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In the present work, we report the results obtained by laser irradiation of a-Si/Co/SiO 2 and a-Si/SiO 2 samples in order to study the influence of the Co film on the a-Si crystallisation process. Both Co and a-Si layers were deposited by electron beam evaporation. Cobalt films of 0.5, 1 and 3 nm were deposited upon a 300 nm thick SiO 2 layer. The thickness of the a-Si layer was fixed at 200 nm. Samples were irradiated by a XeCl excimer laser under fluences of 0.40, 0.45 and 0.50 J cm -2 and I or 10 number of pulses. Grazing incidence XRD and cross-sectional TEM were used for sample characterisation. Results showed the formation of CoSi 2 that, in general, considerably improves the crystallinity of the a-Si layer. In some cases, the presence of the CoSi 2 underlayer allowed the complete crystallisation of the a-Si layer even after the first laser pulse. Without CoSi 2 , the same results were obtained only with a higher number of pulses.

The growth of high-mobility modulation-doped Si/SiGe heterostructures on silicon-on-insulator (SOI) substrates is demonstrated. The structural and electrical properties of the samples are comparable with those of similar samples grown on standard Si substrates. Electron mobilities as high as 2800 cm 2 V −1 s −1 at room temperature and 8.2×10 4 cm 2 V −1 s −1 at 4 K are obtained.

Carbon nitride films deposited on Si (001) substrates at room temperature by XeCl laser ablation of graphite targets in low pressure (1, 5, 10 and 50 Pa) N2 atmosphere at fluence of 12 J/cm2 (∼0.4 GW/cm2) have been investigated by x-ray diffraction and transmission electron microscopy in order to study the structure of the films. The results showed that the samples are constituted of a continuous amorphous film inside which microcrystals of a coherently grown CNx phase are dispersed. This phase is monoclinic with the following lattice parameters: a=b=0.384 nm, c=0.302 nm, α=γ=90°, and β=96.5°. The CNx phase grows with the (001) plane coincident with the (001) plane of the Si substrate and with the [010]CNx direction parallel to the [110]Si one.

Summary form only. The prediction of a covalently bound carbon nitride solid /spl beta/-C/sub 3/N/sub 4/ with characteristics (hardness, bulk modulus) comparable to or even better than those of diamond, stimulated many attempts to synthesise and deposit thin films of this material. Pulsed laser ablation is among the most promising technique to achieve this result.

Carbon nitride films were deposited at 20, 250 and 500°C on 〈111〉 Si substrates by XeCl laser ablation of graphite in low pressure (1–50 Pa) N2 atmosphere at fluences of 12 and 16 J/cm2. Different diagnostic techniques (SEM, TEM, RBS, XPS, XRD) were used to characterize the deposited films. Films resulted plane and well adhesive to their substrates. N/C atomic ratios up to 0.7 were inferred from RBS measurements in films deposited at 20°C and 16 J/cm2. Nitrogen concentration increases with increasing ambient pressure and laser fluence. The N 1s peak of the XPS spectra indicate two different bonding states of nitrogen atoms to C atoms, while the C 1s peak, apart from the two bonding states to nitrogen atoms, indicates one bonding state with regard to carbon atoms. XRD and TEM analyses point to an oriented microcrystalline structure of the films. Heating of the substrate results in a lower nitrogen concentration in respect of films deposited at 20°C in otherwise identical experimental conditions. Optical emission studies of the laser plasma plume indicate a correlation between the emission intensity of the CN radicals in the plume and the nitrogen atom concentration in the films.

Carbon nitride films, deposited on Si(111) substrates at room temperature by XeCl laser ablation of graphite targets in low pressure (1, 5, 10, and 50 Pa) N2 atmosphere at the fluence of 12 J/cm2 (∼0.4 GW/cm2), have been submitted to accurate x-ray diffraction and transmission electron microscopy investigations in order to study the structure of the films. Results showed that the samples are constituted of a continuous amorphous film inside which microcrystals of a new coherently grown CNx phase are dispersed. This new phase has a triclinic crystallographic cell with lattice parameters a=b=0.384 nm, c=0.438±0.007 nm, α=110±1°, β=105±1°, and γ=120°. It coherently grows on the (111) Si plane with the following orientation relationships: (001)CNx∥(111)Si, [100]CNx∥[1-10)]Si, and [010]CNx∥[01-1)]Si.