Nano fabrication and optical characterization of nanostructures

Transcription

1 Introduction to nanooptics, Summer Term 2012, Abbe School of Photonics, FSU Jena, Prof. Thomas Pertsch Nano fabrication and optical characterization of nanostructures Lecture 12 1

2 Optical characterization methods VIS/NIR spectrophotometry (175 nm nm, 1x1mm, angle resolved) FTIR spectroscopy (200nm nm, 1x1mm, angle resolved) spatially resolved spectroscopy with microscope spectrometers (320 nm nm, 10x10µm or VIS 1x1µm) single particle/metaatom spectroscopy (VIS) white light interferometry for measurement of complex parameters ( nm, 2x2mm) SNOM - nearfield scanning microscopy (aperture / scattering / two-tip in VIS/NIR) single photon time correlated microscopy (VIS/NIR, 10 ps resolution) PEEM - photoemission electron microscopy: imaging & spectroscopy (resolution: spatial 20nm, energy 100meV, temporal <15fs)

3 3 Motivation Retrieval of effective parameters R Re Circular dichroism Circular birefringence Refractive index & impedance or Permittivity & Permeability

4 4 White light interferometry

5 5 Experimental method White light Fourier-transform spectroscopy in frequency space Fouriertransformation

6 6 Characterization instrument OSA: Yokogawa AQ6370B WLS: NKT SuperK EXW-6 bandwidth: nm

7 7 Exemplary results

8 8 Exemplary results Fishnet

9 9 Exemplary results Fishnet - measurements wavelength [nm] wavelength [nm] wavelength [nm] wavelength [nm]

10 10 Exemplary results Fishnet effective parameter retrieval 0,2 wavelength [nm] wavelength [nm] wavelength [nm] wavelength [nm]

11 11 Spatially resolved spectroscopy

12 Annealed silver Negative index metamaterial

13 Space-resolved R and T measurements Bruker Vertex 80v (spectrometer) Hyperion 2000 (microscope) Wavelength range: 300 nm 16 µm Resolution: 0,07 cm -1 0,7 pm - 1,8 nm Mag.: 15x NA: 0.4 (~23,6 ) Spot: ~(250 µm)²

14 T/R/A-Measurements at different positions Absorption Reflectance Transmitance

15 15 Characterization of single metaatoms

16 16 Self-assembled nanoparticles SEM measurements 11nm Au spheres dimer trimer quadromer

17 Nanoparticles detection methods Min. size of nanoparticle 40 nm 10 nm 5 nm 2.5 nm Dark field microscopy Attenuated total reflectance microscopy Nonlinear signal detection: THG Interferometric optical detection Modulating the sample positions Photothermal imaging (interference contrast and heterodyne detection) 1 7

18 Nanoparticle optical detection by lateral modulation of sample position P exti( x, y0 sin 2 ft) particle oscillates in the focus P ext I( x, y) ext I sin(2 ft) y 2 ext 2 I 2 sin 2 y 2 (2 ft) DC Component at fundamental Frequency (T1) Component at second Harmonic (T2) Phys. Rev. Lett. 93, 2, 2004

19 Experimental setup x z y Illumination: solid state lasers, and white light source Modulation frequency f=860hz Detection: PMT and Lock-in amplifier in phase with modulation of sample.

20 Test measurements Gold colloids with diameters of 20, 40, and 80 nm from British Biocell was mixed in ethanol in ratio of 1:1:1:200 Particles deposited on 160µm cover slip ethanol 20nm 40nm 80nm 200 : 1 : 1 : 1 Image of sample in dark-field microscope 2 0

21 Test measurements Image of the X component Optical mapping of the transmission at λ = 561 nm recorded at fundamental frequency f=860hz.

22 Nano technology: challenges Properties strong interaction of light need strong polarizability high density of free electrons noble metals (Au, Ag) + Al mesoscopic dimensions of structures (~ 100 nm) hierarchical strongly broken symmetries on multiple length scales Challenges needed complex nano-scaled order principles are not compatible with the isotropic, short ranging character of bonding forces in strongly polarizable media (metal bonds) often thermodynamic metastable states (shallow local energetic minimum) or even unstable states (no energetic minimum) practical stabilization of matter by kinetic slow down of conversion towards stable thermodynamic phase (practically long time scales)

23 Nano-Optics technological approaches TOP DOWN EBL Exposure Resist Funct. Layer(s) Substrate BOTTOM UP diblock copolymer unloaded micelle Development loaded micelle Resist Pattern pulling from solution Dry Etching monolayer Removal of Resist oxygen plasma Final Element gold nanostructure

24 Nano-Optics typical top down technologies lithographic techniques Electron Beam Lithography (EBL) Focused Ion Beam milling (FIB) holographic 3D lithography / multi-photon laser polymerization nano-tip-lithography etching techniques deposition techniques sputtering, evaporation Chemical Vapor Deposition (CVD) Molecular Beam Epitaxy (MBE) atomic layer deposition (ALD) replication technologies Nano Imprint Lithographie (NIL) (XUV lithography, roll-to-roll replication) chemical inversion processes for 3D replication in different classes of materials fiber drawing techniques (low productivity reflects the state of these activities - fundamental research)