Patent ID: 7084661

Claim:
A scanning Kelvin microprobe system for analyzing a surface of a sample, the system comprising: a tip with a predetermined work function for exploring a surface of the sample, and for extracting Kelvin current from a local capacitor toned between the tip and the sample, wherein the tip is a microelectrode having the apex radius of curvature less than about 100 nm; a piezoelectric element for vibrating the tip at a first frequency from about 1 to about 20 kHz; a scan table for placing the sample thereon; a micropositioner for moving the scan table in x and y directions; a piezoelectric translation stage attached to the scan table for moving the sample in the z direction for maintaining a constant sample-tip distance, a signal generator for directing vibration at a second frequency from about 100 to about 500 kHz, to control sample-tip distance for sample-tip capacitance detection; an ultra low noise charge amplifier for converting the Kelvin current extracted by the tip into a voltage; a first lock-in amplifier tuned at the a first frequency, for measuring the voltage and generating contact potential difference image signal; a second lock-in amplifier tuned at the second frequency, for monitoring sample-tip distance and for generating a topographic image signal, the second frequency being above the first frequency, said first frequency and said second frequency being independently selected and non-interfering; and a controller comprising software for opening a file, initializing a card and a motor, starting the first and the second lock-in amplifiers, bringing the sample up, scanning the sample, bringing the sample down, writing data in a file, and closing the file; and a data acquisition system for acquiring said contact potential difference image signal and said topographical image signal.