Typical scanning force microscopy

Typical atomic force microscopy (AFM) and scanning electron microscopy (SEM) images of Te deposited on n-Si are presented in Fig. 2. At the first stages of Te deposition the separate particles with sizes of 104-40 nm are formed. Later, new particles appear and grow forming tendril-like structures. At longer times the deposit covers the whole substrate surface. According to x-ray diffraction (XRD) data, the amorphous product is formed. 

Poled PVDF films show fenoelectiic behavior clearly demonstrating the polarization reversal in the dielectric Itysteresis curve (Nalwa 1995). Locally created domains ate reported (Giithner and Dransfeld 1992) in scanning force microscopy observations in PVDF. Typical values of the spontaneous polarization are 8-10 X 10 Ccm and of the coercive field 50-100 kVmm . For the material properties see Table 7.17. Uniaxially drawn films are much mote anisotropic in piezoelectric properties. The piezoelectric coefficients are higher than e.g. for quartz crystals, but lower than for PZT ceramics. It is highly desirable to improve the piezoelectric coefficients for the possible applications of polymers. 

Why are typical surface science techniques such as low-energy electron diffraction, scanning tunneling and atomic force microscopy generally unsuitable for studying supported catalysts ... 

Figure 8.3 shows the typical force-distance curve for a K-carrageenan film. From the slope of the curve, where the AFM tip is in contact with the film surface. Young s modulus of the K-carrageenan film can be estimated by using the Hertz model with the proper measurement of the AFM tip radius using scanning electron microscopy (SEM) and estimated value of Poisson s ratio based on the characteristics of film surface, which is around 1.4 MPa. 

A new alternative to solve this problem is atomic force microscopy (AFM) which is an emerging surface characterization tool in a wide variety of materials science fields. The method is relatively easy and offers a subnanometer or atomic resolution with little sample preparation required. The basic principle involved is to utilize a cantilever with a spring constant weaker than the equivalent spring between atoms. This way the sharp tip of the cantilever, which is microfabricated from silicon, silicon oxide or silicon nitride using photolithography, mechanically scans over a sample surface to image its topography. Typical lateral dimensions of the cantilever are on the order of 100 pm and the thickness on the order of 1 pm. Cantilever deflections on the order of 0.01 nm can be measured in modem atomic force microscopes. 

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