We present a simple and cost-effective method for the fabrication of antireflective surfaces by self-assembly of block copolymers and subsequent plasma etching. The block copolymers create randomly oriented periodic patterns, which are further transferred into fused silica substrates. The reflection on the patterned fused silica surface is reduced to well below 1% in the ultraviolet, visible, and near-infrared ranges by exploiting subwavelength nanostructures with periodicities down to 48 nm. We show that by choosing the appropriate block copolymers and pattern transfer parameters the optical properties of the antireflective surface can be easily tuned, and the spectral measurements verify a significant reduction of the reflectivity by a factor of 10. The experiments, confirmed with simulations based on rigorous diffraction theory, also show that the tapered shape of the nanostructures gives rise to a graded index surface, resulting in a broad-band antireflective behavior.
The photoluminescence emission of SiGe quantum dot arrays prepared by templated self-assembly, combining extreme-ultraviolet interference lithography and molecular beam epitaxy, were studied. The PL spectra obtained from areas with ordered dots show a pronounced SiGequantum-dot-related signal. The corresponding no-phonon and assisted transversal optical phonon recombinations are well resolved due to the narrow-size distribution of the fabricated quantum dot arrays. Additionally, the dependence of the photoluminescence emission on dot size and Ge concentration is discussed as well as effects of laser power excitation.
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