Narrow Resonance Profiling Research Articles

Understanding of CO2 interaction with thermally grown SiO2 on Si using IBA depth profiling techniques

Interactions between CO2 and SiO2 films thermally grown on Si have been studied using 18O and 13C as isotopic tracers associated with ion beam analysis (IBA) depth profiling techniques. From secondary ion mass spectrometry (SIMS) measurements no carbon from CO2 is detected in the silica while it is found in Si. These results suggest that CO2 diffuses through the silica. Exchanges of oxygen between CO2 and silica can be observed from 18O to 16O SIMS signals variation. The oxygen concentration depth profiles were determined quantitatively using the narrow resonance near 151keV in the 18O(p,α)15N nuclear reaction (Narrow Resonance Profiling, NRP). We demonstrate that two distinct oxygen exchanges processes co-exist and we determine the diffusion coefficient of the CO2 molecule in the silica at 1100°C.

Synthesis of 3C-SiC Nanocrystals at the SiO<SUB>2</SUB>/Si Interface by CO<SUB>2</SUB> Thermal Treatment

We report 3C-SiC nano-crystals synthesis by thermal annealing of SiO2/Si wafers in CO2 gas. The nano-crystals have been characterized using scanning electron microscopy and atomic force microscopy. These results are correlated with selective area electron diffraction paterns, and transmission electron microscopy observations that evidence the formation of cubic SiC nano-crystals epitaxied on Si. In our experimental conditions, the crystals size is in the range 10-60 nm, increasing with the treatment time, as the crystals density. Using isotopic labelled SiO2 associated with Nuclear Reaction Analysis (NRA) and Nuclear Narrow Resonance Profiling (NRP), oxygen exchanges between CO2 and SiO2 could be evidenced.

Thin film depth profiling using simultaneous particle backscattering and nuclear resonance profiling

We report an important extension to the DataFurnace code for Ion Beam Analysis which allows users to simultaneously and self-consistently analyse Rutherford (RBS) or non-Rutherford (EBS) elastic backscattering together with particle-induced gamma-ray (PIGE) spectra. We show that the code works correctly with a well-known sample. Previously it has not been feasible to self-consistently treat PIGE and RBS/EBS data to extract the depth profiles. The PIGE data can be supplied to the code in the usual way as counts versus beam energy, but the differential cross-sections for the PIGE reaction are required. We also compared the results obtained by the new routine with high resolution narrow resonance profiling (NRP) simulations obtained with the stochastic model of energy loss.

An O18 study of the interaction between carbon monoxide and dry thermal SiO2 at 1100 °C

The mechanisms of oxygen exchange between thermal silicon oxide films and carbon monoxide have been studied using O18 as an isotopic tracer. SiO2 layers of natural isotopic composition, obtained by thermal oxidation of silicon, were exposed at 1100 °C to C13O18 gas at pressures ranging from 50 to 350 mbars. O18 concentration depth profiles were determined using the nuclear narrow resonance profiling technique with the narrow resonance near 151 keV in the reaction O18(p,α)N15. The results show that oxygen exchange takes place via two distinct processes and a mechanism for each process is proposed in the present work. The diffusion coefficient of CO molecules in the silica and the oxygen exchange frequency between CO and the silica are also determined.

The contribution of stable isotopic tracing, narrow nuclear resonance depth profiling, and a simple stochastic theory of charged particle energy loss to studies of the dry thermal oxidation of SiC

We present the stochastic approach to calculating fast charged particle energy distributions when penetrating matter, and nuclear reaction yield curves obtained when the energy of a beam incident on a target is scanned about the energy of narrow nuclear resonances, such as 18O(p,α) 15N at 151 keV. In particular we present new calculations that show the insensitivity of the final calculations to the detailed form of the energy loss distribution assumed for independent single ion–atom collisions. We present application of narrow resonance profiling with 18O stable isotopic tracing to the study of the dry thermal oxidation mechanisms of silicon carbide, yielding insights into the process that cannot be obtained by other means.

Depth resolution and narrow nuclear resonance profiling

Abstract The basic stochastic theory of narrow nuclear resonance profiling is presented. We show that nm depth resolution is achievable in some cases. It is shown that the usual notions of depth resolution such as the full width at half maximum of the instrument function, adequate for instrument functions which vary only slowly over the depth range corresponding to the depth resolution, are unsatisfactory for narrow resonance profiling in the near surface region. Here, the system response to a delta function concentration profile varies very rapidly. However, the shape of the excitation curve is very sensitive to certain kinds of small changes in the concentration profile in the surface region. We discuss some first efforts to define a more general concept for depth resolution, consistent with the usually used definitions, intended to adequately express the perceived sensitivity of a measured excitation curve to variations in the underlying concentration profile.

Narrow resonance profiling study of the oxidation of reactively sputtered Ti 1− xAl xN thin films

The bottom electrode structure used with ferroelectric (FE) and high dielectric constant (HDC) materials requires a material to promote FE or HDC cristallisation (Pt or IrO 2) and a material with diffusion barrier properties; this last material being between Pt (or IrO 2) film and Si substrate. TiN, TiAlN and TaSiN have been proposed for diffusion applications. Ti 1− x Al x N films have drawn much attention as alternatives to TiN diffusion barriers. In this paper we have investigated the effect of Al content on the oxidation resistance of Ti 1− x Al x N films prepared by radio frequency reactive sputtering in a mixed Ar+N 2 discharge. The concentration depth profiles of both 18O and 27Al were measured before and after the rapid thermal annealing of samples at 750°C for 30 s in 18O 2, via the narrow resonances of 18O(p,α) 15N at 151 keV (fwhm=100 eV) and 27Al(p,γ) 28Si at 992 keV (fwhm=100 eV). It was found that Al incorporation in the films reduces oxide growth. The Al excitation curves indicate a uniform Al content for as deposited Ti 1− x Al x N, and reveal Al diffusion to the surface during oxidation, which indicates the formation of an Al rich oxide layer at the Ti 1− x Al x N surface. The results suggest that Ti 1− x Al x N films with x>0.39 are promising candidates as electrically conductive diffusion barrier layers.