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A multicomponent Stark structure corresponding to a 4I[sub 13/2]→4I[sub 15/2] transition in the 4f[sup 11] shell of Er[sup 3+] ions is observed in hydrogenated amorphous silicon (a-Si:H subjected to low-temperature (150 °C) anneal. The observation of narrow, strong components indicates that the erbium ions form a highly ordered local surrounding (Er–O–Si nanoclusters) in the labile, disordered structural network of a-Si:H. © 1999 American Institute of Physics. [ABSTRACT FROM AUTHOR]

It is suggested to use a time-modulated-microwave-power (TMWP) discharge regime for obtaining nanocrystalline silicon films by plasma-enhanced chemical-vapor deposition (PECVD) from a silane-hydrogen mixture. Using the TMWP-PECVD technique allows the nanocrystalline silicon films to be grown at a rate of up to 3 Å/s, which is 4-6 times as large as the process rate achieved with the conventional PECVD method. [ABSTRACT FROM AUTHOR]

A modified plasma-enhanced chemical vapor deposition technology is developed for nanocrystalline Si which combines the standard rf glow discharge method and the hollowcathode discharge method in a single process cycle. The volume fraction of nanocrystallites varied monotonically along the layer, whereas their size remained constant. The electrical and optical characteristics of these films were investigated. [ABSTRACT FROM AUTHOR]

Scanning tunneling microscopy and scanning tunneling spectroscopy (STS) are used to investigate the local electronic behavior of Pt-Si nanostructures fabricated in an opal matrix formed by silica spheres of 250 nm diameter. Si and Pt are regularly distributed inside the opal pores and form nanoscale metal-semiconductor-metal junctions. Normalized differential conductance curves enable us to study the distribution of Pt and Si and to detect the presence of regions showing a surface band gap in the range 0.5-0.8 eV, possibly associated with the formation of silicides. STS appears as a suitable technique for the electrical characterization of opal-based nanostructures. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Ultrafast (30 fs) all-optical switching of the reflectivity in an opal–Si three-dimensional photonic crystal is demonstrated in the visible and the near-infrared spectral range. Photoinduced changes turn out to be enhanced around the photonic stop bands and reach 46% at high excitation power. We show that the switching time is as short as 30 fs and is determined by the pump–pulse duration. [Copyright &y& Elsevier]

We present the first femtosecond pump–probe study of the transient reflectivity of an opal filled by silicon around the stop-band. We observe an ultrafast (<30 fs) photoinduced response of the reflectivity of the opal that is synchronous with the pump pulse. In addition, an ultrafast step followed by a multi-exponential picosecond decay is measured that is related to the creation and relaxation of free carriers. [Copyright &y& Elsevier]

We demonstrate ultrafast all-optical switching in a three-dimensional photonic crystal made of an opal-silicon composite. We show that the switching-on time is faster than 30 fs and determined by the pump pulse duration. The switching-off time is in the order of several picoseconds. The maximum transient change in reflectivity reaches values as high as 46% at the highest excitation power. [Copyright &y& Elsevier]