UPORZĄDKOWANE NANOSTRUKTURY UZYSKIWANE NA DRODZE ANODYZACJI ALUMINIUM

Jagiellonian University Department of Physical Chemistry & Electrochemistry Ingardena 3, 30-060 060 Krakow, Poland UPORZĄDKOWANE NANOSTRUKTURY UZYSKIWANE NA DRODZE ANODYZACJI ALUMINIUM Grzegorz D. Sulka

PRESENTATION CONTENTS 1. INTRODUCTION 2. MECHANISM OF AL ANODIZATION 3. STRUCTURAL FEATURES OF ANODIC ALUMINIUM OXIDE (AAO) 4. ANODISING TECHNIQUES 5. ANALYSIS OF DEFECTS IN AAO 6. STRESS INFLUENCE ON AAO 7. RESEARCH PERSPECTIVES

REVOLUTIONARY FORCES

NANOTECHNOLOGY AND NANOSTRUCTURED MATERIALS SiC nanoflowers on Si substrate by CVD VLS growth Ag 2 O nanoparticles by anodizing Quantum corral (blue corral) Fe atoms on Cu (1993) - STM Source: http://www-03. 03.ibm.com/press/us/en/photos..com/press/us/en/photos.wss B.J. Murray et al., Nano Lett., 5 (2005) 2319 GaN nanowire array on Si by MBE Source:Ghim Wei Ho and G.H. Ho, Nanotechnology, 15 (2004) 996 Source: Lorelle Mansfield/NIST

CdSe/ZnS core-shell nanoparticles NANOTECHNOLOGY APPLICATIONS LEDs and flexible displays Labelled breast cancer cells Source: Evident Technologies, www.evidenttech evidenttech.comcom Source: : A.D. Barker, National Cancer Institute Source: Source: : Quantum Dot Corp. Source: Technol. Rev., 109(2) (2006) 78

MACRO AND NANOWORLD

ANODIZATION = CONTROLLED ELECTROLYSIS

NET REACTIONS Cathodic Anodic H O + 2e 2OH + 2 H 2 Al Al 3 + + 3e O2 + 2H2O + 4e 4OH H O + 2e O + 2 2 H 2 Side reactions: 2H2O O2 + 4H + + 4e Overall reactions 3+ 2Al 3H2O Al2O3 + + 6H 2Al 2 + 6OH Al2O3 + 3H O + 6e + 4OH 2H2O + O2 2 2O O2 2SO 2 4 S + 2 O 4e 2 8 + + 2e 4e 2Al 3 2 + 3O Al2O + 6e

ANODIC ALUMINA COATINGS Porous-type coatings Barrier-type coatings Acidic electrolytes, ph < 5 Non limited film thickness Neutral electrolytes, ph = 5-75 Extremely thin and compact dielectric films

POROUS OXIDE COATING Constant current anodising Constant potential anodising

PORE INITIATION Point Defect Model

PORE INITIATION CONDENSATION OF VACANCIES

PORE INITIATION DEFORMATION OF M/O INTERFACE Field-assisted ejection of cations O/E interface M/O interface

PORE INITIATION DEFORMATION OF M/O INTERFACE Uniform film with uniform current distribution Higher current above metal ridges, accompanied by a local Joule heating results in a thicker oxide layer. Simultaneously, the enhanced field-assisted dissolution of oxide tends to flatten the oxide/metal interface Oxide layer grown above the ridges (flaw sites with impurities, scratches) generates a highly localised stress. Cracking of the film and its rapid healing at the high local current density Increasing pore curvature (increasing pore diameter) decreases effective current density across the barrier layer Growth of other pores from other incipient pores is initiated in order to maintain the uniform field strength across the barrier layer

ELEMENTARY PROCESSES STEADY-STATE STATE OXIDE GROWTH The migration process is realised through vacancies inside crystallites

STRUCTURE OF POROUS ANODIC ALUMINA (AAO)

PROPERTIES OF AAO FILMS IMPORTANT FOR NANOTEHNOLOGY ADVANTAGES DISADVANTAGES - Well-defined interpore distance - Close-packed arrangement of cells - High porosity - Simplicity of preparation - Chemical compatibility with organic solvents and aqueous environment - Low mechanical strength - Lack of conductance (barrier layer)

ANODIZED ALUMINIUM DIMENSIONS Interpore distance Interpore distance - D c D = 2 W + D = 1.42 B + c D c 2.5 U p D p W wall thickness (nm) D p pore diameter (nm) B barrier layer thickness (nm) U anodising potential (V)

ANODIZED ALUMINIUM DIMENSIONS Barrier layer Barrier layer thickness - B B 1.0 U

AAO STRUCTURAL FEATUTERS IN VARIOUS ELECTROLYTE Dp 1.08 U D c 2.5 U H 3 PO 4 100 V 200 V H 3 PO 4 100 V 200 V H 2 C 2 O 4 30 V 80 V H 2 C 2 O 4 30 V 80 V H 2 SO 4 15-25 V H 2 SO 4 15-25 V 0 50 100 150 200 250 300 0 100 200 300 400 500 Pore diameter (nm) Interpore distance (nm)

AAO STRUCTURAL FEATUTERS IN VARIOUS ELECTROLYTE SEM 3D SEM 20 wt % H 2 SO 4-8 C, 25 V 0.3 M H 2 C 2 O 4 25 C, 50 V

FABRICATION OF WELL-ORDERED NANOSTRUCTURE ON ANODIZED ALUMINIUM Prepatterned-guided anodization Self-organized two-step anodization

PREPATTERNED-GUDED ANODIZATION Limits of the technique:! limited surface area of the grown nanostructure! time consuming preparation of the mold! high-cost of the mold fabrication

PREPATTERNED-GUDED ANODIZATION AAO array:! Pore diameter: 7 nm! Interpore distance: 13 nm Y. Matsui, K. Nishio,, H. Masuda, Small, 2 (2006) 522-525 525

SELF-ORGANIZED ANODIZATION

SELF-ORGANIZED ANODIZATION Starting material OIM Electropolished Al foil Thickness: 250 µm Purity: 99.997 % SEM

SELF-ORGANIZED ANODIZATION Starting material First step of anodization 20 wt % H 2 SO 4 at 1 C 10 min at 15-25 V

SELF-ORGANIZED ANODIZATION Starting material First step of anodization Oxide removal 6 wt % H 3 PO 4 + 1.8 wt % H 2 CrO 4 60 C, 5-10 min

SELF-ORGANIZED ANODIZATION Starting material First step of anodization Oxide removal Second step of anodization 20 wt % H 2 SO 4 at 8, 1 or 10 C 870 min for 15 V and 45 min for 25 V

SELF-ORGANIZED ANODIZATION 20 wt % H 2 SO 4, 1 C, 21 V Top of AAO Bottom of AAO

SELF-ORGANIZED ANODIZATION He + beam Cross-section of AAO Dissipation diagram

ENHANCED OXIDE DISSOLUTION SEM 3D SEM 20 wt % H 2 SO 4 25 V, V 8 C 25 V, V 10 C

Interpore distance - D c c INTERPORE DISTANCE AND PORE DIAMETER p p Pore diameter - D p D = 2 W + D = 1.42 B + D D = D 2 W = D 1.42 B D c 2.5 U p Dp c 1.08 U c 80 35 70 30 Interpore distance [nm] 60 50 40 30-8 C 20 1 C 10 C 10 1 C, Overflow cell Theoretical, 2.5 nm/v 0 13 15 17 19 21 23 25 27 Pore diameter [nm] 25 20 15-8 C 10 1 C 10 C 5 1 C, Overflow cell Teoretical, 1.08 nm/v 0 13 15 17 19 21 23 25 27 Po te ntial [V] Po te ntial [V]

OVERFLOW CELL

PORE OPENING AND WIDENING Anodization: 0.3 M (COOH) 2, 45 V, 20 o C 40 min 60 min D c = 50 nm 80 min 100 min D c = 66 nm D c = 79 nm

POROSITY AND PORE DENSITY Porosity - α α = 25 2 π α = 10 3 14 n D D p c π 2 D 2 = p 0.907 2 D D p c 2 8 Pore density - n n n = 2 10 3 D 14 2 c 1.85 10 2 U 13 Porosity [%] 20 15 10 5 0 13 15 17 19 21 23 25 27-8 1 10 o C o C o C Pore density [10 10 /cm 2 ] 7 6 5 4 3 2 1 0 10 1 o C o C o C -8 1 o C, Overflow cell 13 15 17 19 21 23 25 27 Pote ntial [V] Pote ntial [V]

CURRENT DENSITY AND POROSITY 60 50-8 1 10 o C o C o C 1000 1 10-8 o C o C o C I [ma/cm 2 ] 40 30 20 ln Ire al [ma/c m 2 ] 100 10 0 13 15 17 19 21 23 25 27 Po te ntial [V] 10 6 8 10 12 14 16 18 20 22 24 Po ro s ity [%] I real = I/α

SELF-ORGANIZED ANODIZATION perfect order (25 V at 8 C, A = 0.25 µm 2 ) SEM 2D FFT 3D SEM FFT Profile 1.6e4 1.4e4 1.2e4 1e4 Arb. units 8000 6000 4000 2000 0 0 0.02 0.04 0.06 Normalized width

SELF-ORGANIZED ANODIZATION defects (25 V at 8 C, A = 1 µm 2 ) SEM 2D FFT 3D SEM 200nm 200nm 0.018 0.016 FFT Profile 0.014 0.012 Arb. units 0.01 8e-3 6e-3 4e-3 2e-3 0 0 10 20 30 40 50 60 70 Normalized width

SELF-ORGANIZED ANODIZATION ( 8 C,, A = 0.34 µm 2 ) 15 V 19 V 25 V 3e-3 3.5e-3 0.012 Arb. units 2.5e-3 2e-3 1.5e-3 1e-3 5e-4 0 10 20 30 40 50 60 Arb. units 3e-3 2.5e-3 2e-3 1.5e-3 1e-3 5e-4 0 10 20 30 40 50 60 Arb. units 0.01 8e-3 6e-3 4e-3 2e-3 0 0 10 20 30 40 50 Normalized width Normalized width Normalized width

SELF-ORGANIZED ANODIZATION (1( 1 C,, A = 0.34 µm 2 ) 15 V 19 V 25 V 4e-3 3.5e-3 3e-3 2.5e-3 0.012 0.01 3e-3 2e-3 8e-3 Arb. units 2.5e-3 2e-3 1.5e-3 Arb. units 1.5e-3 1e-3 Arb. units 6e-3 4e-3 1e-3 5e-4 0 10 20 30 40 50 60 5e-4 0 10 20 30 40 50 2e-3 0 10 20 30 40 50 60 Normalized width Normalized width Normalized width

SELF-ORGANIZED ANODIZATION (10( C,, A = 0.34 µm 2 ) 15 V 19 V 25 V 6e-3 8e-3 5e-3 7e-3 4e-3 6e-3 5e-3 Arb. units 3e-3 2e-3 1e-3 Arb. units 4e-3 3e-3 2e-3 1e-3 0 10 20 30 40 50 0 0 10 20 30 40 50 60 Normalized width Normalized width

SELF-ORGANIZED ANODIZATION spatial order Regularity ratio = H/W 1/2

SPATIAL ORDER AT VARIOUS TEMPERATURES 300 250-8 1 10 o C o C o C H/W1/2 [a.u.] 200 150 100 50 0 13 15 17 19 21 23 25 27 Po te ntial [V]

DEFECTS ANALYSIS - Delanuay triangulations ( 8 C,, 1000 pores) 15 V 19 V 25 V

PERCENTAGE OF DEFECTS Anodising potential [V] Surface area [µm[ 2 ] Percentage of defects [%] - 8 ºC 1 ºC 10 ºC 15 1.24 1.24 30.81 20.87-17 1.32 1.32 29.70 20.43-19 1.48 1.48 30.18 21.15 30.73 21 1.57 1.57 30.06 20.92 29.67 23 1.76 1.76 30.60 20.99 30.50 25 1.76 1.88 9.54 11.70 10.75

DISTRIBUTION DIAGRAMS FOR 15 V interpore distance - 8 o C 1 o C 10 o C Number of pores 500 450 400 350 300 250 200 150 100 50 0 24 258 453 181 59 22 A) -8 o C 29.5 34.5 39.5 44.5 49.5 54.5 59.5 Interpore distance [nm] 3 Number of pores 400 350 300 250 200 150 100 50 0 15 21 54 379 259 215 B) 1 o C 57 40.8 41.5 42.1 42.7 43.3 43.9 44.5 Interpore distance [nm] No pores = 35.03 nm = 3.7 nm

DISTRIBUTION DIAGRAMS FOR 23 V interpore distance - 8 o C 1 o C 10 o C 450 400 422 B) -8 o C 450 400 415 D) 1 o C 450 400 392 F) 10 o C Number of pores 350 300 250 200 150 100 50 0 81 314 134 31 11 7 47.1 51.4 55.7 60 64.3 68.6 72.9 Interpo re dis tance [nm] Number of pores 350 300 250 200 150 100 50 0 17 37 84 284 139 24 59.9 60.3 60.7 61.1 61.5 61.9 62.3 Interpo re dis tance [nm] Number of pores 350 300 250 200 150 100 50 0 3 92 333 125 40 15 43.2 48 52.8 57.6 62.4 67.2 72 Interpo re dis tance [nm] = 30.1 nm = 2.8 nm = 33.6 nm

DISTRIBUTION DIAGRAMS BREADTH Potential [V] Breadth of the distribution diagram [nm] Pore diameter Interpore distance -8 ºC 1 ºC 10 ºC -8 ºC 1 ºC 10 ºC 15 14.0 5.7-35.0 3.7-17 14.0 6.3-34.6 2.4-19 12.6 5.1 13.0 32.9 3.6 35.7 21 10.4 4.9 18.2 32.9 3.1 31.4 23 6.3 4.2 19.6 30.1 2.8 33.6 25 11.5 4.9 15.3 37.0 2.7 34.6

TENSIL STRESS DEVICE 1 pushing screw 2 Al sample 3 stainless steel parts 4 screw 5 ceramic bottom 6 stainless steel plate

HIGH EXTERNAL STRESS - 23 V, 1 C Position B Position between B and C

HIGH EXTERNAL STRESS - 23 V, 1 C Position C

STRESS INFLUENCE ON PORE ORDERING - 23 V, 1 C Position A No stress Sample Low stress Surface area [µm2] Pores number Percent of defects [%] 934 19.2 949 28.3 925 38.1 Non-stressed Low-stressed High stress 1.53 1.53 Highly-stressed Seminarium Zakładu Chemii Fizycznej i Elektrochemii 14 Grudzień 2007

APPLICATIONS OF AAO Biosensors and DNA detection AAO Nanoparticles and their functionalization F. Matsumoto et al., Jpn. J. Appl. Lett., 44 (2005) L355 T. Kondo et al., Electrochem. Solid State Lett., 9 (2006) C189 Nanotubes and drug delivery Carbon nanotubes Nanowires and multifunctional sensors H. Hillebrenner et al.., J. Am. Chem. Soc., 128 (2006) 4236 J. Li et al., Appl. Phys. Lett., 75 (1999) 367 J. Choi et al., Chem. Mater., 15 (2003)( 776 F. Patolsky et al., MRS Bull., February (2007) 142

RESEARCH PERSPECTIVES

CONCLUSIONS The uniformity of the interpore distance and pore diameter increases gradually with increasing anodising potential independently of temperature. t The order in the nanopore arrangement and size of well-ordered domains increase with increasing anodising potential for all studied temperatures. The number of generated defects is independent of the cell potential tial between 15 and 23 V (about 20 % for 1 o C or 30 % for 88 and 10 o C ). The percentage of defect remains constant for all studied temperatures at 25 V (about 10 %). Pore ordering degree depends strongly on an external stress. The ideal triangular lattice of nanopores can be formed by the selfs elf- organized anodization of aluminium at the cell potential of 25 V at 1 o C

Jagiellonian University Department of Physical Chemistry & Electrochemistry Ingardena 3, 30-060 060 Krakow, Poland Co-workers Prof. Victor Moshchalkov, Department of Physics and Astronomy KULeuven, Belgium Dr. Stefan Stroobants, Department of Physics and Astronomy KULeuven, Belgium Prof. Jean-Pierre Celis,, MTM Department, KULEuven, Belgium Prof. Gustaf Borghs,, IMEC, Belgium Prof. Marian Jaskuła Mgr Krzysztof Parkoła Mgr Leszek Zaraska Mgr Wojciech Stępniowski,, Wydział Nowych Technologii i Chemii, WAT, Warszawa Agnieszka Brzózka

Jagiellonian University Department of Physical Chemistry & Electrochemistry Ingardena 3, 30-060 060 Krakow, Poland BIBLIOGRAPHY ON AAO G.D. Sulka,, S. Stroobants,, V. Moshchalkov,, G. Borghs,, J-P. J Celis, J. Electrochem.. Soc., 149(7), D97-D103, D103, (2002). G.D. Sulka,, S. Stroobants,, V. Moshchalkov,, G. Borghs,, J-P. J Celis, Bulletin du Cercle d Etudesd des Métaux, 17(6), P1-1-P1 P1-8, (2002). G.D. Sulka,, S. Stroobants,, V. Moshchalkov,, G. Borghs,, J-P. J Celis, J. Electrochem.. Soc. 151(5), B260-B264, B264, (2004). G.D. Sulka,, K.G. Parkoła, Thin Solid Films, 515(1), 338-345, 345, (2006). G.D. Sulka,, M. Jaskuła, J. Nanosci. Nanotechnol., 6(12), 3803-381 3811,, (2006). G.D. Sulka,, K.G. Parkoła, Electrochim. Acta, 52(5), 1880-1888 1888,, (2007). G.D. Sulka,, V. Moshchalkov,, G. Borghs,, J-P. J Celis, J. Appl. Electrochem., 37(7), 789-797, 797, (2007). G.D. Sulka in: Nanostructured Materials in Electrochemistry, Ali Eftekhari (Ed.), Wiley-VCH 2008, pp. 1-1161 116 G.D. Sulka, L. Zaraska,, W.J. Stępniowski in: Encyclopedia of Nanoscience and Nanotechnology 2 nd Edition,, H.S. Nalwa (Ed.), American Scientific Publishers 2008 in press

Jagiellonian University Department of Physical Chemistry & Electrochemistry Ingardena 3, 30-060 060 Krakow, Poland THANK YOU