Probe detection system

A method of detecting light reflected from an upper surface of a scanning probe, the method including locating a point on the upper surface that is directly above the probe tip followed by directing a light beam on the upper surface at a point directly above a probe tip, collecting light reflected from the upper surface and directing it to a height detector arranged to form an image indicative of the height of the probe tip above a reference level. wherein the step of locating the point on the upper surface includes the steps of:

• (a) directing light onto the upper surface;
• (b) oscillating the probe about its tip so as to change the angle of the upper surface;
• (c) monitoring the output of the height detector;
• (d) changing the position of the point on the upper surface at which the light is incident;
• and
• (e) repeating steps (c) and (d) until variations apparent in the output of the height detector as a result of tilting the probe are minimised.

A method of detecting light reflected from an upper surface of a scanning probe, the method including locating a point on the upper surface that is directly above the probe tip followed by directing a light beam on the upper surface at a point directly above a probe tip, collecting light reflected from the upper surface and directing it to a height detector arranged to form an image indicative of the height of the probe tip above a reference level, wherein the probe comprises a cantilever held at its base end and supporting the tip at or near its free end, the upper surface of the probe that is illuminated by the beam being at or near the cantilever free end, and wherein the step of locating the point on the upper surface includes the steps of:

• (a) directing light onto the upper surface of the cantilever
• (b) moving the base of the cantilever vertically whilst maintaining the tip in a fixed position so as to change the angle of orientation of the cantilever;
• (c) monitoring the output of the height detector;
• (d) changing the position of the point on the upper surface at which the light is incident;
• and
• (e) repeating steps (c) and (d) until variations apparent in the output of the height detector as a result of moving the base of the probe are minimised.

A method of detecting light reflected from an upper surface of a scanning probe, the method including locating a point on the upper surface that is directly above the probe tip followed by a step of directing a light beam on the upper surface at a point directly above a probe tip, collecting light reflected from the upper surface and directing it to a height detector arranged to form an image indicative of the height of the probe tip above a reference level, and wherein the step of locating the point on the upper surface includes the steps of:

• (a) directing light onto the upper surface;
• (b) displacing the probe tip by a known distance;
• (c) monitoring the output of the height detector;
• (d) changing the position of the point on the upper surface at which the light is incident;
• and
• repeating steps (c) and (d) until the output of the height detector corresponds to that expected for the known displacement.

A method of detecting light reflected from an upper surface of a scanning probe, the method including locating a point on the upper surface that is directly above the probe tip followed by a step of directing a light beam on the upper surface at a point directly above a probe tip, collecting light reflected from the upper surface and directing it to a height detector arranged to form an image indicative of the height of the probe tip above a reference level, wherein the step of locating the point on the upper surface includes the steps of:

• (a) directing light onto the upper surface;
• (b) scanning the probe at a speed sufficient to excite transient motion thereof;
• (c) monitoring the output of the height detector;
• (d) changing the position of the point on the upper surface at which the light is incident;
• and
• (e) repeating steps (c) and (d) until variations apparent in the output of the height detector as a result of transient motion are minimised.

A method of collecting data using a scanning probe microscope, the method comprising the steps of:

• (a) moving a probe comprising a cantilever with base and free ends, the free end supporting a sharp tip, into close proximity with a sample surface;
• (b) directing a light beam on an upper surface of the probe at a point directly above the tip;
• and
• (c) scanning the probe across the sample surface whilst collecting and analysing light reflected from the upper surface of the probe, a z driver being operative to drive the base of the probe vertically in response to a feedback signal obtained by analysis of a first component of the collected light, from which is obtained an indication of the deflection of the upper surface of the probe and wherein a second component of collected light is transmitted to an interferometer arranged to detect the path difference between this component and a height reference beam and arranged to form an image indicative of the height of the probe tip above a reference level.