Argon Cluster Ion Beams for Organic Depth Profiling: Results from a VAMAS Interlaboratory Study

Abstract

The depth profiling of organic materials with argon cluster ion sputtering has recently become widely available with several manufacturers of surface analytical instrumentation producing sources suitable for surface analysis. In this work, we assess the performance of argon cluster sources in an interlaboratory study under the auspices of VAMAS (Versailles Project on Advanced Materials and Standards). The results are compared to a previous study that focused on C(60)(q+) cluster sources using similar reference materials. Four laboratories participated using time-of-flight secondary-ion mass spectrometry for analysis, three of them using argon cluster sputtering sources and one using a C(60)(+) cluster source. The samples used for the study were organic multilayer reference materials consisting of a ∼400-nm-thick Irganox 1010 matrix with ∼1 nm marker layers of Irganox 3114 at depths of ∼50, 100, 200, and 300 nm. In accordance with a previous report, argon cluster sputtering is shown to provide effectively constant sputtering yields through these reference materials. The work additionally demonstrates that molecular secondary ions may be used to monitor the depth profile and depth resolutions approaching a full width at half maximum (fwhm) of 5 nm can be achieved. The participants employed energies of 2.5 and 5 keV for the argon clusters, and both the sputtering yields and depth resolutions are similar to those extrapolated from C(60)(+) cluster sputtering data. In contrast to C(60)(+) cluster sputtering, however, a negligible variation in sputtering yield with depth was observed and the repeatability of the sputtering yields obtained by two participants was better than 1%. We observe that, with argon cluster sputtering, the position of the marker layers may change by up to 3 nm, depending on which secondary ion is used to monitor the material in these layers, which is an effect not previously visible with C(60)(+) cluster sputtering. We also note that electron irradiation, used for charge compensation, can induce molecular damage to areas of the reference samples well beyond the analyzed region that significantly affects molecular secondary-ion intensities in the initial stages of a depth profile in these materials.

Solution-processed multilayer small-molecule light-emitting devices with high-efficiency white-light emission

“…Depth profiling was accomplished using the instrument's Ar 2500 þ ion source operated at 5 kV, 3.0 nA and rastered over 0.5 Â 0.5 mm 2 . The depth resolution was determined using a procedure described by Shard et al 38 OLED fabrication. OLEDs were fabricated on glass substrates covered with ITO (sheet resistance of 10 O per square).…”

Systematic Temperature Effects in the Argon Cluster Ion Sputter Depth Profiling of Organic Materials Using Secondary Ion Mass Spectrometry

“…This means that for 1-beam or 2-beam SIMS profiles, the sputtering rates are fairly uniform with dose and that the measured SIMS spectrum changes little with dose. These improvements are clearly seen in the comparison between data using C 60 + primary ions [9] and argon clusters [10] in the depth profiles of Irganox 3114 delta layers in Irganox 1010. Careful studies of such samples show that sample rotation is beneficial [3], achieving depth resolutions measured by the full width at half maximum (FWHM) as low as 4 nm at depths up to 300 nm.…”

Reduction of Sodium Migration in Polymers by Addition of 15-Crown-5 Ether as Getter Substance

“…Furthermore, TOF-SIMS depth profiling after the bias-temperature stress tests by sputtering with large argon clusters 19 is planned in the future as depth profiling with O 2 + was not possible due to charging effects. Furthermore, differential scanning calorimetry measurements are planned to ensure that there is no phase segregation of the crown ether in the polymer matrix.…”