Tapping atomic force microscope with phase or frequency detection

Claim 2

In a method of operating an atomic force microscope including a probe including a probe tip mounted on one end of a lever arm and wherein the probe tip is scanned across the surface of a sample and data representative of the surface of the sample is gathered in relation to the positioning of the lever arm as the probe tip is scanned, the improvement comprising: a) oscillating the probe, including oscillating the probe tip at or near a resonant frequency of the probe or a harmonic of said resonant frequency and with a free oscillation amplitude A o sufficiently great so that the oscillating probe tip does not stick to the surface of the sample when the oscillating probe tip contacts the surface of the sample; b) positioning the oscillating probe tip so that the oscillating probe tip repeatedly taps the surface of the sample with the probe tip repeatedly contacting and breaking contact with the surface of the sample without sticking to the surface of the sample; c) translating the oscillating probe tip across the surface of the sample with the oscillating probe tip repeatedly tapping the surface of the sample; d) controlling the distance between an opposite end of the lever arm opposite the probe tip and the sample so that the amplitude of oscillation of the probe tip is maintained essentially constant at an amplitude setpoint during said translating step; e) detecting changes in phase in the oscillation of the probe tip during translating of the probe tip while the oscillation of the probe tip is maintained at essentially constant amplitude; and f) producing a signal indicative of changes in phase detected in said detecting step.

Claim 3

The method according to claim 1, wherein said detecting step comprises: detecting deflection of said oscillating probe; and measuring a relative phase between a drive signal causing oscillation of said probe and detected deflection of said oscillating probe.

Claim 4

The method according to claim 1, comprising: modulating the oscillating frequency of the oscillating probe during translating at essentially constant amplitude; and said detecting step comprising determining corresponding changes in phase of the oscillating probe tip during translating of said probe.

Claim 5

The method according to claim 1, comprising: providing a probe including a substance selected to interact with a corresponding substance on said sample.

Claim 6

The method according to claim 4, wherein said step of providing a probe comprises: providing a probe coated with an antibody or an antigen.

Claim 7

The method according to claim 1 wherein said oscillating step comprises: oscillating said probe tip with a free oscillation amplitude greater than 10 nm.

Claim 8

The method according to claim 1, wherein said oscillating step comprises: oscillating said probe tip with a free oscillation amplitude greater than 20 nm.

Claim 9

The method according to claim 1, comprising: changing the amplitude setpoint and repeating said steps a) through f) while maintaining the amplitude of oscillation of the probe tip essentially constant at the changed amplitude setpoint.

Claim 10

The method according to claim 8, comprising: comparing signals produced in repeated of steps f) to discriminate a force dependent characteristic of the sample.

Claim 11

The method according to claim 3, comprising: changing the amplitude setpoint and repeating said steps a) through f) while maintaining the amplitude of oscillation of the probe tip essentially constant at the changed amplitude setpoint.

Claim 12

The method according to claim 10, comprising: comparing signals produced in repeated of steps f) to discriminate a force dependent characteristic of the sample.

Claim 13

In a method of operating an atomic force microscope including a probe including a probe tip mounted on one end of a lever arm and wherein the probe tip is scanned across the surface of a sample and data representative of the surface of the sample is gathered in relation to the positioning of the lever arm as the probe tip is scanned, the improvement comprising: a) oscillating the probe, including oscillating the probe tip at or near a resonant frequency of the probe or a harmonic of said resonant frequency and with a free oscillation amplitude A o sufficiently great so that the oscillating probe tip does not stick to the surface of the sample when the oscillating probe tip contacts the surface of the sample; b) positioning the oscillating probe tip so that the oscillating probe tip repeatedly taps the surface of the sample with the probe tip repeatedly contacting and breaking contact with the surface of the sample without sticking to the surface of the sample; c) translating the oscillating probe tip across the surface of the sample with the oscillating probe tip repeatedly tapping the surface of the sample; d) controlling the distance between an opposite end of the lever arm opposite the probe tip and the sample so that the amplitude of oscillation of the probe tip is maintained essentially constant at an amplitude setpoint during said translating step; e) detecting a relative phase between a drive signal causing oscillation of said probe and deflection of said probe; and f) controlling the frequency of the oscillation of the probe so that the relative phase detected in said detecting step is kept essentially constant during scanning.

Claim 14

In a method of operating an atomic force microscope including a probe including a probe tip mounted on one end of a lever arm and wherein the probe tip is scanned across the surface of a sample and data representative of the surface of the sample is gathered in relation to the positioning of the lever arm as the probe tip is scanned, the improvement comprising: a) oscillating the probe, including oscillating the probe tip at or near a resonant frequency of the probe or a harmonic of said resonant frequency and with a free oscillation amplitude A o sufficiently great so that the oscillating probe tip does not stick to the surface of the sample when the oscillating probe tip contacts the surface of the sample; b) positioning the oscillating probe tip so that the oscillating probe tip repeatedly taps the surface of the sample with the probe tip repeatedly contacting and breaking contact with the surface of the sample without sticking to the surface of the sample; c) translating the oscillating probe tip across the surface of the sample with the oscillating probe tip repeatedly tapping the surface of the sample; d) controlling the distance between an opposite end of the lever arm opposite the probe tip and the sample so that the amplitude of oscillation of the probe tip is maintained essentially constant at an amplitude setpoint during said translating step; e) detecting a relative phase between a drive signal causing oscillation of said probe and deflection of said probe; and f) controlling the frequency of the oscillation of the probe so that the relative phase detected in said detecting step is kept essentially constant during scanning.

Claim 15

The method according to claim 12, comprising: g) producing a signal indicative of variations in the frequency of oscillation of the probe as a function of position during translating.

Claim 16

The method according to claim 13, comprising: providing a probe including a substance selected to interact with a corresponding substance on said sample.

Claim 17

The method according to claim 14, wherein said step of providing a probe comprises: providing a probe coated with an antibody or an antigen.

Claim 18

The method according to claim 13, wherein said oscillating step comprises: oscillating said probe tip with a free oscillation amplitude greater than 10 nm.

Claim 19

The method according to claim 13, wherein said oscillating step comprises: oscillating said probe tip with a free oscillation amplitude greater than 20 nm.

Claim 20

The method according to claim 13, comprising: modulating the frequency of oscillation of the probe about the controlled frequency of step f) and determining corresponding changes in the phase of the oscillating probe tip during translating of said probe.

Claim 21

The method according to claim 12, comprising: changing the amplitude setpoint and repeating said steps a) through f) while maintaining the amplitude of oscillation of the probe tip essentially constant at the changed amplitude setpoint.

Claim 22

The method according to claim 13, comprising: changing the amplitude setpoint and repeating said steps a) through g) while maintaining the amplitude of oscillation of the probe tip essentially constant at the changed amplitude setpoint.

Claim 23

The method according to claim 20, comprising: comparing signals produced in repeated of steps f) to discriminate a force dependent characteristic of the sample.

Claim 24

The method according to claim 18, comprising: changing the amplitude setpoint and repeating said steps a) through g) while maintaining the amplitude of oscillation of the probe tip essentially constant at the changed amplitude setpoint.

Claim 25

The method according to claim 22, comprising: comparing signals produced in repeated of steps f) to discriminate a force dependent characteristic of the sample.

Claim 26

In a method of operating an atomic force microscope including a probe including a probe tip mounted on one end of a lever arm and wherein the probe tip is scanned across the surface of a sample and data representative of the surface of the sample is gathered in relation to the positioning of the lever arm as the probe tip is scanned, the improvement comprising: a) oscillating the probe, including oscillating the probe tip at or near a resonant frequency of the probe or a harmonic of said resonant frequency and with a free oscillation amplitude A o sufficiently great so that the oscillating probe tip does not stick to the surface of the sample when the oscillating probe tip contacts the surface of the sample; b) positioning the oscillating probe tip so that the oscillating probe tip repeatedly taps the surface of the sample with the probe tip repeatedly contacting and breaking contact with the surface of the sample without sticking to the surface of the sample; c) translating the oscillating probe tip across the surface of the sample with the oscillating probe tip repeatedly tapping the surface of the sample; d) controlling the distance between an opposite end of the lever arm opposite the probe tip and the sample so that the amplitude of oscillation of the probe tip is maintained essentially constant at an amplitude setpoint during said translating step; e) detecting a relative phase between a drive signal causing oscillation of said probe and deflection of said probe; and f) controlling the frequency of the oscillation of the probe so that the relative phase detected in said detecting step is kept essentially constant during scanning; g) varying the frequency of the oscillation of the probe by an amount Δf around the controlled frequency of step f) and determining a corresponding change Δp in said relative phase; and h) producing a signal indicative of the ratio of Δp/Δf.

Claim 27

In a method of operating an atomic force microscope including a probe including a probe tip mounted on one end of a lever arm and wherein the probe tip is scanned across the surface of a sample and data representative of the surface of the sample is gathered in relation to the positioning of the lever arm as the probe tip is scanned, the improvement comprising: a) oscillating the probe, including oscillating the probe tip at or near a resonant frequency of the probe or a harmonic of said resonant frequency and with a free oscillation amplitude A o sufficiently great so that the oscillating probe tip does not stick to the surface of the sample when the oscillating probe tip contacts the surface of the sample; b) positioning the oscillating probe tip so that the oscillating probe tip repeatedly taps the surface of the sample with the probe tip repeatedly contacting and breaking contact with the surface of the sample without sticking to the surface of the sample; c) translating the oscillating probe tip across the surface of the sample with the oscillating probe tip repeatedly tapping the surface of the sample; d) controlling the distance between an opposite end of the lever arm opposite the probe tip and the sample so that the amplitude of oscillation of the probe tip is maintained essentially constant at an amplitude setpoint during said translating step; e) detecting a relative phase between a drive signal causing oscillation of said probe and deflection of said probe; and f) controlling the frequency of the oscillation of the probe so that the relative phase detected in said detecting step is kept essentially constant during scanning; g) varying the frequency of the oscillation of the probe by an amount Δf around the controlled frequency of step f) and determining a corresponding change Δp in said relative phase; and h) producing a signal indicative of the ratio of Δp/Δf.

Claim 28

The method according to claim 24, comprising: providing a probe including a substance selected to interact with a corresponding substance on said sample.

Claim 29

The method according to claim 25, wherein said step of providing a probe comprises: providing a probe coated with an antibody or an antigen.

Claim 30

The method according to claim 24, wherein said oscillating step comprises: oscillating said probe tip with a free oscillation amplitude greater than 10 nm.

Claim 31

The method according to claim 24, wherein said oscillating step comprises: oscillating said probe tip with a free oscillation amplitude greater than 20 nm.

Claim 32

The method according to claim 24, comprising: changing the amplitude setpoint and repeating said steps a) through g) while maintaining the amplitude of oscillation of the probe tip essentially constant at the changed amplitude setpoint.

Claim 33

The method according to claim 29, comprising: comparing signals produced in repeated of steps g) to discriminate a force dependent characteristic of the sample.