분야
hwpAFM is one of many techniques which fall under the Scanned Probe Microscopy (SPM) family of instruments. In all of these SPM techniques a small probe (10-100 nm radius of curvature) is scanned by a piezoelectric device over a sample to produce an image of the sample surface.The first of the SPM techniques was the Scanning Tunneling Microscope (STM), developed by Binnig&Rohrer, which got them the Nobel prize for Physics in 1986. The contrast mechanism in the STM is based on the tunneling of electrons from a sharp metal probe tip to a conductive sample.
A simple schematic of an AFM instrument is given in Fig.1.In this instrument the probe tip is mounted on the end of a triangular cantilever arm.A piezoelectric device scans the sample beneath the probe tip. As the probe tip undergoes attractive or repulsive forces, the cantilever will bend. This bending of the cantilever can be monitored by bouncing a laser beam off of the cantilever onto a 2 element photodiode(Position Sensitive Photo Diode).In normal operation the tip-sample force is held constant by a computer controlled feedback loop that examines the force and tells the piezoelectric device whether to move the sample closer orfarther away in order to maintain the set force value. The AFM image produced is a measure of the topography of the sample
