Scanning Probe Microscopy Using Quartz Crystal Resonator Yongho

Scanning Probe Microscopy Using Quartz Crystal Resonator Yongho Seo Wonho Jhe School of Physics and Center for Near-field Atom-photon technology, Seoul Nation University in South Korea Creative Research Initiatives Seoul National University Center for Near-field Atom-Photon Technology

QCRs as a Force Sensor AT-cut QCR Z-cut trident QCR Z-cut Tuning fork Low Frequency (32 k. Hz) Flexural Mode k = 103 - 104 N/m High force sensitivity High Frequency (rf) Thickness Shear k = 105 - 106 N/m High Speed High Frequency (1 MHz) Extensional mode k = 105 - 106 N/m High resolution Creative Research Initiatives Seoul National University Center for Near-field Atom-Photon Technology

High Speed NSOM -Shear mode - 2 MHz dithering frequency - make a hole to insert optical fiber tip - easy to replace tip - increased the stability - high Q-value > 103 Creative Research Initiatives Seoul National University Center for Near-field Atom-Photon Technology

Fastest Scanning NSOM Image Topography of CD Optical image of Grating Total time : 20 s Total time : 0. 5 s 7 x 7 mm 2 Y. Seo, et. al, Appl. Phys. Lett. 77 4274 (2000). Creative Research Initiatives Seoul National University Center for Near-field Atom-Photon Technology

Continuous Images using High Speed Shear Force Microscope Slowly diffusing micro-spheres in water 9630 min. 12 min Scanning time 25 s, 5 x 4 mm 2 Y. Seo and W. Jhe, Rev. Sci. Instrum. 73, 2057 (2002) Creative Research Initiatives Seoul National University Center for Near-field Atom-Photon Technology

Tuning Fork Based Electrostatic force microscopy -Ferroelectrics -surface charge in Semiconductor f = 32. 768 KHz k = 1300 N/m L = 2. 2 mm, t = 190 mm, w = 100 mm k = 1300 N/m. Q = 1800, f = 32 k. Hz Creative Research Initiatives Seoul National University Center for Near-field Atom-Photon Technology

Force Sensitivity of Quartz Tuning Fork minimum detectable force = (k/Qf) 1/2 Si Cantilever Quartz Tuning Fork f = 10 - 100 k. Hz k = 1 - 100 N/m f = 10 - 100 k. Hz k = 103 - 105 N/m Q = 102 - 103 ~ 10 nm dithering Q = 103 - 105 < 1 nm dithering Lift mode • Long range electrostatic force • Short range shear force • keep constant gap between tip and sample (~10 nm) • to avoid the strong short range topographic contrast Creative Research Initiatives Seoul National University Center for Near-field Atom-Photon Technology

Tip Manufacture Electrochemical Etching - Co or Ni wire H 3 PO 4 Pt Co, Ni H 3 PO 4 D = 100 mm Creative Research Initiatives 10 mm Seoul National University Center for Near-field Atom-Photon Technology

Tip Attachment -Attach the wire to the tuning fork and make a tip -Use home-made micromanipulator Pt Co, Ni Silver paint H 3 PO 4 Tuning fork Creative Research Initiatives Seoul National University Center for Near-field Atom-Photon Technology

Ferroelectric PZT Thin Film PZT (100 nm) / Pt electrode layer / Si substrate • for high quality nano storage devices : • high ferroelectric properties • long term stability and reliability Creative Research Initiatives Seoul National University Center for Near-field Atom-Photon Technology

Approach Curve in EFM Tip PZT Pt Bias voltage applied between the tip and Pt substrate Creative Research Initiatives Seoul National University Center for Near-field Atom-Photon Technology

Poling and Drawing by EFM polarization poling Line drawing 7 x 7 mm 2 0. 9 x 0. 9 mm 2 long time stable (10 hr) High resolution (50 nm) narrow line width Creative Research Initiatives Seoul National University Center for Near-field Atom-Photon Technology

Patterning and Imaging by EFM Tuning Fork based EFM - polarization images 4 x 4 mm 2 7 x 7 mm 2 Y. Seo, et al, Appl. Phys. Lett. 80 4324, (2002). Creative Research Initiatives Seoul National University Center for Near-field Atom-Photon Technology

Tuning Fork Based Magnetic Force Microscopy MFM contrast - magnetic force gradient between tip and sample Force gradient Frequency shift Phase shift Magnetic force - very weak force (~p. N) Lift mode - keep constant gap between tip and sample (~10 nm) - to avoid the strong short range topographic contrast Creative Research Initiatives Seoul National University Center for Near-field Atom-Photon Technology

Approach Curve of MFM Shear force Approach Withdraw attractive force high S/N ratio high frequency Sensitivity < 3 m. Hz Creative Research Initiatives Seoul National University Center for Near-field Atom-Photon Technology

Tip & Tuning Fork epoxy Co or Ni tip L = 2. 2 mm, t = 190 mm, w = 100 mm spring constant, k = 1300 N/m Creative Research Initiatives Seoul National University Center for Near-field Atom-Photon Technology

Shear Mode MFM Advantage of the shear mode MFM - Perpendicularly recorded sample -longitudinally polarized tip - monopole approximation Creative Research Initiatives Seoul National University Center for Near-field Atom-Photon Technology

Magnetic Force Microscopy Images (a) shear mode, Co tip, perpendicular 100 Mbit / Inch 2 (b) shear mode, Co tip, parallel dithering (c) shear mode, Ni tip hard disk (d) tapping mode 30 x 30 mm 2 Creative Research Initiatives 30 x 30 mm 2 Seoul National University Center for Near-field Atom-Photon Technology

Lift Height & Dithering Amplitude Height (h) dependency Amplitude (a) dependency Tip h a Sample 13 x 3 mm 2 Creative Research Initiatives 3 x 1 mm 2 Seoul National University Center for Near-field Atom-Photon Technology

High Resolution Tuning Fork Based MFM 1 Gbit/inch 2 hard disk Dithering Amplitude : 20 nm lift height : 50 nm Spatial resolution : 50 nm 2 x 2 mm 2 Creative Research Initiatives Seoul National University Center for Near-field Atom-Photon Technology

Atomic Layer of HOPG With Trident QCR (1 MHz) Atomic layer (3Å) 160 x 160 nm 2 Creative Research Initiatives Seoul National University Center for Near-field Atom-Photon Technology

True Atomic resolution AFM in air • • • Mica Ambient condition Non-contact AFM Dithering Amp: 0. 1 nm Triangular structure k = 50, 000 N/m Trident QCR, 1 MHz Piezoelectric detection Corrugation : 0. 3 Å 1 nm x 1 nm, 51 s 2 nm x 2 nm, 51 s Creative Research Initiatives 1 nm x 1 nm 13 s 2 nm x 2 nm, 13 s Seoul National University Center for Near-field Atom-Photon Technology

Summary • AT-cut QCR : High speed NSOM • Tuning fork : High force sensitivity MFM, EFM • Trident QCR : Atomic resolution AFM in air Creative Research Initiatives Seoul National University Center for Near-field Atom-Photon Technology

Thank you !!! Near field Group Researchers Yongho Seo, Ho Jin Cho, Moon Hun Hong, Jun Mo An, Sung Jin Jang, Hwan Sung Choi, Kyeong Ho Kim, Professor Wonho Jhe Creative Research Initiatives Seoul National University Center for Near-field Atom-Photon Technology