The motion of energetic charged particles inside a monocrystalline solid can be strongly influenced by channeling and blocking effects. The present article reviews the theory, the experimental studies, and some of the applications of these effects. The coverage of the published literature extends through June 1973.

Channeling and related effects in the motion of charged particles through crystals

Rutherford backscattering spectrometry (RBS) and related techniques have long been used to determine the elemental depth profiles in films a few nanometres to a few microns thick. However, although obtaining spectra is very easy, solving the inverse problem of extracting the depth profiles from the spectra is not possible analytically except for special cases. It is because these special cases include important classes of samples, and because skilled analysts are adept at extracting useful qualitative information from the data, that ion beam analysis is still an important technique. We have recently solved this inverse problem using the simulated annealing algorithm. We have implemented the solution in the `IBA DataFurnace' code, which has been developed into a very versatile and general new software tool that analysts can now use to rapidly extract quantitative accurate depth profiles from real samples on an industrial scale. We review the features, applicability and validation of this new code together with other approaches to handling IBA (ion beam analysis) data, with particular attention being given to determining both the absolute accuracy of the depth profiles and statistically accurate error estimates. We include examples of analyses using RBS, non-Rutherford elastic scattering, elastic recoil detection and non-resonant nuclear reactions. High depth resolution and the use of multiple techniques simultaneously are both discussed. There is usually systematic ambiguity in IBA data and Butler's example of ambiguity (1990 Nucl. Instrum. Methods B 45 160–5) is reanalysed. Analyses are shown: of evaporated, sputtered, oxidized, ion implanted, ion beam mixed and annealed materials; of semiconductors, optical and magnetic multilayers, superconductors, tribological films and metals; and of oxides on Si, mixed metal silicides, boron nitride, GaN, SiC, mixed metal oxides, YBCO and polymers.

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Elemental thin film depth profiles by ion beam analysis using simulated annealing - a new tool

TOPICAL REVIEW: Elemental thin film depth profiles by ion beam analysis using simulated annealing - a new tool

Activated reactive evaporation has been used to grow copper oxide nanoparticles in the size range of 8–100 nm. X-ray diffraction spectra clearly show the presence of a single Cu2O phase. Detailed x-ray photoelectron spectroscopy studies show an increase in the ionicity of the Cu2O system with decreasing particle size. Depth profiling and finger printing of x-ray photoelectron spectra reveal that the Cu2O nanoparticles are capped with a CuO surface layer of thickness ≈1.6 nm. This study strongly suggests that the stabilization of the cubic Cu2O nanophase is enhanced by the formation of a CuO surface layer.

Surface-modified CuO layer in size-stabilized single-phase Cu2O nanoparticles

In the present study, x-ray diffraction, Raman spectroscopy, spectroscopic ellipsometry, photoluminescence, and x-ray photoelectron spectroscopy techniques were used to study the effect of 120 MeV 107Ag9+ ion irradiation on nanocrystalline Cu2O thin films grown by the activated reactive evaporation technique. The influence of dense electronic excitations during ion irradiation on the structural and optical properties of the Cu2O thin films was studied. Experimental results demonstrate that the phase and the size of nanocrystallites in the Cu2O thin films as well as associated surface states can be tailored by controlling ion fluence. The Cu2O higher symmetry cubic phase is observed to be quite stable under a higher temperature and irradiation-induced thermal spikes, which accompanies ion irradiation.

Modifying the nanocrystalline characteristics: structure, size, and surface states of copper oxide thin films by high-energy heavy-ion irradiation

Optical and structural changes of silica glass substrates implanted with Cu and O ions and subjected to thermal annealing, are examined as a function of the implantation sequence by optical absorption, Rutherford Backscattering Spectrometry (RBS) and thin film X-ray diffraction (XRD) measurements. Before annealing, the distribution of Cu is affected by the implantation sequence and O- followed by Cu-implantation leads to fewer Cu nanoparticles than the Cu- followed by O ion implantation. After annealing, however, the redistribution behavior of Cu and optical absorption features are similar for both co-implanted samples. Nanocrystals of Cu2O are mainly formed by annealing and the absorption peaks at about 340, 450 and 480 nm are observed for the co-implanted samples. The peaks are possibly evidence for the presence of the copper oxide nanocrystals.

High-energy cu and o ion co-implantation into silica glasses

Polycrystalline β‐SiC samples were implanted with 50 keV 15N ions with fluences ranging from 3×1017 to 1.5×1018 ions/cm2 at elevated temperature up to 1100 °C. Nitrogen depth profiles were measured as a function of implantation temperature and annealing temperature using nuclear reaction analysis, Rutherford backscattering spectroscopy, and Auger electron spectroscopy. It was found that the maximum concentration and the width of nitrogen depth profiles implanted at 1100 °C were reduced distinctly in comparison with the profiles implanted below 930 °C or annealed at 1100 °C. The redistribution of nitrogen implanted in SiC at 1100 °C was ascribed to the formation of β‐Si3N4 crystallites in SiC, which was confirmed by x‐ray diffraction at glancing incidence.

Formation of β‐Si3N4 by nitrogen implantation into SiC

Zirconium films were implanted with 15 N ions of energy 50 keV to a total fluence of 1 × 10 18 ions cm -2 in an attempt to study the formation process and thermal stability of ZrN layers produced by high fluence implantation of nitrogen. Subsequent to the implantation at room temperature, samples were annealed at temperatures of 300 °C–900 °C. The depth profiles of the implanted nitrogen were measured by nuclear reaction analysis using the 15 N(p,αγ) 12 C at E R = 429 keV, and the surfaces were examined by thin film X-ray diffraction (XRD) and scanning electron microscopy. There were many blisters 0.2–0.4 μm in diameter on the surface of the as-implanted samples and double peaks were observed in the nitrogen depth profiles; they were in both sides of the mean projected range. It was found that most of the blisters became extinct after annealing above 400 °C, and the XRD peak (111) intensity was increased with the increase in the annealing temperature. Moreover, 14 N and 15 N implantations were superimposed on Zr samples in order to study the atomic migration of nitrogen at each stage of high fluence implantation. It was found that the decrease in the peak at the deeper layers was related to blister extinction and nitrogen diffusion into underling zirconium which could be correlated with radiation damage induced by post-implanted ions.

Thermal behaviour of nitrogen implanted into zirconium

Microstructure of germanium films crystallized by high energy ion irradiation

A 8 MeV multicharged carbon or oxygen beam was used for Rutherford Backscattering Spectrometry (RBS) compositional analysis. Thin films of Co, Cu, Si, and NiCr of a few nm thickness were deposited on carbon substrates by vacuum evaporation or Ar sputtering. The measured results demonstrate that the mass resolution is much better for the heavy-ion RBS than for the He-RBS analysis. For the compositional analysis, a fitting function formula is proposed based on a simple model in which the thin film consists of many islands. The calculated results agree with the measured spectra, which show asymmetry of the peaks. Numerical analyses using the fitting function give reasonable agreement between the expected and measured ratios of mass elements in the films.

Hiroaki Niwa

Papers

High-energy cu and o ion co-implantation into silica glasses

Formation of β‐Si3N4 by nitrogen implantation into SiC

Thermal behaviour of nitrogen implanted into zirconium

Microstructure of germanium films crystallized by high energy ion irradiation

Application of heavy-ion RBS to compositional analysis of thin films