Abstract

A new one-step method, which has been named self-organized formation, for microfabrication of blazed-grating-like structures after bombardment with a focused ion beam (FIB) with an ion energy of 50 keV and a beam current of 0.5 nA is presented. The structure is fabricated by the FIB by raster scanning (not by patterned scanning) upon a substrate of a silicon wafer, Si(100), with total scanning time of 14 min. With this method the parameters are unchanged during the whole process, unlike for the point-by-point direct writing technique, in which the exposure intensity or the electron- or ion-beam dose is changed for each point. The surface roughness of the structure, Ra, is 2.5 nm over an area of 1 μm X 1 μm. To evaluate the performance of this method we carried out a simulation, using the PCGrate program. The simulated diffraction efficiency, of diffraction order �??3 working in the reflection mode, can be as much as 79.1% for the violet wavelength of 400 nm. Using a He�??Ne laser as the light source produced a measured diffraction efficiency of the order of �??2 of 70.4%, which is near the simulated value of 76.9% at a wavelength of 600 nm. The depth and the period of the structure can be controlled by process parameters of the FIB, such as ion energy and ion flux.

© 2004 Optical Society of America

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References

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Appl. Opt.

J. Appl. Phys.

G. Carter, �??The effects of surface ripples on sputtering erosion rates and secondary ion emission yields,�?? J. Appl. Phys. 85, 455�??459 (1999).
[CrossRef]

J. Vac. Sci. Technol. A

R. M. Bradley and J. M. E. Harper, �??Theory of ripple topography induced by ion bombardment,�?? J. Vac. Sci. Technol. A 6, 2390�??2395 (1988).
[CrossRef]

Mater. Sci. Eng. C

H. Jiang, X. Yuan, Z. Yun, Y.-C. Chan, and Y.-L. Lam, �??Fabrication of microlens in photosensitive hybrid sol-gel films using a gray scale mask,�?? Mater. Sci. Eng. C 16, 99�??102 (2001).
[CrossRef]

Opt. Commun.

P. Coudray, P. Etienne, Y. Moreau, J. Porque, and S. I.. Najafi, �??Sol-gel channel waveguide on silicon: fast direct imprinting,�?? Opt. Commun. 143, 199�??202 (1997).
[CrossRef]

Opt. Eng.

Y. Fu and N. K. A. Bryan, �??Investigation of diffractive optical element fabricated on diamond film by use of focused ion beam direct milling,�?? Opt. Eng. 42, 2214-2217 (2003).
[CrossRef]

Opt. Express

Proc. SPIE

L. I. Goray, Modified integral method for weak convergence problems of light scattering on relief grating, in Diffractive and Holographic Technologies for Integrated Photonic Systems, R. I. Sutherland, D. W. Prather, and I. Cindrich, eds., Proc. SPIE 4291, 1-12 (2001).

Trends in Optics and Photonics Series

L. I. Goray and S. Yu. Sadov, �??Numerical modeling of coated gratings. I. Sensitive cases,�?? in Diffractive Optics & Micro-Optics, R. Magnusson, ed., Vol. 75 of OSA Trends in Optics and Photonics Series (Optical Society of America, Washington, D.C., 2002), pp. 365-379.

Other

E. Palik and G. Ghosh, The Electronic Handbook of Optical Constants of Solids (Academic, San Diego, Calif., 1999).

A commonly used software based on the modified integral method for simulation and analysis of gratings; see Internet site <a href="http://www.pcgrate.com">http://www.pcgrate.com</a>

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