V. Kh. Kudoyarova

Time-resolved photoluminescence of erbium centers in amorphous hydrogenated silicon

Abstract A time-resolved photoluminescence (PL) technique is employed to study the mechanisms of excitation and de-excitation of Er 3+ ions in amorphous hydrogenated silicon (a-Si:H) at temperatures 5–300 K. The PL at 1.5 μm is found to arise within times shorter than a 100 ns after irradiation with a nanosecond laser pulse, indicating a fast energy transfer from the electronic excitation of a-Si:H to the Er 3+ ions. The PL transients exhibit a stretched exponential decay with mean lifetime ranging from 20 to 35 μs when the temperature decreases from 300 K down to 5 K. The experimental results support the model of defect-related excitation and de-excitation of the Er 3+ ions.

Study of diamond-like carbon films for protective coatings

Interest in investigating thin films of diamond-like carbon (DLC, a-C:H) has been motivated by the unique properties of this material and the demand of modern technologies. The development of low-temperature methods T3s < 200 °C) for producing DLC films used as protective layers is of practical interest. In this work, a-C:H films were prepared by low-temperature deposition by using three methods: magnetron-sputtering of a graphite target in argon (80%)-hydrogen (20%) atmosphere, magnetron sputtering of graphite target combined with plasma-stimulated, gas-phase deposition from a mixture of gases (10% CH4 + 90% Ar) and rf decomposition of a mixtures of gases (10% CH4 + 90% Ar). A comprehensive investigation of the composition, structure, optical and electrical properties of a-C:H films was performed from the standpoint of the requirements that protective coatings for electrophotograhic information carriers and stable protector for Ag-based optics must meet. The investigation of the composition and structure was performed by elastic recoil detection (ERD), resonance nuclear reaction 16O (α, α) 16O and Raman spectroscopy. The optical properties (the transparency over a wide spectral range and the refractive index) were determined by means of IR-spectroscopy and ellipsometric measurements. It was shown that solid, diamond-like a-C:H films (DLC) can be obtained with low-temperature deposition. It was shown that a protective DLC coating increases the storage time in the air and the strength properties of the a-Se (or a-Se alloy) electrophotographic information carriers. It was determined that a protective DLC coating is an effective and stable protector for Ag-based optics from an attack of active sulfide.

Luminescence of erbium in amorphous hydrogenated silicon obtained by the glow-discharge method

We report the first observation of efficient room-temperature photoluminescence of erbium in amorphous hydrogenated silicon prepared by the plasma chemical-deposition method.

Room-Temperature Photoluminescence of Amorphous Hydrogenated Silicon Carbide Doped With Erbium

Recently the luminescent properties of erbium-doped crystalline silicon (c-Si:Er) have attracted much attention. The reason for this interest originates from the idea to fabricate LED’s which are integrable into silicon electronic devices and emit at a wavelength of 1,537 μm where the absorption of silica glass optical fiber is the lowest. The photoluminescence (PL) of c-Si:Er is strongly quenched with increasing temperature.

Correlation between photoluminescence efficiency and density of paramagnetic defects in Er-doped hydrogenated amorphous silicon

Photoluminescence and electron paramagnetic resonance in layers of hydrogenated amorphous silicon doped with erbium and oxygen have been investigated. The intensity of Er-related photoluminescence (1.54 μm) depends non-monotonically on the ratio between erbium and oxygen content varied from 0.1 to 3. The photoluminescence efficiency correlates with the density of spin centers (most likely Si dangling bonds (DBs)) that gives evidence for the role of Si DBs in the electronic excitation of Er-ions.

The Influence of Deposition Parameters on the Structure of Nanocrystalline Silicon

Abstract The structure, hydrogen content and bonding configurations of nanocrystalline silicon films produced by PECVD using hydrogen-diluted silane have been investigated by Raman and IR-spectroscopies. The film structure has been studied in relation to deposition parameters, such as gas dilution ratio, amount of water vapor in the initial gas, substrate temperature (Ts) and the substrate material. An analysis of Raman spectra has revealed in the films nanocrystallites embedded in amorphous matrix. The crystallite size (L) is in the range 3.6–5.7 nm. The volume fraction of crystallises (Xc) varies between 15% and 81%, depending on preparation conditions. Both L and Xc are primarily influenced by the presence of water vapor in the initial gas and the substrate material, while the effect of Ts is less pronounced. IR data show the presence of bound hydrogen with a total concentration varying between 3 and 13 at.%.

Erbium incorporation in plasma-deposited amorphous silicon

Erbium doped amorphous silicon has been prepared by the evaporation of Er containing metallo-organics inside the plasma of a plasma enhanced chemical vapor deposition (PECVD) system. The samples combine photoluminescence efficiency and photo sensitivity at room temperature. The spatial distribution of Er was found to be inhomogeneous due to insufficient control of the Er source. Electron and hole transport properties as well as defect properties were measured by means of steady-state photocurrent, constant photocurrent method (CPM), modulated photocurrent (MPC) and steady-state photocarrier grating (SSPG) experiments, which are interpreted on the basis of the inhomogeneous distribution of Er over the film thickness.

Photoluminescence and composition of amorphous As2Se3 films modified with Er(thd)3 complex compound

The photoluminescence and composition of amorphous As2Se3 films modified with an Er(thd)3 complex compound have been studied. A band centered at 1.54 μm, characteristic of photoluminescence from Er embedded in amorphous matrices, has been revealed at room temperature. The composition of thin amorphous As2Se3 films modified with an Er(thd)3 complex compound has been examined by methods of nuclear microanalysis: Rutherford backscattering and nuclear resonant reactions. Dependences of the concentrations of Er ions, oxygen, and carbon on the growth conditions of the films are obtained. It is shown that the Er concentration in a thin film varies nonlinearly as the relative concentration of the starting complex compound increases. In addition, the increase in the Er content of a film is accompanied by a simultaneous rise in the content of such light elements as oxygen and carbon. Comparative analysis of the nuclear microanalysis data and IR spectra demonstrates that, in modification of As2Se3 with the Er(thd)3 complex compound by the given method, the nearest environment of Er in the complex compound is partly preserved.

Optical and electrical properties of polyamide acid and metal-polymer complex based on terbium

The basic optical and electrical properties of polyamide acid and its complex with Tb+2 have been studied. The occurrence of room-temperature photoluminescence (PL) with an emission peak at 520 nm is established. The activation energy of conductivity at temperatures above 350 K is 2.1 eV. Polyamide acid is comparable in PL intensity with an electroluminescent polymer, poly(p-phenylvinylene).

Improvement of 1.54 μm luminescence in erbium-doped a-SiOx:H alloys

Abstract Erbium-doped amorphous silicon films have been deposited using magnetron-assisted silane decomposition (MASD) technique. The increase of partial concentration of O 2 in the gas phase above 6.5 mol% during the deposition enhances the intensity of the 1.54 μm Er photoluminescence (PL) at room temperature. The films exhibit an inhomogeneous structure containing oxygen and Er enriched nanoclusters, where the Er ions reside in optically active but electrically passive configuration.