Effect of random surface orientation and tungsten fuzz on tungsten sputtering yields

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http://urn.fi/URN:NBN:fi:hulib-201908233283
Title: Effect of random surface orientation and tungsten fuzz on tungsten sputtering yields
Author: Jussila, Joonas
Contributor: University of Helsinki, Faculty of Science
Publisher: Helsingin yliopisto
Date: 2019
Language: eng
URI: http://urn.fi/URN:NBN:fi:hulib-201908233283
http://hdl.handle.net/10138/304889
Thesis level: master's thesis
Degree program: Teoreettisten ja laskennallisten menetelmien maisteriohjelma
Master's Programme in Theoretical and Computational Methods
Magisterprogrammet i teoretiska och beräkningsmetoder
Specialisation: Teoreettinen fysiikka
Theoretical Physics
Teoretisk fysik
Discipline: none
Abstract: In this thesis, the sputtering of tungsten surfaces is studied under ion irradiation using molecular dynamics simulations. The focus of this work is on the effect of surface orientation and incoming angle on tungsten sputtering yields. We present a simulation approach to simulate sputtering yields of completely random surface orientations. This allows obtaining the total sputtering yields averaged over a large number of arbitrary surface orientations, which are representative to the sputtering yield of a polycrystalline sample with random grain orientations in a statistically meaningful way. In addition, a completely different method was utilised to simulate sputtering yields of tungsten fuzz surfaces with various fuzz structure heights. We observe that the total sputtering yield of the investigated surfaces are clearly dependent on the surface orientation and the sputtering yields of average random surfaces are different compared to the results of any of the low index surfaces or their averages. The low index surfaces and the random surface sputtering yields also show a dependence of the incoming angle of the projectile ions. In addition, we calculate the outgoing angular distribution of sputtered tungsten atoms in every bombardment case, which likewise shows to be a sensitive to the surface orientation. Finally, the effect of fuzz height on the sputtering yield of tungsten fuzz surfaces is discussed. We see that tungsten fuzz significantly reduces the sputtering yield compared to a pristine tungsten surface and the effect is already seen when the fuzz pillar height is a few atom layers.


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