Whispering gallery mode ultrasonically coupled scanning probe microscope

Abstract

Scanning probe microscopes include a probe tip coupled to a tuning fork or other acoustic resonator so as to apply a shear force when contacted to a specimen surface based on an applied acoustic signal. A secondary ultrasonic transducer is in acoustic communication with the specimen and a resonant structure. Probe tip-specimen displacement can be detected based on whispering gallery mode ultrasonic waves in the resonant structure using the secondary transducer, and such displacements maintained using feedback control based on whispering gallery mode acoustic wave magnitude.

1 . A method, comprising:
 scanning an oscillating probe tip over a specimen surface;   coupling an acoustic vibration associated with oscillations of the probe tip to a resonant cavity so as to form a resonant acoustic wave; and   detecting probe tip-specimen separation based on the resonant acoustic wave.   
     
     
         2 . The method of  claim 1 , further comprising scanning the probe tip with respect to the specimen surface and adjusting the probe tip-specimen surface separation so as to maintain a predetermined resonant acoustic wave characteristic. 
     
     
         3 . The method of  claim 2 , wherein the resonant acoustic wave characteristic is an amplitude. 
     
     
         4 . The method of  claim 3 , further comprising storing a plurality of probe tip-specimen displacement adjustments. 
     
     
         5 . The method of  claim 4 , further comprising displaying a specimen image based on the stored displacement adjustments. 
     
     
         6 . The method of  claim 2 , wherein the predetermined resonant acoustic wave characteristic is a substantially constant magnitude. 
     
     
         7 . The method of  claim 1 , wherein the resonant cavity includes a conical portion associated with a range of acoustic resonant frequencies. 
     
     
         8 . The method of  claim 1 , further comprising selecting a probe tip oscillation frequency so as to correspond to a resonance frequency of the resonant cavity. 
     
     
         9 . The method of  claim 1 , wherein the probe tip is secured to a tine of a quartz tuning fork, and further comprising providing the oscillation of the probe tip with the quartz tuning fork. 
     
     
         10 . The method of  claim 1 , wherein the resonant cavity includes a cylindrical section having a diameter associated with an oscillation frequency of the oscillating probe tip. 
     
     
         11 . The method of  claim 1 , further comprising scanning the probe tip with respect to the specimen surface and adjusting the probe tip-specimen surface separation so as to remain substantially constant. 
     
     
         12 . The method of  claim 11 , wherein the probe tip-specimen separation is detected based on a resonant acoustic wave amplitude. 
     
     
         13 . The method of  claim 12 , further comprising storing a plurality of probe tip-specimen displacement adjustments. 
     
     
         14 . The method of  claim 13 , further comprising displaying a specimen image based on the stored displacement adjustments. 
     
     
         15 . The method of  claim 11 , wherein the probe tip-specimen separation is detected based on a resonant acoustic wave characteristic magnitude. 
     
     
         16 . The method of  claim 1 , wherein detecting the probe tip-specimen separation is based detection of the resonant acoustic wave with an ultrasonic transducer secured to a cylindrical dome resonant cavity. 
     
     
         17 . A method, comprising:
 receiving a plurality of probe tip-specimen displacement adjustments and corresponding specimen locations based on resonant detection of a magnitude or phase of an acoustic wave produced by a probe tip; and   displaying a specimen image based on the received probe tip-specimen displacement adjustments and specimen locations.   
     
     
         18 . The method of  claim 17 , wherein the resonant detection is based on a magnitude of the acoustic wave produced by the probe tip. 
     
     
         19 . The method of  claim 17 , wherein the resonant detection is based on a phase of the acoustic wave produced by the probe tip.