Self-organised nanocomposites from porous silicon Evidence of the relationship between nano-scale structure and its electronic properties

The composition study of the oxidized PS layer after Al-film coating has been shown by STM, STS (with tunnel I-V curves) and IR-spectroscopy to be the self-organized Si nanocrystallite. Si_xO_y:Si_zO_yAl or Si-nanocrystallite: Si_xO_y nanocomposites. The electronic properties (tunnel current, capacity, differential capacity relaxation) are determined by the presence of Si-nanocrystallites with size of 2,5-4 nm, and band gap E=2,4-2,8 eV surrounded by the matrix consisting of SiO, SiO_2, Si_2O_3 and Si_xO_yAl nanooxides. (author)Translated from Russian (Presented at Advanced Materials '99, Kiev)Available from British Library Document Supply Centre-DSC:9023.190(9916)T / BLDSC - British Library Document Supply CentreSIGLEGBUnited Kingdo

Nanoimprinted passive optical devices

We report on the feasibility and process parameters of nanoimprint lithography to fabricate low refractive index passive optical devices. Diffraction gratings printed in polymethylmethacrylate (PMMA) exhibit a sharp dispersion with a full width at half maximum of about 20 nm. Waveguides were printed in polystyrene (PS) on silicon oxide and had losses between 8-20 dB cm(-1) at wavelengths between 650-400 nm, respectively. Finally, one-dimensional photonic structures were also printed in PS and their transmission and morphology characterized. The expected Bragg peak was observed in transmission and atomic force microscopy images have shown a good pattern transfer. A square lattice was printed in PMMA and more than 40 print cycles were obtained, i.e., potentially more than 1000 imprints from one master stamp