Articles you may be interested inFormation of nickel silicide and germanosilicide layers on Si(001), relaxed Si Ge ∕ Si ( 001 ) , and strained Si/relaxed Si Ge ∕ Si ( 001 ) and effect of postthermal annealingThe formation of NiSi films on Si was studied using Rutherford backscattering spectrometry, atomic force microscopy, and ellipsometry. NiSi is an attractive candidate for use as a gate contact material due to its low metal-like resistivity and large processing window ͑350-750°C͒. Three phases, Ni 2 Si, NiSi, and NiSi 2 , were identified in this temperature range, and their optical databases in the 2-4 eV photon range were established, and used to model real-time ellipsometry data. It is shown that real-time ellipsometry can be used to monitor and follow the formation of the various Ni-Si phases. We have also observed the onset of agglomeration of the silicide for longer time anneals at temperatures of 500-700°C, which is much lower than 1000°C where agglomeration has been reported to occur.

Poly(p‐phenylenevinylene) (PPV) and its derivatives exhibit strong luminescence, being serious candidates to be used as active layers in organic light‐emitting diodes. However, the structural degradation caused by photo‐oxidation is an obstacle for commercial applications of such materials. Here, we show that spectroscopy ellipsometry is a useful technique to investigate the photo‐oxidation of poly[(2‐methoxy‐5‐hexyloxy)‐p‐phenylenevinylene] (MH‐PPV), a PPV derivative, which emits a red color light. Spectroscopy ellipsometry enables determination of the complex dielectric function—ϵ*(E)—of MH‐PPV thin‐layer films exposed to air, in the 2.1–4.2 eV energy range, as a function of the light exposure time (te). By using the Lorentz model to fit the experimental ϵ*(E) curves, it was inferred that the interactions among polymeric chains increase with te. From ϵ*(E), it is also possible to obtain the complex refractive index, N*(E) = n + ik. At higher energies (where k ≪ n), n increases from 1.32 to 1.40 with the photo‐oxidation progress. The behavior of n was investigated by using the Lorenz–Lorentz equation, taking into account the contribution for n by the chromophores of MH‐PPV. The effect of photo‐oxidation, mainly due to the replacement of vinyl CC by the ketone CO bonds, is confirmed by Fourier transform infrared measurements, an effect that reduces the average effective polymer conjugation length. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1033–1041, 2004

The application of an inexpensive, compact, solid-state, fluorescence-based detector for flow injection analysis to the determination of sulfide by the 'Methylene Blue Method', viz., production of Methylene Blue (MB) via the oxidative coupling of sulfide with N,N-dimethyl-pphenylenediamine (DMPD) in the presence of iron(III), is described. The use of fluorescence-based detection allows the reaction to be performed on-line under less corrosive, albeit sub-optimum, reaction conditions. The detector uses a 670 nm diode laser as the excitation source and inexpensive photodiodes as detector elements; a color filter (used to block scattered laser light) is the only other optical component of the detector. The fluorescence signal resulting from the MB formed on-line is linear over the range 0.75-15.0 mg l 21 injected sulfide, with a limit of detection of 0.08 mg l 21 injected sulfide when 9.0 M H 2 SO 4 is used in the DMPD carrier stream, and 1-2 mg l 21 when less acidic carrier streams are employed. Use of this method for analysis of sulfide unknowns in aqueous solution and in a simulated waste water matrix demonstrates that unknown sulfide samples can be analysed reproducibly.

The primary purpose of this research was to elucidate the mechanism of Si nucleation on SiO2 in a rapid thermal chemical vapor deposition (RTCVD) environment. To this end a combination of in situ real time ellipsometry and atomic force microscopy (AFM) to follow the RTCVD process in real time and measure key nucleation parameters was used. Real time ellipsometry data, in terms of Δ versus time, show significant changes as the deposition evolves from critical nuclei through coalescence to continuous film growth. From these data nuclei parameters such as the incubation time (tinc), coalescence point, nuclei density, and nuclei size are obtained from nucleation models. From the AFM images, nuclei parameters such as nuclei height, radius, and density were collected and compared across processing temperatures. It was found that kinetics rather than thermodynamics controls nuclei growth, and the mechanism depended upon the temperature regime (pressure not varied) due to the higher activation energy (212 kJ/mol) for vertical growth relative to lateral growth (167 kJ/mol). A transition temperature (∼600 °C) was identified where the size, shape, and density of the nuclei abruptly change from small numerous nuclei at temperatures less than 660 °C to large, sparse, disklike nuclei for temperatures greater than 660 °C. The temperature regime also affected the shape of the nuclei during growth with low temperature nuclei becoming flatter with time as the adatoms attached to the nuclei circumference, whereas high temperature nuclei grew taller with time. It is demonstrated that the RTCVD temperature regime dictates both the initial nuclei size and the nuclei growth mechanism with high temperature processes (i.e., highest adatom mobility), yielding the lowest nuclei density, largest nuclei, and roughest final Si film.

Low energy ion pretreatment of silicon dioxide (SiO2) surfaces results in a reduced incubation time (tinc) for polycrystalline silicon (poly-Si) deposition by rapid thermal chemical vapor deposition. By pretreating SiO2 surfaces with inert (He+, Ar+) and chemically active species (H+, N+), it was determined that ion pretreatments reduce tinc and increase the poly-Si nuclei density by creating nucleation sites via a physical damage mechanism, rather than a chemical process.