Scanning polarization force microscopy

Studies of Wetting and Capillary Phenomena at Nanometer Scale with Scanning Polarization Force Microscopy... 

Other noncontact AFM methods have also been used to study the structure of water films and droplets [27,28]. Each has its own merits and will not be discussed in detail here. Often, however, many noncontact methods involve an oscillation of the lever in or out of mechanical resonance, which brings the tip too close to the liquid surface to ensure a truly nonperturbative imaging, at least for low-viscosity liquids. A simple technique developed in 1994 in the authors laboratory not only solves most of these problems but in addition provides new information on surface properties. It has been named scanning polarization force microscopy (SPFM) [29-31]. SPFM not only provides the topographic stracture, but allows also the study of local dielectric properties and even molecular orientation of the liquid. The remainder of this paper is devoted to reviewing the use of SPFM for wetting studies. 

A particular interest of environmental chemists has been the interaction of inorganic and organic matter with bottom sediments in lakes, rivers, and oceans. These surface sediments are not simply unreactive sinks for pollutants but can be studied quantitatively in terms of how many specific chemicals are bonded to a certain amount of sediment, which in turn is influenced by whether the conditions are oxidizing or reducing. Chemists can then study the bioavaU-ability of contaminants in sediments. Furthermore, environmental chemists have studied dissolution and precipitation, discovering that the rates of these processes depend on what happens in surface sediments. Using such techniques as scanning polarization force microscopy, they have been able to quantify pollutant immobilization and bacterial attachment on surface sediments. Specifically, they have used these methods to understand the concentrations and activities of heavy metals in aquatic sediments. 

J. Hu, R. W. Carpick, M. Salmeron, and X.-D. Xiao, Imaging and manipulation of nanometer-size liquid droplets by scanning polarization force microscopy,/ Vac. Sci. Tech. B, 14,1341-1343 (1996). 

J. Hu, X.-D. Xiao, and M. Salmeron, Scanning polarization force microscopy a technique for imaging liquids and weakly adsorbed layers, Appl. Phys. Lett, 67, 476 (1995). 

L. Xu and M. Salmeron, Scanning polarization force microscopy study of the condensation and wetting properties of glycerol on mica, / Phys. Chem. B, 102, 7210 (1998). 

Salmeron and his group, realizing the comphcation introduced by adlayer water on the AFM tip, have developed a technique they call scanning polarization force microscopy (SPFM) [60,61]. In this form of noncontact AFM tip imaging, the metalized AFM tip is electrically biased and responds to the dielectric properties of the water film and any accompanying ions. The method requires the tip to be of the order of 10 nm from the film, so the higher resolution of contact AFM is lost. On the other hand, the electrical properties of the film can be explored. An example of their investigation of thin film water on NaCl (001) [34] is shown in Fig. 6. 

Fig. 6 Scanning polarization force microscopy of NaCl (001). Top topographic profile showing a multiple step 6.5 nm high and a monoatomic step (marked by an arrow) at 30% RH. Bottom contact potential of the same area for different humidity values. From Verdaguer et al. [34]...

Bluhm, H. and Salmeron, M. (1999) Growth of nanometer thin ice films from water vapor studied using scanning polarization force microscopy. J. Chem. Phys., Ill (15), 6947-6954. 

Secondary Electron Microscopy with Polarization Analysis Scanning Force Microscopy Scanning Force Microscope... 

The very new techniques of scanning tunnelling microscopy (STM) and atomic force microscopy (AFM) have yet to establish themselves in the field of corrosion science. These techniques are capable of revealing surface structure to atomic resolution, and are totally undamaging to the surface. They can be used in principle in any environment in situ, even under polarization within an electrolyte. Their application to date has been chiefly to clean metal surfaces and surfaces carrying single monolayers of adsorbed material, rendering examination of the adsorption of inhibitors possible. They will indubitably find use in passive film analysis. 

Therefore we propose here an alternative route to inspect the local dielectric and polarization properties using non-destructive and non-invasive methods based on scanning force microscopy (sfm). Simultaneously, these techniques offer a high resolution in real space being extended down to the atomic scale when inspecting ferroelectric systems under ultra-high... 

Most drugs and proteins are not soluble in commonly used supercritical fluids, and therefore are processed instead by the SC antisolvent technique,the most popularized being the SEDS, process which is illustrated in Fig. 9. SEDS-produced crystals can have extremely smooth surfaces, as shown by scanning electron microscopy and atomic force microscopy, and the surface may be more hydrophobic and less wettable than crystals grown under more polar conditions.A scanning electron micrograph of acetominophen crystals produced by the SEDS process is shown in Fig. 10. 

Figure 33. Atomic force microscopy surfaces of LB films of 38 (a) monolayer (b) 64-layer annealed (c) 64-layer after 10 min at 365nm, polarized -150° with respect to scan direction (d) 64-layer after 20 min at 436 nm, polarized -60° and then 20 min at 365 nm, polarized 30° with respect to scan direction.

Deposition of a5T from a Knudsen cell in high vacuum (HV) or ultra-high vacuum (UHV) at room temperature leads to highly ordered layers on SiOa and other oxidic substrates. The a5T molecules are oriented with their long axes mainly perpendicular to the substrate plane. This can be shown with polarized UV-Vis absorption and FT-IR spectroscopy, NEXAFS, and SFM (scanning force microscopy) measurements. 

Polarized Optical Microscopy Scanning Electron Microscopy Atomic Force Microscopy Transmission Electron Microscope... 

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