Profiling Light Elements Research Articles

The development of a time of flight spectrometer for LARN

An elastic recoil detection time of flight system to depth profile light elements has been developed on ALTAÏS, the new Tandetron accelerator at LARN. The detector mounted at 45° from the beam axis consists of two isochronous electron detectors for the timing signal (START and STOP) and a 450 mm 2 heavy ion PIPS detector that detects the energy of the recoil atoms. The 2MV Tandem accelerator provides heavy ion beams with a maximum energy of 16 MeV depending on the charge transfer efficiency of the gas exchange canal located in the middle of the machine. A large variety of primary ion beams like 28 Si , 35 Cl , 63 Cu , 127 I or 197 Au can be produced with the SINIX heavy ion source and accelerated on the target. Typical current around 1 nA can be obtained. The energy transfer to the recoil atoms is typically in the MeV range and depends on the mass and the energy of the projectile. Some secondary effects like the energy loss in the carbon foils of the timing detector but also in the entrance window of the energy detector should not be neglected if we try to depth profile light elements with this technique. Time resolution of about 1 ns for the electrons detectors is suitable to obtain 1 amu mass resolution. Some examples of applications will be developed in this paper.

Depth profiling of light elements using a nuclear microprobe

In this paper, we present some examples of depth profiling of light elements with a nuclear microprobe performed at LARN during the last decade. Some new possibilities of ion beam microanalysis of light elements with our 2 MV Tandetron accelerator are also discussed.The first example of application consists of depth profiling of nitrogen and aluminium on a SiAl alloy implanted with nitrogen. The nuclear microprobe was used to determine three-dimensional distribution of aluminium, silicon and nitrogen in a specific grain of the implanted alloy. The nitrogen depth profile was measured using the well known 15N(p,αγ)12C nuclear resonant reaction at 429 keV. The aluminium depth profile was measured with the resonant nuclear reaction 27Al(p,γ)28Si at 991.8 keV.Depth profiling of carbon and oxygen is also possible using nuclear reactions induced by 3He particles. Nuclear reactions like 12C(3He,pi)14N (i=0,1,2) or 16O(3He,α0)15O were used to measure local wear tracks on a diamond coating after a fretting test against a Cr steel ball.PIXE microprobe and nuclear reactions induced by deuterons were also used to characterise the gold–silicon alloy formed by the diffusion of silicon into gold foils. The nuclear reaction 28Si(d,p)29Si in a transmission geometry was used in order to depth profile silicon especially in the grain boundaries of the gold–silicon alloy.Some new perspectives of depth profiling light elements are also presented using our new 2 MV Tandetron accelerator, such as high energy 4He microbeams for depth profiling of carbon or nitrogen.

Elastic recoil detection (ERD) of light elements in the near-surface region of Zr and its alloys following corrosion

The use of very heavy ion beams in elastic recoil detection (ERD) measurements makes ERD a semi-universal technique capable of measuring all elements from hydrogen to elements with mass of 100 or above. We have used this technique to profile light elements in the near-surface region of thin foils of Zr-2.5wt.%Nb which had been exposed to a corrosive solution of 0.1% NH 4HF 2 in D 2O. We present results for H, D, C, N, O and F in the near-surface region of such foils, and demonstrate the power of ERD for such studies.

Simultaneous analysis of light elements using non-Rutherford helium backscattering

Non-Rutherford backscattering has been recognized as a valuable analytical approach to profiling light elements with superior sensitivity and large depth accessibility. However in multielemental analysis the scattering cross sections of elements obtained under the same conditions and a proper computer simulation are preferable. Here a data base of non-Rutherford cross sections was determined precisely at the scattering angle of 165° with helium energy ranging from 2.0–9.0 MeV. The data for carbon and nitrogen have been published previously, and now the data for oxygen are presented. In addition, the results have been compiled into the computer simulation program RUMP, which is valid for simultaneously determining both the stoichiometry and depth profiles of light elements in a heavy element matrix. As examples of such application, the BS spectra of a Ti (C, N, O) film and a coated electrode material were measured with a number of incident energies, and consistent sample descriptions were assumed in the simulation.

Depth profiling of hydrogen isotopes in thin, low-Z films by scattering recoil coincidence spectrometry

The technique for profiling light elements in thin, low-Z foils, by means of a coincidence measurement over large solid angles, is demonstrated for hydrogen and deuterium in two separate geometries. A beam of 2.0 MeV 4He particles was used to bombard foils of (i) evaporated carbon, (ii) evaporated carbon which had been implanted with 10 17/cm 2 7.5 keV H + ions and, (iii) evaporated carbon which had been implanted with 5 × 10 16/cm 2 7.5 keV D + ions. Measurements were made, in the latter two cases, with the implanted region facing the beam and away from the beam. Plots of E α versus E H(D), as well as plots of total energies ( E α + E H(D)) clearly show the H (and D) distributions within the foil.

Elastic recoil coincidence spectroscopy (ERCS)

Elastic recoil coincidence spectroscopy (ERCS) is a scattering-recoil coincidence technique with a high sensitivity for profiling light elements ranging from H up to O in thin film samples. In this technique He + ions with energies of at least 2 MeV are incident on a thin target, typically 2 μm thick, and the energies of both forward scattered He ions and elastically recoiled light atoms are detected in coincidence using detectors subtending large solid angles. From each pair of energies the depth where scattering has taken place as well as the mass of recoiled atoms can be derived. ERCS is preferably applied to profile light elements in a heavier matrix and in cases where a low beam current (< 1 nA) or a low total ion dose is required to reduce damage, e.g. to study polymer samples, or for microbeam analysis. A gain in counting rates of 2–3 orders of magnitude compared to conventional elastic recoil detection analysis (ERDA) and a depth resolution of 20 nm can be achieved. In a first experiment, we applied ERCS to profile simultaneously C and O in thin polycarbonate foils and in a second experiment we have analyzed O and B in thin B-diffused Si crystals. In this paper we discuss the basic principles of ERCS and describe in detail the derivation of concentration-versus-depth profiles from coincidence spectra measured for polycarbonate and Si samples.

Non-Rutherford 4He cross sections for ion beam analysis

Increasing use of 4He analysis beams with energies between 2 and 10 MeV for depth profiling and backscattering analysis of thin films and near-surface materials requires accurate measured values of non-Rutherford cross sections for scattering of 4He by the lighter elements. Cross sections for scattering of 4He through large angles deviate from Rutherford at 4He laboratory energy ∼ 2.2 MeV for target nuclei 12C and 16O; deviations for target atomic numbers Z = 20 and 40 occur at 4He energies of about 5 and 10 MeV, respectively. We review the experimental cross section data currently available for large angle scattering of 4He from the light elements (4 ≤ Z ≤ 20) for incident 4He laboratory energies 1.5–10 MeV. For each target element, we indicate energy regions with smooth cross section variation suitable for use for simple backscattering analysis as well as strong narrow resonances that may be used for depth profiling light elements in heavy-element matrices.

Depth profiling of light elements using elastic recoil coincidence spectroscopy (ERCS)

Abstract We have developed elastic recoil coincidence spectroscopy (ERCS), a technique with high sensitivity to profile light elements, ranging from H up to O, in thin polymer foils or in thin samples containing heavier elements. In this technique, MeV He+ ions are incident on a thin target, typically 2 μm thick, and the energies of both the forward-scattered He ions and the elastically recoiled light atoms are detected in coincidence. Concentration-versus-depth profiles can be derived from the measured number of coincidence events for a depth range of up to l μm and for all recoiled light elements. This is done by relating each pair of energies of scattered and recoiled atoms to a depth where scattering has occurred and to the mass of the recoiled elements. To analyze the coincidence spectra and to derive concentration-versus-depth profiles, computer programs have been developed. To demonstrate the capabilities of ERCS we have chosen polycarbonate films (48 at.% C, 9 at.% O) and have derived the expected uniform concentration-depth profiles from the coincidence spectra for a depth range of 1 μm. In a second experiments, ERCS was applied to profile B and O in a thin boron-diffused Si window.

Scattering recoil coincidence spectrometry: A new experimental technique for profiling hydrogen isotopes in low-Z thin films

The new technique for profiling light elements in thin, self-supporting foils, which uses a coincidence measurement over very large solid angles, has been demonstrated experimentally. A beam of 2.0 MeV 4 He particles was used to bombard films of (i) cracked ethylene and (ii) evaporated carbon which was subsequently implanted with 7.5 keV 1 H + ions to a concentration of 10 17 /cm 2 . Plots of E α vs E p clearly show the 1 H distributions in the foil.

Proton backscattering and computer data analysis in the non-rutherford energy region

In recent years it has been found that the method of proton backscattering in the low-MeV energy region can provide advantages that are not attainable by backscattering of other projectiles. Among these are better sensitivity for profiling light elements and larger accessible depth of the sample. For the analysis of multielemental samples, however, a consistent set of experimental scattering cross sections and computer methods in data analysis are needed. In the present study a database of experimental non-Rutherford cross sections for 170° proton backscattering analysis is supplemented with new data for Ti and Al. Examples of recent applications of proton backscattering are presented, literature cross sections and the interference from inelastic and nuclear transformation reactions are investigated and computer methods for data treatment are examined.

Scattering recoil coincidence spectrometry

A spectrometry has been developed which combines Rutherford backscattering spectrometry (RBS) and elastic recoil detection (ERD) into a coincidence measurement over very large solid angles. This highly sensitive method is especially appropriate for profiling light elements in a self-supporting foil which is prone to radiation damage. The large solid angle coincidence idea can also significantly improve analysis by nuclear reactions, including neutron depth profiling.

A magnetic spectrometer method for profiling light elements with energetic ions by elastic recoil detection

Surface and Interface AnalysisVolume 10, Issue 2-3 p. 170-170 Short Abstract A magnetic spectrometer method for profiling light elements with energetic ions by elastic recoil detection C. R. Gossett, C. R. Gossett Naval Research Laboratory, Washington, D.C. 20375, USASearch for more papers by this author C. R. Gossett, C. R. Gossett Naval Research Laboratory, Washington, D.C. 20375, USASearch for more papers by this author First published: March 1987 https://doi.org/10.1002/sia.740100229AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL No abstract is available for this article. Volume10, Issue2-3March 1987Pages 170-170 RelatedInformation

Iterative subtraction of backscattering spectra in determining the depth profile of arsenic implanted in niobium films

2.0 MeV 4He + backscattering has been used to study superconducting niobium films implanted with arsenic up to a high dose. The depth profile of arsenic was determined by using iterative subtractions of spectra and compared with that of AES. The results have shown that the method is applicable for the depth profiling light elements implanted with high doses in heavy substrates.

Use of a magnetic spectrometer to profile light elements by elastic recoil detection

A magnetic spectrometer of limited momentum acceptance, equipped with an energy sensitive detector, is shown to be capable of providing the necessary isotopic identification of each of the recoiling light elements present in a sample. The high precision of the energy analysis provided by the magnetic field, when coupled with the large stopping power of the recoiling light element ions observed in a glancing angle geometry, produces an exceptionally high depth resolution, measured as 2.0 nm for carbon in carbon at the surface with no straggling. The method permits essentially simultaneous profiling of all elements from hydrogen to oxygen. As applied in this laboratory, the recoils from elastic scattering of 3 MeV 4He ions are detected with the spectrometer positioned at an angle of 45° to the beam.

Time-of-flight system for profiling recoiled light elements

The Elastic Recoil Detection method developed at University of Montreal to profile light elements in solids has been improved significantly. In this method, the light elements are ejected out of the sample by an incident 30 MeV 35Cl beam. In the original technique, the concentration profiles are extracted from the energy spectra of the recoiling particles. Some ambiguity occurs when two or more recoil particles have the same energy. This problem can be solved using a time-of-flight technique to measure the masses of the recoil particles. We use a thin carbon foil and a micro-channel plate as a start detector and a Si detector as a stop detector. This system gives a time resolution of 250 ps fwhm for 5.48 MeV alpha particles. It has been used successfully to separate the profiles of H, B, C, N and O. This method should prove useful to complement the profiles of heavy elements obtained by RBS.