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In this work reactive pulsed laser deposition of molybdenum- and tungsten-nitride thin films is investigated. Metallic targets were ablated in low-pressure (1, 10 and 100 Pa) nitrogen atmosphere by KrF excimer laser pulses (fluence ∼6.5 J/cm2). Films were deposited on silicon wafers heated to ∼25, 250 and 500 °C. The characteristics of the films strongly depend on the N2 pressure. By increasing N2 pressure, the nitrogen content increases in the films, which leads to a monotonous increase of the electrical resistivity. Deposition rate decreases at 100 Pa as indicated by Rutherford backscattering spectrometry. At this pressure, hardness of the films significantly decreases also, as shown by microhardness measurements. X-ray diffractometry shows that films crystallinity is improved by increasing the substrate temperature. In addition, atomic force microscopy (AFM) and scanning electron microscopy (SEM) were applied for visualising the film surface.

We report experimental results obtained for electrical and structural characteristics of yttria-stabilised zirconia (YSZ) thin films deposited by pulsed laser deposition (PLD) on Si substrates at room temperature. Some samples were submitted to thermal treatments in different ambient atmospheres (vacuum, N 2 and O 2 ) at a moderate temperature. The effects of thermal treatments on the film electrical properties were studied by C – V and I – V measurements. Structural characteristics were obtained by X-ray diffraction (XRD), X-ray reflectivity (XRR) and transmission electron microscopy (TEM) analyses. The as-deposited film was amorphous with an in-depth non-uniform density. The annealed films became polycrystalline with a more uniform density. The sample annealed in O 2 was uniform over all the thickness. Electrical characterisation showed large hysteresis, high leakage current and positive charges trapped in the oxide in the as-deposited film. Post-deposition annealing, especially in O 2 atmosphere, improved considerably the electrical properties of the films.

All the compounds predicted from the SiNi phase diagram were observed by depositing thin layers of nickel onto silicon in known quantities and ratios to each other using an unreactive substrate such as SiO2. After deposition, the samples were annealed in the temperature range 200–750°C and analysed using 2 MeV 4He+ Rutherford backscattering spectrometry and X-ray diffraction techniques. Ni2Si is the first phase formed at a low temperature (about 250°C). Under silicon-rich conditions the system develops in a reproducible manner, subsequently giving rise, when all the nickel has reacted, to the formation of NiSi and of NiSi2 by reaction at 750°C of the NiSi with silicon. The kinetic diffusion approach accounts for the formation and sequence of Ni2Si and NiSi. The phase Ni5Si2 forms between Ni2Si and nickel under nickel-rich conditions. The phases Ni3Si2 and Ni3Si were observed at 400°C and 450°C respectively.

The reaction between molybdenum thin films and single-crystal Si〈111〉 substrates was studied as a function of the concentrations of impurities (mainly oxygen) in the metal film. At a low oxygen concent (1–2 at.%), only the silicide phase MoSi 2 was observed, and a thickness proportional to the square root of time corresponding to an average activation energy of 3 eV in the temperature range 545–600 °C was found. During the formation of the silicide the oxygen originally present in the molybdenum films accumulates at the interface between the silicon and the MoSi 2 . In contrast, a higher oxygen content (4–5 at.%) prevents the formation of any silicide phases in the above temperature range and leads to the formation of MoSi 2 and Mo 5 Si 3 phases at temperatures near 800 °C. MoSi 2 was always observed at the inner interface with Mo 5 Si 3 on the surface. The oxygen segregates from the silicides and accumulates at the Si-MoSi 2 and MoSi 2 -Mo 5 Si 3 interfaces to form a non-uniform layer of SiO x ( x ⩽ 2).

The backscattering technique has been used to study the interdiffusion process of Cr and Au films deposited on silicon substrates. The results indicate that Au diffuses in Cr with an effective diffusion coefficient D = const. exp (−0.68/ k T) . The activation energy is consistent with a diffusion process which occurs preferentially through grain boundaries. The high value of the diffusion coefficient justifies the presence of Au at the CrSi interface after a low temperature short-time heat treatment. At temperatures above 370 °C (the eutectic point of the SiAu system) and after a long enough heat treatment the gold is completely mixed with silicon.

Solid phase processes were used to obtain epitaxial Ge layers 0.1-0.6 μm thick. The structures were formed by evaporating Pd and Ge onto 〈111〉Ge substrates. The samples were initially heated at 250°C to form PdGe and were subsequently heated at about 450°C to obtain Ge growth. They were analysed by MeV He + backscattering and channelling effect measurements (X-ray diffraction was used to verify the stoichiometry of PdGe). The Pd profile in the grown Ge layer was determined. Channelling measurements showed that the grown Ge layers were well ordered and epitaxial with the underlying substrate.

The following platinum X-ray absorption edges were measured in platinum silicides: Pt2Si L2,3, PtSi L2,3 and PtSi M2,3. The results are compared with the edges measured in platinum metal. As well as the known peak at the edges of index 3, a new strong peak absent in the metal appears at the edges of index 2 of the silicides. This effect is very strong in the M2 edge in spite of the linewidth which is greater than that in L2. The results are interpreted in terms of transitions to empty d states typical of the hybridization (Si p)-(Pt d) which gives rise to states with projections onto j= 3 2 and j= 5 2 so that the peak due to p-d transitions is present in the edges of index 2 and of index 3. The different localization involved in M and L transitions is also discussed.

In this communication reflectance and thermoreflectance spectra of films of PtSi and Pt 2 Si grown on glass substrates are reported and discussed. Weak structures superimposed on the free-carrier response of the reflectance spectra are detected by means of thermoreflectance. Attributions of such structures mainly in terms of d-d transitions are briefly discussed.

The interaction of Ni film deposited on Si has been studied. Growth kinetics of NiSi on (111) and (100) silicon single crystals are reported. Activation energies for NiSi are found to be 1.23 eV for (100) and 1.83 eV for (111).

We investigated the rate of germanide formation and the composition of the resulting compounds when thin (1000–2500 A) palladium films, vacuum evaporated onto various germanium substrates, were annealed at temperatures from 170 to 270°C for 10 min to 27 h. Both phases, Pd2Ge and PdGe, were observed on single-crystal and amorphous (vacuum-deposited) germanium substrates. In all cases the compounds layers grow with a (time) 1 2 dependence and with an activation energy of 1.5 ± 0.1 eV. Moreover the absolute value of the growth rate depends on the crystalline nature of the germanium substrate. On (111) and (100) substrates the rates are similar and they are three times lower than those on amorphous substrates.

Solid phase epitaxial growth was investigated using a structure comprising evaporated silicon on evaporated aluminium on single-crystal silicon. It was found that the growth rate is faster on a 〈100〉 substrate than on a 〈111〉 substrate. On an amorphous SiO 2 substrate the evaporated silicon is transported through the evaporated aluminium and grows on the SiO 2 . This process seems to occur at a slower rate than in the case of a single-crystal substrate. An intermediate growth rate was obtained by using a 〈111〉 Si wafer with a very thin SiO 2 layer. These results indicate that the rate-limiting process for epitaxial growth occurs at the single- crystal silicon-evaporated aluminum interface.

We report on the deposition of thin Yttria-stabilized zirconia (YSZ) films and TiN/YSZ bilayers on Si substrates at room temperature by pulsed KrF excimer laser ablation deposition (PLD). YSZ films were deposited onto (1 0 0) Si substrates by ablating an YSZ target in vacuum and in low-pressure oxygen atmosphere. TiN/YSZ/Si bilayers were deposited in two steps without exposure to the air using a multitarget system: first, an YSZ film was deposited onto a Si substrate by ablating an YSZ target in oxygen ambient gas, then a Ti target was ablated in nitrogen ambient gas. Morphological and structural characteristics were investigated by Rutherford backscattering spectrometry (RBS), scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray reflectivity (XRR) techniques.

The interface reactions in Co/W multilayers (ML) with Co thickness of 1 and 2 nm and W thickness of 1, 2 and 5 nm in as-deposited state and under KrF laser irradiation with fluences F=50–200 mJ/cm2 were studied by different X-ray methods. Superlattice satellites around W (1 1 0) direction were found in as-deposited and irradiated multilayers. The layered structure persists up to the highest applied fluence. Co3W compound is formed at the interfaces. However, the intermixing is low.

We report on the deposition of thin vanadium nitride films by ablating vanadium targets in low-pressure N 2 atmosphere, and on their characterization. The targets were vanadium foils (purity 99.8%). 3 in. Si(1 1 1) wafers were used as substrates. Film characteristics (composition and crystalline structure) were studied as a function of N 2 pressure (0.5–200 Pa), KrF laser fluence (4.5–19 J/cm 2 ), substrate temperature (20–750 °C) and target-to-substrate distance (30–70 mm). Vanadium nitride is already formed at low N 2 ambient pressures (1 Pa) and laser fluences (6 J/cm 2 ) on substrates at room temperature. At the N 2 pressures of 1–10 Pa, the prevalent phase is VN. At higher pressures (100 Pa) and at relatively high laser fluences (16–19 J/cm 2 ), the dominant phase is V 2 N. The crystallinity of the films improves by increasing the substrate temperature. Well-crystallized films are obtained on substrates heated at 500 °C.

Titanium carbide films were deposited on silicon wafers by XeCl (308 nm) excimer laser ablation of titanium in low pressure (10 -6 -10 -1 mbar) methane atmosphere. Series of 10 000 pulses at the repetition rate of 8 Hz were directed to the target surface. The fluence was set at 4.5 and 5.5 J/cm 2 . Pulse duration was about 30 ns. The deposited films were charcterized by different techniques (Rutherford backscattering spectrometry, X-ray diffractometry and scanning electron microscopy). Results show that at both fluences and at pressures below ∼ 10 -5 mbar the deposited films are mainly formed of metallic titanium. In the range 10 -3 -10 -1 mbar, at the fluence of 4.5 J/cm 2 , the deposits are formed of titanium carbide (TiC) with only traces of oxides. At the fluence of 5.5 J/cm 2 the amount of ablated material is too large to undergo complete reaction and mostly metallic titanium is deposited.

Titanium and silicon nitride films were deposited on silicon wafers by XeCl (308 nm) excimer laser ablation of titanium and silicon, respectively, in low pressure (10 −3 −5 mbar) nitrogen-containing atmospheres. Series of 10 000 pulses at a repetition rate of 10 Hz were directed to the target surface. The fluence was set at about 5 J/cm 2 . Pulse duration was about 30 ns. The deposited films were characterized by different techniques (X-ray diffraction, scanning and transmission electron microscopy, etc.). Good quality films with a thickness exceeding 1 μm were obtained under specific experimental conditions.

In this paper the microstructural characterisation of yttria-stabilised zirconia (YSZ) thin films deposited by laser ablation is reported for the as-deposited sample as well as for samples submitted to thermal treatments in different atmospheres (vacuum, N 2 and O 2 ) at a moderate temperature (500 °C). Results obtained by different characterisation techniques such as grazing incidence X-ray diffraction, X-ray reflectivity and transmission electron microscopy evidenced the formation of the cubic YSZ phase after the annealing treatments. On the contrary, the as-deposited sample is amorphous with nanocrystals of the cubic YSZ phase dispersed inside. It also exhibits a difference between the density of the surface region and the region of the interface with the substrate. This latter effect has been attributed to the loss of oxygen atoms during the deposition. The annealing treatments are able to recover the density unhomogeneity present inside the as-deposited sample, the degree of recovering depends on the ambient atmosphere.

The thermal stability of e-beam deposited multilayers (MLs) for soft X-ray reflection optics was studied under XeCl laser processing in vacuum. MLs with five Co/Si/W/Si periods, each 13.5 nm (MLS1) or 18.4 nm (MLS2) were deposited onto oxidized Si and irradiated at the fluences of 0.075–0.62 J cm −2 by 1 or 100 pulses. The samples were analyzed by X-ray diffraction, hard X-ray reflectivity and sheet resistance measurements. The layered structure of our samples persists up to 0.62 J cm −2 per 1 pulse for MLS2 and 0.62 J cm −2 per 100 pulses for MLS1 irradiations. The thermal stability of MLS1 is even better than for W/Si MLs studied previously. In laser irradiated samples the Co 2 Si 3 phase which is normally formed under high pressures (>4 GPa) was found. It has not been reported in the film couples so far. The high thermal stability and Co 2 Si 3 formation in MLS1 are explained by complex Co–Si silicide formation conditions and compressive stress parallel to the surface of irradiated samples.

Silicon carbide films were deposited on Si wafers (at room temperature and 150°C) by XeCl laser (fluence 5 J/cm2, pulse duration 30 ns, repetition rate 10 Hz) ablation of Si in low pressure (0.25–6 mbar) CH4 atmosphere. The deposits were characterized by different diagnostic techniques (XRD, XPS, RBS, etc.). Polycrystalline stoichiometric silicon carbide films ∼ 1 μm thick were obtained under specific conditions after ∼ 104 laser pulses.

Titanium carbide films were deposited on silicon wafers by XeCl (308 nm) excimer laser ablation of titanium in low pressure (10 −3 mbar) methane atmosphere. Series of 10 000 pulses at the repetition rate of 8 Hz were directed to the target surface. The fluence was set at about 5 J cm −2 . Pulse duration was about 30 ns. The deposited films were characterized by different techniques (X-ray diffraction, scanning electron microscopy and Rutherford backscattering spectrometry).

Silicon nitride films were deposited on silicon wafers by XeCl (308 nm) excimer laser ablation of silicon in low pressure (1 × 10 −3 −1 mbar) ammonia atmospheres. Series of 10000 pulses at the repetition rate of 8 Hz were directed to the target surface. The fluence was set at about 5 J/cm 2 . Pulse duration was about 30 ns. The deposited films were characterized by different techniques (X-ray diffraction, infrared spectrophotometry, X-ray photoelectron spectroscopy, Auger electron spectroscopy, scanning electron microscopy, profilometry). Deposition of stoichiometric silicon nitride films with thickness close to 1 μ m (deposition rate ∼ 0.1 nm/pulse) was obtained when ablation was performed in ammonia at the pressure of 1 mbar.

We have succeeded in simultaneously conducting two chemical reactions resulting in the formation of titanium nitride and titanium silicide in well-shaped clearly separated layers as an effect of multipulse excimer laser treatment of a Si wafer with a thin Ti coating in an ambient N 2 gas. We demonstrate by a numerical analysis that the parallel evolution of the two reactions in a one-step process is a consequence of the melting of both the Ti coating and of a thick layer of Si bulk in conditions that completely avoided substance expulsion.

The formation of tungsten silicide induced by XeCl laser irradiation of W(150 nm)/Si and W(500 nm)/Si samples was studied at laser fluences ranging from 0.6 to 1.8 J/cm 2 . Up to 300 subsequent laser pulses were directed to the same irradiation site. After irradiation the samples were examined by different diagnostic techniques: Rutherford backscattering spectroscopy, X-ray scattering, resistometry and surface profilometry. Complete reaction of the 150 nm W film with silicon was obtained between 30 and 100 laser pulses at the fluence of 1.2 J/cm 2 , and after 30 laser pulses and at the fluence of 1.5 J/cm 2 . The sheet resistance of these silicides was 5–10Ω. At the used fluences, only the onset of silicide synthesis at the W-Si interface was observed for the 500 nm W film. Numerical computations of the evolution and depth profiles of the temperature in the samples as a consequence of a laser pulse were performed and compared to the experimental results.

We report a study of the formation of nitride surface layers on titanium foils by multipulse (100 to 2500) XeCl excimer laser (λ = 308 nm) irradiation in N2 and NH3 atmosphere. After irradiation the samples were analyzed by Rutherford backscattering spectroscopy (RBS) and nuclear reaction analysis (NRA) and then examined by electron microscopy (SEM, TEM). The nitridation process was shown to be very efficient with both gases. The amount of nitride has been observed to depend on the number of subsequent laser pulses, on the pulse repetition rate and on the nature of the ambient gas.

Polycrystalline SiC layers were obtained through pulsed annealing of thin (100 nm) carbon films deposited on single-crystalline silicon wafers. The samples were submitted to electron beam irradiation (25 keV, 50 ns) at various current densities in vacuum (∼10 −4 mbar) and to XeCl excimer laser pulses (308 nm, 15 ns) in air. Rutherford backscattering analysis showed that in the e-beam annealed samples mixing of the elements at the interface starts at current densities of about 1200 A/cm 2 . The mixed layer thickness increases almost linearly with current density. At current densities higher than 2400 A/cm 2 ablation of the C film was always observed. Using the XeCl excimer laser, a good intermixing of the deposited C film with the Si substrate was observed after a single 0.3 J/cm 2 pulse. From the RBS spectra a composition of the intermixed layers close to the SiC compound was deduced. Transmission electron microscopy and electron diffraction studies clearly evidenced the formation of SiC polycrystals.

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.