J.H.R. dos Santos

Electronic stopping power of 〈100〉 axial-channelled He ions in Si crystals

Abstract Measurements of the electronic stopping power of He2+ ions along the 〈100〉 direction in Si crystal with energies ranging between 200 keV and 4.5 MeV are presented. The Rutherford backscattering technique has been used with SIMOX samples consisting of a Si single-crystal layer on top of a buried layer of 500 nm SiO2 built into a Si 〈100〉 wafer.

Hafnium diffusion in α-Ti

Abstract The diffusion of Hf in α-Ti has been studied in the temperature range 823–1023 K for the first time using the Rutherford backscattering technique on films 150 A thick deposited on α-Ti samples. The results show that the diffusion coefficients follow a non-regular Arrhenius plot. This behaviour, which has already been observed for α-Zr, is discussed in terms of possible intrinsic and extrinsic diffusional mechanisms.

Au diffusion in α-Ti

The solubility and diffusion of Au in α-Ti have been studied in a 823–1023 K temperature range using the Rutherford backscattering technique. For this purpose we have implanted Au into α-Ti samples. Our results show that the solubility of Au varies between 0.2 and 0.35 at.%. In addition, we found that the diffusion coefficients follow a normal Arrhenius behavior with Q=260 kJ/mol and Do=1.9×10−5 m2/s1. These values are typical for a substitutional diffusion mechanism.

Random stopping power and energy straggling of 16O ions into amorphous Si target

Abstract In the present contribution, we report results on random stopping power and range straggling of 16 O ions into amorphous Si target. The measurements were performed in a 300 keV–13.5 MeV energy interval by using the Rutherford backscattering technique together with a marker system. The present stopping results were compared with the TRIM predictions based on the Ziegler, Biersack and Littmark calculations, the theoretical values being always higher than the experimental ones. On the other hand, the calculated straggling data are compared with the Bohr predictions. For low energies, the calculated values over-estimate the experimental ones. For energies larger than 2 MeV, the experimental results became larger than the Bohr predictions. However, with increasing energies, the experimental results approach the Bohr values, and above 12 MeV a quite good theoretical experimental agreement was found.

Angular dependent energy loss of 0.8–2.0 MeV He ions channeled along the Si〈1 0 0〉 direction

Abstract We present measurements of the electronic stopping power in the 0.8–2.0 MeV energy range of 4 He 2+ ions channeled through the Si〈1 0 0〉 axis as a function of the incident angle. The measurements were carried out using the Rutherford Backscattering (RBS) technique with a SIMOX sample that consists of a single Si crystal on the top of a 500 nm buried layer of SiO 2 built into a Si〈1 0 0〉 wafer. The measured ratios between the angular dependent and random stopping powers have almost the same width near the maximum of the 4 He 2+ stopping power and decrease for higher energies.

Diffusion and solubility of Au implanted into the AZ1350 photoresist

Abstract In the present paper we report diffusion and solubility results for Au into the photoresist AZ1350. Au was implanted into AZ1350 films at very low energy (E=20 keV ) and fluences (Φ=10 12 and 5×10 12 Au/cm2). In this way the radiation damage introduced by the implantation process was minimized and cluster formation was avoided. Annealing was performed in the 150–300°C temperature range and the as implanted and thermal treated samples were analyzed using the Rutherford backscattering (RBS) technique. For the lowest implantation fluence the results have shown a regular atomic diffusion process characterized by an activation energy of E a =640 meV . Instead, for Φ=5×10 12 Au/cm2 the diffusional mechanism has revealed the effects of the radiation damage. In addition solubility measurements indicate that the solubility limit at 250°C is of the order 0.3 at.%.

Channeling energy loss of O ions in Si: The Barkas effect

In this work we report on measurements of channeling stopping powers of 16 O ions along Sih 100 i axial direction for the energy range between 250 keV/u and 1 MeV/u by using the Rutherford backscattering technique with separated by implanted oxygen targets. In connection with the recent developed unitary convolution approximation, we are able to extract the Barkas contribution to the energy loss with high precision. This effect is clearly separated from other processes and amounts to about 15%. The observed Barkas contribution from the valence-electron gas is in agreement with the Lindhard model for higher energies. However, in contrast to recent investigations for Li ions, the Barkas effect at the lowest energies seems to saturate, indicating other non-perturbative terms in the polarization field induced by the O ions in Si. 2002 Elsevier Science B.V. All rights reserved.

Thermal behavior study of Sn and Ag implanted into photoresist film

Abstract The thermal stability of Sn and Ag implanted AZ1350 photoresist films has been investigated via Rutherford backscattering technique. We find that a shallow Sn implantation increases the temperature at which the photoresist starts to decompose. This feature is not observed when Ag is implanted under the same conditions. These results indicate that chemical effects play an important role in the improvement of the photoresist thermal stability. We have also studied the thermal behavior of the implanted Sn and Ag ions. It was found that Sn diffuses regularly while Ag segregates toward the surface.

Range parameters of implanted into Si and SiO2

Abstract In the present contribution, we present range parameter results for 18 O implanted into Si and SiO2 targets in a 25–200 keV energy interval. The 18 O depth profiles were determined by using the 18 O ( p , α ) 15 N nuclear resonant reaction at Er=151.2 keV. As a result, we have obtained the 18 O projected range (Rp) and range straggling (ΔRp) for each one of the implantation energies. The experimental data were compared with the TRIM predictions. Concerning 18 O projected ranges in Si, the theoretical–experimental agreement was fairly good, whereas, for the SiO2 case, it was much poorer. However, large differences were found, for both cases, when the ΔRp experimental values were compared with the theoretical ones.

Energy loss measurements of H2 and H3 molecular beams along random and 〈110〉 directions of Si

Abstract The energy loss of H2 and H3 molecules along the 〈1 1 0〉 and non-aligned directions of Si was measured through the Rutherford backscattering technique in combination with a SIMOX target. The experiments were performed at 300, 500 and 700 keV/atom. The results show the following features: First, the random and channeling molecular stopping powers are larger than the corresponding atomic one. Second, at a given energy per atom, the H3 energy loss is larger than the one of H2. Third, within the experimental errors, the channeling and random molecular stopping powers are equal. Finally, there are strong indications that the contribution of the screened Coulomb explosion to the energy straggling of molecular beam increases with the molecular velocity.