Scanned Probe Microscopy physical principles

Nobel-laureate Richard Feynman once said that the principles of physics do not preclude the possibility of maneuvering things atom by atom (260). Recent developments in the fields of physics, chemistry, and biology (briefly described in the previous sections) bear those words out. The invention and development of scanning probe microscopy has enabled the isolation and manipulation of individual atoms and molecules. Research in protein and nucleic acid stmcture have given rise to powerful tools in the estabUshment of rational synthetic protocols for the production of new medicinal dmgs, sensing elements, catalysts, and electronic materials. 

Physical Principles of Scanning Probe Microscopy Imaging... 

We first experimented with the Quartz Crystal Microbalance (QCM) in order to measure the ablation rate in 1987 (12). The only technique used before was the stylus profilometer which revealed enough accuracy for etch rate of the order of 0.1 pm, but was unable to probe the region of the ablation threshold where the etch rate is expressed in a few A/pulse. Polymer surfaces are easily damaged by the probe tip and the meaning of these measurements are often questionable. Scanning electron microscopy (21) and more recently interferometry (22) were also used. The principle of the QCM was demonstrated in 1957 by Sauerbrey (22) and the technique was developed in thin film chemistiy. analytical and physical chemistry (24). The equipment used in this work is described in previous publications (25). When connected to an appropriate oscillating circuit, the basic vibration frequency (FQ) of the crystal is 5 MHz. When a film covers one of the electrodes, a negative shift <5F, proportional to its mass, is induced ... 

For scanning and manipulating matter at the nanoscale, scanning tunneling microscopy (STM) [199], scanning electron microscopy (SEM), atomic force microscopy (AFM) [197] and scanned-probe microscope (SPM) [201] seem to be the common tools. Current workis mainly focused on using AFM nanoprobes for teleoperated physical interactions and manipulation at the nano scale. Precise manipulation could help scientists better understand the principles of nanorobots [202,203]. 

SPM was invented in 1981 by G. Binnigand H. Rohrer, who won the Nobel Prize in Physics five years later for their invention. There are many kinds of SPMs, such as scanning tunneling microscopy (STM), atomic force microscopy (AFM), scanning near-field optical microscopy (SNOM), and magnetic force microscopy (MFM). All the SPMs are based on similar principles (Fig. 8), although each type of SPM employs a different probe and uses different mode of interaction with the sample surface (for more details about different SPMs, see Ref 7). 

---