Formation and characterization of two-dimensional arrays of pores with very high aspect ratios based on anodic etching of silicon [1] and aluminum [2] will be described. Regular pattern formation by self-organization and by lithographic techniques will be dealt with. In both cases, these pore arrays can be used as two-dimensional photonic crystals, which exhibit an optical bandgap from the infrared to the visible depending on the anodization conditions. Diverse defect structures can be easily introduced by lithographic prepattering. For example wave-guides as well as microcavities have been fabricated and characterized optically. Figure 1 shows a recent macroporous silicon array with an interporedistance of 500 nm and an integrated microcavity. Figure 2 shows monocrystalline alumina photonic crystals with an interpore distance of 200 nm.
Fig.1: SEM image of Si pore arrays with an interpore distance of 500 nm pre-patterned by DUV photolithography. Three microcavities have been integrated with the corresponding waveguide feeders.
Fig. 2: (left) SEM image of self-ordered alumina pore array pre-patterning by e-beam lithography. The interpore distance is 200 nm; (right) Fourier transform of left image showing that the photonic crystals are monocrystalline.
This work has been done in cooperation with Infineon Technologies, University of Kiel, University of Konstanz, and University of Toronto.
[1] F. Müller, A. Birner, U. Gösele, V. Lehmann, S. Ottow, and H. Föll, J. Porous Mater. 7 201-204 (2000)
[2] A.-P. Li, F.Müller, A. Birner, K. Nielsch, and U. Gösele, Adv. Mater. 11, 483 (1999).