Voltage on a quadrant photodiode used with an AFM

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SUMMARY

The discussion focuses on the operation of a quadrant photodiode in an Atomic Force Microscope (AFM) while measuring the deflection of a laser beam over a carbon nanotube. The voltage output from the photodiode varies across quadrants A, B, C, and D as the AFM tip interacts with the nanotube, influenced by the height changes detected by the piezoelectric actuator. Key equations mentioned include λ = 1.2 / V1/2 and λ = h/p, which relate to the measurement principles involved. Understanding the relationship between the voltage changes in the quadrants and the current generated is essential for accurate interpretation of the AFM data.

PREREQUISITES
  • Understanding of Atomic Force Microscopy (AFM) principles
  • Knowledge of quadrant photodiode operation
  • Familiarity with piezoelectric actuators
  • Basic grasp of laser deflection measurement techniques
NEXT STEPS
  • Research the principles of quadrant photodiode voltage output in AFM applications
  • Study the operation and characteristics of piezoelectric actuators in microscopy
  • Learn about laser deflection measurement techniques and their applications in nanotechnology
  • Explore the mathematical relationships in AFM, specifically focusing on λ = h/p and its implications
USEFUL FOR

Researchers and engineers in the fields of nanotechnology, materials science, and microscopy, particularly those working with AFM and photodetection systems.

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Homework Statement


An AFM uses a quadrant photo-diode to measure the deflection of the laser beam. Sketch the voltage in quadrants A, B, C and D as the tip travels on top of a single carbon nano-tube resting on a flat surface when the AFM is operating on tapping mode.
DDI7esS.jpg

Homework Equations


Not sure what to use, or if this is a conceptual problem.
λ= 1.2 / V1/2
λ = h/p

The Attempt at a Solution


I know that the AFM (and the piezoelectric actuator) would have a changing voltage to account for different heights and such, but how does that relate to what voltage is on the photo-diode? How can there be a specific voltage for each quadrant, I'm not getting that.
 

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Did you draw a sketch of the setup? Before finding relevant equations you'll have to understand what leads to a different current in the quadrants.
 

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