Piezoelectric drive

In STM, a sharp metal tip [12] is brought within less than a nanometre of a conducting sample surface, using a piezoelectric drive (fignre B 1,19,11 At these separations, there is overlap of the tip and sample wavefiinctions at the... 

Fig. 7.64. Scheme of operation of piezoelectric drive in STM. (Reprinted with permission of Oxford University Press from C. M. A. Brett and A. M. O. Brett, Electrochemistry Principles, Methods, and Applications, Oxford University... 

Fig. 12.14. Scheme of operation of piezoelectric drives for scanning local probe... 

Not only can experiments be performed in situ, but also the time evolution of surface topography can be monitored. Accurate scanning of the surface is accomplished by means of piezoelectric drives—the size of a piezoelectric crystal changes linearly with the applied potential difference. Drives are applied in x, y and z directions as shown schematically in Fig. 12.14. Generally, successive scans are applied in the x direction incrementing y between scans, so that a series of x-z profiles are recorded. These can be converted by computer software into gray-scale or coloured images if desired. 

S. Sassen, R. Voss, J. Schalk, E. Stenzel, T. Gleissner, R. Gruenberger, F. Neu-bauer, W. Ficker, W. Kupke, K. Bauer, M. Rose, Silicon Angular Rate Sensor for Automotive Applications with Piezoelectric Drive and Piezoresistive Read-out, in Proc. Conf. Transducers, Technical Papers, Institute of Electrical Engineers of Japan, Sendai, Japan, 1999. 

Resonances at 6-25-keV and 136-25-keV are known in Ta. The 6-25-keV resonance of Ta suffers from the same disadvantage as Zn, namely a very narrow natural linewidth which in this instance is 6-5 x 10 mm s. The first experiments in 1964 used a piezoelectric drive to produce the small velocities required [35] the absorbers were TaC and KTaOs and the sources were W in tungsten metal or BajCaWOg = 140 d, see Fig. 

Figure 6.26 STM set up Scanning of the surface takes place in the near field regime in which piezoelectric drives Px and Py raster the STM tip across the surface of a sample. Piezo electric drive Pz ensures that the tip remains a short distance dj (a few A) from surface encouraging a tunnelling current, Ij, to be established under the influence of a tip to surface potential Uj.

An atomic force microscope uses the deflection produced in a fine tip by interactions with atoms in the surface of a membrane to reconstruct the surface structure of that membrane. A piezoelectric drive moves the sample surface under the tip. The motions of the tip are converted into a three-dimensional image of the surface. Atomic force microscopy requires no surface preparation so that the membrane can be observed in its normal environment. 

The operating range of piezoelectric materials is limited to well below their Curie temperature, which is typically 150... 300°C for ceramics and only 70... 90°C for polymers. Piezoelectric drives generally exhibit hysteresis which can be compensated by sophisticated electronic circuitry. For applications where a purely resonant mode of operation is desired, hysteresis poses no problem. 

Fig. 12 shows an experiment [31], analogous to nanoindentation of atomic crystals, in which an indenter is driven into a colloidal single crystal, grown on a (100) template, to observe the resulting dislocation dynamics by both confocal and laser diffraction microscopies. The indenter is simply a commercial sewing needle, which is produced with a hemispherical tip with a diameter of 40 pm. The ratio of the tip and particle radii is similar to that in nanoindentation experiments. The needle is attached to a piezoelectric drive and is moved at a rate of 3.4 pm/h. 

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