Abstract

We present a new class of simple, cheap and stable grayscale photomasks based on the metal-transparent-metallic-oxides (MTMO) systems by laser direct writing in metal films. For obtaining high resolution and grainless grayscale patterns we developed a refinement method of the films, in which the nanometer size effect may play a significant role for the improvement. We propose a layered oxidation model and a grain model for the mechanism of In- and Sn-based MTMO systems. The masks have a wide application wavelength range at least from 350 to 700 nm. Three-dimensional microstructures have been successfully fabricated by using the MTMO grayscale masks.

© 2010 OSA

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  1. J. D. Rogers, A. H. O. Kärkkäinen, T. Tkaczyk, J. T. Rantala, and M. R. Descour, “Realization of refractive microoptics through grayscale lithographic patterning of photosensitive hybrid glass,” Opt. Express 12(7), 1294–1303 (2004).
    [CrossRef] [PubMed]
  2. K. Reimer, H. J. Quenzer, M. Jürss, and B. Wagner, “Micro-optic fabrication using one-level gray-tone lithography,” Proc. SPIE 3008, 279–288 (1997), http://www.mp-cc.de/docs/reiphot.pdf .
    [CrossRef]
  3. M. Christophersen and B. F. Phlips, “Gray-tone lithography using an optical diffuser and a contact aligner,” Appl. Phys. Lett. 92(19), 194102 (2008).
    [CrossRef]
  4. C. M. Waits, A. Modafe, and R. Ghodssi, “Investigation of gray-scale technology for large area 3D siliconMEMS structures,” J. Micromech. Microeng. 13(2), 170–177 (2003).
    [CrossRef]
  5. C. K. Wu, “Method of making high energy beam sensitive glasses,” U.S. Patent, No. 5,078,771 (1992).
  6. G. Gal, “Method for fabricating microlenses,” U.S. Patent No. 5,310,623, 10, (1994).
  7. C. G. Granqvist and A. Hultaker, “Transparent and conducting ITO films: new developments and applications,” Thin Solid Films 411(1), 1–5 (2002).
    [CrossRef]
  8. Z. W. Pan, Z. R. Dai, and Z. L. Wang, “Nanobelts of semiconducting oxides,” Science 291(5510), 1947–1949 (2001).
    [CrossRef] [PubMed]
  9. E. Comini, “Metal oxide nano-crystals for gas sensing,” Anal. Chim. Acta 568(1-2), 28–40 (2006).
    [CrossRef] [PubMed]
  10. B. Krishnamachari, J. McLean, B. Cooper, and J. Sethna, “Gibbs-Thomson formula for small island sizes: Corrections for high vapor densities,” Phys. Rev. B 54(12), 8899–8907 (1996).
    [CrossRef]
  11. E. P. Domashevskaya, O. A. Chuvenkova, V. M. Kashkarov, S. B. Kushev, S. V. Ryabtsev, S. Yu. Turishchev, and Yu. A. Yurakov, “TEM and XANES investigations and optical properties of SnO nanolayers,” Surf. Interface Anal. 38(4), 514–517 (2006).
    [CrossRef]
  12. C. K. Wu, “gray scale all-glass photomasks,” U.S. Patent No. 2005/0053844 A1, (2005).
  13. C. F. Guo, Z. Zhang, S. Cao, and Q. Liu, “Laser direct writing of nanoreliefs in Sn nanofilms,” Opt. Lett. 34(18), 2820–2822 (2009).
    [CrossRef] [PubMed]
  14. C. F. Guo, S. Cao, P. Jiang, Y. Fang, J. Zhang, Y. Fan, Y. Wang, W. Xu, Z. Zhao, and Q. Liu, “Grayscale photomask fabricated by laser direct writing in metallic nano-films,” Opt. Express 17(22), 19981–19987 (2009), http://www.opticsinfobase.org/abstract.cfm?URI=oe-17-22-19981 .
    [CrossRef] [PubMed]

2009 (2)

C. F. Guo, Z. Zhang, S. Cao, and Q. Liu, “Laser direct writing of nanoreliefs in Sn nanofilms,” Opt. Lett. 34(18), 2820–2822 (2009).
[CrossRef] [PubMed]

C. F. Guo, S. Cao, P. Jiang, Y. Fang, J. Zhang, Y. Fan, Y. Wang, W. Xu, Z. Zhao, and Q. Liu, “Grayscale photomask fabricated by laser direct writing in metallic nano-films,” Opt. Express 17(22), 19981–19987 (2009), http://www.opticsinfobase.org/abstract.cfm?URI=oe-17-22-19981 .
[CrossRef] [PubMed]

2008 (1)

M. Christophersen and B. F. Phlips, “Gray-tone lithography using an optical diffuser and a contact aligner,” Appl. Phys. Lett. 92(19), 194102 (2008).
[CrossRef]

2006 (2)

E. Comini, “Metal oxide nano-crystals for gas sensing,” Anal. Chim. Acta 568(1-2), 28–40 (2006).
[CrossRef] [PubMed]

E. P. Domashevskaya, O. A. Chuvenkova, V. M. Kashkarov, S. B. Kushev, S. V. Ryabtsev, S. Yu. Turishchev, and Yu. A. Yurakov, “TEM and XANES investigations and optical properties of SnO nanolayers,” Surf. Interface Anal. 38(4), 514–517 (2006).
[CrossRef]

2004 (1)

J. D. Rogers, A. H. O. Kärkkäinen, T. Tkaczyk, J. T. Rantala, and M. R. Descour, “Realization of refractive microoptics through grayscale lithographic patterning of photosensitive hybrid glass,” Opt. Express 12(7), 1294–1303 (2004).
[CrossRef] [PubMed]

2003 (1)

C. M. Waits, A. Modafe, and R. Ghodssi, “Investigation of gray-scale technology for large area 3D siliconMEMS structures,” J. Micromech. Microeng. 13(2), 170–177 (2003).
[CrossRef]

2002 (1)

C. G. Granqvist and A. Hultaker, “Transparent and conducting ITO films: new developments and applications,” Thin Solid Films 411(1), 1–5 (2002).
[CrossRef]

2001 (1)

Z. W. Pan, Z. R. Dai, and Z. L. Wang, “Nanobelts of semiconducting oxides,” Science 291(5510), 1947–1949 (2001).
[CrossRef] [PubMed]

1997 (1)

K. Reimer, H. J. Quenzer, M. Jürss, and B. Wagner, “Micro-optic fabrication using one-level gray-tone lithography,” Proc. SPIE 3008, 279–288 (1997), http://www.mp-cc.de/docs/reiphot.pdf .
[CrossRef]

1996 (1)

B. Krishnamachari, J. McLean, B. Cooper, and J. Sethna, “Gibbs-Thomson formula for small island sizes: Corrections for high vapor densities,” Phys. Rev. B 54(12), 8899–8907 (1996).
[CrossRef]

Cao, S.

C. F. Guo, Z. Zhang, S. Cao, and Q. Liu, “Laser direct writing of nanoreliefs in Sn nanofilms,” Opt. Lett. 34(18), 2820–2822 (2009).
[CrossRef] [PubMed]

C. F. Guo, S. Cao, P. Jiang, Y. Fang, J. Zhang, Y. Fan, Y. Wang, W. Xu, Z. Zhao, and Q. Liu, “Grayscale photomask fabricated by laser direct writing in metallic nano-films,” Opt. Express 17(22), 19981–19987 (2009), http://www.opticsinfobase.org/abstract.cfm?URI=oe-17-22-19981 .
[CrossRef] [PubMed]

Christophersen, M.

M. Christophersen and B. F. Phlips, “Gray-tone lithography using an optical diffuser and a contact aligner,” Appl. Phys. Lett. 92(19), 194102 (2008).
[CrossRef]

Chuvenkova, O. A.

E. P. Domashevskaya, O. A. Chuvenkova, V. M. Kashkarov, S. B. Kushev, S. V. Ryabtsev, S. Yu. Turishchev, and Yu. A. Yurakov, “TEM and XANES investigations and optical properties of SnO nanolayers,” Surf. Interface Anal. 38(4), 514–517 (2006).
[CrossRef]

Comini, E.

E. Comini, “Metal oxide nano-crystals for gas sensing,” Anal. Chim. Acta 568(1-2), 28–40 (2006).
[CrossRef] [PubMed]

Cooper, B.

B. Krishnamachari, J. McLean, B. Cooper, and J. Sethna, “Gibbs-Thomson formula for small island sizes: Corrections for high vapor densities,” Phys. Rev. B 54(12), 8899–8907 (1996).
[CrossRef]

Dai, Z. R.

Z. W. Pan, Z. R. Dai, and Z. L. Wang, “Nanobelts of semiconducting oxides,” Science 291(5510), 1947–1949 (2001).
[CrossRef] [PubMed]

Descour, M. R.

J. D. Rogers, A. H. O. Kärkkäinen, T. Tkaczyk, J. T. Rantala, and M. R. Descour, “Realization of refractive microoptics through grayscale lithographic patterning of photosensitive hybrid glass,” Opt. Express 12(7), 1294–1303 (2004).
[CrossRef] [PubMed]

Domashevskaya, E. P.

E. P. Domashevskaya, O. A. Chuvenkova, V. M. Kashkarov, S. B. Kushev, S. V. Ryabtsev, S. Yu. Turishchev, and Yu. A. Yurakov, “TEM and XANES investigations and optical properties of SnO nanolayers,” Surf. Interface Anal. 38(4), 514–517 (2006).
[CrossRef]

Fan, Y.

C. F. Guo, S. Cao, P. Jiang, Y. Fang, J. Zhang, Y. Fan, Y. Wang, W. Xu, Z. Zhao, and Q. Liu, “Grayscale photomask fabricated by laser direct writing in metallic nano-films,” Opt. Express 17(22), 19981–19987 (2009), http://www.opticsinfobase.org/abstract.cfm?URI=oe-17-22-19981 .
[CrossRef] [PubMed]

Fang, Y.

C. F. Guo, S. Cao, P. Jiang, Y. Fang, J. Zhang, Y. Fan, Y. Wang, W. Xu, Z. Zhao, and Q. Liu, “Grayscale photomask fabricated by laser direct writing in metallic nano-films,” Opt. Express 17(22), 19981–19987 (2009), http://www.opticsinfobase.org/abstract.cfm?URI=oe-17-22-19981 .
[CrossRef] [PubMed]

Ghodssi, R.

C. M. Waits, A. Modafe, and R. Ghodssi, “Investigation of gray-scale technology for large area 3D siliconMEMS structures,” J. Micromech. Microeng. 13(2), 170–177 (2003).
[CrossRef]

Granqvist, C. G.

C. G. Granqvist and A. Hultaker, “Transparent and conducting ITO films: new developments and applications,” Thin Solid Films 411(1), 1–5 (2002).
[CrossRef]

Guo, C. F.

C. F. Guo, S. Cao, P. Jiang, Y. Fang, J. Zhang, Y. Fan, Y. Wang, W. Xu, Z. Zhao, and Q. Liu, “Grayscale photomask fabricated by laser direct writing in metallic nano-films,” Opt. Express 17(22), 19981–19987 (2009), http://www.opticsinfobase.org/abstract.cfm?URI=oe-17-22-19981 .
[CrossRef] [PubMed]

C. F. Guo, Z. Zhang, S. Cao, and Q. Liu, “Laser direct writing of nanoreliefs in Sn nanofilms,” Opt. Lett. 34(18), 2820–2822 (2009).
[CrossRef] [PubMed]

Hultaker, A.

C. G. Granqvist and A. Hultaker, “Transparent and conducting ITO films: new developments and applications,” Thin Solid Films 411(1), 1–5 (2002).
[CrossRef]

Jiang, P.

C. F. Guo, S. Cao, P. Jiang, Y. Fang, J. Zhang, Y. Fan, Y. Wang, W. Xu, Z. Zhao, and Q. Liu, “Grayscale photomask fabricated by laser direct writing in metallic nano-films,” Opt. Express 17(22), 19981–19987 (2009), http://www.opticsinfobase.org/abstract.cfm?URI=oe-17-22-19981 .
[CrossRef] [PubMed]

Jürss, M.

K. Reimer, H. J. Quenzer, M. Jürss, and B. Wagner, “Micro-optic fabrication using one-level gray-tone lithography,” Proc. SPIE 3008, 279–288 (1997), http://www.mp-cc.de/docs/reiphot.pdf .
[CrossRef]

Kärkkäinen, A. H. O.

J. D. Rogers, A. H. O. Kärkkäinen, T. Tkaczyk, J. T. Rantala, and M. R. Descour, “Realization of refractive microoptics through grayscale lithographic patterning of photosensitive hybrid glass,” Opt. Express 12(7), 1294–1303 (2004).
[CrossRef] [PubMed]

Kashkarov, V. M.

E. P. Domashevskaya, O. A. Chuvenkova, V. M. Kashkarov, S. B. Kushev, S. V. Ryabtsev, S. Yu. Turishchev, and Yu. A. Yurakov, “TEM and XANES investigations and optical properties of SnO nanolayers,” Surf. Interface Anal. 38(4), 514–517 (2006).
[CrossRef]

Krishnamachari, B.

B. Krishnamachari, J. McLean, B. Cooper, and J. Sethna, “Gibbs-Thomson formula for small island sizes: Corrections for high vapor densities,” Phys. Rev. B 54(12), 8899–8907 (1996).
[CrossRef]

Kushev, S. B.

E. P. Domashevskaya, O. A. Chuvenkova, V. M. Kashkarov, S. B. Kushev, S. V. Ryabtsev, S. Yu. Turishchev, and Yu. A. Yurakov, “TEM and XANES investigations and optical properties of SnO nanolayers,” Surf. Interface Anal. 38(4), 514–517 (2006).
[CrossRef]

Liu, Q.

C. F. Guo, Z. Zhang, S. Cao, and Q. Liu, “Laser direct writing of nanoreliefs in Sn nanofilms,” Opt. Lett. 34(18), 2820–2822 (2009).
[CrossRef] [PubMed]

C. F. Guo, S. Cao, P. Jiang, Y. Fang, J. Zhang, Y. Fan, Y. Wang, W. Xu, Z. Zhao, and Q. Liu, “Grayscale photomask fabricated by laser direct writing in metallic nano-films,” Opt. Express 17(22), 19981–19987 (2009), http://www.opticsinfobase.org/abstract.cfm?URI=oe-17-22-19981 .
[CrossRef] [PubMed]

McLean, J.

B. Krishnamachari, J. McLean, B. Cooper, and J. Sethna, “Gibbs-Thomson formula for small island sizes: Corrections for high vapor densities,” Phys. Rev. B 54(12), 8899–8907 (1996).
[CrossRef]

Modafe, A.

C. M. Waits, A. Modafe, and R. Ghodssi, “Investigation of gray-scale technology for large area 3D siliconMEMS structures,” J. Micromech. Microeng. 13(2), 170–177 (2003).
[CrossRef]

Pan, Z. W.

Z. W. Pan, Z. R. Dai, and Z. L. Wang, “Nanobelts of semiconducting oxides,” Science 291(5510), 1947–1949 (2001).
[CrossRef] [PubMed]

Phlips, B. F.

M. Christophersen and B. F. Phlips, “Gray-tone lithography using an optical diffuser and a contact aligner,” Appl. Phys. Lett. 92(19), 194102 (2008).
[CrossRef]

Quenzer, H. J.

K. Reimer, H. J. Quenzer, M. Jürss, and B. Wagner, “Micro-optic fabrication using one-level gray-tone lithography,” Proc. SPIE 3008, 279–288 (1997), http://www.mp-cc.de/docs/reiphot.pdf .
[CrossRef]

Rantala, J. T.

J. D. Rogers, A. H. O. Kärkkäinen, T. Tkaczyk, J. T. Rantala, and M. R. Descour, “Realization of refractive microoptics through grayscale lithographic patterning of photosensitive hybrid glass,” Opt. Express 12(7), 1294–1303 (2004).
[CrossRef] [PubMed]

Reimer, K.

K. Reimer, H. J. Quenzer, M. Jürss, and B. Wagner, “Micro-optic fabrication using one-level gray-tone lithography,” Proc. SPIE 3008, 279–288 (1997), http://www.mp-cc.de/docs/reiphot.pdf .
[CrossRef]

Rogers, J. D.

J. D. Rogers, A. H. O. Kärkkäinen, T. Tkaczyk, J. T. Rantala, and M. R. Descour, “Realization of refractive microoptics through grayscale lithographic patterning of photosensitive hybrid glass,” Opt. Express 12(7), 1294–1303 (2004).
[CrossRef] [PubMed]

Ryabtsev, S. V.

E. P. Domashevskaya, O. A. Chuvenkova, V. M. Kashkarov, S. B. Kushev, S. V. Ryabtsev, S. Yu. Turishchev, and Yu. A. Yurakov, “TEM and XANES investigations and optical properties of SnO nanolayers,” Surf. Interface Anal. 38(4), 514–517 (2006).
[CrossRef]

Sethna, J.

B. Krishnamachari, J. McLean, B. Cooper, and J. Sethna, “Gibbs-Thomson formula for small island sizes: Corrections for high vapor densities,” Phys. Rev. B 54(12), 8899–8907 (1996).
[CrossRef]

Tkaczyk, T.

J. D. Rogers, A. H. O. Kärkkäinen, T. Tkaczyk, J. T. Rantala, and M. R. Descour, “Realization of refractive microoptics through grayscale lithographic patterning of photosensitive hybrid glass,” Opt. Express 12(7), 1294–1303 (2004).
[CrossRef] [PubMed]

Turishchev, S. Yu.

E. P. Domashevskaya, O. A. Chuvenkova, V. M. Kashkarov, S. B. Kushev, S. V. Ryabtsev, S. Yu. Turishchev, and Yu. A. Yurakov, “TEM and XANES investigations and optical properties of SnO nanolayers,” Surf. Interface Anal. 38(4), 514–517 (2006).
[CrossRef]

Wagner, B.

K. Reimer, H. J. Quenzer, M. Jürss, and B. Wagner, “Micro-optic fabrication using one-level gray-tone lithography,” Proc. SPIE 3008, 279–288 (1997), http://www.mp-cc.de/docs/reiphot.pdf .
[CrossRef]

Waits, C. M.

C. M. Waits, A. Modafe, and R. Ghodssi, “Investigation of gray-scale technology for large area 3D siliconMEMS structures,” J. Micromech. Microeng. 13(2), 170–177 (2003).
[CrossRef]

Wang, Y.

C. F. Guo, S. Cao, P. Jiang, Y. Fang, J. Zhang, Y. Fan, Y. Wang, W. Xu, Z. Zhao, and Q. Liu, “Grayscale photomask fabricated by laser direct writing in metallic nano-films,” Opt. Express 17(22), 19981–19987 (2009), http://www.opticsinfobase.org/abstract.cfm?URI=oe-17-22-19981 .
[CrossRef] [PubMed]

Wang, Z. L.

Z. W. Pan, Z. R. Dai, and Z. L. Wang, “Nanobelts of semiconducting oxides,” Science 291(5510), 1947–1949 (2001).
[CrossRef] [PubMed]

Xu, W.

C. F. Guo, S. Cao, P. Jiang, Y. Fang, J. Zhang, Y. Fan, Y. Wang, W. Xu, Z. Zhao, and Q. Liu, “Grayscale photomask fabricated by laser direct writing in metallic nano-films,” Opt. Express 17(22), 19981–19987 (2009), http://www.opticsinfobase.org/abstract.cfm?URI=oe-17-22-19981 .
[CrossRef] [PubMed]

Yurakov, Yu. A.

E. P. Domashevskaya, O. A. Chuvenkova, V. M. Kashkarov, S. B. Kushev, S. V. Ryabtsev, S. Yu. Turishchev, and Yu. A. Yurakov, “TEM and XANES investigations and optical properties of SnO nanolayers,” Surf. Interface Anal. 38(4), 514–517 (2006).
[CrossRef]

Zhang, J.

C. F. Guo, S. Cao, P. Jiang, Y. Fang, J. Zhang, Y. Fan, Y. Wang, W. Xu, Z. Zhao, and Q. Liu, “Grayscale photomask fabricated by laser direct writing in metallic nano-films,” Opt. Express 17(22), 19981–19987 (2009), http://www.opticsinfobase.org/abstract.cfm?URI=oe-17-22-19981 .
[CrossRef] [PubMed]

Zhang, Z.

C. F. Guo, Z. Zhang, S. Cao, and Q. Liu, “Laser direct writing of nanoreliefs in Sn nanofilms,” Opt. Lett. 34(18), 2820–2822 (2009).
[CrossRef] [PubMed]

Zhao, Z.

C. F. Guo, S. Cao, P. Jiang, Y. Fang, J. Zhang, Y. Fan, Y. Wang, W. Xu, Z. Zhao, and Q. Liu, “Grayscale photomask fabricated by laser direct writing in metallic nano-films,” Opt. Express 17(22), 19981–19987 (2009), http://www.opticsinfobase.org/abstract.cfm?URI=oe-17-22-19981 .
[CrossRef] [PubMed]

Anal. Chim. Acta (1)

E. Comini, “Metal oxide nano-crystals for gas sensing,” Anal. Chim. Acta 568(1-2), 28–40 (2006).
[CrossRef] [PubMed]

Appl. Phys. Lett. (1)

M. Christophersen and B. F. Phlips, “Gray-tone lithography using an optical diffuser and a contact aligner,” Appl. Phys. Lett. 92(19), 194102 (2008).
[CrossRef]

J. Micromech. Microeng. (1)

C. M. Waits, A. Modafe, and R. Ghodssi, “Investigation of gray-scale technology for large area 3D siliconMEMS structures,” J. Micromech. Microeng. 13(2), 170–177 (2003).
[CrossRef]

Opt. Express (2)

J. D. Rogers, A. H. O. Kärkkäinen, T. Tkaczyk, J. T. Rantala, and M. R. Descour, “Realization of refractive microoptics through grayscale lithographic patterning of photosensitive hybrid glass,” Opt. Express 12(7), 1294–1303 (2004).
[CrossRef] [PubMed]

C. F. Guo, S. Cao, P. Jiang, Y. Fang, J. Zhang, Y. Fan, Y. Wang, W. Xu, Z. Zhao, and Q. Liu, “Grayscale photomask fabricated by laser direct writing in metallic nano-films,” Opt. Express 17(22), 19981–19987 (2009), http://www.opticsinfobase.org/abstract.cfm?URI=oe-17-22-19981 .
[CrossRef] [PubMed]

Opt. Lett. (1)

C. F. Guo, Z. Zhang, S. Cao, and Q. Liu, “Laser direct writing of nanoreliefs in Sn nanofilms,” Opt. Lett. 34(18), 2820–2822 (2009).
[CrossRef] [PubMed]

Phys. Rev. B (1)

B. Krishnamachari, J. McLean, B. Cooper, and J. Sethna, “Gibbs-Thomson formula for small island sizes: Corrections for high vapor densities,” Phys. Rev. B 54(12), 8899–8907 (1996).
[CrossRef]

Proc. SPIE (1)

K. Reimer, H. J. Quenzer, M. Jürss, and B. Wagner, “Micro-optic fabrication using one-level gray-tone lithography,” Proc. SPIE 3008, 279–288 (1997), http://www.mp-cc.de/docs/reiphot.pdf .
[CrossRef]

Science (1)

Z. W. Pan, Z. R. Dai, and Z. L. Wang, “Nanobelts of semiconducting oxides,” Science 291(5510), 1947–1949 (2001).
[CrossRef] [PubMed]

Surf. Interface Anal. (1)

E. P. Domashevskaya, O. A. Chuvenkova, V. M. Kashkarov, S. B. Kushev, S. V. Ryabtsev, S. Yu. Turishchev, and Yu. A. Yurakov, “TEM and XANES investigations and optical properties of SnO nanolayers,” Surf. Interface Anal. 38(4), 514–517 (2006).
[CrossRef]

Thin Solid Films (1)

C. G. Granqvist and A. Hultaker, “Transparent and conducting ITO films: new developments and applications,” Thin Solid Films 411(1), 1–5 (2002).
[CrossRef]

Other (3)

C. K. Wu, “Method of making high energy beam sensitive glasses,” U.S. Patent, No. 5,078,771 (1992).

G. Gal, “Method for fabricating microlenses,” U.S. Patent No. 5,310,623, 10, (1994).

C. K. Wu, “gray scale all-glass photomasks,” U.S. Patent No. 2005/0053844 A1, (2005).

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Figures (12)

Fig. 1
Fig. 1

SEM images of different Sn and In films with the same thickness of 20 nm. (a), (b) and (c) 20 nm Sn films deposited in one time (20 nm), twice (10 nm×2) and four times (5 nm×4), respectively. (d), (e) and (f) 20 nm In film prepared by one time deposition, four times of deposition (film not surface oxidized in the deposition intervals) and four times of deposition (5 nm×4, with surface oxidation for each layer), respectively.

Fig. 2
Fig. 2

Schematic illustration of the metallic films with the same nominal thickness prepared by routine method (route 1-2-3-4) and the refinement (route 1-2-3′-4’-5′-6’). The latter is composed of two layers of refined grains as a result of the interdiction of homoepitaxy caused by the oxide coating on the metal surface.

Fig. 3
Fig. 3

(a) XRD spectra of 20 nm Sn films heated at different temperatures for 5 min, showing the phase evolution from Sn to SnO, orthorhombic (o-) SnO2 and finally to tetragonal (t-) SnO2. (b) NUV-vis spectra of the films annealed at different temperatures, the t-SnO2 film has an OD less than 0.04 from 350 to 700 nm.

Fig. 4
Fig. 4

NUV-vis spectra of In films with different thicknesses (upper part), and those of the films annealed at 350 °C for one hour (below). Spectra of an In film and the corresponding In2O3 film are in the same color.

Fig. 5
Fig. 5

(a) and (b) Grayscale patterns written in the refined and roughly surfaced 20 nm Sn films, respectively. The latter does not reveal fine structures of the wolf. The insets are magnified images of the wolf’s eye, clearly showing that the refined film possess much better gray levels and finer features.

Fig. 6
Fig. 6

(a)-(c) A set of grayscale pattern fabricated in a refined In film. (d) and (e) Complex grayscale patterns written under 2.5-10 mW 1.0 μs pulse exposure and 1.5-8 mW 1.0 ms pulse exposure, respectively. Image (e) is color-inverted.

Fig. 7
Fig. 7

TEM images of Sn films exposed under (a) 200 ns and (b) 1.0 ms pulse. There are several subgrains in the domain of an original Sn film and they may be in different structures.

Fig. 8
Fig. 8

Bright field images of (a) as-deposited 20 nm In film and laser exposed areas of the film with powers of (b) 0.9 mW and (c) 1.1 mW. Moiré fringes as a symbol of layered oxidation are found in (b). The inset in (b) is a magnified TEM image, showing the Moiré fringes.

Fig. 9
Fig. 9

(a)-(e) SAED patterns of 20 nm In films exposed at different laser power with the pulse width of 200 ns, showing the phase evolution from In to In2O3. (f) SAED pattern of an In film exposed at 0.3 mW, pulse width is 1.0 ms.

Fig. 10
Fig. 10

Schematic illustration of (a) layered oxidation model and (b) grain model for explaining the grayscale features of MTMO systems. Layered oxidation model is suit for In and short pulse exposure of Sn (the Sn and a-SnOx system) while grain model is suit for long pulse exposure of Sn (the Sn-SnO-SnO2 system).

Fig. 11
Fig. 11

Simulation of the In2O3/In bilayer’s OD at wavelengths of 365 and 532 nm, showing that the film achieves the minimum OD before complete oxidation. In is 20 nm thick before being oxidized. The inset shows the OD or T of the In film versus film thickness.

Fig. 12
Fig. 12

SEM images of (a) surface relief phase grating with a period of 5 μm and (b) microlens array fabricated in a SU-8 film by using MTMO grayscale masks. The inset in (b) shows that the surface of the lenses is very smooth. (c) Focusing effect of the microlens array. (d) Optical image of a MTMO grayscale pattern, which can be used as an amplitude grating or a mask for fabricating surface relief grating.

Equations (1)

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p ( r ) = p 0 exp ( γ r ρ k T )

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