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Sputtering soft materials with molecular projectiles: a microscopic view
Author(s) -
Delcorte A.,
Garrison B. J.,
Hamraoui K.
Publication year - 2011
Publication title -
surface and interface analysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.52
H-Index - 90
eISSN - 1096-9918
pISSN - 0142-2421
DOI - 10.1002/sia.3405
Subject(s) - projectile , polyatomic ion , sputtering , nucleon , ion , chemistry , fragmentation (computing) , atomic physics , ionization , molecular dynamics , cluster (spacecraft) , chemical physics , materials science , physics , nanotechnology , computational chemistry , thin film , organic chemistry , computer science , metallurgy , programming language , operating system
The sputtering of bulk organic samples by molecular projectiles is modeled using molecular dynamics simulations. A coarse‐grained representation of entangled polyethylene oligomers (1.4 kDa) is used as a model of an amorphous soft material. In this study, a variety of projectiles are compared, including C 60 , coronene and a series of polystyrene molecular cluster (0.6–110 kDa). The polystyrene clusters bridge the gap between the polyatomic ions (SF 5 , C 60 ) used in secondary ion mass spectrometry (SIMS) and the large organic microdroplets generated, e.g. in desorption electrospray ionization. In addition, they allow us to explore a wide range of energies/nucleon (0.1–18 eV/nucleon) with projectiles of similar nature and the same total kinetic energy (10 keV). Two regions of sputtering can be distinguished. Above 1 eV/nucleon (smaller projectiles), the sputtering yield depends only on the total projectile energy and not on the projectile nuclearity. Below 1 eV/nucleon (larger projectiles), yields are influenced by both the projectile energy and their nuclearity. Larger projectiles also eject fewer fragments and induce significantly less damage in the sample. A region of intact molecular emission, without induced fragmentation, exists in the < 1 eV/nucleon range. For large clusters, an energy of < 1 eV/nucleon still provides a sputtered mass from the target that is larger than 10 kDa. This region of molecular emission with minimal fragmentation, also attainable with large gas clusters, offers new analytical perspectives. Copyright © 2010 John Wiley & Sons, Ltd.