Search

Silicon nitride phases are of technological interest for example as gate dielectric in thin film and field effect transistors. The present study compares nitrogen with ammonia plasma immersion ion implantation (PIII) of silicon before and after an annealing step. Nitrogen, silicon and hydrogen depth profiles were obtained by Rutherford backscattering spectrometry (RBS) and nuclear reaction analysis (NRA). For ammonia plasma immersion implantation significantly higher nitrogen concentrations are obtained than for nitrogen implantation as well as the maximum of the nitrogen profile is buried. It turns out that despite the excess of H compared to N in the plasma only a maximum of 2.5 at.% of H is incorporated in a stoichiometric Si3N4 film in the as implanted state. Upon annealing, hydrogen-free silicon nitride films are obtained. The structure has been examined by transmission electron microscopy (TEM). XTEM shows that the initially amorphous SixNyH films are converted into crystalline α-Si3N4 after the annealing step.

In the present work we report on measurements of the electronic stopping power of 1.2 MeV 7Li+ ions channeled through the Si 〈1 0 0〉 axis as a function of the incident angle between −1.2° and 1.2°. The experiments were done using the Rutherford backscattering technique with a SIMOX sample. The measured ratio α between the channeling and random stopping powers as a function of the angle show an upside down Gaussian-like angular dependence with a minimum of α=0.84±0.04 and a FWHM of 0.67°±0.10°. From the experimental data the impact parameter dependent energy loss is estimated and compared with first order calculations.

In this work, we demonstrate that by post-implantation bombardment of 2.0 MeV Au-implanted suprasil by MeV heavy ions such as silicon, one can assist the formation of Au nanoclusters. We will also demonstrate the relationship between the energy deposited in electronic excitations by the MeV Si ions in the Au-implanted layer with the size of these nanoclusters as well as with the optical absorption band due to formation of Au nanoclusters. The optical absorption band characteristic of the Au-implanted suprasil as well as the TEM results were used to monitor the formation of the metallic clusters before and after post-implantation bombardment.

Implantation of 2 MeV ions of Au or Cu into single crystals of MgO (1 0 0) at room temperature results in the spontaneous formation of metallic nanoclusters for implantation fluences above a threshold value. The formation and growth of these clusters may be induced by post implantation bombardment with silicon ions which stop beyond the implantation layer, as well as by thermal annealing. We have compared spontaneous nanocluster formation, ion bombardment induced cluster formation and post thermal annealing. The size and number of nanoclusters were studied by optical absorption spectroscopy and using the Mie and Doyle theories which relate the optical absorption bands to the formation of nanoclusters. The post bombardment of the gold implanted samples was made with 1.2, 2.0 and 5.0 MeV silicon ions. The depth and distribution of the gold and silicon were observed using RBS.

MeV ions passing through polymer films modify their electrical and optical properties and these changes are related to changes in the chemical structures of the polymers. The effects of certain cross linking enhancers, such as sulfur and other pendant molecules, on the ion beam modification process were investigated. Stacked, thin films of polyethersulfone, polyvinyl chloride and polystyrene were bombarded with MeV helium ions and the induced changes in the chemical structure of the polymers were studied with Raman microprobe analysis and RBS combined with in situ residual gas analysis. FTIR spectroscopy was used to categorize the changes in the optical properties. The results were then compared with those from previously studied polyethylene and polyvinylidene chloride polymers.

We report measurements on the electronic stopping power of 7 Li ions along the 〈1 0 0〉 Si direction in the energy region between 1 and 8 MeV. The measurements were carried out using the standard RBS/Channeling technique with SIMOX targets. The results show that the stopping power decreases for increasing energies, from 48 eV/A at 1 MeV down to 19 eV/A at 8 MeV. The general features obtained for the stopping power of 7 Li resemble those obtained for He ions measured previously.

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.

We report measurements of $^{10}\mathrm{B}$ stopping powers in random and Si 〈100〉 directions. The measurements were carried out in the 500\char21{}9000 keV energy range for the channeling case and in the 300\char21{}800 keV for the random one. For the channeling measurements, the low energy data (500\char21{}800 keV) follow a ${\mathrm{v}}^{\mathrm{s}}$ regime with s=0.90\ifmmode\pm\else\textpm\fi{} 0.06 whereas, for the random data, dE/dx\ensuremath{\propto}${\mathrm{v}}^{\mathrm{s}}$ with s=1.1\ifmmode\pm\else\textpm\fi{}0.2. Both results are in good agreement with the prediction of current theories. On the other side, the experimental random $^{10}\mathrm{B}$ stopping power values (for energies up to 650 keV) are in fair agreement with the ones obtained from a scaling procedure by Ziegler, Biersack, and Littmark. However, for energies higher than 650 keV, slight but systematic differences are observed.

In the present work we report measurements of 10B stopping powers in channeled Si 〈100〉 direction. The measurements were carried out with a SIMOX sample in the energy range of 500–9000 keV using a backscattering method. In the lower energy region (up to 800 keV) the results follow an d E d x ∝ Ep regime with p = 0.55 ± 0.05 in good agreement with current theories. In addition, the obtained values show a maximum at around 5 MeV, which arises from the maximum contribution of the L shell to the total electronic stopping power. This behavior is in agreement with predictions by recent calculations using the Plane-Wave Born approximation.

We have demonstrated that the post bombardment of 3.6 MeV Au implanted suprasil by 1.2 MeV boron, 2.0 MeV boron and 0.9 MeV alpha particles can induce the formation of Au nanoclusters. We have also demonstrated that post bombardment increases the annealing temperatures necessary for Au cluster formation beyond 1000°C. The optical absorption band characteristic of the Au implanted suprasil was used to monitor the formation of the metallic clusters before and after post bombardment as well as at each annealing temperature.

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.

In this paper, we present the results of our investigation of producing nanoclusters of gold in silica at fluences of two orders of magnitude less than what is traditionally used This is accomplished by implanting 2.0 MeV Au into silica followed by MeV bombardment by MeV Si ions. The size of the nanoclusters, ranging from one to 10 nanometers, is controlled by the implantation dose and by the total electronic energy deposited by each post bombarding ion in the implanted layer. By both indirect measurement methods, such as optical absorption spectrophotometry (non-destructive), and direct methods, such as transmission electron microscopy (destructive) we show how and at what concentrations gold nucleates to form nanoparticles by radiation-enhanced nucleation at a dose below that needed for spontaneous nanoparticle formation.