Depth profiling cross‐linked poly(methyl methacrylate) films: a time‐of‐flight secondary ion mass spectrometry approach
Bibliographic record
Abstract
Rationale In order to determine the degree of cross‐linking on the surface and its variations in a nanometer‐scale depth of organic materials, we developed an approach based on time‐of‐flight secondary ion mass spectrometry (TOF‐SIMS), which provides rich chemical information in the form of fragment ions. TOF‐SIMS is extremely surface‐sensitive and capable of depth profiling with the use of a sputter ion beam to remove controllable amounts of substance. Methods Poly(methyl methacrylate) (PMMA) films spin‐coated on a Si substrate were cross‐linked using a recently developed, surface sensitive, hyperthermal hydrogen projectile bombardment technique. The ion intensity ratio between two ubiquitous hydrocarbon ions, C 6 H – and C 4 H – , detected in TOF‐SIMS, denoted as ρ, was used to assess the degree of cross‐linking of the PMMA films. The cross‐linking depth of the PMMA films was revealed by depth profiling ρ into the polymer films using a C 60 + sputter beam. Results The control PMMA film spin‐coated on a Si substrate was characterized by ρ = 32% on its surface when using a 25 keV Bi 3 + primary ion beam. This parameter on the PMMA films subjected to HHIC treatment for 10, 100 and 500 s increased to 45%, 56% and 65%, respectively. The depth profiles of ρ obtained using a 10 keV C 60 + ion beam resembled an exponential decay, from which the cross‐linking depth was estimated to be 3, 15 and 39 nm, respectively, for the three cross‐linked PMMA films. Conclusions We demonstrated that the ion intensity ratio of C 6 H – to C 4 H – detected in TOF‐SIMS provides a unique and simple means to assess the degree of cross‐linking of the surface of PMMA films cross‐linked by the surface sensitive hyperthermal hydrogen projectile bombardment technique. With a C 60 + sputter beam, we were able to depth profile the PMMA films and determine cross‐linking depths of the cross‐linked polymer films at nanometer resolutions. Copyright © 2017 John Wiley & Sons, Ltd.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".