Er-doped Oxidized Porous Silicon Waveguides

The present work reports Er-doped channel oxidized porous silicon waveguides (OPSWG) formed from n+-type Si by the two-step anodisation process. Er has been introduced into porous silicon before oxidation by a cathodic treatment in 0.1 M Er (NO3)3 aqueous solution. A correlation between Er concentration and refractive index profiles has shown dominant core doping with Er relative to cladding regions. Reported Er concentration of 0.8 at.% in the OPSWG is large enough to attain the amplification effect

PICTS-спектроскопия синтетического НРНТ-алмаза в области температур 300-550 К

The electrically active defects in synthetic single crystals of HPHT diamond have been investigated using photo-induced current transient spectroscopy (PICTS). It has been found that kinetics of photocurrent is of complex nature in the temperature range 400-550 K. Detailed analysis of photocurrent relaxation on the basis of approximation by the sum of two exponential components has been performed. It is shown that their contributions cannot be interpreted as the result of thermal emission from two independent local levels. These defects are suggested to be responsible for the long photocurrent stabilization in detectors made of HPHT diamonds.Методом фотоэлектрической релаксационной спектроскопии исследованы электрически активные дефекты в синтетическом монокристалле НРНТ-алмаза. Обнаружен сложный характер кинетики спада фототока в области 400-550 K. Детальный анализ релаксации фототока проведен на основе приближения суммой двух экспоненциальных компонент. Показано, что их вклады невозможно интерпретировать как результат термоэмиссии носителей заряда с двух независимых локальных уровней. Предполагается, что обнаруженные дефекты определяют долговременные процессы стабилизации тока фотоионизации детекторов на основе НРНТ-алмаза

Deposition of Erbium Containing Film in Porous Silicon from Ethanol Solution of Erbium Salt

Electrochemical treatment of porous silicon (PS) in ethanol solution of Er(NO3)3 was investigated to obtain material suitable for optoelectronic application. The voltammograms of n+-type and p-type PS vs. an Ag/AgCl reference electrode were examined and compared with these of a Pt electrode. The basic cathode reactions were marked out the voltammograms: (i) the formation and the adsorption of atomic hydrogen; (ii) the formation of molecular hydrogen; (iii) the electrolysis of water and ethanol. No zones relating to on electrochemical transitions of Er ions were revealed on the voltammograms. Nevertheless, with the cathode polarization, the formation of an Er-containing deposit was observed at the surface of the cathode. The IR and SIMS analysis were used to study the composition of the deposits. The scheme of the electrochemical and chemical reactions at the cathode is discussed

Upconversion Luminescence of Er3+ Ions from Barium Titanate Xerogel Powder and Target Fabricated by Explosive Compaction Method

Photo- and cathodoluminescence in the visible range from erbium-doped barium titanate xerogels obtained in the form of a powder and a target pressed from it by explosive compaction are investigated. The powder and target exhibit upconversion luminescence of erbium ions excited at wavelengths in the regions 950–1000 and 1450–1550 nm that is characterized by strong bands at 650 and 520–560 nm and a weak band at ~820 nm that correspond to the 4F9/2 → 4I15/2, 2H11/2 → 4I15/2, 4S3/2 → 4I15/2, and 4I9/2 → 4I15/2 transitions of Er3+. The target also demonstrates cathodoluminescence at room temperature and liquid nitrogen temperature with the strongest bands at 650, 520, and 538 nm

Photolumnescence from erbium incorporated in oxidized porous silicon.

In the present work, photoluminescence (PL) and photoluminescence excitation (PLE) spectroscopy were used to study oxidized porous silicon (OPS) doped with Er by electrochemical migration. Three types of OPS were investigated: (a) partially oxidized PS (POPS); (b) fully oxidized PS (FOPS); (c) oxidized PS co-doped with Fe (OPS:Fe). The OPS consists of oxide, Si nanoclusters and voids, and their composing fractions are dependent on the PS porosity and oxidation regime. The main result of this work is the assessment that the location of Er ions in composing fractions of OPS has a profound effect on the PL and PLE spectra. We show that for both POPS and FOPS, Er exhibits a broad 1530nm PL spectrum similar to that observed in the Er-doped silica glasses. For POPS, the PLE spectrum of the 1530 nm Er PL band consists of a superposition of sharp peaks, which are attributed to the absorption transitions of Er ions incorporated into the oxide fraction, and a broad band, which is related to the absorption band of Si nanoclusters. For FOPS, the PLE spectrum consists just of sharp peaks. In contrast to POPS and FOPS, for OPS:Fe, Er PL spectrum consists of 21 highly resolved peaks. PLE spectrum of the strongest 1535nm PL peak represents a wide band which is attributed to the absorption band of Fe:O nanoclusters formed inside OPS:Fe. Mechanism of excitation and luminescence of Er ions in OPS is presented

Comparison of HPHT and LPHT annealing of Ib synthetic diamond

Defect transformations in type Ib synthetic diamond annealed at a temperature of 1870 °C under stabilizing pressure (HPHT annealing) and in hydrogen atmosphere at normal pressure (LPHT annealing) are compared. Spectroscopic data obtained on the samples before and after annealing prove that the processes of nitrogen aggregation and formation of nitrogen‑nickel complexes are similar in both cases. Essential differences between HPHT and LPHT annealing are stronger graphitization at macroscopic imperfections and enhanced lattice distortions around point defects in the latter case. The lattice distortion around point defects is revealed as a considerable broadening of zero-phonon lines of “soft” (vacancy-related) optical centers. It was found that LPHT annealing may enhance overall intensity of luminescence of HPHT-grown synthetic diamonds

Comparison of HPHT and LPHT annealing of Ib synthetic diamond

Defect transformations in type Ib synthetic diamond annealed at a temperature of 1870 °C under stabilizing pressure (HPHT annealing) and in hydrogen atmosphere at normal pressure (LPHT annealing) are compared. Spectroscopic data obtained on the samples before and after annealing prove that the processes of nitrogen aggregation and formation of nitrogen-nickel complexes are similar in both cases. Essential differences between HPHT and LPHT annealing are stronger graphitization at macroscopic imperfections and enhanced lattice distortions around point defects in the latter case. The lattice distortion around point defects is revealed as a considerable broadening of zero-phonon lines of "soft" (vacancy-related) optical centers. It was found that LPHT annealing may enhance overall intensity of luminescence of HPHT-grown synthetic diamonds

Oxidized porous silicon: From dielectric isolation to integrated optical waveguides

A brief review of 20-years research of formation, processing and utilizing of oxidized porous silicon (OPS) is presented. Electrolytes to form porous silicon (PS) layers, special features of PS chemical cleaning and thermal oxidation are discussed. OPS application for dielectric isolation of components of bipolar ICs and for the formation of silicon-on-insulator structures has been demonstrated. Although these OPS-based techniques have found limited current commercial use, experience gained is applicable to the fabrication of optoelectronic devices. Specifically, integrated optical waveguides based on OPS have been developed

Fabrication of photoluminescent amorphous pillar silicon structures

Fabrication of amorphous pillar silicon structures showing visible photoluminescence (PL) by naked eye is reported. Some attempts involving silicon etching processes were previously performed by other authors, but PL from the resulting pillar structures was never observed. The pillar silicon structures were grown by Plasma Enhanced Chemical Vapour Deposition (PECVD) of hydrogenated amorphous silicon (α-Si:H) over the surface of porous aluminum oxide films, previously formed by anodization process. Alumina pore dimensions varied between 4-200 nm, depending on the parameters of the anodization process. The size of the grown α-Si:H pillars was quite homogeneous and could be tightly controlled by the anodization conditions. Immediately after PECVD process, PL from the pillar structure was very weak and not visible by naked eye, but after a short electrochemical treatment in 1% wt HF at 2 mA/cm2 it became quite bright and visible at normal daylight. A red shift, very similar to the one shown by porous silicon formed on monocrystalline substrates, was observed during samples drying after the electrochemical treatment