Creative Research Initiatives Seoul National University Center for Near-field Atom-Photon Technology...
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Creative Research InitiativesSeoul National UniversityCenter for Near-field Atom-Photon Technology
Yongho Seo
Wonho Jhe
School of Physics and Center for Near-field Atom-photon technology,
Seoul Nation University in South Korea
Scanning Probe Microscopy Using Quartz Crystal Resonator
Creative Research InitiativesSeoul National UniversityCenter for Near-field Atom-Photon Technology
High Frequency (rf)Thickness Sheark = 105 - 106 N/m
High Speed
Low Frequency (32 kHz)Flexural Mode k = 103 - 104 N/mHigh force sensitivity
Z-cut Tuning fork
AT-cut QCRZ-cut trident QCR
QCRs as a Force Sensor
High Frequency (1 MHz)Extensional mode k = 105 - 106 N/m
High resolution
Creative Research InitiativesSeoul National UniversityCenter for Near-field Atom-Photon Technology
-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
High Speed NSOM
Creative Research InitiativesSeoul National UniversityCenter for Near-field Atom-Photon Technology
Optical image of Grating
Total time : 0.5 s
7x7 m2
Optical image of Grating
Total time : 0.5 s
7x7 m2
Fastest Scanning NSOM Image
Topography of CD
Total time : 20 s
Topography of CD
Total time : 20 s
Y. Seo, et. al, Appl. Phys. Lett. 77 4274 (2000).
Creative Research InitiativesSeoul National UniversityCenter for Near-field Atom-Photon Technology
Slowly diffusing micro-spheres in water
Scanning time 25 s, 5 x 4 m2
0 min.
Continuous Images usingHigh Speed Shear Force
Microscope
3 min.6 min.9 min.12 min
Y. Seo and W. Jhe, Rev. Sci. Instrum. 73, 2057 (2002)
Creative Research InitiativesSeoul National UniversityCenter for Near-field Atom-Photon Technology
f = 32.768 KHz
k = 1300 N/m
f = 32.768 KHz
k = 1300 N/m
Tuning Fork Based Electrostatic force microscopy
-Ferroelectrics-surface charge in Semiconductor
L = 2.2 mm, t = 190 m, w = 100 m k = 1300 N/m.Q = 1800, f = 32 kHz
Creative Research InitiativesSeoul National UniversityCenter for Near-field Atom-Photon Technology
minimum detectable force = (k/Qf) 1/2
f = 10 - 100 kHzk = 1 - 100 N/mQ = 102 - 103 ~ 10 nm dithering
f = 10 - 100 kHzk = 103 - 105 N/mQ = 103 - 105 < 1 nm dithering
Si Cantilever Quartz Tuning Fork
Force Sensitivity of Quartz Tuning Fork
• 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
Lift mode
Creative Research InitiativesSeoul National UniversityCenter for Near-field Atom-Photon Technology
H3PO4
H3PO4
- Co or Ni wire
Pt Co, Ni
D = 100 m 10 m
Tip Manufacture Electrochemical Etching
Creative Research InitiativesSeoul National UniversityCenter for Near-field Atom-Photon Technology
-Attach the wire to the tuning fork and make a tip-Use home-made micromanipulator
Pt
Co, NiH3PO4
Tuning fork
Silver paint
Tip Attachment
Creative Research InitiativesSeoul National UniversityCenter for Near-field Atom-Photon Technology
• for high quality nano storage devices : • high ferroelectric properties • long term stability and reliability
PZT (100 nm) / Pt electrode layer / Si substratePZT (100 nm) / Pt electrode layer / Si substrate
Ferroelectric PZT Thin Film
Creative Research InitiativesSeoul National UniversityCenter for Near-field Atom-Photon Technology
Bias voltage applied between the tip and Pt substrate
PZT
Pt
Tip
Approach Curve in EFM
Creative Research InitiativesSeoul National UniversityCenter for Near-field Atom-Photon Technology
7 x 7 m2 0.9 x 0.9 m2
polarization polingpolarization poling Line drawingLine drawing
long time stable
(10 hr)
long time stable
(10 hr)High resolution (50 nm)
narrow line width
High resolution (50 nm)
narrow line width
Poling and Drawing by EFM
Creative Research InitiativesSeoul National UniversityCenter for Near-field Atom-Photon Technology
Tuning Fork based EFM - polarization imagesTuning Fork based EFM - polarization images
4 x 4 m2 7 x 7 m2
Patterning and Imaging by EFM
Y. Seo, et al, Appl. Phys. Lett. 80 4324, (2002).
Creative Research InitiativesSeoul National UniversityCenter for Near-field Atom-Photon Technology
Frequency shift Phase 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
Creative Research InitiativesSeoul National UniversityCenter for Near-field Atom-Photon Technology
ApproachWithdraw
high S/N ratiohigh frequency Sensitivity < 3 mHz
Shear force
attractive force
Approach Curve of MFM
Creative Research InitiativesSeoul National UniversityCenter for Near-field Atom-Photon Technology
L = 2.2 mm, t = 190 m, w = 100 m spring constant, k = 1300 N/m
Co or Ni tipCo or Ni tip
Tip & Tuning Fork
epoxy
Creative Research InitiativesSeoul National UniversityCenter for Near-field Atom-Photon Technology
- Perpendicularly recorded sample -longitudinally polarized tip- monopole approximation
Advantage of the shear mode MFMAdvantage of the shear mode MFM
Shear Mode MFM
Creative Research InitiativesSeoul National UniversityCenter for Near-field Atom-Photon Technology
(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 m2 30 x 30 m2 30 x 30 m2 30 x 30 m2
100 Mbit / Inch2
hard disk
100 Mbit / Inch2
hard disk
Magnetic Force Microscopy Images
Creative Research InitiativesSeoul National UniversityCenter for Near-field Atom-Photon Technology
Amplitude (a) dependencyAmplitude (a) dependency
3 x 1 m213 x 3 m2
Lift Height & Dithering Amplitude
Height (h) dependencyHeight (h) dependency
h a
Tip
Sample
Creative Research InitiativesSeoul National UniversityCenter for Near-field Atom-Photon Technology
1 Gbit/inch2 hard diskDithering Amplitude : 20 nmlift height : 50 nmSpatial resolution : 50 nm2 x 2 m2
High Resolution Tuning Fork Based MFM
Creative Research InitiativesSeoul National UniversityCenter for Near-field Atom-Photon Technology
160 x160 nm2
Atomic layer (3Å)
Atomic Layer of HOPG With Trident QCR (1MHz)
Creative Research InitiativesSeoul National UniversityCenter 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, 1MHz
• Piezoelectric detection
• Corrugation : 0.3 Å
1nm x 1nm, 51 s
2nm x 2nm, 51 s
1nm x 1nm 13 s
2nm x 2nm, 13 s
Creative Research InitiativesSeoul National UniversityCenter 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 InitiativesSeoul National UniversityCenter for Near-field Atom-Photon Technology
Thank you !!!
Near field Group ResearchersYongho Seo, Ho Jin Cho, Moon Hun Hong, Jun Mo An, Sung Jin Jang,
Hwan Sung Choi, Kyeong Ho Kim,Professor
Wonho Jhe