Search results for "backscattering"
showing 10 items of 42 documents
Ordering effects in extreme high-resolution depth profiling with MeV ion beams
2012
Abstract The continuing development of depth profiling with MeV ion beam methods with depth resolutions in the nanometre, and even sub-nanometre, regime implies the resolved depth become comparable with the interatomic spacing. To investigate how short-range ordering influences depth profiles at these resolutions, we have employed a mathematical modelling approach. The radial, g ( r ) and depth distribution, g ( z ) functions were calculated for (1 0 0) surface, random and amorphous Si structures at 300 K produced using molecular dynamics simulations with the EDIP quasi-empirical potential. The results showed that short-range ordering lead to reduction of the scattering yield below the deep…
Characterization of alpha sources prepared by direct evaporation using Rutherford backscattering spectrometry
1997
Abstract Standardization of solutions containing alpha emitting nuclides by direct evaporation onto metal supports is a widely used technique due to its simplicity in providing good quantitative results. In order to avoid inhomogeneity in the deposition surface, polished stainless steel disks and a spreading agent are generally used. These sources are usually measured by alpha spectrometry using passivated implanted silicon detectors. The resolution of the source is a measure of the thickness and homogeneity of the evaporated layer. Rutherford backscattering of He+ and H+ was here used to measure directly this thickness and homogeneity. The results were in agreement with semiconductor detec…
Synthesis and characterization of cobalt silicide films on silicon
2006
Cobalt silicide has emerged as a leading contact material in silicon technology due to its low resistivity, high stability and small lattice mismatch. In this study, 0.2-0.4 mu m thick Co films were deposited on Si(100) wafers by RF magnetron sputtering at room temperature, and annealed at temperatures from 600 to 900 degrees C in vacuum. As-deposited and annealed samples were characterized by Rutherford backscattering spectrometry (RBS), nuclear reaction analysis (NRA), X-ray diffraction (XRD) and scanning electron microscopy (SEM). Although the Si substrates were sputter cleaned before the deposition, all the samples showed a thin oxide layer at the Si/Co interfaces. Annealing up to 700 d…
Characterization of 233U alpha recoil sources for 229()Th beam production
2019
Radioactive $^{233}$U alpha recoil sources are being considered for the production of a thorium ion source to study the low-energy isomer in $^{229}$Th with high-resolution collinear laser spectroscopy at the IGISOL facility of the University of Jyv\"askyl\"a. In this work two different $^{233}$U sources have been characterized via alpha and gamma spectroscopy of the decay radiation obtained directly from the sources and from alpha-recoils embedded in implantation foils. These measurements revealed rather low $^{229}$Th recoil efficiencies of only a few percent. Although the low efficiency of one of the two sources can be attributed to its inherent thickness, the low recoil efficiency of th…
Time-of-flight telescope for heavy-ion RBS
2007
Abstract This paper describes a time-of-flight (TOF) spectrometer for Heavy-Ion Rutherford Backscattering Spectrometry (HI-RBS) recently installed at IMEC for thin film analysis. The TOF telescope allows the use of ion beams heavier than He, with advantages in terms of depth and mass resolution and sensitivity compared to conventional RBS based on planar Si detectors. The start timing-signal is produced by the secondary electrons emitted from a thin C foil when traversed by a backscattered ion; the electrons are deflected in an electrostatic mirror towards a Micro-channel plate (MCP) assembly which provides a fast timing response. The stop signal is obtained directly from a second MCP assem…
Structural characterization of a-plane Zn1−xCdxO (0 < x <0.085) thin films grown by metal-organic vapor phase epitaxy.
2006
Zn1−xCdxO(11math0) films have been grown on (01math2) sapphire (r–plane) substrates by metal-organic vapor phase epitaxy. A 800-nm-thick ZnO buffer, deposited prior to the alloy growth, helps to prevent the formation of pure CdO. A maximum uniform Cd incorporation of 8.5 at. % has been determined by Rutherford backscattering spectrometry. Higher Cd contents lead to the coexistence of Zn1−xCdxO alloys of different compositions within the same film. The near band-edge photoluminescence emission shifts gradually to lower energies as Cd is incorporated and reaches 2.93 eV for the highest Cd concentration (8.5 at. %). The lattice deformation, due to Cd incorporation, has been described using a n…
Characterization of alpha sources by Rutherford backscattering spectrometry
1996
Radioactive sources for alpha spectrometry are usually prepared by electrodeposition onto stainless steel backings (and sometimes heated). In earlier work, using the conventional method with passivated implanted planar silicon detectors for the measurements, several sources had been characterized in terms of various parameters by fitting the data of each spectrum to a certain mathematical function. In the present work, the Rutherford Backscattering Spectrometry (RBS) technique with a 1.6 MeV He+ beam was used to study the influence of those factors on the surface distribution and depth profiles of the thin radionuclide layers. Simulations of the measurements using the RUMP computer code wer…
THE COMPTON BACKSCATTERING POLARIMETER OF THE A4 EXPERIMENT
2005
Abstract The A4 collaboration at the Institut fur Kernphysik, University of Mainz, is conducting experiments on single-spin asymmetries in the elastic electron–nucleon-scattering which require polarized beams. In order to measure the absolute beam polarization, we have installed a Compton backscattering polarimeter in front of the target, using for the first time the internal cavity concept. A maximum intra-cavity intensity of 90 W has been measured, and in August 2003, first backscattered photons have been detected. Recently, first Compton asymmetries have been measured.
The optical system of the A4 laser Compton polarimeter
2007
Compton backscattering polarimeters for experiments at sub-mA accelerator facilities use optical cavities to increase the laser light intensity. Therefore, parasitic properties of the optical elements have an increased influence on the polarization state of the light and need to be analyzed carefully. This contribution shows examples of such difficulties and the possible solutions, found during the setup of the A4 Compton backscattering polarimeter at the MAMI accelerator facility of the university of Mainz.
Semipermeable membrane to retain platinum atoms in the electrodeposition process of alpha spectrometry sources
1998
Abstract In earlier work alpha sources electrodeposited on stainless steel backings were analyzed by X-ray fluorescence (XRF) and Rutherford backscattering spectrometry (RBS) finding that during the electrodeposition process large quantities of platinum from the anode were deposited on the cathode surface jointly with the actinides. In the present work, a method to retain platinum atoms using an electrodeposition cell with a semipermeable membrane located between anode and cathode is proposed and tested. The XRF and RBS of alpha sources electrodeposited using this method show that there is less platinum on the stainless steel backing, thereby improving the quality of sources to be measured …