L. Amaral

X-ray diffraction measurements of plasma-nitrided Ti–6Al–4V

Abstract A systematic study was undertaken with samples of commercial Ti–6Al–4V nitrided in a conventional d.c. plasma equipment. As treatment parameters, we have used: nitriding time (from 15 to 360 min); nitriding atmosphere (H 2 –20% N 2 and H 2 –60% N 2 ); total pressure (from 10 mPa to 1 kPa) and cathode temperature (from 673 to 943 K). X-ray diffraction measurements show that the effect of nitriding on the near-surface composition of (α+β)–Ti–6Al–4V is a very complex function of the process parameters. Among these, it appears that the sample temperature plays the more dramatic role. For temperatures below 773 K, E-Ti 2 N and δ-δ-TiN are clearly present only for a long period of treatment in a N/H=3/2 atmosphere. For the N/H=1/4 atmosphere, these nitrides are not present in the XRD pattern of samples treated at 773 K, even for a long treatment time such as 240 min. However, samples treated at 943 K show well-resolved E-Ti 2 N and δ-TiN reflections, even for short treatment times such as 15 min.

Ion beam mixing of Fe thin film and Si substrate

Abstract Samples consisting of thin Fe film (40 nm) deposited on (100) Si substrate were irradiated at different temperatures with a Xe + beam (0.2−2.0 × 10 16 cm −2 at 380 keV) and analysed by Rutherford backscattering spectrometry (RBS) and conversion electron Mossbauer spectrometry (CEMS). The intermixing was found to be controlled by cascade mixing when performed at temperatures below ⋍160°C and by radiation enhanced diffusion (RED) at higher temperatures. A combination of Fe 3 Si, FeSi and β-FeSi 2 phases composes the intermixed layer, being the latter phase the predominant compound product, for T ≤ 300°C. When Xe + irradiation is conducted at 400°C the α-FeSi 2 phase is additionally formed. In this case the most abundant phases are Fe 3 Si and FeSi.

Damage accumulation in neon implanted silicon

Damage accumulation in neon-implanted silicon with fluences ranging from 5×1014to5×1016Necm−2 has been studied in detail. As-implanted and annealed samples were investigated by Rutherford backscattering spectrometry under channeling conditions and by transmission electron microscopy in order to quantify and characterize the lattice damage. Wavelength dispersive spectrometry was used to obtain the relative neon content stored in the matrix. Implantation at room temperature leads to the amorphization of the silicon while a high density of nanosized bubbles is observed all along the ion distribution, forming a uniform and continuous layer for implantation temperatures higher than 250°C. Clusters of interstitial defects are also present in the deeper part of the layer corresponding to the end of range of ions. After annealing, the samples implanted at temperatures below 250°C present a polycrystalline structure with blisters at the surface while in the other samples coarsening of bubbles occurs and nanocaviti...

Defect evolution and characterization in He-implanted LiNbO3

Abstract Lithium niobate single crystals have been implanted with 20 keV He+ ions to a fluence of 1×10 16 cm −2 at room temperature. Heat treatments up to 270°C showed a strong build-up of damage in the He-implanted region with an apparent activation energy of 0.14±0.02 eV , while higher temperatures caused a damage reduction in this area. The damage built-up at 270°C is stable even during annealing for 4 h at this temperature. Transmission electron microscopy (TEM) demonstrated that He bubbles are formed in the He-implanted layer during the heat treatment.

A 5 Gb/s Radiation Tolerant Laser Driver

A laser driver for data transmission at 5 Gb/s has been developed as a part of the Giga Bit Transceiver (GBT) project. The Giga Bit Laser Driver (GBLD) targets High Energy Physics (HEP) applications for which radiation tolerance is mandatory. The GBLD ASIC can drive both VCSELs and some types of edge emitting lasers. It is essentially composed of two drivers capable of sinking up to 12 mA each from the load at a maximum data rate of 5 Gb/s, and of a current sink for the laser bias current. The laser driver include also pre-emphasis and duty cycle control capabilities.

Phase transformation and corrosion behavior of stainless steel bombarded by pulsed energetic ion beams

The treatment of stainless steel by pulsed energetic nitrogen ion irradiation in the millisecond regime may cause phase transformations close to the surface. The characterization of the phases was done by measurements of Moβbauer and grazing incidence X-ray diffraction. The results indicate transformations of the austenitic phase into Cr 2 N, Fe 2 N and the γ N -phase (paramagnetic and magnetic) in dependence on the bombardment conditions and the nitrogen depth profiles measured by nuclear reaction analysis. Some samples were studied by depth selective conversion electron Moβbauer spectroscopy. One of these samples contained three new phases: Fe 2 N, γ N2 -phase (paramagnetic) and γ N1 -phase (magnetic). The magnetic phase is found predominantly in the surface region, whereas the Fe 2 N and the γ N2 -phase (paramagnetic) reach their maximum concentration at a depth of approximately 100 nm. The other sample contained four new phases: the three phases mentioned above and additionally α-(Fe,Ni)-martensite, indicating the formation of Cr 2 N. This phase reaches its maximum concentration at a depth of approximately 40 nm. Thus, by interaction of different mechanisms, i.e. segregation of Cr and formation of Fe-Ni rich clusters by radiation enhanced diffusion, the α-(Fe,Ni)-phase is formed on the expense of the other phases. Hardness was measured as Vickers hardness and current-density/potential-curves in a 5 N H 2 SO 4 -solution were performed as corrosion tests. The influence of the different surface phases on mechanical and chemical properties are discussed.

Diffusion of Ag implanted into the AZ1350 photoresist

Abstract In the present work we report Ag diffusion results in the photoresist AZ1350. We have implanted Ag into AZ1350 films at very low energy (E=30 keV) and increasing fluences, Φ=1012 at/cm2, 5×1012 and 5×1013 Ag/cm2. Annealing was performed in the 150–270 °C temperature range and the as-implanted and diffused depth profiles were analyzed using the Rutherford backscattering technique. For the lowest implantation fluence the results show a regular atomic diffusion characterized by an activation energy of Ea=650 meV. This feature shows that in this particular case we have minimized the radiation damage introduced by the implantation process and avoided the cluster formation. Instead for Φ=5×1012 Au/cm2 it is already possible to observe the effects of the radiation damage on the diffusion process. However even for the highest implanted fluence no evidence of cluster formation and diffusion is observed.

Modification of stainless steel and aluminium with pulsed energetic ion beams in the millisecond regime

Abstract In this contribution we are reporting about experimental results on the surface treatment of aluminium and stainless steel by pulsed energetic nitrogen and neon ion beam irradiation in the millisecond pulse range. The characterization of the modified near surface layers of stainless steel by CEMS and aluminium by XPS showed that phase transformations, iron nitride and aluminium nitride formation took place. Results of nitrogen depth-profiling by NRA and RBS indicate that for stainless steel the diffusion process is depending on the pulse duration and the time between two pulses, and for aluminium on the energy density, respectively. Microscopic investigations of the pulse treated surfaces showed crater formation and in some cases surface melting for both materials. Cross-sectional investigations of irradiated aluminium and stainless steel show the modification of the substructure by subsurface melting and grain refining down to 50 μm and 200 μm below the surface, respectively. Microhardness measurements indicate a hardness increase for most of the treated samples in dependence on the irradiation parameters.

Solid state reaction crystallization and amorphization on thin film Fe-Zr multilayers

We study in this paper the thin multilayered film of the system FexZr1-x using conversion electron Mössbauer spectroscopy (CEMS) as well as Rutherford backscattering spectroscopy (RBS). The solid state reaction (SSR) at 500°C for thex=0.33 andx=0.67 concentrations produces crystalline and amorphous phases. For the concentrationx=0.50 only an amorphous phase is obtained. For reactions at 700°C, besides Fe-Zr phases, another one is observed in the CEMS spectrum. This phase may be associated with some FeSi compound since the RBS profile shows the presence of Si at the surface.

Thermal behavior study of Sb implanted into photoresist film

Abstract The thermal stability of Sb implanted AZ1350 photoresist films has been investigated via the Rutherford backscattering technique. We find that a shallow Sb implantation raises the temperature at which the photoresist starts to decompose considerably. Comparison of the present results with those of Ag, Sn and Bi into the same photoresist indicates that not only radiation but also chemical effects have to be considered in order to explain the improvement of the photoresist thermal stability.