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Measurements of angle-resolved light scattering in porous silicon films are presented. Scattering rings are observed, and their aperture allowed to measure optical briefringence. The briefringence changes when pores are filled with liquids, after thermal annealing, and when the porous silicon layer is chemically etched in HF for different times.

An observation is presented of a large laser-induced growth in light absorption in free-standing porous silicon films, in wavelengths ranging from 500-700 nm.

Electrical transport and light emission properties of plasma-enhanced chemical vapor deposition grown light emitting devices (LEDs) based on nanocrystalline silicon have been studied. Various active layer compositions have been used. Electroluminescence and current-voltage measurements have been performed on metal-oxide-semiconductor structures. We found that Poole–Frenkel emission and trap-assisted tunneling between traps located at the nanocrystalline silicon interfaces are consistent with the measurements. The interface trap density was estimated. Its dependence on the composition of the active layer is discussed. We propose an equivalent electrical circuit model for the LED based on complex impedance measurements. Nanocrystalline silicon electroluminescence in the near infrared region is explained by hot-electron injection and impact ionization mechanism. It is concluded that the trap-assisted tunneling and charge trapping limit the external power efficiency of this kind of devices. [ABSTRACT FROM AUTHOR]

Porous silicon free-standing microcavity structures, with different layer designs, have been fabricated. Single microcavities show transmission resonances in the technologically relevant wavelength region of 1.55 μm with quality factors up to 3380. High-order cavities show sub-nm transmission peaks over the whole stop band. Coupled microcavity structures, where splitting of the degenerate cavity mode occurs, lead to multiple transmission peaks in a limited region of the stop band. We also report incident angle-dependent measurements, where transmission peak blueshift and splitting of transverse electric and transverse magnetic polarized modes due to porous silicon birefringence were observed. [ABSTRACT FROM AUTHOR]

Macroporous silicon with two-dimensional periodicity has been produced by electrochemical etching, using a p-type doped silicon substrate. The structure shows photonic energy gaps in the infrared region, as demonstrated by variable angle reflectance measurements. The agreement between measurement and band calculations confirms the high quality of the samples. The use of an optimized electrolyte allows the fabrication of very high quality samples, with high aspect ratio and low roughness both at the surface and on the pore walls. The best results are obtained with aprotic and protophilic solvents. [ABSTRACT FROM AUTHOR]

The real and imaginary parts of third-order nonlinear susceptibility χ[sup (3)] have been measured for silicon nanocrystals embedded in SiO[sub 2] matrix, formed by high temperature annealing of SiO[sub χ] films prepared by plasma-enhanced chemical vapor deposition. Measurements have been performed using a femtosecond Ti-sapphire laser at 813 nm using the Z-scan technique with maximum peak intensities up to 2 × 10[sup 10] W/cm². The real part of χ[sup (3)] shows positive nonlinearity for all samples. Intensity-dependent nonlinear absorption is observed and attributed to two-photon absorption processes. The absolute value of χ[sup (3)] is on the order of 10[sup -9] esu and shows a systematic increase as the silicon nanocrystalline size decreases. This is due to quantum confinement effects. [ABSTRACT FROM AUTHOR]

The peculiar excitation features accessible by near-field optical microscopy have prospect for coupling flight sources to microoptical devices. Near-field scanning optical microscopy (NSOM) is used to carry out near-field optical spectroscopy (NFOS).