Scanning thermal microscopy images

Figure 5.36. Scanning thermal microscopy images of 35 fim via holes patterned in a photoBCB thin film over a copper substrate before plasma treatment to remove polymer residues. DC thermal images (left) and AC phase images (right) are shown for frequencies of IkHz (top) and 30kHz (bottom). (From Meyers et al. [174], (2000) American Chemical Society used with permission.) (See color insert.)...

Flammiche A, Flourston D J, Pollock FI M, Reading M and Song M 1996 Scanning thermal microscopy sub-surface imaging, thermal mapping of polymer blends, localised calorimetry J. Vac. Sol. Technol. B 14 1486... 

Microthcrmal analysis combines thermal analysis with atomic force microscopy. It is actually a family of scanning thermal microscopy techniques in which ihcrmal properties of a surface arc measured as a function of temperature and used to produce a thermal image. In microthcrmal analysis the tip of an atomic force microscope is replaced by a thermally sensitive probe such as a thermistor or thermocouple. The surface temperature can be changed externally or by the probe acting both as a heater and as a temperature-measuring device. 

The diermal conductivity contrast image obtained by scanning thermal microscopy represents a convolution of the true thermal transport properties of the specimen with artefacts arising from changing tip-sample thermal contact area caused by any surface roughness of the specimen [48]. When the probe encounters a depression on the surface, the area of contact between the tip and sample increases, resulting in increased heat flux from the tip to the sample. More power is required to maintain the tip temperature at the set-point value and... 

Figure 9.10 Thermal images of a PVC/PB immiscible blend. (Reprinted with permission from Journal Of Vacuum Science and Technology B., Scanning thermal microscopy Subsurface imaging, thermal mapping of polymer blends, and localized calorimetry by A. Hammiche, D.J. Hourston, H. M. Pollock et al., 14, 2, 1486-1491. Copyright (1996) American Institute of Physics)...

Scanning thermal microscopy (SThM) was used to estimate the surface distribution of the microthermal properties (for details see Ref 21). As can be seen from the images obtained in this mode (Figure 8, substantial thermal contrast for PB and PS phases can be detected at the probe temperature above 50 C. A geometrical contribution is also clearly visible However, taking into account that the effective thermal contact area for polymeric materials is about 1 pm [21], we can refer the major contribution in different thermal re onse for the polymer film to different thermal conductivities of glassy and rubber phases. 

The analysis of thermal image obtained from scanning thermal microscopy is not always trivial. The thermal signal is a function of the electrical power dissipated (P) in the tip, which... 

Fig. 5 Scanning electron microscopy images of colloids with a rough shell. CoUoids a before thermal treatment, b hollow colloids after thermal treatment at 500 °C, and c a broken empty shell. Reproduced by permission of The Royal Society of Chemistry [31]...

Scanning thermal microscopy (SThM) is a contact AFM technique that allows spatial mapping of temperature or thermal conductivity across a sample surface in addition to topography. Most thermal probes utilize a temperature-sensitive resistor placed on the end of the tip. These resistor probes can be fabricated from a V-shaped Wollaston wire made of a platinum inner core and outer sheath of silver, in which the silver sheath is etched away at the V-shaped tip. Eigure 19 shows a Wollaston wire probe. In passive mode, the tip is scanned across a heated sample under constant-force feedback (contact mode) and a small current is passed through the probe to sense the tip resistance. The resistance value at any point is a measure of the local temperature, and thus a temperature map and topographic image may be produced simultaneously. 

It is possible to image the thermal pattern over a surface by having a thermocouple junction on the probe tip of an AFM the technique is called scanning thermal microscopy (SThM). Thermocouple junctions 100-500 nm in diameter have been produced that have a lOnm resolution (low to high temperature). By sending a thermal pulse through the substrate, differences in surface temperature may indicate poor thermal contact (i.e. poor adhesion). 

For the detailed study of reaction-transport interactions in the porous catalytic layer, the spatially 3D model computer-reconstructed washcoat section can be employed (Koci et al., 2006, 2007a). The structure of porous catalyst support is controlled in the course of washcoat preparation on two levels (i) the level of macropores, influenced by mixing of wet supporting material particles with different sizes followed by specific thermal treatment and (ii) the level of meso-/ micropores, determined by the internal nanostructure of the used materials (e.g. alumina, zeolites) and sizes of noble metal crystallites. Information about the porous structure (pore size distribution, typical sizes of particles, etc.) on the micro- and nanoscale levels can be obtained from scanning electron microscopy (SEM), transmission electron microscopy ( ), or other high-resolution imaging techniques in combination with mercury porosimetry and BET adsorption isotherm data. This information can be used in computer reconstruction of porous catalytic medium. In the reconstructed catalyst, transport (diffusion, permeation, heat conduction) and combined reaction-transport processes can be simulated on detailed level (Kosek et al., 2005). 

Petroff and Lang (1977) combined DLTS with scanning electron microscopy in a method that allows spatial imaging of deep states in the plane of a junction. The scanned electron beam is pulsed on and off and the resulting thermally stimulated current or capacitance transient is analyzed using the usual DLTS methods. 

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