Ming-Yaw Ng and Wei-Chih Liu Department of Physics, NTNU

1. From 4.7GB to 100 GB -- Theoretical study of the AgOx-type super-resolution near-field structure Ming-Yaw Ng and Wei-Chih Liu Department of Physics, NTNU

2. Outline • Introduction • Working mechanisms of the AgOx-type super-resolution near-field structure (Super-RENS) • Simulation results: random nanoparticles in AgOx layer periodic nanoparticles in AgOx layer frequency dependence of the AgOx –type Super-RENS • Conclusions

3. http://www.nano.gov

4. Comparison of optical disks TB Advantages • capacity >100 Giga Byte • >20 DVD movies • >100部中國25史 • >150 music CD Super-RENS disk>100GB Pit Length < 0.1m > 150 CDs 50 CDs HD-DVD/25GB Track Pitch=0.35m Pit Length=0.2m CD/650MB Track Pitch=1.6m Pit Length=0.83m GB DVD/4.7GB Track Pitch=0.74m Pit Length=0.4m 7 CDs MB 2005 2010 1990 2000 1980

5. Near-field optical data storage systems (?) Far-field optical data storage systems (CD-R, CD-RW, DVD….) 50 nm 100 nm 200 nm 400 nm 1000 nm Mark size

8. recording 物理雙月刊（廿三卷二期）2001年4月

9. TEM image of cross-section of the AgOx-type Super-resolution near-field structure (Super-RENS) disk Silver nanoclusters 10nm ZnS-SiO2 AgOx ZnS-SiO2 W.-C. Liu, C.-Y. Wen, K.-H. Chen, W. C. Lin, and D. P. Tsai, Appl. Phys. Lett. 78, 685 (2001).

10. Focusing laser beam NA = 0.6 marks Mark size > λ Mark size < λ

11. Focusing laser beam NA = 0.6 AgOx (15nm) marks Mark size < λ

12. DVD disk substrate ZnS-SiO2 (20 nm) AgOx (15 nm) Ag nanoclusters ZnS-SiO2 (20 nm) Recording mark Ge2Sb2Te5 (15 nm) Focusing laser beam

13. Localized surface plasmon of the AgOx –type Super-RENS with silver nanoparticles TE mode TM mode

14. Far-field difference signals of the AgOx-type Super-RENS disks with random silver nanoparticles

15. Nonlinear optical response from random silver nanoparticles

16. Near-field images of AgOx-type Super-RENS disks with periodic silver nanoparticles Period = 150 nm

17. Far-field difference signals of the AgOx-type Super-RENS disk

18. n = 0.17 k = 1.95 for λ= 405 nm n = 0.14 k = 4.15 for λ= 650 nm Optical constant of bulk silver ‘Handbook of Optical Constants of Solids’, Ed. By Edward D. Palik, Academic Press, Inc., (1985)

19. Near-field images of the AgOx-type Super-RENS disks with silver nanoparticles

20. Far-field difference signals of the AgOx-type Super-RENS disk

21. Far-field difference signals of the AgOx-type Super-RENS disk

22. Scattering efficiency of single silver nanoparticle

23. Conclusions • Super-RENS was a multilayered structure , which could achieve resolution beyond optical diffraction limit. • The AgOx layer of the AgOx-type Super-RENS scattered the incident Gaussian beam and enhanced the localized surface plasmons. • The AgOx-type Super-RENS disks could transfer the evanescent light from sub-wavelength recording marks into propagation light. • The far-field signals of specific mark size could be controlled by periodic silver nanoparticles or nanoclusters. • The silver nanoparticles with highly scattering efficiency in AgOx layer of the AgOx– type Super-RENS disks have better resolution capability even though it is illuminated with incident light of longer wavelength