Molecular depth‐profiling of polycarbonate with low‐energy Cs⁺ ions

Abstract

In this work, we explored the possibility of performing molecular depth-profiling by using very low-energy (about 200 eV) monoatomic Cs(+) ions. We show, for the first time, that this simple approach is successful on polymer layers of polycarbonate (PC). Under 200 eV Cs(+) irradiation of PC, a fast decrease of all characteristic negatively charged molecular ion signals is first observed but, rather surprisingly, these signals reach a minimum before rising again. A steady state is reached at which time most specific PC fragments are detected, some with even higher signal intensity (e.g. C(6)H(5)O(-)) than before irradiation. It is believed that the implanted Cs plays a major role in enhancing the negative ionisation of molecular fragments, leading to their easy detection for all the profile, although some material degradation obviously occurs. In the positive ion mode, all molecular fragments of the polymer disappear very rapidly, but clusters combining two Cs atoms and one molecular fragment (e.g. Cs(2)C(6)H(5)O(+)) are detected during the profile, proving that some molecular identification remains possible. In conclusion, this work presents a simple approach to molecular depth-profiling, complementary to cluster ion beam sputtering.

Hybrid Organic/Inorganic Materials Depth Profiling Using Low Energy Cesium Ions

“…Intensity oscillations are also noticed at the organic/ metal interface. This behavior is common with low energy Cs + depth profiling as was shown in previous works [18,24]. The initial drop is caused by rapid fragmentation of the Tyr molecules induced by the Cs + ions, leading to the formation of free radicals.…”

“…Cs high reactivity ensures a negative ion signal enhancement, along with free radicals scavenging [18]. This source already proved its efficiency on both inorganics [19][20][21][22] and organics [23][24][25]. In this paper, we analyze model systems made of different metals (gold or chromium) and tyrosine multilayer systems deposited on silicon substrates.…”

Molecular depth profiling with reactive ions, or why chemistry matters in sputtering

“…[5] Recently, very low energy cesium ions have also proven to be quite efficient for molecular depth profiling of polymers. In 2007, Mine et al published the first molecular depth profile on a polymer, [6] i.e. polycarbonate (PC), sputtered with low-energy (200 eV) Cs C ions.…”

Surface analysis of diblock copolymer films by TOF‐SIMS in combination with AFM

“…[11][12][13][14][15] Recently, successful molecular depth profiling of organic materials with low energy Cs + , O 2 + , or massive gas cluster ion beams was shown. [16][17][18] The effect of chemical structure, interactions, and processing conditions on the surface behavior of a two-phase polymer mixture has been studied by XPS, AFM, and SIMS. [19] In this study, the characterization of the morphology of polystyrene-b-poly(2-ethyl hexyl acrylate) (PS-PEHA) where the PS blocks are perdeuterated, using time-of-flight secondary ion mass spectrometry (TOF-SIMS) and atomic force microscopy (AFM), is reported.…”