Ambient imaging, silicon

In contrast to many other surface analytical techniques, like e. g. scanning electron microscopy, AFM does not require vacuum. Therefore, it can be operated under ambient conditions which enables direct observation of processes at solid-gas and solid-liquid interfaces. The latter can be accomplished by means of a liquid cell which is schematically shown in Fig. 5.6. The cell is formed by the sample at the bottom, a glass cover - holding the cantilever - at the top, and a silicone o-ring seal between. Studies with such a liquid cell can also be performed under potential control which opens up valuable opportunities for electrochemistry [5.11, 5.12]. Moreover, imaging under liquids opens up the possibility to protect sensitive surfaces by in-situ preparation and imaging under an inert fluid [5.13]. 

The AFM used in this study was a Nanoscope II system (Digital Instrument Inc.) operated at ambient conditions. Two AFM scan heads (700 nm range and 8000 nm range) with silicon nitride probes were employed. The AFM was operated in the height imaging mode and at low scan frequency (< 2 Hz). AFM analysis was conducted ex-situ on the fresh film, after H2 pretreatment, after S addition, and after the catalytic reaction. Four areas from each piece of catalysts were imaged before and after each reaction. The areas scanned varied from 100 xlOO nm to 4000 x 4000 nm. ... 

The surface topography of the obtained MDF cement specimens was studied by AFM (NT-MDT model NTGRA PREVIA EC), operated at ambient atmosphere. AFM data were collected in semi contact mode using a silicone cantilever (CSG 10, force constant 0.15 N/m, tip radius 10 nm). The average roughness was calculated with the AFM manufacturer s provided software on images of 5 x 5 pm scan size. 

Eaton et al. used FV mapping for imaging of a phase-separated blend of PMMA and poly(dodecyl methacrylate) (PDDMA) [190,191). Unmodified silicon nitride cantilevers were used in ambient conditions in air or in water using a liquid cell. Differences in pull-off forces correlated with features in topography, making it possible to distinguish between the PDDMA-rich... 

FIGURE 4.10 Atomic force images from 1x1 tm scans on 5 nm thick PFOM fihn on silicon equilibrated at ambient 50% relative humidity, 0.26 nm nns ronghness (a), the same PFOM film as in (a) following equilibration in a vacuum desiccator, 0.17 nm rms roughness (b), and an uncoated silicon strip, 0.09 nm rms roughness (c). 

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