From 4.7GB to 100 GB -- From 4.7GB to 100 GB -- Theoretical study of the AgOTheoretical study of the AgOxx-type -type

super-resolution near-field structuresuper-resolution near-field structure

Ming-Yaw Ng and Wei-Chih LiuMing-Yaw Ng and Wei-Chih Liu

Department of Physics, NTNUDepartment of Physics, NTNU

OutlineOutline

IntroductionIntroductionWorking mechanisms of the AgOWorking mechanisms of the AgOxx-type sup-type sup

er-resolution near-field structure (Super-REer-resolution near-field structure (Super-RENS)NS)

Simulation results:Simulation results: random nanoparticles in AgOrandom nanoparticles in AgOxx layer layer

periodic nanoparticles in AgOperiodic nanoparticles in AgOxx layer layer

frequency dependence of the AgOfrequency dependence of the AgOx x –type Super-RENS–type Super-RENS

ConclusionsConclusions

http://www.nano.gov

1980 1990 2000 2005 2010MB

GB

TB Advantages capacity >100 Giga Byte

>20 DVD movies

>100部中國 25史 >150 music CD

CD/650MBTrack Pitch=1.6mPit Length=0.83m

7 CDs

> 150 CDs

50 CDs HD-DVD/25GBTrack Pitch=0.35mPit Length=0.2m

Super-RENS disk >100GB

Pit Length < 0.1m

Comparison of optical disks

DVD/4.7GBTrack Pitch=0.74mPit Length=0.4m

Optical diffraction limit 0.66numerical aperture NANA

Near-field optical data storage

systems

(?)

Far-field optical data storage

systems

(CD-R, CD-RW, DVD….)

Mark size

200 nm

100 nm

50 nm 1000 nm

400 nm

物理雙月刊（廿三卷二期） 2001 年 4 月

recording

ZnS-SiO2 AgOx ZnS-SiO210nm

TEM image of cross-section of the AgOx-type Super-resolution near-field structure

(Super-RENS) disk

Silver nanoclusters

W.-C. Liu, C.-Y. Wen, K.-H. Chen, W. C. Lin, and D. P. Tsai, Appl. Phys. Lett. 78, 685 (2001).

Mark size > λ

Focusing laser beamNA = 0.6

marks

Mark size < λ

Focusing laser beamNA = 0.6

Mark size < λ

marks

AgOx (15nm)

DVD disk substrate

ZnS-SiO2 (20 nm)

ZnS-SiO2 (20 nm)

AgOx (15 nm)

Ge2Sb2Te5 (15 nm)

Recording mark

Ag nanoclusters

Focusing laser beam

TM modeTM mode

Localized surface plasmon of the AgOLocalized surface plasmon of the AgOxx –type –type

Super-RENS with silver nanoparticlesSuper-RENS with silver nanoparticles

TE modeTE mode

Far-field difference signals of the AgOFar-field difference signals of the AgOxx-type -type

Super-RENS disks with random silver Super-RENS disks with random silver nanoparticlesnanoparticles

Nonlinear optical response from random silver nanoparticles

Near-field images of AgONear-field images of AgOxx-type Super-RENS -type Super-RENS

disks with periodic silver nanoparticlesdisks with periodic silver nanoparticlesPeriod = 150 nmPeriod = 150 nm

Far-field difference signals of the AgOFar-field difference signals of the AgOxx-type -type

Super-RENS diskSuper-RENS disk

Optical constant of bulk silverOptical constant of bulk silver

‘Handbook of Optical Constants of Solids’, Ed. By Edward D. Palik, Academic Press, Inc., (1985)

n = 0.14 k = 4.15 for λ= 650 nm

n = 0.17 k = 1.95 for λ= 405 nm

Near-field images of the AgONear-field images of the AgOxx-type Super--type Super-

RENS disks with silver nanoparticlesRENS disks with silver nanoparticles

Far-field difference signals of the Far-field difference signals of the AgOAgOxx-type Super-RENS disk-type Super-RENS disk

Far-field difference signals of the Far-field difference signals of the AgOAgOxx-type Super-RENS disk-type Super-RENS disk

Scattering efficiency of single silver nanoparticleScattering efficiency of single silver nanoparticle

ConclusionsConclusions Super-RENS was a multilayered structure , which could achieve Super-RENS was a multilayered structure , which could achieve

resolution beyond optical diffraction limit.resolution beyond optical diffraction limit. The AgOThe AgOxx layer of the AgO layer of the AgOxx-type Super-RENS scattered the in-type Super-RENS scattered the in

cident Gaussian beam and enhanced the localized surface plasmcident Gaussian beam and enhanced the localized surface plasmons.ons.

The AgOThe AgOxx-type Super-RENS disks could transfer the evanescent -type Super-RENS disks could transfer the evanescent light from sub-wavelength recording marks into propagation liglight from sub-wavelength recording marks into propagation light.ht.

The far-field signals of specific mark size could be controlled bThe far-field signals of specific mark size could be controlled by periodic silver nanoparticles or nanoclusters.y periodic silver nanoparticles or nanoclusters.

The silver nanoparticles with highly scattering efficiency in AgThe silver nanoparticles with highly scattering efficiency in AgOOxx layer of the AgO layer of the AgOxx– type Super-RENS disks have better resol– type Super-RENS disks have better resolution capability even though it is illuminated with incident light ution capability even though it is illuminated with incident light of longer wavelengthof longer wavelength