[SOLVER Scanning Probe Microscope]

[Image]

SNOM head with non optical tip-sample distance control.
("Tuning fork" SNOM head)

A Shear-force mechanism is widely used to regulate fiber tip-sample separation in SNOM. In our SNOM construction we are using a tuning fork with attached tapered fiber and piezoelectric element to apply lateral vibration to the system: A Q-factor of tuning fork without fiber is commonly 104 2x104 (in air), after attaching the tapered fiber Q-factor decreases to 103 5x103. Usually a resonant frequency changes weakly (it is about 32Hz). A electrical response of tuning fork is used to control the tip-sample separation and for measuring an AFM profile. At the same time it's possible to record the optic signal from light-conducting fiber by means of photoelectric device or photodiode while the scanning progress. The SNOM resolution capability (AFM-resolution and optical resolution) depends on the light-conducting fiber point curvature radius and on the probe-oscillation amplitude. We have obtained 50nm AFM resolution (Shear force microscope) using own light-conducting fiber.

Main features:

  1. NT-MDT SNOM has non optical feedback control system which consists of tuning fork and light conducting tapered fiber attached to the piezoelectric element apply vibration to the system.
  2. Minimum amplitude of micro fiber top oscillations is 10 nm.
  3. Maximum AFM resolution 50 nm (depends on curvature radii of micro fiber tip).
  4. Z Resolution: 1-10A
  5. Resonant frequency of system is about 32 kHz ( +/-0,5 kHz).
  6. NT-MDT-SNOM gives you possibility of using micro fibers of any manufactures.
  7. The microscope has external input which allows to use customer receiving-amplifying equipment.
The scheme is as the following:
micro fiber tip output - customer receiving-amplifying
equipment - NT-MDT-SNOM
Ext. Input at:Umax = +5 B
Umin = -5 B
Sensitivity:Umin = (10/216)B (16-bit-DAC)

Optical fiber characteristics:
Optical fiber tip apperture - 100nm (50nm)
Maximal optical input - 8 mW
optical efficiency 10-3 (10-4) for 100 nm radii of fiber
optical efficiency 10-6 (10-7) for 30 nm radii of fiber

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