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Abstract With a view to creating Si LEDs, the structural and luminescent properties of SiOxNy films containing Si nanocrystals in the SiOxNy matrix are studied experimentally. It is found that the film structure (nanocrystal size and concentration, the presence of an amorphous phase, etc.) and the spectrum and intensity of photoluminescence (PL) and electroluminescence (EL) are strongly dependent on the Si stoichiometric excess δ and annealing conditions. At δ≈ 10%, unannealed films are amorphous and contain Si clusters of size < 2 nm, as deduced from the TEM and microdiffraction data obtained. Annealing at 800–1000°C for 10–60 min produces Si crystals 3–5 nm in size with a concentration of ≈1018 cm−3. The annealed films exhibit room-temperature PL and EL over the wavelength range 400–850 nm with intensity peaks located at 50–60 and 60–70 nm, respectively. The PL and EL spectra are found to be qualitatively similar. This suggests that both the PL and the EL should be associated with the formation of luminescent centers at nanocrystal–matrix interfaces and in boundary regions. However, the two phenomena should differ in the mechanism by which the centers are excited. With the EL, excitation should occur by impact processes due to carrier heating in high electric fields. It is found that as δ increases, so does the proportion of large amorphous Si clusters with a high density of dangling bonds. This enhances nonradiative recombination and suppresses luminescence.

The structure of porous Si1–xGex films was characterized using Raman spectroscopy. As the film porosity increases the sizes of Si1–xGex nanocrystals decrease, and also the film composition slightly modifies in favor of Ge. The Si1–xGex nanocrystals were estimated to be 12.0 nm, 16.1 nm and 19.3 nm average diameter in three porous samples prepared from undoped Si0.87Ge0.13 films with 20 min, 10 min and 2 min etch times, respectively, at the same current density 22 mA cm^–2. The final Ge fractions were determined for the samples as 17.4%, 14.5% and 13.0%, respectively. It is seen by this study that Raman spectroscopy is, as it has always been for bulk Si1–xGex alloys, a very useful technique for characterizing the structure of porous Si1–xGexfilms.

Porous nanocrystalline films were prepared by stain etching and subsequent annealing in hydrogen at 600 °C. The structural properties of the as-etched and annealed films were investigated using Raman scattering and various X-ray techniques. It was shown that the as-etched film had a thickness of ~2 μm and consisted of two sublayers of different porosity and amorphous-like microstructure The annealing did not change essentially the porosity and thickness but resulted in notable crystallinity transformation. The results of Raman spectroscopy and X-ray measurements and modelling revealed the presence of germanium nanocrystals with mean sizes of about 8–10 nm in the annealed films.

Abstract: Polycrystalline silicon deposited on insulating substrates has been chemically-etched to form thin films of porous material exhibiting room temperature visible photoluminescence with emission wavelengths of around 650 nm. Material of 4000 thickness was quickly converted to porous silicon within 15 s of etching, with an etch rate of 1–1.5 m/h. In contrast to anodization, chemical-etching parameters have little effect on modulating the resultant peak wavelength. Peak photoluminescence intensity was achieved 8–12 s of etching in 1:3:5 parts HF:HNO3:H2O at room temperature with ambient lighting. The chemical etching process and its etch characteristics have been discussed in relation to its suitability for large area thin film devices.

Two different polymorphic forms of free base phthalocyanine films have been grown on glass substrates by ultrahigh vacuum organic molecular beam deposition. Postgrowth annealing of films grown at room temperature leads to transformation from the α to the β1 phase. The effects of annealing lead to a number of transition states whose morphological, structural, and spectroscopic properties can be identified using atomic force and optical interference microscopy, X-ray diffraction, and Raman and electronic absorption spectroscopy. Detailed morphological studies indicate that the transition occurs via a discrete number of nucleations and is preceded by an elongation of the α crystallites. Quantitative analysis of the crystallites and domain size shows that the individual β1 crystals grow but are confined to domains of similar orientation. The film thickness plays a critical role and three regimes have been identified. The α → β1 transformation is only complete for films thicker than ~940 Å, and thick films lead to a higher degree of orientation and larger domains.

A new approach to the problem of preparation of laterally structured luminescent porous silicon is proposed. The effect is based on the photosensitivity of chemical etching of silicon. Contrary to the other technique recently reported where the porous layer was modified with light assisted chemical dissolution, a one stage anodisation-free process is used. Any desired lateral structure can be produced, depending on the illumination pattern, which is defined by optical imaging. A 2D micro-array was prepared as an example of this fast mask-free technology with an accuracy of 5 μm. Samples have a broadband visible photoluminescence centred at 680 nm when illuminated with UV or blue light. The results are analysed to determine the possible achievable accuracy of the technique and to improve our understanding of the mechanism of light assisted etching.

The structure, optical properties and surface morphology of thin films of metal free phthalocyanine (H2Pc) deposited in an ultra-high vacuum environment by organic molecular beam deposition have been studied using a variety of ex-situ techniques. The growth conditions have a strong influence on the properties of the films. H2Pc undergoes a phase transition (α→β) at a deposition temperature of ∽330°C, or upon post annealing a film grown at room temperature. Both the structure and optical properties of the films change and powder X-ray diffraction, electronic absorption spectroscopy, Raman and photoluminescence spectroscopies are used to characterise the differences between the two phases. Atomic force microscopy and Nomarski interference microscopy show that the lower temperature α-phase is characterised by a smooth morphology with spherical islands that show no apparent long-range order. By contrast, the β-phase has a much greater root mean square roughness and long thin needle-like crystals are observed on the surface of the films. The morphology of the β-phase depends on the method of preparation and there are two distinct types, β1 and β2. The crystallites show a preferential orientation and alignment with respect to each other for growth at room temperature followed by annealing (β1), but are randomly oriented for films grown at elevated substrate temperatures (β2).

A storage disease characterised by widespread vacuolation of cells throughout the body was diagnosed in a newborn calf of the Salers breed. Extraction and analyses of water soluble material showed that the storage material was oligosaccharide in nature and was probably derived from the core region of the heterosaccharide moiety of glycoproteins. Glycosidase analyses showed that the disease was due to a deficiencv of acidic β-mannosidase. (New Zealand Veterinary Journal 38, 102-5, 1990)

We present an investigation into a new technique for producing luminescent porous silicon with controlled lateral microstructure. The process is based on the effect of laser-assisted stain etching of silicon with hydrofluoric acid solution. With the further goal of preparing two-dimensional periodical arrays of luminescent microdots, we studied the accuracy of the technique by etching single submillimetre structures with a low-power laser. The size and exact position of the etched area are controlled by laser focusing and movement, respectively, with submillimetre accuracy. Samples exhibit orange luminescence when illuminated with UV or blue light. We have studied the dependence of the efficiency of the luminescence, the structure and the rate of etching on parameters such as the HF concentration, the intensity and wavelength of illumination and the doping level of the silicon wafer. Optimization of the process parameters, and consistency with assumed mechanisms of luminescence and etching process, are discussed. © 1998 John Wiley & Sons, Ltd.

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The ceroid-lipofuscinoses (Batten's disease) are a group of recessively inherited lysosomal storage diseases of children and animals in which there is intracellular accumulation of a fluorescent lipopigment in a wide variety of cells. Lipopigment bodies isolated from pancreas, liver, kidney and brain tissue from a heifer affected with ceroid-lipofuscinosis contained between 55 and 62% protein. A dominant component comigrated on LDS-PAGE with the major low molecular weight protein stored in ovine ceroid-lipofuscinosis. It was identified by amino acid sequence and mass spectroscopy as the full subunit c of mitochondrial ATP synthase, normally found only in the inner mitochondrial membrane, where it is estimated to account for 2–4% of the membrane protein. In pancreatic lipopigment it accounted for at least 40% of the total lipopigment mass and this storage was considered specific to the disease. No other mitochondrial proteins were found in storage bodies. These results are similar to those found in studies on the ovine and the late infantile and juvenile human forms of the disease. It is concluded that bovine ceroid-lipofuscinosis is also a proteolipid proteinosis in which subunit c of mitochondrial ATP synthase is specifically stored in lysosome derived organelles.

We present an investigation into a new technique for producing luminescent porous silicon with controlled lateral microstructure. The process is based on the effect of laser‐assisted stain etching of silicon with hydrofluoric acid solution. With the further goal of preparing two‐dimensional periodical arrays of luminescent microdots, we studied the accuracy of the technique by etching single submillimetre structures with a low‐power laser. The size and exact position of the etched area are controlled by laser focusing and movement, respectively, with submillimetre accuracy. Samples exhibit orange luminescence when illuminated with UV or blue light.

The molecular crystal α-monoclinic selenium has been found to be inadequately described by previous calculations of molecular eigenvalues. A simple band model for monoclinic selenium is proposed on the basis of a new determination of the eigenvalues for the Se8 ring molecule and consideration of the intermolecular interactions arising from the symmetry of the crystal structure. The model is supported by near-normal incidence polarization-dependent reflectivity measurements at room temperature and 77 K over the energy range 1.5-4.5 eV. This interpretation is further supported by a Lorentzian analysis of the data.