Displacement detection mechanism and scanning probe microscope using the same
View Patent ↗A displacement detection mechanism for a vibrationally driven cantilever includes a vibration frequency detector comprised of an LC resonator that detects a change of capacitance between the cantilever and a sample surface due to a change of vibration of the cantilever, and an F-V converter or an FM demodulator that detects a voltage based on the vibration frequency, whereby displacement of the cantilever can be detected. The displacement detection mechanism can be used in a scanning probe microscope to perform shape measurement and physical property measurement without the presence of light.
1. A scanning probe microscope, comprising:
a cantilever having a probe at a tip thereof;
cantilever vibrator means for vibrating the cantilever;
a sample table on which a sample is to be placed in opposed relation to the tip of the probe;
an X-Y drive mechanism and a Z drive mechanism for driving a surface of the sample and the probe relatively to each other in an X direction and a Y direction, and a Z direction, respectively;
a cantilever displacement detection portion for detecting a displacement of the cantilever, the cantilever displacement detection portion comprising capacitance change detection means for detecting a change of capacitance between the cantilever and a reference surface due to a change of vibration of the cantilever, the capacitance change detection means comprising vibration frequency detection means for detecting a vibration frequency of the cantilever based on the change of capacitance, the vibration frequency detection means comprising
an LC resonator that is connected electrically to the cantilever and that detects a change of resonance frequency of the LC resonator based on the change of capacitance, and
electrical signal detection means for detecting an electric signal based on the detected vibration frequency,
wherein the capacitance is expressed by an equation having at least three parameters including length of the probe and length and width of the cantilever, and
wherein the cantilever displacement detection portion recognizes the vibration frequency of the cantilever based on the change of capacitance, and evaluates the displacement of the cantilever based on the electric signal;
a control portion for obtaining shape data and physical property data of the surface of the sample from displacement information of the cantilever detected by the cantilever displacement detection portion; and
an illumination device for irradiating at least one of the surface of the sample and the probe with light,
wherein the scanning probe microscope detects differences of shape and physical property information of the surface of the sample between presence and absence of the light applied from the illumination device.
2. A scanning probe microscope according to claim 1 , wherein the cantilever displacement detection portion detects a vibration amplitude, a vibration frequency, and a phase of the cantilever.
3. A scanning probe microscope according to claim 1 , wherein the cantilever displacement detection portion detects a vibration amplitude of the cantilever vibrated by the cantilever vibrator means, the vibration amplitude having the same frequency component as a frequency component of the cantilever vibrator means.
4. A scanning probe microscope according to claim 1 , wherein the cantilever displacement detection portion detects a difference between a phase of the cantilever vibrated by the cantilever vibrator means from a phase of the cantilever vibrator means.
5. A scanning probe microscope according to claim 1 , wherein the cantilever displacement detection portion detects a vibration amplitude and a phase of the cantilever vibrated by an alternating electric field applied between the surface of the sample and the probe.
6. A scanning probe microscope according to claim 5 , wherein the cantilever displacement detection portion detects a vibration amplitude of the cantilever vibrated by the alternating electric field applied between the surface of the sample and the probe, the vibration amplitude having the same frequency component as a frequency component of the alternating electric field.
7. A scanning probe microscope according to claim 5 , wherein the cantilever displacement detection portion detects a difference between a phase of the cantilever vibrated by the alternating electric field applied between the surface of the sample and the probe, and a phase of the alternating electric field.
8. A scanning probe microscope according to claim 5 , wherein the cantilever displacement detection portion detects a vibration amplitude and a phase of the cantilever vibrated by the alternating electric field applied between the surface of the sample and the probe, the vibration amplitude and the phase having a frequency component that is at least twice or more of a frequency component of the alternating electric field.
9. A scanning probe microscope according to claim 1 , wherein the scanning probe microscope detects differences of shape and physical property information of the surface of the sample due to a difference in frequency of the light applied from the illumination device.
10. A scanning probe microscope according to claim 1 , wherein the scanning probe microscope detects differences of a shape and physical property information of the surface of the sample due to a difference in intensity of the light applied from the illumination device.