Scanning probe microscope and operation method
View Patent ↗A scanning probe is microscope has a cantilever having a probe at a disal end thereof and an oscillator for generating a resonance signal near a resonance of the cantilever. A vibrating device receives the resonance signal as a driving signal for vibrating the cantilever. A variable gain amplifier adjusts a gain of displacement signal corresponding to displacement of the vibrating cantilever so as to satisfy the equation G=(A/A 0 )*G 0 to control a quality factor value of the cantilever resonance to an optimal quality factor value, where G represents a gain value of the variable gain amplifer, A represents a preselected oscillation amplitude of the oscillator, A 0 represents an initial oscillation amplitude of the oscillator, and G 0 represents a gain value of the variable gain amplifier when the initial oscillation amplitude of the oscillator is A 0 .
1. A scanning probe microscope comprising:
a cantilever having a probe at a distal end thereof;
an oscillator for generating a resonance signal near a resonance of the cantilever;
vibrating means connected to receive the resonance signal generated by the oscillator as a driving signal for vibrating the cantilever while the probe is in close proximity to a surface of a sample;
extracting means for extracting a displacement signal corresponding to displacement of the cantilever during vibration thereof;
a variable gain amplifier for adjusting a gain of the displacement signal extracted by the extracting means so as to satisfy the equation G=(A/A 0 )*G 0 to control a quality factor value of the cantilever resonance to an optimal quality factor value, where G represents a gain value of the variable gain amplifier, A represents a preselected oscillation amplitude of the oscillator, A 0 represents an initial oscillation amplitude of the oscillator, and G 0 represents a gain value of the variable gain amplifier when the initial oscillation amplitude of the oscillator is A 0 ; and
an adder for superimposing an output signal from the variable gain amplifier with an output signal from the oscillator to generate a signal for use as the driving signal received by the vibrating means for vibrating the cantilever.
2. A scanning probe microscope according to claim 1 ; wherein the vibrating means comprises a plurality of piezoelectric elements.
3. A scanning probe microscope according to claim 1 ; further comprising displacement detection means for detecting an oscillation amplitude of the cantilever during vibration thereof corresponding to the displacement signal.
4. A scanning probe microscope according to claim 3 ; further comprising a preamplifier for amplifying the displacement signal and for outputting the amplified displacement signal to the variable gain amplifier via the extracting means.
5. A scanning probe microscope according to claim 4 ; wherein the extracting means comprises a phase shifter.
6. A scanning probe microscope comprising:
a cantilever having a probe at a distal end thereof;
an oscillator for generating a resonance signal near a resonance of the cantilever;
vibrating means connected to receive the resonance signal generated by the oscillator as a driving signal for vibrating the cantilever while the probe is in close proximity to a surface of a sample;
extracting means for extracting a displacement signal corresponding to displacement of the cantilever during vibration thereof;
a variable gain amplifier for adjusting a gain of the displacement signal extracted by the extracting means so as to satisfy the expression G∝1/L to control a quality factor value of the cantilever resonance to an optimal quality factor value, where G represents a gain value of the variable gain amplifier and L represents a distance between the probe and the sample; and
an adder for superimposing an output signal from the variable gain amplifier with an output signal from the oscillator to generate a signal for use as the driving signal received by the vibrating means for vibrating the cantilever.
7. A scanning probe microscope according to claim 6 ; wherein the vibrating means comprises a plurality of piezoelectric elements.
8. A scanning probe microscope according to claim 7 ; further comprising displacement detection means for detecting an oscillation amplitude of the cantilever during vibration thereof corresponding to the displacement signal.
9. A scanning probe microscope according to claim 8 ; further comprising a preamplifier for amplifying the displacement signal and for outputting the amplified displacement signal to the variable gain amplifier via the extracting means.
10. A scanning probe microscope according to claim 9 ; wherein the extracting means comprises a phase shifter.
11. A method of operating a scanning probe microscope having a cantilever probe with a probe tip at a distal end thereof for scanning a surface of a sample, comprising the steps of:
displacing the cantilever probe so that the probe tip approaches the surface of the sample;
acquiring a point corresponding to a first position of the cantilever probe at which a distance between the probe tip and the surface of the sample is zero;
displacing the cantilever probe to a second position different from the first position using the acquired point as a reference by raising the probe tip to a first distance from the surface of the sample;
controlling at the second position of the cantilever probe a quality factor value of the resonance of the cantilever probe to an optimal quality factor value;
displacing the cantilever probe to a third position different from the second position so that probe tip is disposed at a second distance from the surface of the sample different from the first distance; and
controlling at the third position of the cantilever probe a quality factor value of the resonance of the cantilever probe to an optimal quality factor value.