Optical manipulation of semiconductor nanoparticles Ashida lab Nawaki Yohei Contents Introduction Optical fabrication and manipulation Advantage of particles Photo Induced force Resonant force ID: 1032029
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1. Optical fabrication and Optical manipulation of semiconductor nanoparticlesAshida lab. Nawaki Yohei
2. ContentsIntroductionOptical fabrication and manipulationAdvantage of particlesPhoto Induced forceResonant forcePurposePrevious studyMy studyExperimental setupAblation and ManipulationScanning electric microscopyOptical fabricationTablet of GaNCrystal of GaNOptical manipulationZinc oxideSummary1
3. Ablation and manipulation2IntroductionAblation laserManipulation laserAblationFabrication method of particlesusing laser sputteringManipulationTransporting method by the resonant radiation forceSi substrate
4. Low-dimensional structures3IntroductionDOSDOSDOSDOSEEEEBulkThin filmQuantum wireNano particleenhancement of oscillator strength
5. Photo induced force4IntroductionGradient ForceScattering and Absorption pressureOptical axisPhoto induced forceGradient forceScattering and Absorption pressurePhoto induced force: 光誘起力Gradient force: 勾配力Scat. And abs. pressure: 散逸力
6. Gradient force5IntroductionThe force pushing objects to the focal pointStabilization pointElectrical gradientGaussian beam
7. Scattering and Absorption force6IntroductionThe force arising from the momentum transfer from the light powerscatteringabsorption
8. Manipulation in various scale7IntroductionMicroparticleNanoparticleAtom1mm~1nm~1mm~1nmOptical tweezersStructural dependenceNo Structural dependenceLaser coolingNo resonanceresonanceStructural dependenceresonanceorNo resonanceIt’s difficult for optical manipulation.
9. Energy of applied light≠Energy of exciton levelEnergy of applied light=Energy of exciton levelResonant or Non-resonant light8IntroductionNon resonantResonantResonantResonant Ea
10. Enhancement by resonant light9IntroductionRef: T.Iida and H. Ishihara Phys. Rev. Lett. 90, 057403 (2003)Using resonant lightPhoto induced force is drastically enhanced.Numerical calculation example (CuCl)100 times of gravitational acceleration
11. Previous study10PurposeOur group has succeeded manipulation of nanoparticlesWide-gap semiconductorCuClZnOK. Inaba phys.stat.sol. (b)243, No.14, (2006)S. Okamoto master thesis (2011)
12. My study11PurposeGaN bulkGaN particlesManipulated GaN particlesablationmanipulation
13. Fabrication method12Experimental setupNd:YAGTi:sapphireablation lasermanipulation laserwavelength :525nmpulse duration :10ns SHGwavelength :726nmcryostatSi substratesampleback substratefront substrateVacuum state (300K)Superfluid He state (2K)wavelength :718nmpulse duration :100fs
14. Observation method13Experimental setupElectron beamSecondary electronsampleCharacter X-rayCathode LuminescenceSEM measurementCL measurementEnergy Dispersive X-ray SpectrometryScanning electron microscopeScanning electron microscope: 走査型電子顕微鏡Secondary electron: 二次電子Cathode luminescence :電子線励起による発光Character X-ray: 特性X線To analyze elementTo take 2D image
15. Optical fabrication14
16. Gallium Nitride15AblationGaN: 3.4eVcf. ZnSe, SiC, ZnO, CuClGaN has wide controllable range of bandgapwith ternary crystal semiconductor InN, AlN.0.7eV~6.1eVCrystal growth is difficultBlue- and UV-Light emitting diode and laserWide-gap semiconductor
17. Tablet of GaN16AblationPress!PowderTablet
18. SEM images17AblationAblation conditionsVacuum stateNd:YAG power 0.5mJI could fabricate particles...
19. Element analysis18AblationEDS dataGa mapping imageSEM imageNitrogen peak was expected.
20. 19Particles were oxidized.
21. Crystal of GaN20AblationCrystalTablets included many impurity.The reason why is that oxidized particle were fabricated.The surface of powders were oxidized.I used crystal of GaN
22. SEM image21AblationVacuum stateAblation conditionsNd:YAG power :1.5mJ
23. Element analysis22AblationA broken piece by ablationGa mapping imageSEM imageEDS dataNitrogen was observed.
24. Element analysis23AblationFabricated particle by ablationGa mapping imageSEM imageEDS dataNitrogen peak was expected.
25. 24Particles have nitrogen defect.
26. Superfluid Helium condition25AblationSuperfluid HeliumLow temperatureViscosity becomes zero.Resonant energy very sharpSmall destabilizing effectSuitable for optical manipulationThe particles can be cool rapidly.For ablation
27. Crystal of GaN26AblationSuperfluid He stateAblation conditionsNd:YAG power 0.5mJ
28. Crystal of GaN27AblationGa mapping imageSEM imageNitrogen peak was expected. EDS data
29. 28Particles have nitrogen defect.
30. Results29AblationThe particles had nitrogen defect and contained oxygen.Tablet from powder Vacuum condition superfluid He conditionIn such conditionCrystal Vacuum condition superfluid He condition
31. Optical manipulation30
32. Zinc Oxides31manipulationBand-gap energy of ZnO is 3.4eV.Wide-gap semiconductor1mm1 cmPolygonal shape ZnO is very stable material, because It’s oxidation products.
33. Problem of size distribution32manipulationAdvantage of particleDensity of stateSize distributionDensity of state becomes cloudy.Density state become sharply.
34. Pulse laser spectra33manipulationPulse durationPeak energySpectrum width1ps100fs3.38eV3.38eV2meV20meVfs pulse laserps pulse laserResonance radiusunder 100nm radiusspecific radiusY. Saito Master thesis (2009)
35. Decrease of size distribution34manipulationY. Saito Master thesis (2009)fs pulse laserps pulse laserThe Size distribution reduced in response to spectrum width.I try to measure size distribution from spectrum width of photoluminescence.
36. Summary35Optical fabricationI can’t fabricate GaN particlesOptical manipulationThe particles fabricated by ablation have nitrogen defect and contained oxygen.I try to measure size distribution from spectrum width of photoluminescence.
37. Appendix36
38. Photo induced force37AppendixGradient forceRadiation pressureOptical letters vol.11, No. 5, 288 (1986)
39. First experiment38Appendixtransparent latex spheressizematerial0.59, 1.31, 2.68mmCW argon laserl = 0.5145mmw0= 6.2mmPower 19mWThe author measured sphere moved at 26±5mm/secsampleslaserTEM00
40. Laser cooling39
41. Quantum confinement40Appendixa > aba :ドット半径ab :励起子ボーア半径 ドット内に励起子が閉じ込められる2a2abΔE量子サイズ効果によりエネルギーレベルが変化2a弱閉じ込めモデル2a2abab > a強閉じ込めモデル励起子ボーア半径CuClドット半径0.68nm数nm弱閉じ込めモデル励起子の重心運動が量子化