomic ions Ta+, an additional emission channel, thermal evaporation/surface ionization, is identified at target temperatures T > 2300 K. No evaporated cluster ions are observed. (C) 2004 Elsevier B.V. All rights reserved.

Item Type:	Journal Article
Subjects:	Q Science > QC Physics
Journal or Publication Title:	INTERNATIONAL JOURNAL OF MASS SPECTROMETRY
Publisher:	ELSEVIER SCIENCE BV
ISSN:	1387-3806
Date:	September 2004
Volume:	237
Number:	1
Number of Pages:	9
Page Range:	pp. 55-63
Identification Number:	10.1016/j.ijms.2004.06.010
Publication Status:	Published
URI:	http://wrap.warwick.ac.uk/id/eprint/8076

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