1. Yongho Seo Center for Near-field Atom-photon technology, Seoul Nation University, Rep. of Korea & Department of Physics, University of Virginia Kyungho Kim, Hyunjun Jang, Wonho Jhe School of Physics and Center for Near-field Atom-photon technology, Seoul Nation University, Rep. of Korea Magnetic Force Microscopy using Quartz Tuning Fork

2. - Self actuating - Self sensing - No light - No alignment - optical deflection - laser diode - photo diode - optical alignment - addition actuator Quartz Crystal Tuning fork Quartz Tuning Fork as a Force Sensor Micro-machined Cantilever

3. Force sensitivity (Qf/k) 1/2 f ~ 10 - 100 kHz k ~ 1 - 100 N/m Q ~ 10 2 ~ 10 nm dithering f ~ 32 - 100 kHz k ~ 10 3 - 10 5 N/m Q ~ 10 4 (10 6 in vacuum) < 1 nm dithering CantileverTuning Fork Force Sensitivity of Quartz Tuning Fork Low force sensitivity Low thermal noise due to high stiffness High resolution by small dithering amplitude

4. Hal Edwards, et. al. (1997) Todorovic and Schultz (1998) Previous works : MFM using tuning fork

5. f = 32.768 KHz k = 1300 N/m Q = 1300 f = 32.768 KHz k = 1300 N/m Q = 1300 Tuning Fork based Electrostatic force microscopy -Ferroelectrics -surface charge in Semiconductor L = 2.2 mm, t = 190 m, w = 100 m

6. 7 x 7 m 2 0.9 x 0.9 m 2 poling Line drawing EFM images using Tuning Fork Surface polarization images of PZT film 4 x 4 m 2 7 x 7 m 2 Y. Seo, et al, Appl. Phys. Lett. 80 4324, (2002). dot

7. Frequency shiftPhase shift MFM contrast - magnetic force gradient between tip and sample Lift mode - keep constant gap between tip and sample (~10 nm) - to avoid the strong short range topographic contrast Magnetic force - very weak force (~pN) Force gradient Tuning Fork Based Magnetic Force Microscopy

8. Shear force Attractive force Approach Curve of MFM Approach Withdraw high S/N ratio high frequency Sensitivity < 3 mHz f = 0.1 Hz 0.01 Hz1 mHz

9. H 3 PO 4 - Co or Ni wire Pt Co, Ni D = 100 m10 m Tip Manufacture Electrochemical Etching

10. -Attach the wire to the tuning fork and make a tip -Use home-made micromanipulator Pt Co, Ni H 3 PO 4 Tuning fork Silver paint Tip Attachment

11. L = 2.2 mm, t = 190 m, w = 100 m spring constant, k = 1300 N/m Co or Ni tip Tip & Tuning Fork epoxy

12. - Perpendicularly recorded sample -longitudinally polarized tip - monopole approximation Advantage of the shear mode MFM Shear Mode MFM

13. (a) shear mode, Co tip, perpendicular (b) shear mode, Co tip, parallel dithering (c) shear mode, Ni tip (d) tapping mode (a) shear mode, Co tip, perpendicular (b) shear mode, Co tip, parallel dithering (c) shear mode, Ni tip (d) tapping mode 30 x 30 m 2 100 Mbit / Inch 2 hard disk 100 Mbit / Inch 2 hard disk Magnetic Force Microscopy Images

14. Amplitude (a) dependency 3 x 1 m 2 13 x 3 m 2 Lift Height & Dithering Amplitude Height (h) dependency h a Tip Sample

15. 1 Gbit/inch 2 hard disk Dithering Amplitude : 20 nm lift height : 50 nm Spatial resolution : 50 nm 2 x 2 m 2 High Resolution Tuning Fork Based MFM

16. Summary MFM using Tuning Fork High resolution. low power dissipation at low temperature. No laser : dark environment. Cryogenic experiment (Vortex in superconductor).