Crystallization of Glass

Transcription

1 Winter School 2007 Kyoto Laser Patterning of s in T.Komatsu, Nagaoka niversity of Technology, Japan Plan of my talk 1. Basic concept of crystallization in glass 2. What is laser-induced crystallization (LIC)? 3. Patterning and Mechanism of LIC. Key materials in information technology Structure: Inversion Symmetry No second-order order optical nonlinearity No ferroelectric properties Not active in light control SHG / Hybrid Materials Free energy Super-cooled liquid transition Structural relaxation Phase separation lization I or Super-cooled liquid Melt I lization of Nanocrystals / Hybrid Materials RT Tg Tm Liquid Materials design based on glass crystallization T g I : Nucleation rate : growth rate Control T m Microstructure design Oriented ceramics Single crystals Devices

2 Transparent nanocrystallized glass 15K2O.15Nb2O5.70TeO2 Nanocrystals (~20nm) K[Nb 1/3 Te 2/3 ] 2 O 4.8 Distorted fluorite-type SH intensity (arb. units) Light wave conversion SHG Angle of incidence (degree) Highly oriented crystallized glass BaO-TiO TiO2-GeO2 glasses Ba2TiGe TiGe2O8 crystal 532 nm d:~20 pm/v 1064 nm Light transmit c-axis (polarization) fiber Ti:LiNbO3 Single crystal Tunable Optical Switch Nonlinear optical crystals: SHG Ferroelectrics: Electro-optic optic effect Electrode On, OFF LiNbO3 ON 90 o OFF New Tunable Optical Switch using line Electrode On, OFF fiber We need a technique available for spatially selected crystallization of glass Telecommunication network system Network (glass) Link High speed Huge capacity WDM Amplification Node Slow switching rate O/E/O O/O/O Laser-induced micro-fabrication in glass 1) Hill et al. (1978): Ge-dope SiO2 fiber + λ=488nm Refractive index change 2) Osterberg et al. (1986): Ge-dope SiO2 fiber + λ=1064nm Second harmonic generation (SHG) New challenge in glass science and technology : SiO2, Photosensitive glass Laser: Excimer, Femtosecond Phenomenon: Refractive index change, hole Local anisotropy Patterning and Designing of lization? 12

3 Laser crystallization (LC) in a-sia Engineering High-quality poly-si TFT Chalcogenide glasses: DVD Ge2Sb2Te5 LD laser: amorphous-crystal transformation (nano-pulse) Laser Irradiation in SiO2 glass V excimer laser a-si LC technique Mobility Ge Poly-crystalline Si amorphous crystal A.V.Kolobov et al. Nature Mater. 3 (2004) 703 amorphous Ref. A.T.Voutsas, Appl. Sur. Sci (2003) KrF excimer laser: λ=248 nm Femtosecond pulsed laser: λ=800 nm K.Sugioka, Ceramics 38(2003)880. K.Miura et al. Appl.. Phys. Lett., 71(1997)3329. Refractive index change, Abration,, Crack, growth rate maxmax in oxide glasses V.M.Fokin et al., J. Non-Cryst Cryst.. Solids 351 (2005) 789. Li2O.2SiO O.2SiO2 70 μm/s Na2O.2SiO O.2SiO2 CaO.MgO.2SiO2 (Diopside 2MgO.2Al2O3.5SiO.5SiO2 (Cordierite) 2BaO.TiO2.2SiO.2SiO2 (Fresnoite 1 μm/s Diopside) ) 230 μm/s 9 μm/s Fresnoite) ) 430 μm/s ~1 μs s for ~ 1nm growth CW YAG laser crystallization Temp. laser irradiated spot Distance lization temp. transition temp. Heat dissipation Nano-pulse YAG laser no crystallization Lattice vibration (~10 13 /s) : ~femtosecond Heat dissipation R.Sato, Y.Benino, T.Fujiwara, T.Komatsu, J. Non-Cryst Cryst.. Solids 289 (2001) 228. BaO-Sm2O3-TeO2 Sm2Te Te6O15 cw Nd:YAG λ=1064 nm 15 crystals

4 Rare-earth earth Atom Heat Processing 6 F 9/2 1 Absorption of 1064 nm (Nd:YAG( Laser) 2 Non-radiative relaxation: Thermal heating CW Nd:YAG laser irradiation 1 Sm H 5/2 Absorbance Sm2O3.35Bi.35Bi2O3.55B2O nm 20 o C 7.95cm o C 7.32cm o C 7.32cm Wavelength (nm) Heater plate 1064 nm YAG laser Laser power: P=0.6 ~ 1.0 W Scanning speed: S=1 ~ 10 μm/s Sm2O3-Bi Bi2O3-B2O3 glass SmxBi Transition metal atom heat processing α(1064nm)=6.0 cm -1 T g =670 o C T x =780 o C SHG High orientation c 300 μm

5 I or 1 Tg Super-cooled liquid I Melt Tm Ostwald-Miers range 2 1: sual crystallization in electric furnace 2: Laser-induced crystallization New challenge in nucleation and crystal growth science 25 Homogeneous crystal growth 1. Nucleation should be avoided. 2. Matching of crystal growth rate and laser scanning speeds would be necessary I or Super-cooled liquid I OM Melt Tg T()* T(I)* Tm composition Laser-irradiated condition Tm T(I)* T()* Tg Center of laser irradiation D: size of crystal D Distance 27 Cross-section section of crystal line Patterning of crystals in glass Sm2O3-MoO MoO3-B2O3 glasses S=10μm/s β -Sm2(MoO4)3 A Laser Surface B Heated region Narrow Deep growth front Morphology? Kinetics? Interface? distribution? 1. Rare-earth/transition earth/transition metal atom heat processing 2. Bending crystal lines 3. Quality of crystal lines and light transmission Sm2O3-Bi Bi2O3-B2O3 SmxBi Sm2O3-BaO BaO-B2O3 β-bab2o4 Li2O-Nb Nb2O5-SiO2 LiNbO3 SiO2-Al Al2O3-CaO-NaF-CaF2 CaF2 Li2O-FeO FeO-Nb2O5-P2O5 LiFePO4

6 0.9 W 0.8 W 10Sm2O3.35Bi.35Bi2O3.55B2O3 Tg=474 o C, Tx=574 o C Sm2O3-Bi Bi2O3-B2O3 glass YAG laser Power: 0.66W Scanning speed: 10μm/s SmxBi Electric Furnace Surface crystallized glass Bending / Quality of crystal lines 8Sm2O3.37Bi.37Bi2O3.55B2O3 glass 0.66 W SmxBi Temp. >> Tx 60μm SmxBi 0.6 W 50μm Temp. < Tx Refractive index change Random orientation Polarization optical microscopy 50 μm 8Sm2O3-37Bi 37Bi2O3-55B2O3 glass SmxBi P=0.9 W S=4 μm/s Second scan Sm2O3-Bi2O3-B2O3 glass SmxBi CW Nd:YAG laser with λ=1064nm P=0.9W, S=5μm/s Critical angle for total reflection n Δn (%) 5.43 θ MAX 36 λ=632.8 nm First scan θ

7 Polarized micro-raman scattering spectra Smx Same crystal orientation y(zz)y y Incident Raman laser scattering light z Gradual change in the crystal structure Polarization direction of incident laser x y Laser scanning direction 10Sm2O3.40BaO.50B.40BaO.50B2O3 Electric furnace: 760 o C, 1h β-bab2o4 YAG laser irradiation Surface: (110) orientation c β-bab2o4 crystal line (110) 15 lines c-axis Single crystal line? c-axis Polycrystal line θ (deg.) Micro-Raman spectra: β-bab2o4 y-cut β-bab2o4

8 Azimuthal dependence of SHG θ Linearly polarized YAG laser: 1064 nm Sample IR cut filter Stage SH intensity: 532 nm as a function of θ β-bab 2 O 4 Trigonal system R3c (a= nm,, c= nm) Stacking of Planar B3O6B rings in c-axis Origin of optical nonlinearity: polarizability in B3O6 B Electric field in incident light B3O6 unit Strong SHG no SHG at θ=0, 180 o at θ=90, 270 o θ: angle between E and B3O6 plane Single crystal line: strong θ dependence E SHG microscope observations β-bab2o4 line Intensity (arb. units) Azimuthal dependence of SHG β-bab2o4 crystal lines 10Sm 2O 3 40BaO 50B 2O 3 10Dy 2O 3 45BaO 45B 2O 3 Y-cut β-bab2o4 single crystal Intensity (arb. units) Y-cut β-bab2o4 Sm2O3-BaO BaO-B2O3 β-bab2o4 c-axis c Surface: (110) orientation β-bab2o Rotation angle (deg.) Rotation angle (deg.) c c-axis (110) B3O6 unit Single crystal line!!

9 LiNbO 3 0.5CuO-40Li 2 O-32Nb 2 O 5-28SiO 2 0.3wt%CuO-Li 2 O-Nb 2 O 5 -SiO 2 P = 1.3 W Laser irradiation S = 7 μms Yb: : Fiber laser(λ = 1080 nm) -1 Scanning direction Polarized micro-raman spectra LiNbO 3 crystal Y-cut single crystal Width: 5μm High orientation: c-axis c growth SHG from crystal line H-H 90 E In E out P=1.7 W, S=2 μm/s H-H 45 H-H 0 I 2w (H-H) = A d 33 cos 4 θ Oxyfluoride glass: fluoride crystal 43SiO 2-22Al 2 O 3-5CaO-13NaF-17CaF 2-3NiO T g =573 o C, T p =617 o C h~1 μm, W~3 μm Intensity (arb.units) D(CaF 2 ) 50 crystal lines (220) 15 nm glass E In E out Z X Y CaF θ (degree)

10 +0.5ErF 3 lization of oxyfluoride glass Laser-induced crystallization 4 E(CaF S 3/2 4 I 2 ) 15/2 λ ex =488 nm Oxyfluoride glass Oxyfluoride base glass Intensity (arb. units) 2 H 11/2 4 I 15/2 Line part I or I (fluoride) (fluoride) I (oxide) (oxide) part Laser irradiated region Fluoride nanocrystal Wavelength (nm) Tg Tm Li2O-FeO FeO-Nb2O5-P2O5 glass Nd:YAG laser: P=0.07 W, S=10 μm/s Highly oriented LiFePO4 crystals Combination of Laser irradiation and simple chemical etching Refractive index change Molar volume Laser irradiated P=0.8 W P=0.7 W cooling More open structure Base glass heating Cathode materials for Li-ion ion battery CuO-dope BaO-TiO2-GeO2 glass Laser irradiation with low powers

11 (a) t =10min Patterning: P=0.85 W, S=10 μm/s Etching: 1N HNO3, 35 min 1N HNO3 (b) t =35min -shape groove -groove depth: 3.5 μm Etching lization 15μm Etching rate Refractive index > glass > crystal 61 NiO-doped BaO-TiO2-GeO2 glass Etching of crystal dots P=0.95 W t=60 s Summary Original t=4 min lization of glass + Laser-induced crystallization t=10 min t=18 min Design of / Hybrid Materials line New micro-devices!! 64

12 Laser-induced crystallization Progress in laser technology High power laser ltra short pulse (femtosecond( femtosecond) ) laser Short wavelength laser Conventional technique: everybody can use! High potential in micro-fabrication Spatially selected Direct and non-contact process Fast and easily automated Patterning of crystals by laser irradiation 1. Factors system glass compositions Laser irradiation conditions Laser power Laser scanning speed 2. Mechanism Laser-induced nucleation Very rapid crystal growth: 1 ~ 10 μm/s Large temperature gradient in laser irradiated spot (region): large diffusions