Determination of chemical composition in multilayer polymer film using ToF-SIMS

Time-of-flight secondary ion mass spectrometry is a widely used surface analytical technique, which can provide chemical information from both the uppermost surface and underneath the surface for various materials.

Mechanical Behavior Of Elastomeric Stamps During Microcontact Printing Patterns: Direct Observation Of Stamps And Inks

Microcontact printing is a straightforward and effective method for generating surface patterns of micron or submicron lateral dimensions. The fidelity of the ultimate pattern is a complex interplay of mechanical behavior of the elastomeric stamp, fluid transfer between surfaces and the ability of the ink to self-assemble on the new surface. We present here experimental observations and modeling of stamp deformation during precise external loads and visualization of inked surfaces by high contrast analytical methods. Stamp behavior was observed visually in an inverted microscope and load-displacement relationships used to determine onset of failure modes such as roof collapse and buckling of slender relief features as a function of stamp geometry. The load was applied with a glass sphere so as to obviate problems with alignment and to precisely determine contact areas.A “robotic stamper” fabricated from an AFM instrument can deliver ink under conditions of precise load. Surfaces inked with varying densities or combinations of SAMs can be imaged with excellent contrast by scanning surface potential microscopy (SSPM). The same area of the sample can then be examined using time-of-flight SIMS or other surface analytical technique with no additional etching or sample preparation. In this way the fidelity and density of the patterned monolayers can be evaluated. The effect of load on ink pattern quality can also be established.

Towards compositional imaging using auger electron signals

Auger electron spectroscopy (AES) is a well established, quantitative surface analytical technique with reasonable accuracy of the order of 1% of an atomic monolayer. When it is combined with a small electron beam diameter, high resolution concentration maps of the surface distribution of elements can be obtained. This has been demonstrated to be a useful and powerful method in surface analysis. However, because of the rather low efficiency of Auger electron production (∼ 10-5 - 10-4 per incident electron) long frame scan times (of the order of hours) have to be employed in the case of multi-element composite samples. The raw images often reflect not only surface elemental distribution but also electron beam fluctuations. In addition, subsurface atomic number variations as well as local surface topography are known to alter the contrast of these images. In order to quantify Auger maps to give concentration distribution of the surface elements, sample and instrumental effects have to be separated.

Spatially Resolved Photoelectron Spectroscopy: Recent Progress and Future Plans

X-ray photoelectron spectroscopy (XPS or ESCA) was not developed by Siegbahn and co-workers as a surface analytical technique, but rather as a general probe of electronic structure and chemical reactivity. The method is based on the phenomenon of photoionisation: The absorption of monochromatic radiation in the target material (free atoms, molecules, solids or liquids) causes electrons to be injected into the vacuum continuum. Pseudo-monochromatic laboratory light sources (e.g. AlKα) have mostly been used hitherto for this excitation; in recent years synchrotron radiation has become increasingly important. A kinetic energy analysis of the so-called photoelectrons gives rise to a spectrum which consists of a series of lines corresponding to each discrete core and valence level of the system. The measured binding energy, EB, given by EB = hv−EK, where EK is the kineticenergy relative to the vacuum level, may be equated with the orbital energy derived from a Hartree-Fock SCF calculation of the system under consideration (Koopmans theorem).

Imaging XPS. A Contribution to 3D X-ray Analysis

X-ray photoelectron spectrometry (XPS) has been a well established surface analytical technique for approximately 20 years. Fhotoelectrons are ejected by characteristic x-radiation. In our investigations we use Alκα-radiation. The depth from which l-l/e of the measured signal comes, is restricted to a few nanometers by inelastic mean free paths of photoelectrons in solids.