PMID- 30968864
OWN - NLM
STAT- PubMed-not-MEDLINE
LR  - 20191120
IS  - 1364-5528 (Electronic)
IS  - 0003-2654 (Linking)
VI  - 144
IP  - 10
DP  - 2019 May 13
TI  - Effect of energy per atom (E/n) on the Ar gas cluster ion beam (Ar-GCIB) and 
      O(2)(+) cosputter process.
PG  - 3323-3333
LID - 10.1039/c8an02452a [doi]
AB  - Gas cluster ion beam (GCIB) is a promising technique for preserving molecular 
      structures during ion sputtering and successfully profiling biological and soft 
      materials. However, although GCIB yields lower damage accumulation compared with 
      C60+ and monoatomic ion beams, the inevitable alteration of the chemical 
      structure can introduce artifacts into the resulting depth profile. To enhance 
      the ionization yield and further mask damage, a low-energy O2+ (200-500 V) 
      cosputter can be applied. While the energy per atom (E/n) of GCIB is known to be 
      an important factor influencing the sputter process, the manner through which E/n 
      affects the GCIB-O2+ cosputter process remains unclear. In this study, 
      poly(ethylene terephthalate) (PET) was used as a model material to investigate 
      the sputter process of 10-20 kV Ar1000-4000+ (E/n = 2.5-20 eV per atom) with and 
      without O2+ cosputter at different energies and currents. Time-of-flight 
      secondary ion mass spectrometry (ToF-SIMS) with Bi32+ as the primary ion was used 
      to examine surfaces sputtered at different fluences. The sputter craters were 
      also measured by alpha-step and atomic force microscopy in quantitative imaging 
      mode. The SIMS results showed that the steady-state cannot be obtained with E/n 
      values of less than 5 eV per atom due to damage accumulation using single GCIB 
      sputtering. With a moderate E/n value of 5-15 eV per atom, the steady-state can 
      be obtained, but the  approximately 50% decay in intensity indicated that damage cannot be 
      masked completely despite the higher sputter yield. Furthermore, the surface 
      Young's modulus decreased with increasing E/n, suggesting that depolymerization 
      occurred. At an E/n value of 20 eV per atom, a failed profile was obtained with 
      rapidly decreased sputter rate and secondary ion intensity due to the ion-induced 
      crosslink. With O2+ cosputtering and a moderate E/n value, the oxidized species 
      generated by O2+ enhanced the ionization yield, which led to a higher ion 
      intensity at steady-state in general. Because higher kinetic energy or current 
      density of O2+ led to a larger interaction volume and more structural damage that 
      suppressed molecular ion intensity, the enhancement from O2+ was most apparent 
      with low-energy-high-current (200 V, 80 muA cm-2) or high-energy-low-current (500 
      V, 5 muA cm-2) O2+ cosputtering with 0.5 muA cm-2 GCIBs. In these cases, little or 
      no intensity drop was observed at the steady-state.
FAU - Wang, Shin-Kung
AU  - Wang SK
AD  - Department of Materials Science and Engineering, National Taiwan University, 
      Taipei 106, Taiwan. shyue@gate.sinica.edu.tw.
FAU - Chang, Hsun-Yun
AU  - Chang HY
FAU - Chu, Yi-Hsuan
AU  - Chu YH
FAU - Kao, Wei-Lun
AU  - Kao WL
FAU - Wu, Chen-Yi
AU  - Wu CY
FAU - Lee, Yi-Wei
AU  - Lee YW
FAU - You, Yun-Wen
AU  - You YW
FAU - Chu, Kuo-Jui
AU  - Chu KJ
FAU - Hung, Shu-Hang
AU  - Hung SH
FAU - Shyue, Jing-Jong
AU  - Shyue JJ
LA  - eng
PT  - Journal Article
PL  - England
TA  - Analyst
JT  - The Analyst
JID - 0372652
EDAT- 2019/04/11 06:00
MHDA- 2019/04/11 06:01
CRDT- 2019/04/11 06:00
PHST- 2019/04/11 06:00 [pubmed]
PHST- 2019/04/11 06:01 [medline]
PHST- 2019/04/11 06:00 [entrez]
AID - 10.1039/c8an02452a [doi]
PST - ppublish
SO  - Analyst. 2019 May 13;144(10):3323-3333. doi: 10.1039/c8an02452a.