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Surface study of nano-template anodic porous alumina pre-irradiated by ArF laser
Radiation Measurements 44 (2009) 1130–1133
Contents lists available at ScienceDirect
Radiation Measurements journal homepage: www.elsevier.com/locate/radmeas
Surface study of nano-template anodic porous alumina pre-irradiated by ArF laser B. Jaleh a, *, S. Saramad b, M. Farshchi-Tabrizi a, c a
Physics Department, Bu- Ali Sina University, Postal code 65174, Hamedan, Iran Physics Department, Amirkabir University of Technology (Tehran Polytechnic), P.O. Box. 15875-4413, Tehran, Iran c Max-Plank Institute for polymer Research, 55128 Mainz, Germany b
a r t i c l e i n f o
a b s t r a c t
Article history: Received 14 October 2008 Received in revised form 21 October 2009 Accepted 22 October 2009
Nano-porous alumina membranes have widely used as matrix for the fabrication of nanomaterials for many applications including quantum-dot arrays, magnetic storage devices and composites for catalysis, due to their remarkable hardness, thermal and anti corrupted stability, uniform pore size and high pore density. In this experiment three sets of aluminum samples were chosen for fabrication nano-porous anodic alumina. One set has select for laser cleaning before chemical treatment and the two others with and without chemical treatment without laser irradiation. Anodic aluminum oxide (AAO) films were characterized with Scanning Electron Microscope (SEM) and Atomic Force Microscope (AFM) micrograph and the SEM results were analyzed by Linear-Angular Fast Fourier Transform (LA-FFT) technique to investigate the arrangement and ordering of pores. According to these results the laser irradiated sample has much better regularity in comparison with the usual one. Ó 2009 Elsevier Ltd. All rights reserved.
Keywords: Alumina membranes ArF laser Fast fourier transform Nano-porous
1. Introduction As well-known self assembly nano-template anodic porous alumina (Al2O3) membranes have been intensively studied over the last five decades (Lei et al., 2007; Jagminas et al., 2003). Recently, nano-porous anodic aluminum oxide (AAO) with a hexagonal arrangement of monodisperse nano-pores with electrochemical method has been widely used in the fabrication of non-materials and nanostructures. This trend originated from the discovery of self-ordered alumina membranes (Masuda and Fukuda, 1995). By filling the pores of the AAO, arrays of aligned nanowires or nanotubes uniform in diameter and length, are obtained reproducibly and economically. Different steps must be performed to produce highly ordered porous anodic alumina films, such as heat treatment, electro-polishing, one or multi-step anodizing. Self-organization of anodic alumina has been mostly achieved by two-step anodizing after electro-polishing. The best self-ordering voltages have been found to be 25, 40 and 195 V, when anodizing is performed in sulfuric, oxalic, and phosphoric acids, respectively, within a range of concentration and temperature of the electrolytes. Polishing and dissolving away the oxide film after each anodizing step are key parameters that can strongly affect the arrangement of nano-pores and ordered domains.
* Corresponding author. Tel.: þ98 9122114707; fax: þ98 8118280440. E-mail address: [email protected] (B. Jaleh). 1350-4487/$ – see front matter Ó 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.radmeas.2009.10.092
At the beginning of first step of anodizing process, the pores nucleate at almost random positions, i.e., varied surface defects. Then in a chemical process the alumina layer must be removed during a long period of time without damaging the aluminum substrate. The remaining periodic concave patterns on the aluminum substrate act as self-assembled masks for the second anodizing process and the pore growth accurately occurred on the concave pattern created during the first step of anodizing. The anodized pure aluminum foils have highly ordered hexagonally packed nano-pore arrays with central, cylindrical, uniformly size holes ranging from 4 to 200 nm in diameter. The pore diameter in such membrane could be adjusted by changing the experimental conditions. Since, any excessive particle can directly disrupt the nucleation of the pores and affect the self-ordering of the structure, complete removal of airborne particle contamination and monolayer residuals from surface for microelectronics and other particlesensitive applications is a critical and exacting problem facing manufacturing engineers. In this experiment, organic residues, films, particles, and other low density contaminants are removed with excimer laser, without harsh chemical or plasma treatment and then the LA-FFT technique is applied to SEM micrographs to clarify the degree of ordering of the pores. The results reveal that different nano-scale morphologies obtained by specific laser irradiation pretreatments can have a significant effect on the self-ordering of pores in anodic alumina.
B. Jaleh et al. / Radiation Measurements 44 (2009) 1130–1133
1131
Fig. 1. Ablation depth versus laser fluence for Al.
2. The physics of interaction of laser with surface Removal of extremely small particulates, bound tightly to wafer surfaces, requires 100 000 psi water jets to dislodge. Ablation can be one or a mix of two processes: ‘‘photothermal’’ and ‘‘photochemical’’. A photochemical or electronic process is often referred to as a non-thermal process because the removal of material is caused by a direct breaking of atomic bonds as energy is absorbed. In contrast, the absorbed laser energy is converted to lattice vibrational energy (thermal) to melt and vaporize the material in a photothermal process. To directly break atomic bonding, the intensity of the laser beam should be higher than a threshold value, which is mainly dependant on the material to be ablated and the wavelength of the laser (Elliot, 1995). For example, when the thermal diffusion length of the metal for 30 ns pulses is in micrometer range, the laser beam induces melting and vaporizing of the material, by which liquid metal can be driven out of the bore under the force of vapor pressure. The expulsion of liquid material is clearly visible by the ‘‘frozen’’ melt at the edge of ablation area (Basting and Marowsky, 2005). For 193 nm ArF laser, aluminum absorption is approximately 1.3 106 cm1, reflectivity is approximately 90%, so aluminum is only partially planarized with 3 J/cm2 and full fluence of 10 J/cm2 is needed to fully planarize the layer (Elliot, 1995). Both the photothermal and photochemical processes liberate molecular-sized material from the surface. The two processes can occur in varying degrees of combination in micromachining that uses high-intensity excimer lasers (Duley, 1996). At intensities below the ablation threshold, the absorbed energy heats the substrate and raises the substrate temperature higher than its boiling or sublimation point. Consequently, the material begins to liberate. So excimer lasers have been demonstrated as substitute for conventional cleaning. Surface cleaning is critical because of its impact on product quality and manufacturing yields. Contamination and process-related defects that can be reduced by cleaning account for over 20% of all process defects. Particles below 1 mm in size are very strongly adhered to surfaces by Van der Waals, capillary force and static forces. These particles are not easily removed by mechanical or chemical means. The mechanism for removal of particulates is intense absorption of UV photons by the particles, followed by expansion of the particle. The rapid acceleration of particle is the result of atomic vibration and rotational excitation caused by the intense UV absorption. The heat produced by the pulsed laser exposure drives the reaction. Expansion is followed by acceleration and expulsion of the particle away from the surface. Many types of particles can be ejected by laser irradiating
Fig. 2. AFM images of AAOs which anodized at the same conditions (a) anodizing with electro-polishing; (b) anodizing with laser cleaning before electro-polishing.
normal to the surface on which they reside. This reaction occurs without melting or damage to the underlying layer. After ejection, the particles slow down rapidly within about 10 mm of the surface (Basting and Marowsky, 2005).
3. Experimental procedure Three sets of aluminum were chosen for fabrication nanoporous anodic alumina. One set has selected for laser cleaning before chemical treatment and the two others with and without chemical treatment without laser irradiation. Three Pure Al foil specimens 99.95% Al, (0.3 mm thick, Merck) were annealed at 500 C for 75 min. The oxide layer of specimens was thinned out, by immersing in H3PO4 and H2CrO4 (6% wt and 1.8% wt respectively) aqueous solution at 70 C for 40 min. The laser exposure setup in air consists of a homogenizer and an adjustable fine exposure mount. The homogenizer is used to flatten radial distribution to improve the beam quality and spatial uniformity. The target is an Al sample with 99.95% purity. The 193 nm excimer laser (Lambda PhysikÔ, LPX 210) with 400 mJ/ pulse and 15 ns pulse duration was used at 1–10 Hz pulse repetition rate. Five laser pulses with width of 15 ns and fluence of 0.15 J/cm2 per pulse is used for cleaning and removing the particles from the first sample. For the first sample after laser irradiation and for the second sample (non-irradiated one), the electro-polishing process was carried out in an electrolyte of HClO4-C2H5OH (1:4 V/V) at 35 V and 6 C for 1 min, which is the optimum electro-polishing voltage for our experimental condition (Rahimi et al., 2008). Procedure for the three specimens was followed by first step of anodizing at 40 V in 0.3 M oxalic acid for 4 h at 18 C. The first formed oxide layer was removed by hot-dipping the specimens in H3PO4 and H2CrO4 (6% wt and 1.8% wt respectively) aqueous solution at 70 C for 40 min. AAOs were obtained by repeating the anodizing process at the same solution and temperature for 200 min as second step. The ordered nano-pore AAOs were
1132
B. Jaleh et al. / Radiation Measurements 44 (2009) 1130–1133
Fig. 3. SEM images of AAOs which anodized at the same conditions (a) Anodizing without electro-polishing; (b) anodizing with electro-polishing; (c) anodizing with laser cleaning before electro-polishing.
examined by SEM (CamScan MV2300) and AFM (Nanowizard, JPK, Germany) to study the surface conditions of different samples. 4. Results and discussions In this experiment we studied the laser exposure at different fluence. The information on threshold fluence for ablation can also be extracted from the experimental data. As shown in Fig. 1, ablation depth (mm/pulse) in terms of fluence can be describes with a linear relation. The corresponding fluence at zero ablation depth
is the threshold fluence. So, for laser cleaning, 150 mJ/cm2 fluence will be sufficient. By increasing the laser fluence higher than 280 mJ/cm2 the aluminum is ablated and important damages will be induced on the surface. The AFM image of the sample before the laser treatment (Fig. 2(a)), shows a large non-uniformity. But the laser irradiated sample (Fig. 2 (b)) has much better regularity in pore arrangement. Since the visual examination of the surface is only relative, LA-FFT technique is developed based on MATLAB software to clarify the degree of ordering of the pores. Moreover, we applied this
Fig. 4. FFT images of SEM micrographs of AAOs which anodized at the same conditions (a) anodizing without electro-polishing; (b) anodizing with electro-polishing; (c) anodizing with laser cleaning before electro-polishing; (d), (e), (f) linear FFT pattern obtained from FFT images of SEM micrographs of AAOs of (a), (b), (c).
B. Jaleh et al. / Radiation Measurements 44 (2009) 1130–1133
technique to large areas of the sample including a few domains, instead of small ordered areas within the domains, which provides information about the domain size in addition to the ordering degrees and therefore, makes the result more trustable. The two dimensional FFT images of SEM images in Fig. 3 are shown in Fig. 4(a)–(c). Each point in FFT image represents an intensity magnitude and also for each point there is a correspondent point respect to the center of FFT image (there is 180 symmetry in FFT). As a second step, points with magnitudes from 25 to 100% of maximum intensity are calculated and plotted in polar coordinate, which is called LA-FFT pattern (Fig. 4(d)–(f)). Each line in this pattern is obtained by connecting each pair of FFT intensity magnitudes; and the whole angles are calculated respect to the line connected two points which have maximum intensity (pair of maximum FFT intensity magnitude). Decision on the range of percentage was based on comparison the results obtained from different percents of maximum intensity magnitudes. Derived from this method, the highest ordering of nano-pores is signified as three lines or three groups of overlapped lines having the angles of 60 respects to each other. On the contrary, the scattered linear pattern attributes disorder. As expected, photochemical ablation sample in comparison to non electro-polished one has better regularity. This regularity is reflected in Fig. 4(e) in three distinct groups having the angles of 60 respects to each other with definite angle width. These three distinct groups are not clear in Fig. 4(d), because the three main lines related to each domain are distributed in different angles, which shows the existence of more different domains in this sample. According to these results, since the laser irradiated one before electro-polishing (Fig. 4(f)) has smaller angle width in
comparison to the non-irradiated (Fig. 4(e)), it has also better regularity.
1133
electro-polished
sample
5. Conclusion This study reveals that different nano-scale morphologies obtained by specific laser irradiation pretreatments can have a significant effect on the self-ordering of pores in anodic alumina. The SEM results were analyzed by LA-FFT technique, to investigate the arrangement and ordering of pores. The results show that laser treatment can improve the regularity of the structure. The ordered arrays of pores obtained with the present process have a wide variety of applications in electronic, optoelectronic, and micromechanical devices. References Basting, D., Marowsky, G., 2005. Excimer Laser Technology. Springer-Verlag, Berlin Heidelberg. Duley, W.W., 1996. UV Lasers: Effects and Applications in Materials Science. Cambridge University, New York. Elliot, D.J.,1995. Ultraviolet Laser Technology and Application. Academic Press, New York. Jagminas, A., Lichusina, S., Kurtinaitiene, M., Selskis, A., 2003. Concentration effect of the solutions for alumina template ac filling by metal arrays. Appl. Surf. Sci. 211,194–202. Lei, Y., Cai, W., Wilde, G., 2007. Highly ordered nanostructures with tunable size, shape and properties: a new way to surface nano-patterning using ultra-thin alumina masks. Progr. Mater. Sci. 52, 465–539. Masuda, H., Fukuda, K., 1995. Ordered metal nanohole arrays made by a two-step replication of honeycomb structures of anodic alumina. Science 268, 1466–1468. Rahimi, M.H., Tabaian, S.H., Hoveyda Marashi, S.P., Amiri, M., Dalaly, M.M., Saramad, S., Ramazani, A., Zolfaghari, A., 2008. The effect of aluminum electropolishing on nano-pores arrangement in anodic alumina membranes. Int. J. Modern. Phys. B 22, 3267–3277.
Contents lists available at ScienceDirect
Radiation Measurements journal homepage: www.elsevier.com/locate/radmeas
Surface study of nano-template anodic porous alumina pre-irradiated by ArF laser B. Jaleh a, *, S. Saramad b, M. Farshchi-Tabrizi a, c a
Physics Department, Bu- Ali Sina University, Postal code 65174, Hamedan, Iran Physics Department, Amirkabir University of Technology (Tehran Polytechnic), P.O. Box. 15875-4413, Tehran, Iran c Max-Plank Institute for polymer Research, 55128 Mainz, Germany b
a r t i c l e i n f o
a b s t r a c t
Article history: Received 14 October 2008 Received in revised form 21 October 2009 Accepted 22 October 2009
Nano-porous alumina membranes have widely used as matrix for the fabrication of nanomaterials for many applications including quantum-dot arrays, magnetic storage devices and composites for catalysis, due to their remarkable hardness, thermal and anti corrupted stability, uniform pore size and high pore density. In this experiment three sets of aluminum samples were chosen for fabrication nano-porous anodic alumina. One set has select for laser cleaning before chemical treatment and the two others with and without chemical treatment without laser irradiation. Anodic aluminum oxide (AAO) films were characterized with Scanning Electron Microscope (SEM) and Atomic Force Microscope (AFM) micrograph and the SEM results were analyzed by Linear-Angular Fast Fourier Transform (LA-FFT) technique to investigate the arrangement and ordering of pores. According to these results the laser irradiated sample has much better regularity in comparison with the usual one. Ó 2009 Elsevier Ltd. All rights reserved.
Keywords: Alumina membranes ArF laser Fast fourier transform Nano-porous
1. Introduction As well-known self assembly nano-template anodic porous alumina (Al2O3) membranes have been intensively studied over the last five decades (Lei et al., 2007; Jagminas et al., 2003). Recently, nano-porous anodic aluminum oxide (AAO) with a hexagonal arrangement of monodisperse nano-pores with electrochemical method has been widely used in the fabrication of non-materials and nanostructures. This trend originated from the discovery of self-ordered alumina membranes (Masuda and Fukuda, 1995). By filling the pores of the AAO, arrays of aligned nanowires or nanotubes uniform in diameter and length, are obtained reproducibly and economically. Different steps must be performed to produce highly ordered porous anodic alumina films, such as heat treatment, electro-polishing, one or multi-step anodizing. Self-organization of anodic alumina has been mostly achieved by two-step anodizing after electro-polishing. The best self-ordering voltages have been found to be 25, 40 and 195 V, when anodizing is performed in sulfuric, oxalic, and phosphoric acids, respectively, within a range of concentration and temperature of the electrolytes. Polishing and dissolving away the oxide film after each anodizing step are key parameters that can strongly affect the arrangement of nano-pores and ordered domains.
* Corresponding author. Tel.: þ98 9122114707; fax: þ98 8118280440. E-mail address: [email protected] (B. Jaleh). 1350-4487/$ – see front matter Ó 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.radmeas.2009.10.092
At the beginning of first step of anodizing process, the pores nucleate at almost random positions, i.e., varied surface defects. Then in a chemical process the alumina layer must be removed during a long period of time without damaging the aluminum substrate. The remaining periodic concave patterns on the aluminum substrate act as self-assembled masks for the second anodizing process and the pore growth accurately occurred on the concave pattern created during the first step of anodizing. The anodized pure aluminum foils have highly ordered hexagonally packed nano-pore arrays with central, cylindrical, uniformly size holes ranging from 4 to 200 nm in diameter. The pore diameter in such membrane could be adjusted by changing the experimental conditions. Since, any excessive particle can directly disrupt the nucleation of the pores and affect the self-ordering of the structure, complete removal of airborne particle contamination and monolayer residuals from surface for microelectronics and other particlesensitive applications is a critical and exacting problem facing manufacturing engineers. In this experiment, organic residues, films, particles, and other low density contaminants are removed with excimer laser, without harsh chemical or plasma treatment and then the LA-FFT technique is applied to SEM micrographs to clarify the degree of ordering of the pores. The results reveal that different nano-scale morphologies obtained by specific laser irradiation pretreatments can have a significant effect on the self-ordering of pores in anodic alumina.
B. Jaleh et al. / Radiation Measurements 44 (2009) 1130–1133
1131
Fig. 1. Ablation depth versus laser fluence for Al.
2. The physics of interaction of laser with surface Removal of extremely small particulates, bound tightly to wafer surfaces, requires 100 000 psi water jets to dislodge. Ablation can be one or a mix of two processes: ‘‘photothermal’’ and ‘‘photochemical’’. A photochemical or electronic process is often referred to as a non-thermal process because the removal of material is caused by a direct breaking of atomic bonds as energy is absorbed. In contrast, the absorbed laser energy is converted to lattice vibrational energy (thermal) to melt and vaporize the material in a photothermal process. To directly break atomic bonding, the intensity of the laser beam should be higher than a threshold value, which is mainly dependant on the material to be ablated and the wavelength of the laser (Elliot, 1995). For example, when the thermal diffusion length of the metal for 30 ns pulses is in micrometer range, the laser beam induces melting and vaporizing of the material, by which liquid metal can be driven out of the bore under the force of vapor pressure. The expulsion of liquid material is clearly visible by the ‘‘frozen’’ melt at the edge of ablation area (Basting and Marowsky, 2005). For 193 nm ArF laser, aluminum absorption is approximately 1.3 106 cm1, reflectivity is approximately 90%, so aluminum is only partially planarized with 3 J/cm2 and full fluence of 10 J/cm2 is needed to fully planarize the layer (Elliot, 1995). Both the photothermal and photochemical processes liberate molecular-sized material from the surface. The two processes can occur in varying degrees of combination in micromachining that uses high-intensity excimer lasers (Duley, 1996). At intensities below the ablation threshold, the absorbed energy heats the substrate and raises the substrate temperature higher than its boiling or sublimation point. Consequently, the material begins to liberate. So excimer lasers have been demonstrated as substitute for conventional cleaning. Surface cleaning is critical because of its impact on product quality and manufacturing yields. Contamination and process-related defects that can be reduced by cleaning account for over 20% of all process defects. Particles below 1 mm in size are very strongly adhered to surfaces by Van der Waals, capillary force and static forces. These particles are not easily removed by mechanical or chemical means. The mechanism for removal of particulates is intense absorption of UV photons by the particles, followed by expansion of the particle. The rapid acceleration of particle is the result of atomic vibration and rotational excitation caused by the intense UV absorption. The heat produced by the pulsed laser exposure drives the reaction. Expansion is followed by acceleration and expulsion of the particle away from the surface. Many types of particles can be ejected by laser irradiating
Fig. 2. AFM images of AAOs which anodized at the same conditions (a) anodizing with electro-polishing; (b) anodizing with laser cleaning before electro-polishing.
normal to the surface on which they reside. This reaction occurs without melting or damage to the underlying layer. After ejection, the particles slow down rapidly within about 10 mm of the surface (Basting and Marowsky, 2005).
3. Experimental procedure Three sets of aluminum were chosen for fabrication nanoporous anodic alumina. One set has selected for laser cleaning before chemical treatment and the two others with and without chemical treatment without laser irradiation. Three Pure Al foil specimens 99.95% Al, (0.3 mm thick, Merck) were annealed at 500 C for 75 min. The oxide layer of specimens was thinned out, by immersing in H3PO4 and H2CrO4 (6% wt and 1.8% wt respectively) aqueous solution at 70 C for 40 min. The laser exposure setup in air consists of a homogenizer and an adjustable fine exposure mount. The homogenizer is used to flatten radial distribution to improve the beam quality and spatial uniformity. The target is an Al sample with 99.95% purity. The 193 nm excimer laser (Lambda PhysikÔ, LPX 210) with 400 mJ/ pulse and 15 ns pulse duration was used at 1–10 Hz pulse repetition rate. Five laser pulses with width of 15 ns and fluence of 0.15 J/cm2 per pulse is used for cleaning and removing the particles from the first sample. For the first sample after laser irradiation and for the second sample (non-irradiated one), the electro-polishing process was carried out in an electrolyte of HClO4-C2H5OH (1:4 V/V) at 35 V and 6 C for 1 min, which is the optimum electro-polishing voltage for our experimental condition (Rahimi et al., 2008). Procedure for the three specimens was followed by first step of anodizing at 40 V in 0.3 M oxalic acid for 4 h at 18 C. The first formed oxide layer was removed by hot-dipping the specimens in H3PO4 and H2CrO4 (6% wt and 1.8% wt respectively) aqueous solution at 70 C for 40 min. AAOs were obtained by repeating the anodizing process at the same solution and temperature for 200 min as second step. The ordered nano-pore AAOs were
1132
B. Jaleh et al. / Radiation Measurements 44 (2009) 1130–1133
Fig. 3. SEM images of AAOs which anodized at the same conditions (a) Anodizing without electro-polishing; (b) anodizing with electro-polishing; (c) anodizing with laser cleaning before electro-polishing.
examined by SEM (CamScan MV2300) and AFM (Nanowizard, JPK, Germany) to study the surface conditions of different samples. 4. Results and discussions In this experiment we studied the laser exposure at different fluence. The information on threshold fluence for ablation can also be extracted from the experimental data. As shown in Fig. 1, ablation depth (mm/pulse) in terms of fluence can be describes with a linear relation. The corresponding fluence at zero ablation depth
is the threshold fluence. So, for laser cleaning, 150 mJ/cm2 fluence will be sufficient. By increasing the laser fluence higher than 280 mJ/cm2 the aluminum is ablated and important damages will be induced on the surface. The AFM image of the sample before the laser treatment (Fig. 2(a)), shows a large non-uniformity. But the laser irradiated sample (Fig. 2 (b)) has much better regularity in pore arrangement. Since the visual examination of the surface is only relative, LA-FFT technique is developed based on MATLAB software to clarify the degree of ordering of the pores. Moreover, we applied this
Fig. 4. FFT images of SEM micrographs of AAOs which anodized at the same conditions (a) anodizing without electro-polishing; (b) anodizing with electro-polishing; (c) anodizing with laser cleaning before electro-polishing; (d), (e), (f) linear FFT pattern obtained from FFT images of SEM micrographs of AAOs of (a), (b), (c).
B. Jaleh et al. / Radiation Measurements 44 (2009) 1130–1133
technique to large areas of the sample including a few domains, instead of small ordered areas within the domains, which provides information about the domain size in addition to the ordering degrees and therefore, makes the result more trustable. The two dimensional FFT images of SEM images in Fig. 3 are shown in Fig. 4(a)–(c). Each point in FFT image represents an intensity magnitude and also for each point there is a correspondent point respect to the center of FFT image (there is 180 symmetry in FFT). As a second step, points with magnitudes from 25 to 100% of maximum intensity are calculated and plotted in polar coordinate, which is called LA-FFT pattern (Fig. 4(d)–(f)). Each line in this pattern is obtained by connecting each pair of FFT intensity magnitudes; and the whole angles are calculated respect to the line connected two points which have maximum intensity (pair of maximum FFT intensity magnitude). Decision on the range of percentage was based on comparison the results obtained from different percents of maximum intensity magnitudes. Derived from this method, the highest ordering of nano-pores is signified as three lines or three groups of overlapped lines having the angles of 60 respects to each other. On the contrary, the scattered linear pattern attributes disorder. As expected, photochemical ablation sample in comparison to non electro-polished one has better regularity. This regularity is reflected in Fig. 4(e) in three distinct groups having the angles of 60 respects to each other with definite angle width. These three distinct groups are not clear in Fig. 4(d), because the three main lines related to each domain are distributed in different angles, which shows the existence of more different domains in this sample. According to these results, since the laser irradiated one before electro-polishing (Fig. 4(f)) has smaller angle width in
comparison to the non-irradiated (Fig. 4(e)), it has also better regularity.
1133
electro-polished
sample
5. Conclusion This study reveals that different nano-scale morphologies obtained by specific laser irradiation pretreatments can have a significant effect on the self-ordering of pores in anodic alumina. The SEM results were analyzed by LA-FFT technique, to investigate the arrangement and ordering of pores. The results show that laser treatment can improve the regularity of the structure. The ordered arrays of pores obtained with the present process have a wide variety of applications in electronic, optoelectronic, and micromechanical devices. References Basting, D., Marowsky, G., 2005. Excimer Laser Technology. Springer-Verlag, Berlin Heidelberg. Duley, W.W., 1996. UV Lasers: Effects and Applications in Materials Science. Cambridge University, New York. Elliot, D.J.,1995. Ultraviolet Laser Technology and Application. Academic Press, New York. Jagminas, A., Lichusina, S., Kurtinaitiene, M., Selskis, A., 2003. Concentration effect of the solutions for alumina template ac filling by metal arrays. Appl. Surf. Sci. 211,194–202. Lei, Y., Cai, W., Wilde, G., 2007. Highly ordered nanostructures with tunable size, shape and properties: a new way to surface nano-patterning using ultra-thin alumina masks. Progr. Mater. Sci. 52, 465–539. Masuda, H., Fukuda, K., 1995. Ordered metal nanohole arrays made by a two-step replication of honeycomb structures of anodic alumina. Science 268, 1466–1468. Rahimi, M.H., Tabaian, S.H., Hoveyda Marashi, S.P., Amiri, M., Dalaly, M.M., Saramad, S., Ramazani, A., Zolfaghari, A., 2008. The effect of aluminum electropolishing on nano-pores arrangement in anodic alumina membranes. Int. J. Modern. Phys. B 22, 3267–3277.