WO2000046569A1

WO2000046569A1 - System and method of multi-dimensional force sensing for atomic force microscopy

Info

Publication number: WO2000046569A1
Application number: PCT/US2000/002952
Authority: WO
Inventors: Vladimir Mancevski; Juricic Davor; Paul Mcclure
Original assignee: Xidex Corporation
Priority date: 1999-02-05
Filing date: 2000-02-04
Publication date: 2000-08-10
Also published as: AU2870700A

Abstract

A system and method for a force sensing scanning microscopy tool is provided by the present invention. The tool has several components including a resonating oscillator (100) coupled to an AFM tip (102). The tip (102) modulates the resonances of the oscillator (100) in response to surface force interactions with the surface (106) of a sample (104). A 3-D mechanical actuator moves the tip (102) relative to the sample (104). A feedback control system directs the 3-D mechanical actuator to reposition the tip (102) in order to maintain a constant modulation of the resonances. An output from the feedback control system is then used by a data acquisition and control system that processes the output signal to produce a representation of the surface force tip interactions.

Description

SYSTEM AND METHOD OF MULTI -DIMENSIONAL FORCE SENSING FOR ATOMIC FORCE MICROSCOPY

RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No. 60/118,756 filed on 5 February 1999. Additionally, this application incorporates by reference the prior U.S. Provisional Application No. 60/118,756 filed on 5 February 1999 entitled

"Multidimensional Force Sensing System for Atomic Force Microscopy" to Vladimir Mancevski , Davor Juricic and Paul F. McClure. This application also incorporates by reference U.S. Patent Application No. 09/404,880 entitled "Multi-Dimensional Sensing System for Atom Force

Microscopy" to Vladimir Mancevski, hereinafter "MANCEVSKI.' Furthermore, this application also incorporates by reference U.S. Patent Application No. 09/407,394 entitled "Method For Manufacturing Carbon Nanolobes As Functional Elements of Mems Devices" to Vladimir Mancevski.

TECHNICAL FIELD OF THE INVENTION

The present invention relates generally to the field of force measurement using atomic force microscopy (AFM) and, more particularly, to a force measurement system for determining the topography of a local region of interest by means of atomic force microscopy. BACKGROUND OF THE INVENTION

In conventional atomic force microscopy (AFM) , the function of the force sensor is to detect the magnitude of the surface force or its gradient in a vertical, Z, direction. This force sensor is then used to create a one- dimensional profile of the surface. However, only the vertical component of the surface force is measured, as illustrated in FIGURE 1.

Force sensing with an AFM probe is governed by the laws of molecular interactions and other surface physics phenomena. The profile of the surface force is a function of the tip-surface gap. This phenomena is well known to those skilled in the art of AFM. For conventional non- contact mode, the AFM cantilever is resonated in first bending mode with a small amplitude within the attractive region of the surface force/gradient . This region is illustrated in FIGURE 2A. A change in the tip-surface distance shifts the cantilever resonance. A feedback loop uses the resonance shift to keep the tip at a constant force gradient. In the conventional "tapping" mode, the amplitude of the cantilever vibration is larger and the tip dips in and out of the attractive to the repulsive region of the surface force/gradient, as shown in FIGURE 2B. As a result, the amplitudes and the frequency of the cantilever vibration shift. In the tapping mode, a feedback loop uses the amplitude change to keep the tip at a constant force/gradient . The conventional approach fails to take into effect the direction of the surface force/gradient and therefore changes in surface slope are reported as vertical topography .

One prior art embodiment, shown in FIGURE 3, operates in a non-contact mode and has a cantilever that resonates in a vertical Z direction and dithers (a nonresonant vibration) in a lateral Y direction. This is sufficient to detect two components of the surface force: however, the force sensitivity in lateral direction is not as good as the force sensitivity in vertical direction. This is due to the dithering in the lateral Y direction as opposed to resonating.

It would be desirable to operate an AFM device capable of sensing all three components (X, Y, and Z) of the surface force/gradient by means of resonant vibration.

Furthermore, it would be desirable to sense all three components (X, Y, and Z) with a more desirable resonance as opposed to a less desirable dither.

SUMMARY OF THE INVENTION

The present invention provides a non-contact force measurement AFM system and method that substantially eliminates or reduces disadvantages and problems associated with previously developed non-contact force measurement systems and methods .

More specifically, a system and method for a force sensing scanning microscopy tool is provided by the present invention. This tool has several components including a resonating oscillator coupled to an AFM tip. Resonances of the oscillator are modulated in response to surface force interactions between the surface of a sample and the tip. A 3-D mechanical actuator moves the tip relative to the sample. A feedback control system directs the 3-D mechanical actuator to position the tip relative to the sample surface while a sensing system monitors shifts of the resonances. An output from the feedback control system is than used by a data processing system to produce a representation of the surface force tip interactions. In one embodiment, this representation can take the form of a 3-D topographical representation of the sample surface.

The present invention provides an important technical advantage by detecting all three components of a surface force/gradient proximate to a sample surface. BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention and the advantages thereof, reference is now made to the following description taken in conjunction with the accompanying drawings in which like reference numerals indicate like features and wherein:

FIGURE 1 shows a prior art AFM force sensor;

FIGURES 2A and 2B illustrate the surface force interactions versus tip-sample distance; FIGURE 3 shows a prior art cantilever that resonates in a vertical and a lateral direction;

FIGURE 4A illustrates an AFM oscillator that oscillates in multiple natural modes;

FIGURE 4B illustrates the force components, F Fy, and F_z;

FIGURE 5 illustrates the response of the first few natural resonant modes of an AFM tip;

FIGURE 6 shows how the Van der Walls interaction shifts the natural frequencies; . FIGURE 7 shows how the natural frequencies are effected as AFM tip is moved from point A to point A' ;

FIGURE 8 shows how the natural frequencies are effected as AFM tip is moved from point A' to point A' ' ;

FIGURE 9 provides a flow chart illustrating one control logic;

FIGURES 10A, 10B, and IOC depict the various scan steps provided by the flow chart of FIGURE 9;

FIGURE 11 depicts an example of a paddle-shaped oscillator used in one embodiment of the present invention; FIGURE 12 depicts the effect of the surface force/gradient modeled as three springs acting on the oscillator tip; FIGURE 13 shows that the surface force/gradient is non-linear with respect to the tip-surface distance;

FIGURE 14 illustrates that the surface force/gradient is non-linear with respect to the tip-surface distance; FIGURE 15A, 15B, 15C, 15D, 15E and 15F depict six separate, measurable resonances;

FIGURE 16 illustrates how the first bending mode is affected by the force component Fz;

FIGURE 17 shows that the first torsional mode is affected mainly by the force component Fy ;

FIGURE 18 depicts the second bending mode;

FIGURE 19 shows that the frequency shifts can be approximated as a linear response;

FIGURE 20 depicts the integrated force effect of the surface on the AFM tip;

FIGURE 21 illustrates an embodiment of an AFM tip for scanning Reentrant Sidewalls;

FIGURE 22 depicts a torsional oscillator mounted to the mode at the center of the "H" ; FIGURE 23 illustrates the first "H" twisters mode of the oscillator shown in FIGURE 22; and

FIGURE 24 shows an AFM mounted tip at or near the mode of the second bending mode .

DETAILED DESCRIPTION OF THE INVENTION

Preferred embodiments of the present invention are illustrated in the FIGURES, like numerals being used to refer to like and corresponding parts of the various drawings .

The system and method of force/gradient detection of the present invention relies on the use of at least two separate resonances to detect at least two components of the surface force/gradient. Ideally, each resonance corresponds to a single force/gradient component. In principle the present invention operates by positioning a resonating oscillator with at least two resonant modes with respect to a three-dimensional surface. Submerging the tip of the oscillator into the surface force shifts relevant resonant frequencies and/or amplitudes of the oscillator. The term "oscillator" as used in conjunction with the present invention is for an AFM probe that has multiple resonate modes. The term "cantilever " is used for an AFM probe that utilizes only the primary bending mode. A second embodiment of the present invention detects all three (Z, Y, and Z) components of the surface force/gradient .

The magnitude of the resonance shifts will depend on the actual tip-sample distance magnitude and direction. In one embodiment the tip-sample distance is controlled by a 3-D mechanical actuator. This 3-D mechanical actuator moves the tip to a specified or set distance from the sample surface and oscillates the tip in all directions with an AC amplitude. This specified or set distance may be a constant or varying distance. In the attractive atomic region, the resonance frequency will decrease, and if the tip crosses into the repulsive atomic force region, the resonant frequency will increase. A feedback loop uses the resonance shifts to keep the tip at a constant surface force/gradient in all three directions. The feedback signal controls the XYZ stage of the 3-D mechanical actuator. In one embodiment the XYZ stage is repositioned in order to keep the force/gradient at a specified level. The XYZ stage can be repositioned in order to return the frequencies of the resonances to their original values, to maintain a constant surface force/gradient or. to achieve a desired frequency and amplitude of the resonances.

The function of the force sensor of the present invention is to detect the magnitude and direction of the surface forces or their gradients (force derivative / distance) . These surface forces/gradients are then used to profile a sample's surface in all three dimensions. FIGURE 4A illustrates an AFM oscillator 100 which oscillates in multiple natural modes, generating time-varying tip displacements in the X, Y, and Z directions. This embodiment uses an oscillator with an AFM tip 102. FIGURE 4B illustrates the force components, F_x,

Fy and F_z and their gradients Fχ , Fy' and F_z' . These force components shift the natural frequencies of the oscillator's natural resonant modes. Sensing these shifts enables one to sense all three force/gradient components (F_x , Fy, and F_z) as tip 102 is positioned with respect to sample 104.

FIGURE 5 illustrates one response of the first few natural resonant modes of oscillator 100 outside the Van der Walls force region. FIGURE 5 is a graph of amplitude of these modes versus frequency for the first bending, first torsion, second bending, and the second torsion natural modes. As tip 102 approaches surface 106, the Van der Walls interaction shifts the natural frequencies downward of the first bending, first torsion, second bending, and second torsion natural frequencies by a delta frequency w, as illustrated in FIGURE 6. In FIGURE 7, tip 102 is moved from point A to point

Aη_ . This shifts the torsional modes to lower frequencies and shifts the bending modes to higher frequencies. In FIGURE 8, as the tip is moved from point Aη_ to A₂ the natural frequencies of both the first and second bending and first and second torsional modes, increase as shown.

The logic behind these FIGURES is readily extendable to the third dimension. FIGURES 5-8 are two-dimensional for illustration purposes. However, the logic behind these figures is readily extended to the third dimension. Furthermore, these FIGURES illustrate the responses at one specific embodiment while the response of other embodiment may vary.

One embodiment of the present invention uses control logic to make the force/gradient magnitude | F₂ ' | at A2 equal to the |FQ' | at AQ . This allows the tip-sample distance to be maintained at a constant value. This process includes several steps as illustrated in the flow chart provided by FIGURE 9. From point A₀ , the AFM tip is moved to predicted point A]_ in step 120. Point A]_ is a point that is predicted to have a force/gradient vector F]_' equal to F_Q' as illustrated in FIGURE 10A. Ai is in a plane containing point AQ and orthogonal to force vector

FQ' . In step 122, the force vector F_]_' is measured and resolved into components as illustrated in FIGURE 10B. If there are no topographical changes from point A ]_ than F]_' is of the same direction and magnitude of vector F_Q'. Otherwise, in step 124, the tip is moved to a point A2 having a force vector F2 ' equal in magnitude to F_Q' . This requires applying a correction factor to point ]_ in the direction of Fη_' that adjusts the magnitude of the vector F₂' to be equal to that of F₀' as illustrated in FIGURE

IOC. This correction factor repositions the tip to point A2 , such that the AFM tip is maintained at a constant tip- sample distance. The direction and magnitude may be determined by resolving F_Q' and F]_' into their F_x' , Fy' , and F_z' components. In step 126, the correction factor is applied, moving the tip to point A2 as illustrated in

FIGURE 10D. This is one method of control logic. Other logic systems maybe employed to gather data. For example, one could record a historical surface force/gradient base on an AFM tip IO2 positioning by the XYZ stage. By retracing the prior flight of AFM tip 102, one can compare the present surface force/gradient profile to a historical profile. Furthermore, this can be done as a calibration or other quality assurance check on a known surfaces. Another embodiment may use this comparison to detect changes or flaws of the surface.

A further embodiment may use the historical profiles or data recorded as an earlier part of the current profile to improve the accuracy of the predicted point Aη_ . Another processing technique post processes all data recorded from a sample surface. This allows integrated effects from the surface on the tip to be taken into account . Integrated effects are the cumulative effect of forces from a relevant volume of the sample acting on the tip. The normal assumption stated above is valid for the special case of an infinite homogenous plane. Other control logics can consider the integrated effects of a non-infinite, non-homogenous plane.

Another embodiment of the present invention uses an AFM oscillator that can excite resonance modes such as bending, second bending, lateral bending, and torsion. However, those higher or more complex resonance modes require a greater bandwidth in the AFM sensing systems. Using an AFM oscillator that can excite at higher order resonance modes allows the present invention to take advantage of multi-dimensional sensing systems such as those disclosed in MANCEVSKI that is capable of sensing angular displacements and vibrations as well as linear displacements and vibrations. Therefore, an oscillator that resonates in bending and torsional modes is preferred but not required. A lateral bending mode produces in-plane motion, as seen from a sensing system located above the oscillator as disclosed in MANCEVSKI.

It is desirable to keep all relevant resonances within the bandwidth of a sensing system, such as a position- sensitive detector (PSD) , the associated electronics, and the data acquisition, and control system bandwidth. The bandwidth of the PSD sensor disclosed in MANCEVSKI is approximately 250 kHz. However, there are sensing techniques that will allow bandwidths in the MHz region and beyond. One embodiment of a personal computer-based data acquisition and control system has a bandwidth of under 1 MHz for a single channel. However, the present invention need not be limited to this specific PC-based data acquisition and control system. Any data acquisition and control system known to those skilled in the art may be utilized in other embodiments of the present invention. The oscillator must be designed such that it allows for excitation of multiple resonance modes. The oscillator should have at least two distinct resonant modes, where each resonant mode is ideally dependent on only one of the surface force/gradient components (main effect) and is independent of the other two (cross-coupling effect) . Some cross-coupling among force/gradient components and resonances can be tolerated. A carefully designed experiment can empirically determine the relationship or cross-coupling between the resonances and the force/gradient components through Design of Experiment (DOE) techniques as known to those skilled in the art. Furthermore, if the cross-coupling effect is at least an order of magnitude less than the main effect, the cross- coupling may be neglected. Otherwise, the feedback control system needs to compensate for cross-coupling effects. These resonances should have a high Q or sensitivity, that will enable detection of resonance shifts in response to surface force/gradient changes. (i.e., the frequency shift resolution has to be sufficient.) Failure to detect resonant frequency shifts can cause loss of control and snapping of the oscillator tip to the surface.

With these criteria in mind, an embodiment of an oscillator has led to the oscillator of the shape, size and composition provided in FIGURE 11. FIGURE 11 has an example of a paddle-shaped oscillator made of a single crystal silicon. This oscillator can be excited in resonance modes such as bending, lateral bending, and torsion. This is achieved by selecting the shape and the thickness of the oscillator. The length-to-width ratio of the oscillator contributes to promoting the bending modes. The paddle shape of the oscillator allows excitation of the torsional modes. The thickness of the oscillator can command that the lateral bending does not occur. The relevant resonances are dependent upon the overall dimensions of the oscillator (i.e., its length, width and thickness) . The resonance frequencies are dependent on where k is the stiffness and m is the mass. Hence, smaller oscillators having less mass have higher resonance frequencies. The oscillator depicted in FIGURE 11 may have a thickness, t, of approximately 0.15 microns, a width, w, of the paddle of approximately 110 microns, a length, d, of the paddle of 90 microns, and an arm with a width of 20 microns and a length, 1, of 140 microns. These dimensions are used to illustrate one possible embodiment of a paddle- shaped oscillator. However, the present invention need not be limited to this specific set of dimensions or shapes. This allows the oscillator to have at least two distinct resonant modes . Each resonant mode may be dependent upon only one of the surface force/gradient components and is independent of any cross-coupling effects from other surface force/gradient components.

In order that the resonances have a high Q, the oscillator may be manufactured from a single silicon crystal cantilever. Other embodiments may include such materials as silicon nitride or composite layered material. Furthermore, Q is affected by the quality and surface of the oscillator structure.

Mathematically, the effect of the surface gradient can be modeled as a spring between the oscillator tip and the constant, as shown in FIGURE 12, wherein oscillator 100 and tip 102 are acted upon by the Van der Walls force gradient, F' , and act upon the tip as three independent springs. The three components of a three-dimensional force/gradient are modeled by the three virtual springs 108, 110, and 112 with variable spring constants k]_, k2 , and k₃ that are a function of the tip-surface distance. As shown in FIGURES 13 and 14, the surface force/gradient is non-linear with respect to the tip-surface distance. Therefore, the modeled spring constant is also non-linear. However, for small amplitudes of vibration of the oscillator tip, the spring constant is linear with respect to the tip-surface distance. To maintain linear response, the oscillator should vibrate with a small amplitude that keeps the oscillator in a linear mode of operation.

It should be noted that this is only one of an infinite number of possible mathematical models. This mathematical model described a manner in which a matrix can be created to eliminate cross-coupling effects.

Another method may involve the use of neural networks coupled to multiple input/multiple output (MIMO) systems. This type of learning system would be capable of eliminating cross-coupling effects and/or automatically compensating for changes as they occur in the environment. FIGURES 15A through 15F show at least six separate, measurable resonances, three bending and three torsional, for an oscillator as depicted in FIGURE 11. FIGURE 15A depicts the first bending mode. FIGURE 15B depicts the first torsional mode. FIGURE 15C depicts the second bending mode. FIGURE 15D depicts the third bending mode. FIGURE 15 depicts the second torsional mode. FIGURE 15F depicts the third torsional mode. The simulations presented in FIGURES 15A through 15F show that all six resonances were within a 70 kHz bandwidth. In a numerical experiment, the resonances of the free vibrations of the oscillator were as follows:

FIGURE 16 illustrates how the first bending mode is affected mainly by the force/gradient component ¥_% ' .

FIGURE 17 shows that the first torsional mode is affected mainly by the force component Fy' . The second bending mode depicted in FIGURE 18 is mainly affected by the force component F_x' . These effects are for illustrative purposes only and may be unique to this specific embodiment.

For the purpose of conducting AFM measurements, in at least two of the three dimensions (vertical, lateral, and longitudinal), one need monitor at least two resonances. FIGURE 19 shows that the frequency shifts are generally linear within limited regions which correlate to the X, Y, and Z components of the surface force/gradient. Use of more than three resonances with the help of neural networks can be used to increase the confidence of the measurement.

One specific advantage of the present invention is the ability for the controller to determine via a smart feedback loop, a better point A]_ which was illustrated in FIGURES 8-10. This involves considering the integrated force effect as depicted in FIGURE 20. Here atoms in a three dimensional region near the apex of the scanning probe tip 102 act on tip 102. The force on tip 102 results from the integrated effect of the individual forces between atoms in tip 102 and the atoms in the surface feature. These forces are illustrated as vectors 130.

Another embodiment would allow tip 102 to be positioned using the force/gradient in real time in order to "fly" in proximity to the sample surface.

Post-processing of the recorded data can then be used to reconstruct the surface of the sample. This would reduce the incidence of crushing the AFM tip and increase the scanning speed. In yet another embodiment, repeated sampling of a known sample allows the accuracy of the present invention to be improved by tracking the repeatability of the system on a known sample. By sampling a known surface, a new AFM tip can be calibrated by developing a correction factor or matrix that matches the obtained result to the expected result .

In another embodiment of the present invention the oscillator may be illuminated by a laser associated with the position sensing system. The amplitude, intensity, frequency and/or phase of the laser may be modulated. This modulation allows the resonance of the oscillator to be multiplexed. This step of multiplexing filters and suppresses noise. The laser can be tuned in order to provide data from specific points during a mode of resonance of the oscillator. This increases the sensing systems sensitivity to changes at sensed points. This noise suppression technique may be applied to existing cantilever based systems.

In yet another embodiment of the present invention, the standard AFM tip can be replaced with the structure depicted in FIGURE 21. Support structure 132 is attached to an AFM oscillator or cantilever. The support structure may be constructed of silicon, silicon nitride, carbon nanotubes or other materials used as AFM tips as known to those skilled in the art. Nanotubes 134 are grown from support 132. Nanotubes 134 maybe oriented in any direction relative to the structure 132. However, FIGURE 21 illustrates nanotubes 134 oriented in lateral or vertical directions as to enable imaging of reentrant side walls and trench bottoms. Nanotubes 134 can be grown in accordance with the teaching of U.S. Patent Application Serial No. 09/407,394 entitled "Method for Manufacturing Carbon Nanotubes as Functional Elements of Mems Devices."

In another embodiment of the present invention nanotubes 134 oscillates in at least one resonance mode. In this embodiment it is possible to design or tune the nanotubes 134 to participate in specific mode(s) of resonance .

In yet another embodiment of the present invention the AFM tip 102 comprises a waveguide. This waveguide may pass optical energy from the end of the tip proximate to the sample surface to an opening in the oscillator. The optical energy may be monitored from this surface. This optical energy may be modulated in intensity, frequency or phase by the nanotube and the resonance modes. This may eliminate the need for external lasers to illuminate the oscillator if the optical energy is generated in the nanotube itself.

In another embodiment the oscillator may be an "H" shaped in order to improve force/gradient sensitivity. The largest contributor to the value of Q is the energy dissipation in the clamping system. With that in mind an oscillator 136 depicted in FIGURES 22 and 23 is an "H" shaped structure mounted at a nodal point. Placing the scanning probe tip at or near the node of a particular resonance mode enhances the sensitivity to a given direction of motion and decreases the sensitivity to other directions. For example, by placing the tip at or near the second bending mode of an oscillator 136 as shown in

FIGURE 24, increases sensitivity to lateral motion and decreases sensitivity to vertical motion. In this case, the energy dissipation associated with clamping will be significantly reduced, thus resulting in much higher Q. That the node and the clamping point coincide in this oscillator can be achieved by exciting the third torsional (or first "H-twist") mode of the oscillator shown in Figure 22. The characteristic shape of the "H-twist" mode is shown in Figure 23. The value of (k/w)¹/² for the "H-twist" mode of oscillator G is only about a factor of 2 higher than value of (k/w)¹/² for the first bending mode, both determined for the same probe location. If Q for the "H-twist" mode can be increased by a factor much greater than 2 due to the improved mounting concept, then it would have the best force/gradient sensitivity. The (k/w)¹/² can be used to further optimize the location of the probe on that oscillator surface.

The present invention provides a force measurement AFM system and method that substantially eliminates or reduces disadvantages and problems associated with previously developed non-contact, contact or tapping force measurement systems and methods .

More specifically, a system and method for a force sensing scanning microscopy tool is provided by the present invention. This tool has several components including a resonating oscillator coupled to an AFM tip. The surface force phenomena interact with the tip to modulate the resonances of the oscillator. A 3-D mechanical actuator moves the tip relative to the sample. A feedback control system directs the 3-D mechanical actuator to reposition the tip in order to return the frequencies of the resonances to the original values, to maintain a constant surface force/gradient, or to achieve a desired frequency and amplitude of the resonances according to a predetermined logic. An output from the feedback control system is than used by a data acquisition and control system that processes the output signal to produce a representation of the surface force/gradient tip interactions. In one embodiment, this representation can take the form of a 3-D topographical representation of the sample surface.

The present invention provides an important technical advantage by detecting at least two components of a surface force/gradient on a sample. The components of the surface force/gradient are determined by resolving the component effects on at least two resonance modes of an AFM oscillator.

Although the present invention has been described in detail, it should be understood that various changes, substitutions and alterations can be made hereto without departing from the spirit and scope of the invention as described by the appended claims .

Claims

WHAT IS CLAIMED IS:

1. An atomic force sensing scanning microscopy tool, comprising: a resonating oscillator coupled to an AFM tip wherein at least one resonance mode of said oscillator is modulated in response to surface force/gradient interactions between a sample and the AFM tip; a 3-D mechanical actuator to position said tip relative to said sample; a sensing system operable to provide at least one output representative of said at least one modulated resonance mode; and a feedback control system operable to direct said 3-D mechanical actuator.

2. The atomic force sensing microscopy tool of Claim

1, further comprising: a data processing system that produces a representation of said tip interactions with said sample.

3. The atomic force sensing microscopy tool of Claim

2, wherein said representation is a 3-D topographical representation of said surface force interactions.

4. The atomic force sensing microscopy tool of Claim

3, wherein said surface force interactions are selected from the group consisting of electrostatic force, magnetic force, atomic force, electromagnetic force, and surface force .

5. The atomic force sensing microscopy tool of Claim 1, wherein said resonance modes comprise bending, lateral bending and torsion.

6. The atomic force sensing microscopy tool of

Claim 5 wherein said resonance modes comprise higher order modes .

7. The atomic force sensing microscopy tool of Claim 1, wherein said oscillator is paddle shaped and made of a single silicon crystal.

8. The atomic force sensing microscopy tool of Claim 1, wherein a ratio of dimensions of said oscillator promotes specific modes of said at least one resonance mode .

9. The atomic force sensing microscopy tool of Claim 1, wherein a shape of said oscillator promotes specific modes of resonance.

10. The atomic force sensing microscopy tool of Claim 1, wherein said oscillator has at least two resonant modes wherein each resonant mode is dependent on only one surface force/gradient component .

11. The atomic force sensing microscopy tool of Claim 1, wherein said feedback control system is operable to position said tip in order to maintain a constant modulation of said at least one resonance of said oscillator.

12. The atomic force sensing microscopy tool of Claim 1, wherein said sensing system comprises a PSD sensing system.

13. The atomic force sensing microscopy tool of Claim 1, wherein said sensing system comprises a multidimensional sensing system.

14. An AFM method of force sensing, comprising the steps of : resonating an oscillator coupled to an AFM tip at at least one natural mode; modulating said at least one natural mode with surface force phenomena interactions between said tip and a sample surface; positioning said tip relative to said surface with a 3-D mechanical actuator; sensing said at least one modulated natural mode, wherein said sensing system provides at least one output representative of said at least one modulated natural mode; and directing the positioning of 3-D mechanical actuator with a feedback control system.

15. The method of Claim 14, further comprising the steps of : processing said at least one output with a data processing system to produce a representation of said tip interactions with said sample.

16. The method of Claim 15, wherein said representation is a 3-D topographical representation of said surface force phenomena.

17. The method of Claim 14, wherein said oscillator can be excited to higher resonance modes.

18. The method of Claim 17, wherein said resonance modes comprise first bending, first lateral bending and first torsion and their higher modes. 24

19. The method of Claim 14, wherein a shape of said oscillator is tuned to promote a specific resonance mode.

20. The method of Claim 14, wherein said oscillator has at least two natural modes wherein each natural mode is dependent on only one surface force/gradient component .

21. The method of Claim 14, further comprising the steps of: repositioning said tip in order to maintain a constant modulation of said at least one natural mode.

22. The method of Claim 14, wherein said data acquisition and control system includes a multi-dimensional sensing system.

23. An atomic force sensing scanning microscopy tool, comprising: a resonating cantilever coupled to an AFM tip wherein at least one resonance mode of said oscillator is modulated in response to surface force/gradient interactions between said tip and a sample and wherein said tip is an AFM tip with a carbon nanotube grown on said tip; a 3-D mechanical actuator to position said tip relative to said sample; a sensing system operable to provide at least one output representative of said at least one modulated resonance mode; and a feedback control system operable to direct said 3-D mechanical actuator.

24. The atomic force sensing microscopy tool of Claim 23, wherein said carbon nanotube oscillates in at least one resonance mode and wherein said carbon nanotube is grown either orthogonal or along a primary axis of said AFM tip.

25. The atomic force sensing microscopy tool of Claim 24, further comprising: a data processing system to process an output of said feedback control system and produce a representation of said tip interactions with said sample.

26. An AFM method of force sensing, comprising the steps of: resonating a carbon nanotube coupled to an AFM tip in at least one resonance mode; modulating said at least resonance of said nanotube with surface force/gradient phenomena interactions between said nanotube and a sample surface; positioning said tip relative to said sample surface with a 3-D mechanical actuator to position said tip relative to said sample; directing the positioning of 3-D mechanical actuator with a feedback control system; sensing said at least one modulated resonance mode with a sensing system, wherein said sensing system provides at least one output representative of said at least one modulated resonance mode; and processing an output of said feedback control system with a data acquisition system to produce a representation of said tip interactions with said sample wherein said data acquisition system includes a multi dimensional sensing system.

27. An AFM tip comprising: a structural element ; and at least one nanotube grown on said structural element, wherein said nanotube is grown at any orientation relative to said structural element.

28. The AFM tip of Claim 27, wherein said at least one carbon nanotube is oriented in a lateral or vertical direction from the AFM tip.

29. The AFM tip of Claim 28, wherein said AFM tip is a carbon nanotube .

30. The AFM tip of Claim 29, wherein said structural element has a first end coupled to an AFM cantilever or AFM oscillator and a second end opposite said first end, and wherein said at least one carbon nanotube is grown at said second end.

31. The method of Claim 30, wherein said at least one carbon nanotube is grown along or orthogonal to a primary axis of said AFM tip.

28

32. A force sensing scanning microscopy tool, comprising: a resonating oscillator coupled to an AFM tip wherein said tip modulates at least on a one resonance of said oscillator in response to surface force interactions with a sample and wherein said at least one resonance is modulated by at least one component of a surface force vector acting on said tip; a 3-D mechanical actuator to position said tip relative to said sample; a feedback control system operable to position said 3- D mechanical actuator according to a specified control logic; a sensing system operable to provide at least one output representative of said at least one modulated resonance mode; and a data processing system to process said at least one output and produce a representation of said tip interactions with said sample.

33. The atomic force sensing microscopy tool of Claim 32, wherein said control logic requires that said at least one resonance is maintained at a set amplitude (s) and/or frequency (s) .

34. The atomic force sensing microscopy tool of Claim 33, wherein said feedback control system comprises: a neural network; and at least one input/at least one output system coupled to said neural network wherein at least one input of said at least one input/at least one output system is said at least one output from said sensing system and at least one output is used to drive said 3-D actuator.

35. The atomic force sensing microscopy tool of Claim 33, wherein said feedback control system comprises a neural network .

36. The atomic force sensing microscopy tool of Claim 33, wherein said at least one output of. said sensing system is calibrated by comparison of said at least one output to an expected output from a known surface.

37. The atomic force sensing microscopy tool of Claim 34, wherein said neural network is operable to eliminate cross-coupling effects of said at least one surface force/gradient components on said at least one resonance .

38. The atomic force sensing microscopy tool of Claim 32, wherein said control logic accounts for integrated volumetric force effects of said sample on said AFM tip in directing said 3-D actuator.

39. The atomic force sensing microscopy tool of Claim 38, wherein said integrated effects are effects of a portion of said sample on which surface forces have already been measured, on said AFM tip.

40. The atomic force sensing system of Claim 32, wherein said data processing system is operable to post process said at least one output of said sensing system in order to account for surface force/gradients from the entire sample on said tip.

41. The atomic force sensing microscopy tool of Claim 33, wherein said control logic directs said 3-D mechanical actuator to be driven through a previously recorded path and said data processing system is operable to: recall a previously recorded output of said feedback control system relating to said previously recorded path; record a current output of said feedback control system as said actuator is driven through said previously recorded path; and compare and process said previously recorded output and said current output to render a representation of surface phenomena at said sample.

42. The atomic force sensing microscopy tool of Claim 33, wherein said control logic directs said 3-D mechanical actuator to be driven through an estimated path.

43. The atomic force sensing microscopy tool of Claim 42, wherein said estimated path is selected from the group consisting of a prerecorded path, a computed path based on a computer generated model of said surface, and a computed path based on a previously computed representation of said surface.

44. The method of Claim 34, wherein said oscillator is coupled to said AFM tip at a node of an oscillating mode of said oscillator.

45. The method of Claim 34, wherein said oscillator is coupled to said 3-D mechanical actuator at a node of an oscillating mode of said oscillator.

46. The atomic force sensing microscopy tool of

Claim 45, wherein said oscillator is an "H" shaped oscillator coupled to said actuator at a node located in the bar of said "H" shaped oscillator resulting in a higher sensitivity to said at least one resonances of said oscillator.

47. An AFM oscillator comprising: a structural element, wherein said structural element oscillates in at least one resonance mode, wherein said at least one resonance mode contains at least one node located within said structural element .

48. The AFM oscillator of Claim 47, wherein said structural element is clamped to a support structure at said at least one node.

49. The AFM oscillator of Claim 48, wherein an AFM tip is coupled to said structural element at said at least one node .

50. The AFM oscillator of Claim 47, wherein said structural element is an "H" shaped oscillator.