Exposure mode imaging

Figure Bl.19.13. (a) Tliree STM images of a Pt(l 11) surface covered witli hydrocarbon species generated by exposure to propene. Images taken in constant-height mode. (A) after adsorption at room temperature. The propylidyne (=C-CH2-CH2) species that fomied was too mobile on the surface to be visible. The surface looks similar to that of the clean surface. Terraces ( 10 mn wide) and monatomic steps are the only visible features. (B) After heating the adsorbed propylidyne to 550 K, clusters fonn by polymerization of the C H...

Whenever possible, we perform experiments in the same part of the surface before and after some operation. The operation may involve exposure of the surface to a reactant such as water or 02, for example or it may be some switch in the functionality of the microscope, for instance, imaging first in AFM mode and then in STM mode. For reactions, we simply stop the scan and retract the tip by up to 1000 nm, which ensures it does not crash when we admit gases or vapors to the chamber via the high-precision leak valves. 

Measures in UV reflectivity mode are thus possible, using a 400 nm peaked narrowband filter. However, because of the glass optics absorption below 400 nm and the low sensor sensitivity in the UV, the quality of the images in UV reflection mode is not particularly good, because of the long exposure time need for compensating the low illumination on the sensor. 

Figure 7.22 shows the microscopic image of a typical laser-induced micronotch on a single-mode fiber (Coming SMF-28e). The laser power was set to 10 W and the exposure duration was 300 ms. Figure 7.23 shows the interference spectra of MZIs with the length of 5,10, 20, and 40 mm, respectively. The typical interference... 

---