Nanoscale Imaging of Buried Structures via Scanning Near-Field Ultrasound Holography

G. S. Shekhawat and V. P. Dravid , Science, 310, 89(2005).

Journal Club Presentation30/10/06Onur Basarir

BackgroundAFM (Atomic Force Microscopy)

AFM

Superb spatial resolution, but nothing about subsurface properties.

Motivation

• Near field SPM Excellent lateral resolution

• Ultrasound Non-destructive and depth sensitive

• Holography Sensitive to phase

1 - Ultrasonic Force Microscopy

O. Kolosov et.al, PRL, 81, 1046 (1998)

F. Dinelli,et.al, PRB, 61,13995(2000).

2 – Acoustic Force Microscopy

U. Rabe et.al. ,Ultrasonics, 38, 430(2000).

3 – Heterodyne Force Microscopy

M T Cuberes et al 2000 J. Phys. D: Appl. Phys. 33 2347-2355

Drawbacks of these Techniques

• Contact mode• Amplitude measurements

Setup

Setup for non-contact operation

Lock-in

f2

f1

f2-f1

Results I

Nanostructures 500 nm below the surface

Results II

Results III

Results IV

Conclusion

• Non-invasive: based on acoustic waves• Sub-surface: transparent to acoustic

waves• Nano-scale resolution

Contact AFM

Non-Contact AFM

Tapping Mode AFM