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16. Luminescence of black silicon fabricated by high-repetition rate femtosecond laser pulses.

Author

Chen, Tao, Si, Jinhai, Hou, Xun, Kanehira, Shingo, Miura, Kiyotaka, and Hirao, Kazuyuki

Subjects
PHOTOLUMINESCENCE, SILICON, FEMTOSECOND lasers, IRRADIATION, LASERS
Abstract

We studied the photoluminescence (PL) from black silicon that was fabricated using an 800 nm, 250 kHz femtosecond laser in air. By changing the scan velocity and the fluence of the femtosecond laser, the formation of the PL band between the orange (600 nm) and red bands (near 680 nm) could be controlled. The red band PL from the photoinduced microstructures on the black silicon was observed even without annealing due to the thermal accumulation of high-repetition rate femtosecond laser pulses. The orange band PL was easily quenched under 532 nm cw laser irradiation, whereas the red band PL was more stable; this can be attributed to 'defect luminescence' and 'quantum confinement', respectively. [ABSTRACT FROM AUTHOR]

Published
2011
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17. Formation of a Cr3+-rich luminescent thin phase along a grain boundary of alpha-Al2O3

Author

Kezuka, Yuki, Tochigi, Eita, Shibata, Naoya, Moon, Chiwon, Kanehira, Shingo, Hirao, Kazuyuki, and Ikuhara, Yuichi

Subjects
Bicrystal, Luminescence, Alumina, Ruby, Grain boundary, Transmission electron microscopy
Abstract

An α-Al2O3 bicrystal doped with Cr3+ was fabricated by diffusion bonding at high temperatures. It was found that a ruby phase with approximately 200 nm thickness was formed along the grain boundary. This thin phase shows Cr3+:Al2O3-induced luminescence, confirmed by confocal micro-luminescence spectroscopy.

Published
2011

20. Morphology change from nanocrack into periodic pore array formed by femtosecond laser pulses

Author

Moon, Chiwon, Kanehira, Shingo, Miura, Kiyotaka, Tochigi, Eita, Shibata, Naoya, Ikuhara, Yuichi, Hirao, Kazuyuki, Moon, Chiwon, Kanehira, Shingo, Miura, Kiyotaka, Tochigi, Eita, Shibata, Naoya, Ikuhara, Yuichi, and Hirao, Kazuyuki

Abstract

Defects inside single crystals are an important concern because they directly affect the physical or chemical properties of the material, especially in sapphire used as substrates for semiconductors. We have investigated the thermally activated transformations of nanometer-scale cracks and phase transitions inside sapphire by femtosecond laser irradiation and successive heat treatments. The nanocracks transformed into periodic arrays of pores and dislocations that aligned along the {1Ī02} planes after heat treatments above 1300 °C. The amorphous phase at the focal point recovered into the initial single crystalline phase after the heat treatments. Our study provides useful information on the recovery behavior of nanometer-scale defects in a single crystal.

Published
2011

21. Morphology change from nanocrack into periodic pore array formed by femtosecond laser pulses

Author

60418762, 90127126, Moon, Chiwon, Kanehira, Shingo, Miura, Kiyotaka, Tochigi, Eita, Shibata, Naoya, Ikuhara, Yuichi, Hirao, Kazuyuki, 60418762, 90127126, Moon, Chiwon, Kanehira, Shingo, Miura, Kiyotaka, Tochigi, Eita, Shibata, Naoya, Ikuhara, Yuichi, and Hirao, Kazuyuki

Abstract

Defects inside single crystals are an important concern because they directly affect the physical or chemical properties of the material, especially in sapphire used as substrates for semiconductors. We have investigated the thermally activated transformations of nanometer-scale cracks and phase transitions inside sapphire by femtosecond laser irradiation and successive heat treatments. The nanocracks transformed into periodic arrays of pores and dislocations that aligned along the {1Ī02} planes after heat treatments above 1300 °C. The amorphous phase at the focal point recovered into the initial single crystalline phase after the heat treatments. Our study provides useful information on the recovery behavior of nanometer-scale defects in a single crystal.

Published
2011

22. Luminescence of black silicon fabricated by high-repetition rate femtosecond laser pulses

Author

60418762, 90127126, Chen, Tao, Si, Jinhai, Hou, Xun, Kanehira, Shingo, Miura, Kiyotaka, Hirao, Kazuyuki, 60418762, 90127126, Chen, Tao, Si, Jinhai, Hou, Xun, Kanehira, Shingo, Miura, Kiyotaka, and Hirao, Kazuyuki

Abstract

We studied the photoluminescence (PL) from black silicon that was fabricated using an 800 nm, 250 kHz femtosecond laser in air. By changing the scan velocity and the fluence of the femtosecond laser, the formation of the PL band between the orange (600 nm) and red bands (near 680 nm) could be controlled. The red band PL from the photoinduced microstructures on the black silicon was observed even without annealing due to the thermal accumulation of high-repetition rate femtosecond laser pulses. The orange band PL was easily quenched under 532 nm cw laser irradiation, whereas the red band PL was more stable; this can be attributed to "defect luminescence" and "quantum confinement", respectively.

Published
2011

24. Space-selective phase separation inside a glass by controlling compositional distribution with femtosecond-laser irradiation

Author

60704757, 60418762, 90402958, 50402962, 40378807, 90127126, Shimizu, Masahiro, Miura, Kiyotaka, Sakakura, Masaaki, Nishi, Masayuki, Shimotsuma, Yasuhiko, Kanehira, Shingo, Nakaya, Takayuki, Hirao, Kazuyuki, 60704757, 60418762, 90402958, 50402962, 40378807, 90127126, Shimizu, Masahiro, Miura, Kiyotaka, Sakakura, Masaaki, Nishi, Masayuki, Shimotsuma, Yasuhiko, Kanehira, Shingo, Nakaya, Takayuki, and Hirao, Kazuyuki

Published
2010

25. Phase control of iron silicides using femtosecond laser irradiation

Author

40378807, 60418762, 90127126, Kanehira, Shingo, Sakakura, Masaaki, Shimotsuma, Yasuhiko, Eida, Masaaki, Miura, Kiyotaka, Hirao, Kazuyuki, 40378807, 60418762, 90127126, Kanehira, Shingo, Sakakura, Masaaki, Shimotsuma, Yasuhiko, Eida, Masaaki, Miura, Kiyotaka, and Hirao, Kazuyuki

Published
2010

26. Crack Propagation in a Ruby Single Crystal by Femtosecond Laser Irradiation

Author

Moon, Chiwon, Kanehira, Shingo, Nishi, Masayuki, Miura, Kiyotaka, Nakaya, Takayuki, Tochigi, Eita, Shibata, Naoya, Ikuhara, Yuichi, Hirao, Kazuyuki, Moon, Chiwon, Kanehira, Shingo, Nishi, Masayuki, Miura, Kiyotaka, Nakaya, Takayuki, Tochigi, Eita, Shibata, Naoya, Ikuhara, Yuichi, and Hirao, Kazuyuki

Published
2009

27. Crack Propagation in a Ruby Single Crystal by Femtosecond Laser Irradiation

Author

50402962, 60418762, 90127126, Moon, Chiwon, Kanehira, Shingo, Nishi, Masayuki, Miura, Kiyotaka, Nakaya, Takayuki, Tochigi, Eita, Shibata, Naoya, Ikuhara, Yuichi, Hirao, Kazuyuki, 50402962, 60418762, 90127126, Moon, Chiwon, Kanehira, Shingo, Nishi, Masayuki, Miura, Kiyotaka, Nakaya, Takayuki, Tochigi, Eita, Shibata, Naoya, Ikuhara, Yuichi, and Hirao, Kazuyuki

Published
2009

30. Photoinduced microchannels inside silicon by femtosecond pulses

Author

60418762, 90127126, Chen, Tao, Si, Jinhai, Hou, Xun, Kanehira, Shingo, Miura, Kiyotaka, Hirao, Kazuyuki, 60418762, 90127126, Chen, Tao, Si, Jinhai, Hou, Xun, Kanehira, Shingo, Miura, Kiyotaka, and Hirao, Kazuyuki

Abstract

We reported on the fabrication of microchannels in the interior of silicon wafers using a femtosecond laser of 800 nm wavelength, which was in the absorption region of silicon. The scanning electron micrographs showed that microchannels were induced inside the silicon wafer when the femtosecond laser beam was focused inside the wafer. The aspect ratio of the microchannel cross section decreased with the increase in scan velocity of the laser. The formation of the photoinduced microchannels probably resulted from the microexplosions due to both the linear absorption and avalanche ionization.

Published
2008

31. Ion exchange in glass using femtosecond laser irradiation

Author

60418762, 90127126, Kanehira, Shingo, Miura, Kiyotaka, Hirao, Kazuyuki, 60418762, 90127126, Kanehira, Shingo, Miura, Kiyotaka, and Hirao, Kazuyuki

Abstract

We explain the occurrence of ion exchange and an index profile around the focal point inside a commercial crown glass formed by femtosecond laser irradiation. The index profile in the photoinduced area has a ring-shaped pattern, which indicates that local densification occurred in the glass. An irregular surface reflecting the density distribution is formed around the focal point by dry etching process using a focused ion beam. By the irradiation of femtosecond laser pulses, the effect of ion exchange between the focal point and the surrounding area is also observed in the area in which local densification occurred.

Published
2008

33. Formation of Si structure in glass with a femtosecond laser

Author

60418762, 90127126, 40378807, 90402958, Miura, Kiyotaka, Hirao, Kazuyuki, Shimotsuma, Yasuhiko, Sakakura, Masaaki, Kanehira, Shingo, 60418762, 90127126, 40378807, 90402958, Miura, Kiyotaka, Hirao, Kazuyuki, Shimotsuma, Yasuhiko, Sakakura, Masaaki, and Kanehira, Shingo

Published
2008

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