The Scanning Probe Microscope (SPM)
Scanning probe microspoes (SPM) all scientist to image, characterize and even manipulate material structures at exceedingly small scales including features of atomic proportions. A wide variety of material structures and properties can be studied such as man-made and natural systems, including biological systems. The family of scanning probe microscopes uses no lenses, but rather a probe that interacts with the sample surface. The type of interaction measured between the probe tip and the sample surface defines the type of scanning probe microscope being used. The Scanning Tunneling Microscopy (STM) relies on the electrical conductivity of the sample, so at least some features on the sample surface must be electrically conductive to some degree. The Atomic Force Microscopy (AFM) is used for studies of non-conductors and is the technique most commonly used for studies of macromolecules and biological specimens. AFM has been used for measurements on a wide variety of sample types, including: surfaces and nanostructures of inorganic and synthetic materials, polymers and polymer matrix and biological structures of biological materials.
The resolution of the microscopes is not limited by diffraction, but only by the size of the probe-sample interaction volume, which can be as small as a few picometers. Hence the ability to measure small local differences in object height is unparalleled. Laterally the probe-sample interaction extends only across the tip atom or atoms involved in the interaction. Unlike electron microscope methods, specimens do not require a partial vacuum but can be observed in air at standard temperature and pressure or while submerged in a liquid reaction vessel.
Our MulitModeTM SPM is from Digital Instruments. It included STM, AFM and lateral force microscopy (LFM). Scanners with large scan ranges up to 125 microns on the X-Y axes, and a Z range up to 5 microns, as well as high-resolution scanners with 10 microns X-Y axes and 2.5 microns Z range are available. The tip/cantilever holders include: tapping mode/contact mode in air, tapping mode/force modulation in fluid, STM converter.
