Detection system for atomic force microscopes

Abstract

A scanning probe microscope is provided with a piezo-ceramic tube to carry the sensitive probe at its free end to translationally move the probe in the X and Y directions. Large stationary surfaces can then be scanned by probe tip motion. The tube is also capable of movement in the Z direction so that the tip can follow the contours of the surface. Optical detection means track the motion of the probe tip and generate signals corresponding to and representative of surface contours. In one mode of operation, the signals are used in a feed back loop to keep constant the spacing between the tip and the surface, in which case the error or control signals represent the contours.

What is claimed as new is:  
     
       1. A scanning force microscope device comprising in combination: 
       a. a sensing probe having a substantially reflective surface on one side and a scanning tip on the opposite side, said tip adapted to be positioned adjacent a surface to be scanned;  
       b. illuminating means positionally decoupled from said sensing probe and independent of probe motion for generating a radiant energy beam and for applying said beam to said reflective surface;  
       c. position control means coupled to said sensing probe for moving said scanning tip substantially parallel to a surface to be scanned in a predetermined pattern and for moving said scanning tip orthogonal to the surface to follow the contours of the surface;  
       d. beam positioning means adapted to receive said radiant energy beam from said illuminating means for directing said radiant energy beam to said reflective surface to follow said sensing probe through lateral motion of said probe; and  
       e. detector means adapted to receive the energy beam reflected from said reflective surface through said position control means and operable in response to movement of said reflected energy beam corresponding to position changes of said sensing probe relative to the surface to be scanned to produce a motion representing signal corresponding to tip movement following the contours of the scanned surface,  
       whereby tip motion in a direction orthogonal to scanning motion results in a series of electrical signals corresponding to and representative of the surface contours of the scanned surface. surface. 
     
     
       2. The microscope device of claim  1  wherein said illuminating means include a laser. 
     
     
       3. The microscope device of claim  1  wherein said illuminating means include a lens for focussing said energy beam to said reflective surface. 
     
     
       4. The microscope device of claim  3  wherein said lens narrowly focuses said radiant energy beam at said scanning probe reflective surface. 
     
     
       5. The microscope device of claim  1  wherein said detecting means are comprised of at least two photodetecting cells. 
     
     
       6. The microscope device of claim  1  further including compensating means for correcting for errors at said detection means resulting from lateral movement of said reflective surface. 
     
     
       7. The microscope device of claim  6  wherein said compensating means include a lens and further include computer means employing software algorithms operable in response to applied detector means signals for compensating for errors arising from scanning tip lateral movement. 
     
     
       8. The microscope device of claim  1  wherein said beam positioning means include a directing lens and lens moving means independent of said position control means for moving said lens in coordination with tip motion. 
     
     
       9. The microscope device of claim  1  wherein said beam positioning means include a directing mirror and mirror moving means independent of said positioning means for moving said mirror in coordination with tip motion. 
     
     
       10. In a scanning force microscope having a sensitive probe with a tip mounted for movement in response to relative vertical distance changes between the sensing tip and a sample surface as the tip moves laterally with respect to the sample surface, apparatus for sensing the vertical movement of the tip relative to the surface being scanned and for creating a signal representative of such vertical movement comprising: 
       a. a reflective surface carried by the sensitive probe tip;  
       b. an energy source positionally decoupled from lateral movement of the sensitive probe tip for emitting a radiant energy beam including focussing  focusing means for applying said beam to said reflective surface;  
       c. control means for moving the sensitive probe tip laterally in a raster fashion over the surface of a sample to be scanned and including beam directing means for causing said radiant energy beam to follow the motion of the probe tip;  
       d. driving means for moving the sensitive probe tip in a vertical direction towards and away from the surface of the sample to be examined; and  
       e. detection means positioned to receive said energy beam through said control means after reflection from said reflective surface for signalling changes in the beam position, said changes corresponding to and representative of vertical displacement of the sensitive probe tip during raster motion over the sample surface.  
     
     
       11. In a scanning force microscope having a sensitive probe with a tip mounted for movement in response to relative vertical distance changes between the sensing tip and a sample surface as the tip moves laterally with respect to the sample surface, apparatus for sensing the vertical movement of the tip relative to the surface being scanned and for creating a signal representative of such vertical movement comprising: 
       f. a reflective surface carried by the sensitive probe tip;  
       g. an energy source for emitting a radiant energy beam including directing means for applying said beam to said reflective surface;  
       h. control means for moving the sensitive probe tip laterally in a raster fashion over the surface of a sample to be scanned and including beam directing means for causing said radiant energy beam to follow the motion of the probe tip;  
       i. driving means for moving the sensitive probe tip in a vertical direction towards and away from the surface of the sample to be examined;  
       j. means for creating an image of said probe in space at a point in space such that said image does not appear to move when said probe is moved; and  
       k. detection means positioned to receive said energy beam after reflection from said reflective surface for signalling changes in the beam position, said changes corresponding to and representative of vertical displacement of the sensitive probe tip during raster motion over the sample surface.  
     
     
       12. The microscope device of claim  11  further including compensating means including computer means responsive to the raster location of the sensitive probe tip relative to the sample surface and the distance between said energy source, said control means, the sensitive probe tip and said detection means for correcting beam positional errors. 
     
     
       13. The microscope device of claim  11  wherein said energy source is a laser. 
     
     
       14. The microscope device of claim  11  wherein said detecting means include at least two photodetecting cells. 
     
     
       15. In a scanning force microscope having a sensitive probe with a tip mounted for movement in response to relative vertical distance changes between the sensing tip and a sample surface as the tip moves laterally with respect to the sample surface, apparatus for sensing the vertical movement of the tip relative to the surface being scanned and for creating a signal representative of such vertical movement comprising: 
       a. a reflective surface carried by the sensitive probe tip;  
       b. an energy source for emitting a radiant energy beam including directing means for applying said beam to said reflective surface;  
       c. control means for moving the sensitive probe tip laterally in a raster fashion over the surface of a sample to be scanned and including beam directing means for causing said radiant energy beam to follow the motion of the probe tip;  
       d. driving means for moving the sensitive probe tip in a vertical direction towards and away from the surface of the sample to be examined;  
       e. detection means positioned to receive said energy beam after reflection from said reflective surface for signalling changes in the beam position, said changes corresponding to and representative of vertical displacement of the sensitive probe tip during raster motion over the sample surface; and  
       f. a lens system attached to a deformable ceramic transducer having an axis to create an image of the probe substantially at a selected point along the axis of said transducer at which the probe image appears to be stationary, notwithstanding lateral movement of the probe.  
     
     
       16. The microscope device of claim  15  wherein said deformable transducer is a cylinder. 
     
     
       17. The microscope device of claim  15  wherein said selected point is the midpoint of the transducer axis. 
     
     
       18. The microscope device of claim  15  further including a mirror system attached to a deformable ceramic transducer having an axis to create an image of the probe substantially at a selected point along the axis of said transducer at which the probe image appears to be stationary, notwithstanding lateral movement of the probe. 
     
     
       19. In a scanning force microscope having a sensitive probe tip mounted for vertical movement in response to relative force changes between the tip and a sample surface as a function of the relative lateral motion of the tip over the sample surface, apparatus for sensing vertical movement of the tip and for creating signals representative of such tip movement corresponding to sample surface contours as a function of lateral position comprising: 
       a. a reflective surface carried by the sensitive probe tip;  
       b. a light source for emitting a radiant energy beam;  
       c. directing means for applying said beam to said reflective surface;  
       d. scanning means for moving the sensitive probe tip in a raster fashion over the sample surface in a plane substantially parallel to the sample surface;  
       e. deploying means for moving the sensitive probe tip in a vertical direction relative to the sample surface;  
       f. steering means for moving said light beam in coordination with the raster motion of the sensitive probe tip; and  
       g. detection means isolated from and independent of probe tip movement responsive to the light beam reflected from said reflective surface through said scanning means for signalling changes in light beam position resulting from movement of the sensitive probe tip,  
       whereby detection mean output signals correspond to and are representative of the vertical motion of the sensitive probe tip and represent the contours of a scanned surface. 
     
     
       20. In a scanning force microscope having a sensitive probe tip mounted for vertical movement in response to relative force changes between the tip and a sample surface as a function of the relative lateral motion of the tip over the sample surface, apparatus for sensing vertical movement of the tip and for creating signals representative of such tip movement corresponding to sample surface contours as a function of lateral position comprising: 
       a. a reflective surface carried by the sensitive probe tip;  
       b. a light source for emitting a radiant energy beam;  
       c. directing means for applying said beam to said reflective surface;  
       d. scanning means for moving the sensitive probe tip in a raster fashion over the sample surface in a plane substantially parallel to the sample surface;  
       e. deploying means for moving the sensitive probe tip in a vertical direction relative to the sample surface;  
       f. steering means for moving said light beam in coordination with the raster motion of the sensitive probe tip;  
       g. detection means responsive to the light beam reflected from said reflective surface for signalling changes in light beam position resulting from movement of the sensitive probe tip; and  
       h. means for creating an image of said probe in space at a point in space such that said image does not appear to move when said probe is moved, whereby detection mean output signals correspond to and are representative of the vertical motion of the sensitive probe tip and represent the contours of a scanned surface.  
     
     
       21. The microscope device of claim  20  including a lens system attached to a deformable ceramic transducer having an axis, said lens system creating said image of the probe substantially at a selected point along the axis of said transducer at which point said probe image appears to be stationary, notwithstanding lateral movement of the probe. 
     
     
       22. The microscope device of claim  20  wherein said energy source is a laser. 
     
     
       23. The microscope device of claim  20  wherein said detecting means include at least two photodetecting cells. 
     
     
       24. The scanning force microscope of claim  20 , wherein said steering means include mirror elements. 
     
     
       25. The scanning force microscope of claim  20 , wherein said steering means include lens elements. 
     
     
       26. The scanning force microscope of claim  20 , wherein said steering means include mirror elements and lens elements to direct said light beam from said light source to said reflective surface of the sensitive probe tip. 
     
     
       27. A scanning force microscope comprising: 
       
         a. a reflective sensing probe;  
       
       
         b. means for scanning the sensing probe in relationship to a surface to be scanned;  
       
       
         c. a radiant energy source for applying an energy beam to the sensing probe during scanning;  
       
       
         d. a detector responsive to the radiant energy beam reflected from the sensing probe during scanning for determining information related to the surface to be scanned, and  
       
       
         e. optical means for maintaining a first focal point in the radiant energy beam fixed with respect to the radiant energy source or the detector and a second focal point fixed with respect to the sensing probe. 
       
     
     
       28. The scanning force microscope of claim  27 , wherein the first focal point is fixed with respect to the radiant energy source. 
     
     
       29. The scanning force microscope of claim  27 , wherein the first focal point is fixed with respect to the detector. 
     
     
       30. The scanning force microscope of claim  27 , wherein the first focal point is fixed with respect to both the detector and the radiant energy source. 
     
     
       31. The scanning force microscope of claim  30 , wherein the optical means further comprises: 
       
         means for guiding the radiant energy beam through the first focal point to the second focal point for reflection by the sensing probe and for guiding the reflected radiant energy beam from the sensing probe back through the first focal point to the detector. 
       
     
     
       32. The scanning force microscope of claim  31 , further comprising: 
       
         means for exciting the probe into vibration at or near its resonance mode; and  
       
       
         means for detecting changes in the sensing probe vibration resulting from proximity of the sensing probe to the surface to be detected. 
       
     
     
       33. The scanning force microscope of claim  32 , wherein the means for detecting changes in the sensing probe vibration further comprises: 
       
         means for detecting changes in the resonant parameters of the vibration. 
       
     
     
       34. The scanning force microscope of claim  32 , wherein the means for detecting changes in the sensing probe vibration further comprises: 
       
         means for detection changes in the amplitude of the vibration. 
       
     
     
       35. The scanning force microscope of claim  32 , wherein the means for detecting changes in the sensing probe vibration further comprises: 
       
         means for detecting changes in the phase of the vibration. 
       
     
     
       36. The scanning force microscope of claim  27 , further comprising: 
       
         means for exciting the probe into vibration at or near its resonance mode; and  
       
       
         means for detecting changes in the sensing probe vibration resulting from proximity of the sensing probe to the surface to be detected. 
       
     
     
       37. The scanning force microscope of claim  36 , wherein the means for detecting changes in the sensing probe vibration further comprises: 
       
         means for detecting changes in the resonant parameters of the vibration. 
       
     
     
       38. The scanning force microscope of claim  36 , wherein the means for detecting changes in the sensing probe vibration further comprises: 
       
         means for detection changes in the amplitude of the vibration. 
       
     
     
       39. The scanning force microscope of claim  36 , wherein the means for detecting changes in the sensing probe vibration further comprises: 
       
         means for detecting changes in the phase of the vibration. 
       
     
     
       40. A scanning force microscope for determining information about a surface to be scanned, comprising: 
       
         a. a sensing probe;  
       
       
         b. means for moving the sensing probe in relationship to the surface to be scanned;  
       
       
         c. means for exciting the probe into vibration at or near the probe's resonance mode; and  
       
       
         d. means for detecting changes in the sensing probe vibration resulting from proximity of the sensing probe to the surface to be detected, including means for detecting changes in the resonant parameters of the vibration. 
       
     
     
       41. A scanning force microscope for determining information about a surface to be scanned, comprising: 
       
         a. a sensing probe;  
       
       
         b. means for moving the sensing probe in relationship to the surface to be scanned;  
       
       
         c. means for exciting the probe into vibration at or near the probe's resonance mode; and  
       
       
         d. means for detecting changes in the sensing probe vibration resulting from proximity of the sensing probe to the surface to be detected, including means for detecting changes in the amplitude of the vibration. 
       
     
     
       42. A scanning force microscope for determining information about a surface to be scanned, comprising: 
       
         a. a sensing probe;  
       
       
         b. means for moving the sensing probe in relationship to the surface to be scanned;  
       
       
         c. means for exciting the probe into vibration at or near the probe's resonance mode; and  
       
       
         d. means for detecting changes in the sensing probe vibration resulting from proximity of the sensing probe to the surface to be detected, including means for detecting changes in the phase of the vibration. 
       
     
     
       43. A scanning force microscope for determining information about a surface to be scanned, comprising: 
       
         a. a sensing probe;  
       
       
         b. means for scanning the sensing probe in relationship to the surface to be scanned;  
       
       
         c. means for exciting the probe into vibration at or near the probe's resonance mode;  
       
       
         d. means for detecting changes in the sensing probe vibration resulting from proximity of the sensing probe to the surface to be detected;  
       
       
         e. a light source for applying light to said sensing probe. 
       
     
     
       44. The invention of claim  43 , further comprising: 
       
         means for detecting light reflected from said sensing probe. 
       
     
     
       45. A method for determining information from a surface to be scanned comprising the steps of: 
       
         a. scanning a reflective sensing probe in relationship to the surface to be scanned;  
       
       
         c. applying an energy beam from an energy source to the sensing probe during scanning;  
       
       
         d. determining information related to the surface to be scanned by applying a portion of the energy beam reflected by the sensing probe to a detector; and  
       
       
         d. during scanning, maintaining a first focal point in the energy beam fixed with respect to the energy source or the detector and a second focal point fixed with respect to the sensing probe. 
       
     
     
       46. The invention of claim  45 , wherein the step of maintaining the first focal point further comprises the step of: 
       
         maintaining the first focal point fixed with respect to the radiant energy source. 
       
     
     
       47. The invention of claim  45 , wherein the step of maintaining the first focal point further comprises the step of: 
       
         maintaining the first focal point fixed with respect to the detector. 
       
     
     
       48. The invention of claim  45 , wherein the step of maintaining the first focal point further comprises the step of: 
       
         maintaining the first focal point fixed with respect to the detector and energy source. 
       
     
     
       49. The invention of claim  48 , further comprising the steps of: 
       
         guiding the radiant energy beam through the first focal point to the second focal point for reflection by the sensing probe; and  
       
       
         guiding the reflected radiant energy beam from the sensing probe back through the first focal point to the detector. 
       
     
     
       50. The invention of claim  49 , further comprising the steps of: 
       
         exciting the probe into vibration at or near its resonance mode; and  
       
       
         detecting changes in the sensing probe vibration resulting from proximity of the sensing probe to the surface to be detected. 
       
     
     
       51. The invention of claim  50 , wherein the step of detecting changes in the sensing probe vibration further comprises the step of: 
       
         detecting changes in the resonant parameters of the vibration. 
       
     
     
       52. The invention of claim  50 , wherein the step of detecting changes in the sensing probe vibration further comprises the step of: 
       
         detecting changes in the amplitude of the vibration. 
       
     
     
       53. The invention of claim  50 , wherein the step of detecting changes in the sensing probe vibration further comprises: 
       
         detecting changes in the phase of the vibration. 
       
     
     
       54. The invention of claim  50 , further comprising the step of: 
       
         exciting the probe into vibration at or near its resonance mode; and  
       
       
         detecting changes in the sensing probe vibration resulting from proximity of the sensing probe to the surface to be detected. 
       
     
     
       55. The invention of claim  54 , wherein the step of detecting changes in the sensing probe vibration further comprises the step of: 
       
         detecting changes in the resonant parameters of the vibration. 
       
     
     
       56. The invention of claim  54 , wherein the step of detecting changes in the sensing probe vibration further comprises the step of: 
       
         detecting changes in the amplitude of the vibration. 
       
     
     
       57. The invention of claim  54 , wherein the step of detecting changes in the sensing probe vibration further comprises the step of: 
       
         detecting changes in the phase of the vibration. 
       
     
     
       58. A method for determining information about a surface to be scanned, comprising the steps of: 
       
         moving a sensing probe in relationship to the surface to be scanned including the steps of: mounting the sensing probe adjacent a moving end of a motion generation, supporting the motion generator adjacent a fixed end thereof, and providing an optical path between the fixed and moving ends;  
       
       
         exciting the probe into vibration at or near the probe's resonance mode; and  
       
       
         detecting changes in the sensing probe vibration resulting from proximity of the sensing probe to the surface to be detected; and  
       
       
         mounting a light source in said optical path mounted adjacent said fixed end to apply light to the sensing probe. 
       
     
     
       59. The invention of claim  58 , further comprising the step of: 
       
         detecting light reflected from said sensing probe.