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The evaporation from the silicon melt, during Czochralski process, is an important effect for Phosphorus and Antimony dopants. The evaporation rate γ was deduced from the measured axial profile of the resistivity converted into the concentration. For the heavily doped crystals, the value of γ is very similar for both P and Sb: in the order of 5.5×10 −5 cm/s (which is significantly lower than the previously reported evaporation rates). It was concluded that the rate-limiting step for the evaporation process is neither the evaporation reaction itself nor the impurity transport through the flowing gas, but rather the transport through the melt that strongly depends on the melt convection. For low Phosphorus concentration, the transport through the gas is severely slowed-down – due to a change in the dominant gaseous species, from P 2 to P 1 – and becomes a limiting step. The evaporation rate is decreased and, in fact, becomes negligible.

This study investigates the impact of the arsenic and phosphorus concentration on the oxygen content in heavily doped silicon crystals. The resistivity and the oxygen measurements were made on 200 mm crystals grown with the Czochralski method. The oxygen concentration, measured by Gas Fusion Analysis, decreases with the increase of dopant concentration. Two mechanisms related to the effect of the arsenic and phosphorus concentration on the oxygen contents are discussed: one is the possible inhibition of the oxygen segregation inside the silicon crystal due to the lattice deformation and the other is the oxygen evaporation enhancement from the melt through dopant-oxides formation.

This work proposes some improvements over the current state-of-the-art of carbon measurement in silicon by means of Fourier Transform Infrared Spectroscopy (FTIR) at low temperature (77 K), as described in the ASTM F1391-93 (2000) standard method.

The calibration factors for the determination of boron and phosphorus concentration in single crystal silicon by low temperature Fourier transform infrared spectroscopy are examined, with the aim of comparing the behaviour of float-zone and Czochralski samples. It is shown that common calibration factors, derived from a correlation with four-point probe resistivity measurement, can be applied to both material types. Moreover, no significant difference in carrier mobility is observed between FZ and CZ, as determined by Hall effect measurements, in a wide oxygen range: 2–9×1017 cm-3, confirming that the same conversion algorithm to deduce the carrier concentration from the resistivity measurement can be applied.

A novel method for the quantitative measurement of nitrogen in Czochralski silicon by means of low temperature Fourier transform infrared spectroscopy (LT-FTIR) is presented, based on measurement in the far-infrared range. Its main advantage is the high sensitivity to nitrogen, 5×1012 at. cm−3. The method consists in measuring the sample at a temperature less than 15 K, in the spectral range 190–300 cm−1, where the absorption bands related to the electronic transition of the N–O species are present. The samples are prepared by means of a thermal treatment at a suitable temperature (e.g. 650 °C) for a long enough time in order to reach the saturation of the N–O concentration and, therefore, assure that an equilibrium situation is obtained.

Silicon crystals doped with nitrogen from the melt contain shallow thermal donors (STDs) detected both optically and electrically. Annealing samples at 600 and 650 °C results in a saturated STD concentration that depends on the nitrogen concentration approximately by a square-root law. This indicates the involvement of only one nitrogen atom in every STD species. The model of STDs consistent with the present data is the NOm complex of a nitrogen interstitial and m oxygen atoms; the concentration of every STD species reaches the equilibrium value during annealing. The temperature dependence of the equilibrium reaction constant allows us to estimate the average number of oxygen atoms m of the STD complexes as 3.

Indium is becoming one of the most important dopant species for silicon crystals used in photovoltaics. In this work we have investigated the behavior of indium in silicon crystals grown by the Czochralski pulling process. The experiments were performed by growing 200 mm crystals, which is a standard diameter for large volume production, thus the data reported here are of technological interest for the large scale production of indium doped p-type silicon. The indium segregation coefficient and the evaporation rate from the silicon melt have been calculated to be 5 × 10−4 ± 3% and 1.6 × 10−4 cm·s−1, respectively. In contrast to previous works the indium was introduced in liquid phase and the efficiency was compared with that deduced by other authors, using different methods. In addition, the percentage of electrically active indium at different dopant concentrations is calculated and compared with the carrier concentration at room temperature, measured by four-point bulk method.

A case of rectus sheath haematoma and essential thrombocytosis during anticoagulation treatment is described. The difficulties encountered in reaching a clinical, differential diagnosis between rectus sheath haematoma and other abdominal acute conditions are stressed. Computed tomography may prevent inappropriate surgical treatment and its role is emphasized.

The shallow dopants B, P, Al, As, and Sb in Si have been investigated by low-temperature Fourier-transform infrared absorption measurements. Experimental procedures are described to obtain quantitative results for the B and P concentration with improved precision. New calibration factors, based on a correlation with four point probe resistivity measurements, are given which can be used in the concentration range from 1010 to 1016 cm−3. Preliminary results are reported for Al, As, and Sb.

Infrared transmission spectroscopy has been used to study CO adsorption at 77 K on clean and D/sub 2/-pretreated ZnO surfaces. Two physisorbed species are present: one is localized on the free surface hydroxyls and the other is a liquid-like physisorbed chemisorbed species. Three CO chemisorbed species are detected, characterized by different chemisorption energies, as shown from the three different ranges of CO coverage in which they arise and reach their saturation. The comparison between CO adsorption on clean and D/sub 2/-pretreated samples shows that (1) the least energetic CO chemisorption occurs on the sites involved in the irreversible D/sub 2/ chemisorption, and (2) the other two CO species involve sites interacting with the reversible D/sub 2/ species. Models for the chemisorption sites are proposed: consideration of the sites present on the (1010), (1120) and (1011) faces allows us to explain the experimental data and to indicate their possible relevance for the synthesis of methanol. 36 refs. 10 figs.

The infrared spectrum (700–4000 cm–1) of quasi-stoichiometric microcrystalline ZnO has been recorded at various temperatures (97–523 K) and following various redox treatments.A broad band centred at ca. 1500 cm–1, produced on samples cooled down to 97 K in oxygen, is ascribed to the increasing concentration of un-ionized donor centres.The disappearance of all phonon and surface impurity (OH, carbonate-like species) bands, caused by heating the samples to 433 K both in vacuo and in a hydrogen atmosphere, is ascribed to the phonon–plasmon coupling in microcrystals possessing a rather high concentration of electrons in the conduction band.

The infrared spectrum (700–4000 cm–1) of quasi-stoichiometric microcrystalline ZnO has been recorded at various temperatures (97–523 K) and following various redox treatments.A broad band centred at ca. 1500 cm–1, produced on samples cooled down to 97 K in oxygen, is ascribed to the increasing concentration of un-ionized donor centres.The disappearance of all phonon and surface impurity (OH, carbonate-like species) bands, caused by heating the samples to 433 K both in vacuo and in a hydrogen atmosphere, is ascribed to the phonon–plasmon coupling in microcrystals possessing a rather high concentration of electrons in the conduction band.