Three dimensional distributions of arsenic and platinum within NiSi contact and gate of an n-type transistor

Atom probe tomography was used to study the redistribution of platinum and arsenic atoms after Ni(Pt) silicidation of As-doped polycrystalline Si. These measurements were performed on a field-effect transistor and compared with those obtained in unpatterned region submitted to the same process. These results suggest that Pt and As redistribution during silicide formation is only marginally influenced by the confinement in microelectronic devices. On the contrary, there is a clear difference with the redistribution reported in the literature for the blanket wafers. Selective etching used to remove the non-reacted Ni(Pt) film after the first rapid heat treatment may induce this difference. © 2011 American Institute of Physics.

Durability and photo-electric characteristics of a mille-feuille structured amorphous selenium (a-Se)-arsenic selenide (As2Se3) multi-layered thin film

A mille-feuille structured amorphous selenium (a-Se)-arsenic selenide (As2Se3) multi-layered thin film and a mixed amorphous Se-As2Se3 film is compared from a durability perspective and photo-electric perspective. The former is durable to incident laser induced degradation after numerous laser scans and does not crystallise till 105 of annealing, both of which are improved properties from the mixed evaporated film. In terms of photo-electric properties, the ratio between the photocurrent and the dark current improved whereas the increase of the dark current was higher than that of As2Se3 due to the unique current path developed within the mille-feuille structure. Implementing this structure into various amorphous semiconductors may open up a new possibility towards structure-sensitive amorphous photoconductors. © 2013 Elsevier B.V.

Evolution from point defects to arsenic clusters in low-temperature grown GaAs/AlGaAs multiple quantum wells

Optical transient current spectroscopy (OTCS), photoluminescence (PL) spectroscopy and excitonic electroabsorption spectroscopy have been used to investigate the evolution of defects in the low-temperature grown GaAs/AlGaAs multiple quantum well structures during the postgrowth rapid thermal annealing. The sample was grown at 350 degrees C by molecular beam epitaxy on miscut (3.4 degrees off (001) towards (111)A) (001) GaAs substrate. After growth, the sample was subjected to 30s rapid thermal annealing in the range of 500-800 degrees C. It is found that the integrated PL intensity first decreases with the annealing temperature, then gets a minimum at 600 degrees C and finally recovers at higher temperatures. OTCS measurement shows that besides As,, antisites and arsenic clusters, there are several relatively shallower deep levels with excitation energies less than 0.3 eV in the as-grown and 500 degrees C-annealed samples. Above 600 degrees C, OTCS signals from As,, antisites and shallower deep levels become weaker, indicating the decrease of these defects. It is argued that the excess arsenic atoms group together to form arsenic clusters during annealing. (C) 2000 Elsevier Science B.V. All rights reserved.

Effect of arsenic precipitates on Fermi level in GaAs grown by molecular-beam epitaxy at low temperature

A simple model is presented to discuss the effect of As precipitates on the Fermi level in GaAs grown by molecular-beam epitaxy at low temperature (LT-GaAs). This model implements the compensation between point defects and the depletion of arsenic precipitates. The condition that the Fermi level is pinned by As precipitates is attained. The shifts of the Fermi level in LT-GaAs with annealing temperature are explained by our model. Additionally, the role of As precipitates in conventional semi-insulating GaAs is discussed. (C) 2000 American Institute of Physics. [S0021-8979(00)09905-9].

Arsenic clusters on the surface of vertically aligned InAs islands on GaAs substrate by annealing

The formation of arsenic clusters in a system of vertically aligned InAs quantum islands on GaAs during thermal annealing under As overpressure has been investigated by transmission electron microscopy (TEM) and Raman scattering. Semicoherent arsenic clusters, identified by TEM examination, have been formed on the surface of the GaAs capping layer. The existence of arsenic precipitates is also confirmed by Raman spectra, showing new peaks from the annealed specimen at 256 and 199 cm(-1). These peaks have been ascribed to A(1g) and E-g Raman active phonons of crystalline arsenic. The phenomenon can be understood by a model of strain-induced selected growth under As overpressure. (C) 1999 American Institute of Physics. [S0003-6951(99)02045-8].

Rapid thermal annealing of arsenic implanted Si1-xGex epilayers

Rapid thermal annealing of arsenic implanted Si1-xGex was studied by secondary ion-mass spectroscopy (SIMS) and spreading resistance probe (SRP) over a wide range of Ge fractions (0-43%). Redistribution of the implanted arsenic was followed as a function of Ge content and annealing temperature. Arsenic concentration profiles from SIMS indicated that the behavior of implanted arsenic in Si1-xGex after RTA was different from that in Si, and the Si1-xGex samples exhibited box-shaped, concentration-dependent diffusion profiles with increasing Ge content. The maximum concentrations of electrically active arsenic in Si1-xGex was found to decrease with increasing Ge content. Experimental results showed that the arsenic diffusion is enhanced with increasing temperature for certain Ge content and strongly dependent on Ge content, and the higher Ge content, the faster As diffusion.

Excess arsenic in GaAs grown at low temperatures by molecular beam epitaxy

The structural properties of GaAs grown at low temperatures by molecular beam epitaxy (LTMBE GaAs) were studied. The excess arsenic atoms in LTMBE GaAs exist in the form of arsenic interstitial couples (i,e, two ns atoms share the one host site), and cause an increase in the lattice parameter of LTMBE GaAs. Annealing at above 300 degrees C, the arsenic interstitial couples decomposed, and As precipitates formed, resulting in a decrease in the lattice parameter.

Health effects of arsenic；fluorine；and selenium from indoor burning of Chinese coal

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Capillary electrophoretic analysis of arsenic species with indirect laser induced fluorescence detection

The development of a method for determining arsenic species by capillary zone electrophoresis (CZE) with indirect laser-induced fluorescence (LIF) is described in this paper. The buffer pH, the concentration of fluorescein, the nature and the concentration of the background electrolytes (BGEs) were defined. When 2.0 mM NaHCO3 (pH 9.28) with 10(-7) M fluorescein was used as the buffer, arsenite (As(lll), dimethylarsonic acid (DMA), monomethylarsonic acid (MMA), and arsenate (As(V)) were all separated from one another. The limits of detection for the four arsenic species were p p in the range of 0.12-0.54 mg/L. This method was used in the analysis of spiked arsenic species in tap and mineral water to demonstrate its usefulness. The results showed that both the recovery and the reproducibility of the developed method were acceptable.

Determination of arsenic species by capillary zone electrophoresis with large-volume field-amplified stacking injection

Determination of arsenic species by large-volume field amplified stacking injection-capillary zone electrophoresis (LV-FASI-CZE) is reported in this paper. Whole column injection was employed. The optimum buffer pH for the separation of weak acids was discussed. It was found that the optimum buffer to analyze the stacked arsenate (As(V)), monomethylarsonate (MMA), and dimethylarsinate (DMA) was 25 mm phosphate at pH 6.5. However, the optimum buffer to analyze the concentrated arsenite (As(III)) was 20 mm phosphate - 10 mm borate at pH 9.28. The limits of detection of the method developed were 0.026 mg/L for As(III), 0.023 mg/L for As(V), 0.043 mg/L for MMA, and 0.018 mg/L for DMA. An enrichment factor of 34-100 for several arsenic species was obtained. In the end, this method was applied to determine the arsenic concentration in the environmental reference materials to show the usefulness of the method developed.