Scanning probe microscope and measurement range adjusting method for scanning probe microscope

1. A scanning probe microscope comprising:

a cantilever having a probe that is to be contacted or approached on a surface of a sample;

a displacement detector that detects a signal indicating a displacement of the cantilever;

a probe microscope controller that acquires measurement data based on the signal while the surface of the sample is relatively scanned with the probe and while maintaining a predetermined physical quantity between the cantilever and the surface of the sample constant; and

a processor that operates to perform a process including:

calculating a measurement width MW and an offset value OV from a minimum value S min and a maximum value S max of the signal with the following Equations (1) and (2) when a prescanning operation of roughly scanning the surface of the sample with the probe is performed before the measurement data is acquired by the probe microscope controller, wherein

MW =( S max −S min )  Equation (1)

OV =( MW/ 2)+ S min   Equation (2); and

adjusting at least one of the offset value OV and the measurement width MW based on a temporal variation of the signal at the same position on the surface of the sample when the prescanning operation is performed.

2. The scanning probe microscope according to claim 1 ,

wherein the processor operates to perform the process further including:

determining a gain for amplifying the signal based on the measurement width and the adjusted offset value,

wherein the scanning probe microscope further comprises:

an amplifier that amplifies the signal based on the gain determined by the processor to generate an amplified signal, and

wherein the probe microscope controller acquires the measurement data based on the amplified signal.

3. The scanning probe microscope according to claim 2 ,

wherein the amplifier includes an automatic gain control circuit.

4. A measurement range adjusting method for a scanning probe microscope having a cantilever having a probe that is to be contacted or approached on a surface of a sample, the method comprising:

calculating a measurement width MW and an offset value OV from a minimum value S min and a maximum value S max of a signal indicating a displacement of a cantilever with the following Equations (1) and (2) when a prescanning operation of roughly scanning the surface of the sample with the probe is performed;

adjusting at least one of the offset value OV and the measurement width MW based on a temporal variation of the signal at the same position on the surface of the sample when the prescanning operation is performed, wherein

MW=S max −S min )  Equation (1)

OV =( MW/ 2)+ S min   Equation (2); and

acquiring measurement data based on the signal while the surface of the sample is relatively scanned with the probe and while maintaining a predetermined physical quantity between the cantilever and the surface of the sample constant.

5. A non-transitory computer readable recording medium storing computer readable instructions for a processor that controls a scanning probe microscope having a cantilever having a probe that is to be contacted or approached on a surface of a sample, wherein the instructions, when executed by the processor, cause the scanning probe microscope to perform:

calculating a measurement width MW and an offset value OV from a minimum value S min and a maximum value S max of a signal indicating a displacement of a cantilever with the following Equations (1) and (2) when a prescanning operation of roughly scanning the surface of the sample with the probe is performed, wherein

MW =( S max −S min )  Equation (1)

OV =( MW/ 2)+ S min   Equation (2);

adjusting at least one of the offset value OV and the measurement width MW based on a temporal variation of the signal at the same position on the surface of the sample when the prescanning operation is performed; and

acquiring measurement data based on the signal while the surface of the sample is relatively scanned with the probe and while maintaining a predetermined physical quantity between the cantilever and the surface of the sample constant.