Blue Luminescent Properties of Silicon Nanowires Grown by a Solid-Liquid-Solid Method

Silicon nanowires (SiNWs) were grown directly from n-(111) single-crystal silicon (c-Si) substrate based on a solid-liquid-solid mechanism, and Au film was used as a metallic catalyst. The room temperature photoluminescence properties of SiNWs were observed by an Xe lamp with an exciting wavelength of 350 nm. The results show that the SiNWs exhibit a strongly blue luminescent band in the wavelength range 400-480 nm at an emission peak position of 420 nm. The luminescent mechanism of SiNWs indicates that the blue luminescence is attributed to the oxygen-related defects, which are in SiOx amorphous oxide shells around the crystalline core of SiNWs.

Optical emission and electron capture of rare-earth trivalent ions located at distinct sites in SnO(2) thin films

We present photoluminescence and decay of photo excited conductivity data for sol-gel SnO(2) thin films doped with rare earth ions Eu(3+) and Er(3+), a material with nanoscopic crystallites. Photoluminescence spectra are obtained under excitation with several monochromatic light sources, such as Kr(+) and Ar(+) lasers, Xe lamp plus a selective monochromator with UV grating, and the fourth harmonic of a Nd: YAG laser (4.65eV), which assures band-to-band transition and energy transfer to the ion located at matrix sites, substitutional to Sn(4+). The luminescence structure is rather different depending on the location of the rare-earth doping, at lattice symmetric sites or segregated at grain boundary layer, where it is placed in asymmetric sites. The decay of photo-excited conductivity also shows different trapping rate depending on the rare-earth concentration. For Er-doped films, above the saturation limit, the evaluated capture energy is higher than for films with concentration below the limit, in good agreement with the different behaviour obtained from luminescence data. For Eu-doped films, the difference between capture energy and grain boundary barrier is not so evident, even though the luminescence spectra are rather distinct.

Optical and transport properties of rare-earth trivalent ions located at different sites in sol-gel SnO2

Photoluminescence and photo-excited conductivity data as well as structural analysis are presented for sol-gel SnO2 thin films doped with rare earth ions Eu3+ and Er3+, deposited by sol-gel-dip-coating technique. Photoluminescence spectra are obtained under excitation with various types of monochromatic light sources, such as Kr+, Ar+ and Nd:YAG lasers, besides a Xe lamp plus a selective monochromator with UV grating. The luminescence fine structure is rather different depending on the location of the rare-earth doping, at lattice symmetric sites or segregated at the asymmetric grain boundary layer sites. The decay of photo-excited conductivity also shows different trapping rate depending on the rare-earth concentration. For Er-doped films, above the saturation limit, the evaluated capture energy is higher than for films with concentration below the limit, in good agreement with the different behaviour obtained from luminescence data. For Eu-doped films, the difference in the capture energy is not so evident in these materials with nanoscocopic crystallites, even though the luminescence spectra are rather distinct. It seems that grain boundary scattering plays a major role in Eu-doped SnO2 films. Structural evaluation helps to interpret the electro-optical data. © 2010 IOP Publishing Ltd.

Analysing DBD plasma lamp intensity versus power consumption using a push-pull pulsed power supply

In this paper characteristic of a DBD (Dielectric Barrier Discharge) plasma lamp is investigated based on the lamp intensity and power consumption. A pulsed power supply with controllable parameters based on a push-pull converter is developed for lamp excitation at different voltage levels and repetition rate. The experimentations were conducted for 28 different operating points with the frequency range of 2 kHz to 15 Khz at output voltage levels of between 7.4 kV up to 13 kV. The obtained results show the feasibility of finding an optimum operation point due to nonlinear behaviour of the DBD lamp.

A class E resonant inverter for use as electronic fluorescent lamp ballast

Class E Resonant Inverters are theoretically capable of delivering any power to a load and achieve 100% efficiency at any frequency of operation. In practice efficiency in the “high 90's” can be achieved into megahertz frequencies regardless of inverter output powers. The topology also allows the manipulation of output power through sub-optimal operation, with a negligible efficiency penalty. The 24W inverter discussed in this paper was specifically designed to harness the benefits, and discuss the shortcomings, of the Class E topology for use in the growing market for portable, battery powered lighting. It exhibits a peak recorded power efficiently of over 98%, and a conservatively measured efficiency of 95% across a range of dimming settings.

Hanukkah lamp from Italy Coin

Obverse: 1 Lira silver coin. Reverse: Hanukkah lamp from Italy.

Hanukkah lamp from North Africa Coin

Obverse: Silver 1 Lira coin. Reverse: Hanukkah lamp from North Africa

Hanukkah lamp from Babylon Coin

Silver 5 Lirot coin. Obverse: Number 5. Reverse: Hanukkah lamp from Babylon.

Hanukkah lamp from Russia Coin

Silver 5 Lirot coin. Obverse: 5 Lirot, emblem of the state of Israel. Reverse: Russian Hanukkah lamp.

Hanukkah lamp from Damascus Coin

Obverse: 10 Lirot silver coin. Reverse: Hanukkah lamp from Damascus, 18th century.

Hanukkah lamp from Damascus Coin

Obverse:10 Lirot silver coin. Reverse: Hanukkah lamp from Damascus, 18th century.

Hanukkah lamp from Holland Coin

Obverse: 10 Lirot silver coin, flower motifs on the sides. Reverse: Hanukkah lamp from Holland.

Hanukkah lamp from Corfu Coin

Obverse: 1 Sheqel silver coin, emblem of the State of Israel. Reverse: Hanukkah lamp from Corfu, 19th century

Hanukkah lamp from Corfu Coin

Obverse: 1 Sheqel silver coin. Reverse: Hanukkah lamp from Corfu, 19th century.