X-ray photoelectron spectroscopy: Towards reliable binding energy referencing

The review describes the status of the studies and the recent achievements in the field of photoalignment of liquid crystals. An update classification of photoaligning materials and exposure schemes, and analyzes of the relationship between the molecular structure of the materials and characteristics of LC alignment are provided. In addition, bulk mediated photoalignment and combination of photoalignment with other alignment methods are discussed. Along with traditional, recently proposed applications of the photoalignment technique are considered.

Photoalignment of liquid crystals: basics and current trends

Lipid Imaging with Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS)

Cluster secondary ion mass spectrometry (cluster SIMS) has played a critical role in the characterization of polymeric materials over the last decade, allowing for the ability to obtain spatially resolved surface and in-depth molecular information from many polymer systems. With the advent of new molecular sources such as , , , and , there are considerable increases in secondary ion signal as compared to more conventional atomic beams (Ar+, Cs+, or Ga+). In addition, compositional depth profiling in organic and polymeric systems is now feasible, without the rapid signal decay that is typically observed under atomic bombardment. The premise behind the success of cluster SIMS is that compared to atomic beams, polyatomic beams tend to cause surface-localized damage with rapid sputter removal rates, resulting in a system at equilibrium, where the damage created is rapidly removed before it can accumulate. Though this may be partly true, there are actually much more complex chemistries occurring under polyatomic bombardment of organic and polymeric materials, which need to be considered and discussed to better understand and define the important parameters for successful depth profiling. The following presents a review of the current literature on polymer analysis using cluster beams. This review will focus on the surface and in-depth characterization of polymer samples with cluster sources, but will also discuss the characterization of other relevant organic materials, and basic polymer radiation chemistry. © 2009 Wiley Periodicals, Inc., Mass Spec Rev 29:247–293, 2010

Cluster secondary ion mass spectrometry of polymers and related materials.

Mass spectrometry imaging for drug distribution studies.

An Ar Gas Cluster Ion Beam (GCIB) has been shown to remove previous Ar+ ion beam-induced surface damage to a bulk polyimide (PI) film. After removal of the damaged layer with a GCIB sputter source, XPS measurements show minor changes to the carbon, nitrogen and oxygen atomic concentrations relative to the original elemental bulk concentrations. The GCIB sputter depth profiles showed that there is a linear relationship between the Ar+ ion beam voltage within the range from 0.5 to 4.0 keV and the dose of argon cluster ions required to remove the damaged layer. The rate of recovery of the original PI atomic composition as a function of GCIB sputtering is similar for carbon, nitrogen and oxygen, indicating that there was no preferential sputtering for these elements. The XPS chemical state analysis of the N 1s spectra after GCIB sputtering revealed a 17% damage ratio of altered nitrogen chemical state species. Further optimization of the GCIB sputtering conditions should lead to lower nitrogen damage ratios with the elemental concentrations closer to those of bulk PI. Copyright © 2010 John Wiley & Sons, Ltd.

Removal of Ar+ beam-induced damaged layers from polyimide surfaces with argon gas cluster ion beams†

We have applied sputtering using a buckminsterfullerene (C60) ion beam for XPS analysis. A practical sputter rate of 2.4 nm min−1 for SiO2 was obtained for sputtering an area of 5 mm × 5 mm using a 5 kV C60 ion beam with an energy of 83 eV per carbon atom. Extremely low sputtering degradation of polytetrafluoroethylene was observed in these conditions. The results were compared with argon ion beam energies of 500 V and 5 kV. These are the first results utilizing a C60 ion beam for XPS analysis with limited sputtering damage. Copyright © 2004 John Wiley & Sons, Ltd.

Extremely low sputtering degradation of polytetrafluoroethylene by C60 ion beam applied in XPS analysis

Intercalation of iodine into the Bi 2 Sr 2 Ca n -1 Cu n O y ( n =1,2,3) superconductors has been studied. A variety of measurements indicate charge transfer is associated with the intercalation process, both directly to the BiO layers and also to the superconducting CuO 2 sheets. Changes in T c on intercalation can be understood in terms of hole doping to the CuO 2 planes. Hall coefficient measurements on a single crystal n =2 sample supported an increase in hole concentration, and an XPS study clearly showed the ionic character for the intercalated iodine, accompanied by changes in the Fermi level. Investigation of the c -axis resistivity, also on n =2 single crystals, indicated a change from the semiconductive behaviour of the parent crystal to an apparently metallic character, though the c -axis resistivity remained high.

Charge transfer associated with iodine intercalation in Bi2Sr2Can−1CunOy, n=1−3

X-ray photoelectron spectroscopy depth profiling of polyimide thin films on silicon substrates using an Ar cluster ion beam results in an extremely low degradation of the polyimide chemistry. In the range from 2.5 to 20 kV, a lower cluster ion energy produces a lower sputter induced damage to the polymer and results in an improved polyimide to silicon interface width. The sputtering rates of the polyimide are found to increase exponentially with an increase in the Ar cluster ion energy.

X-ray photoelectron spectroscopy study of polyimide thin films with Ar cluster ion depth profiling

Three-dimensional (3D) chemical images reveal the surface and subsurface distribution of pharmaceutical molecules in a coronary stent coating and are used to visualize the drug distribution as a function of elution time. The coronary stent coating consists of 25% (w/w) sirolimus in a poly(lactic-co-glycolic acid) (PLGA) matrix and is spray-coated onto metal coupons. Information regarding the 3D distribution of sirolimus in PLGA as a function of elution time was obtained by time-of-flight secondary ion mass spectrometry (TOF-SIMS) imaging using a Au(+) ion beam for analysis in conjunction with a C(60)(+) ion beam for sputter depth profiling. The examined formulation is shown to have large areas of the surface as well as subsurface channels that are composed primarily of the drug, followed by a drug-depleted region, and finally, a relatively homogeneous dispersion of the drug in the polymer matrix. Elution is shown to occur from the drug-enriched surface region on a relatively short time scale and more gradually from the subsurface regions of homogeneously dispersed drug. Bulk composition was also probed by X-ray photoelectron spectroscopy (XPS) depth profiling and confocal Raman imaging, the results of which substantiate the TOF-SIMS 3D images. Finally, the effectiveness of a C(60)(+) ion beam for use in 3D characterization of organic systems is demonstrated against another polyatomic ion source (e.g., SF(5)(+)).

Three-dimensional time-of-flight secondary ion mass spectrometry imaging of a pharmaceutical in a coronary stent coating as a function of elution time.

Noriaki Sanada

Papers

Removal of Ar+ beam-induced damaged layers from polyimide surfaces with argon gas cluster ion beams†

Extremely low sputtering degradation of polytetrafluoroethylene by C60 ion beam applied in XPS analysis

Charge transfer associated with iodine intercalation in Bi2Sr2Can−1CunOy, n=1−3

X-ray photoelectron spectroscopy study of polyimide thin films with Ar cluster ion depth profiling

Three-dimensional time-of-flight secondary ion mass spectrometry imaging of a pharmaceutical in a coronary stent coating as a function of elution time.