Surface structuring topography

Various effects have been observed when solid surfaces are bombarded with energetic particles. Incident ion beams can produce 1) trapping, reemission and reflection of the incident ions 2) desorption of surface layers, 3) emission of electrons and photons, 4) changes in surface structure, topography and composition, and 5) emission of neutral or ionized atoms from the solid. The last effect is called sputtering and leads to the erosion of the target surface. 

Another characteristic of a polymer surface is the surface structure and topography. With amorphous polymers it is possible to prepare very smooth and flat surfaces (see Sect. 2.4). One example is the PMIM-picture shown in Fig. 7a where the root-mean-square roughness is better than 0.8 ran. Similar values are obtained from XR-measurements of polymer surfaces [44, 61, 62], Those values compare quite well with observed roughnesses of low molecular weight materials. Thus for instance, the roughness of a water surface is determined by XR to 0.32 nm... 

The diagrams in Fig. llc-f can be measured by the force probe method, when the amplitude and phase are measured as the tip approaches and retracts the surface vertically. In the non-contact range, both the amplitude and the phase retain their constant values (Fig. llc,e). When the tip enters the intermittent contact range (Zphase reduces almost linearly on approaching the surface. The deviation of the amplitude signal from a certain set-point value As is used by a feedback loop to maintain the separation Zc between the tip and sample constant, and hereby visualise the surface structure. When the surface composition is uniform, the amplitude variation is mainly caused by the surface topography. However, if the surface is heterogeneous, the variation in the amplitude can be affected by local differences in viscoelasticity [108-110 ] and adhesion [111] of the sample (Sect. 2.2.2). 

Unlike the lattice imaging which can be performed by blunt tips, the finite size and 3D shape of the tip become important for imaging of the surface structure on the nanometer scale, where the tip shape and the surface topography may su-... 

Lectins, sugar-binding proteins, have become powerful molecular probes to investigate the structure, topography and dynamics of cell-surface saccharide determinants (1). The utility of these proteins in the study of the surface properties of a variety of cell types has stimulated renewed interest in the determination of the molecular basis of their saccharide specificity. Furthermore lectins provide relatively simple models for the investigation of noncovalent interactions between saccharides and proteins. 

Preliminary models of the surface topography, for example, can be determined by atomic-probe methods, ion-scattering, electron diffraction, or Auger spectroscopy. The chemical bonds of adsorbates can be estimated from infrared spectroscopy. The surface electronic structure is accessible by photoelectron emission techniques. In case the surface structure is known, its electronic structure has to be computed with sophisticated methods, where existing codes more and more rely on first principles density functional theory (DFT) [16-18], or, in case of tight-binding models [19], they obtain their parameters from a fit to DFT data [20]. The fit is not without ambiguities, since it is unknown whether the density of states used for the fit is really unique. 

Yoon [83] studied by X-ray photoelectron spectroscopy the surface structure of segmented poly(ether urethane)s and poly(ether urethane urea)s with various perfluorinated chain extenders and noticed that the surface topography of such polymers depended strongly on the extent of phase separation. 

Figure 10 shows this effect. At the left side the topography and a line scan of the uncoated fiber reinforced material is shown. At the right side of Fig. 10 the roughness of the clearcoat, coated directly on the substrate and dried under varying conditions is represented. The higher drying temperature causes a more distinct surface structure. 

The catalyst particle is usually a complex entity composed of a porous solid, serving as the support for one or more catalytically active phase(s). These may comprise clusters, thin surface mono- or multilayers, or small crystallites. The shape, size and orientation of clusters or crystallites, the extension and arrangement of different crystal faces together with macrodcfects such as steps, kinks, etc., are parameters describing the surface topography. The type of atoms and their mutual positions at the surface of the active phase or of the support, and the type, concentration and mutual positions of point defects (foreign atoms in lattice positions, interstitials, vacancies, dislocations, etc.) define the surface structure. 

Polyimide surface modification by a wet chemical process is described. Poly(pyromellitic dianhydride-oxydianiline) (PMDA-ODA) and poly(bisphenyl dianhydride-para-phenylenediamine) (BPDA-PDA) polyimide film surfaces are initially modified with KOH aqueous solution. These modified surfaces are further treated with aqueous HC1 solution to protonate the ionic molecules. Modified surfaces are identified with X-ray photoelectron spectroscopy (XPS), external reflectance infrared (ER IR) spectroscopy, gravimetric analysis, contact angle and thickness measurement. Initial reaction with KOH transforms the polyimide surface to a potassium polyamate surface. The reaction of the polyamate surface with HC1 yields a polyamic acid surface. Upon curing the modified surface, the starting polyimide surface is produced. The depth of modification, which is measured by a method using an absorbance-thickness relationship established with ellipsometry and ER IR, is controlled by the KOH reaction temperature and the reaction time. Surface topography and film thickness can be maintained while a strong polyimide-polyimide adhesion is achieved. Relationship between surface structure and adhesion is discussed. 

Hellmann R., Drake B., and Kjoller K. (1992) Using atomic force microscopy to study the structure, topography, and dissolution of albite surfaces. 7th Int. Symp. Water-Rock Interact. 149-152. 

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