Nanotechnology for Electronic Materials and Devices (eBook)

A Hybrid Route from CMOS to Nano and Molecular Electronics.- From SOI Basics to Nano-Size MOSFETs.- Strategies of Nanoscale Semiconductor Lasers.- Silicon Nanocrystal Nonvolatile Memory.- Novel Dielectric Materials for Future Transistor Generations.- Scanning Force Microscopies for Imaging and Characterization of Nanostructured Materials.- Simulation of Nano-CMOS Devices: From Atoms to Architecture.- Lattice Polarons and Switching in Molecular Nanowires and Quantum Dots.

"6 Scanning Force Microscopies for Imaging and Characterization of Nanastructured Materials (p. 223-224)

Bartosz Such, Franci szek Krok, and Marek Szymonski

6.1. INTRODUCTION

The growing tendency to miniaturize devices used in every-day life (e.g., integrated circuits or technologies for optical information transfer), as well as exciting prospects of new emerging technologies (quantum electronics, biochips, etc.) are prompting a huge interest in nanotechnology and the science of nanostructured materials. In particular, there is a need to develop efficient technologies for the preparation of surfaces with desired structure and electronic properties.

In light of those advances, designing analytical and nondestructive tools for the characterization of surface electronic and chemical properties with nanometer resolution is of utmost importance. Such tools are important for both nanostructure characterization and nanomanipulation of small-size assemblies of atoms and/or molecules on crystal surfaces in order to construct nanodevices. Furthermore, local determination of surface morphology and mechanical as well as electronic properties might be important for practical functioning of various nanosensors and nanodevices in biological objects.

6.2. SCANNING PROBE MICROSCOPY

Scanning probe microscopy (SPM) is commonly used for imaging and characterizing surface structure in the range between hundreds of micrometers and a few nanometers with atomic structure details. In some way, it represents the development of the concept of a profilometer. The heart of every SPM is a sharp tip acting as a probe (see Fig. 6.1). The detailed design of its support as well as the interaction that is probed by the tip are dependent on the specific type of SPM. A tip is scanned over a sample (or a sample is scanned against a tip) by a piezoelectric scanner, usually in the form of a tube.

The tube is divided into four sectors along its axis, which bend according to the voltage applied across them. Since the tube is long (up to several centimeters) and typical scan ranges are small (below 100 urn) the curvature of the tip path is negligible. The piezotube is also used for varying the tip-surface distance . Modem designs give an accuracy on the order of picometers in both vertical and horizontal directions. However, for some applications (such as biological studies), scan ranges exceeding 100 urn are required.

For that purpose, SPM designs in which the scanning motion is accomplished by two perpendicular piezoelements are used. In order to control the tip position with an accuracy of picometers, the entire instrument must be rigorously separated from external vibrations. Various systems of spring suspension and eddy current damping are used."