Jiayong Tang

Cross sections for non-Rutherford backscattering of 4He from five light elements

Abstract We report the results of measured cross sections for backscattering of 4 He from Al and Si at a scattering angle of 170 ± 1.5° (lab) for 4 He laboratory energies between 2.0 and 9.0 MeV; and the cross sections for backscattering of 4 He from F, Mg and Cl at a scattering angle of 165 ± 1.5° (lab) for 4 He laboratory energies between 1.6 and 5.0 MeV, 2.0 and 8.4 MeV and 2.0 and 8.7 MeV, respectively. Experimental results show that, for F, Mg, Al, Si and Cl, the upper energies at which the backscattering cross section can still be predicted by the Rutherford scattering formula, are 2.60, 3.20, 3.60, 3.80 and 4.50 MeV, respectively. When the energy is higher than the upper value, the backscattering cross section shows a continuous nuclear resonance distribution for F, Al and Cl. For silicon, a strong narrow isolated resonance is found at 4.370 MeV (± 10 keV ). The cross section is 2.90 times Rutherford at 4.370 MeV and the resonance width Γ λ is 20 keV. A much stronger isolated narrow resonance is at 5.375 MeV ( ± 10 keV ). The cross section is 9.50 times Rutherford at 5.375 MeV and the resonance width Γ λ is 10 keV. These two resonances may be used for backscattering analysis.

PIXE analysis of ancient Chinese Qing dynasty porcelain

Abstract The major and minor chemical compositions and trace element content of white glaze made in Qing dynasty at kuan kiln have been determined by PIXE. Experimental results show that trace element contents RbSrZr are useful to distinguish the place of production of ancient porcelain. In the porcelain from different kilns situated in a same province, the trace element contents can be different from each other. Determining and comparing the major and minor compositions and trace elemental concentrations in white glaze by PIXE technique, we can distinguish a precious Qing dynasty porcelain made at kuan kiln from a fake.

Microbeam PIXE observation of the AuFe incoherent phenomenon over dimensions of several hundred micrometers

Abstract A proton microbeam with 2 μm lateral resolution was used to probe gold-bearing mineral samples from two different sources. The elemental distributions of gold and iron within regions of several hundred micrometers were observed to be incoherent, i.e., less Au was found in an area that was rich in Fe, and vice versa, indicating that the gold was present as discrete inclusions of microscopic size in these gold-bearing mineral samples. On the other hand, the distributions of gold and silver were found to be positively correlated even down to dimensions of several hundred micrometers. A possible explanation is given and briefly discussed.

The role of energetic atoms in the deposition of Au/Au(001) thin films : a computer simulation study

The behavior of Au/Au (100) thin film growth with energetic deposition has been investigated by kinetic Monte Carlo simulations with the description of the deposition process of energetic atoms based on molecular dynamics simulation results. We present the simulation results on the morphology, islands distribution, Bragg intensity and roughness of homoepitaxial Au (100)-films growth with energetic deposition at various substrate temperatures. We found the energetic atoms can promote the nucleation and island growth in the early stages of film growth and thus enhance the smoothness of the film surface at the temperatures of film growth in three-dimensional mode and in quasi-two-dimensional mode. The atomistic mechanism that promotes the nucleation and island growth and enhances the smoothness of the film surface is discussed.

Measured stopping powers for 1–6 MeV 7Li ions in C, Al, Cu, Ag, Au and Pb foils and in a thin Si crystal

Abstract Stopping powers for 1–6 MeV 7Li ions in C, Al, Cu, Ag, Au and Pb foils and in a thin Si crystal were measured in transmission geometry, with the uncertainties less than 6%. The measured data were compared with the available literature data and the values of TRIM-91 and TRIM-95, and the results were discussed in detail.

Simultaneous analysis of light elements using non-Rutherford helium backscattering☆

Abstract 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.

MeV ion beam mixing of Au/Si and Au/Ge systems

Abstract An experimental apparatus for X - Y electrostatic scanning implantation of MeV ions and in situ Rutherford backscattering analysis has been set up on a 3 MV tandem accelerator at Fudan University. MeV ion beam mixing in Au/Si and Au/Ge systems has been studied. The uniformity of the scanning beam was checked by the implanted Au + ion distribution in a Si wafer. Au thin films with thickness of about 32 nm were evaporated on Si and Ge single-crystal substrates, and the samples were then bombarded by 1 MeV Ag + ions with various fluences at room temperature and analyzed in situ using the 2 MeV He + ion RBS technique.

An integrated computer system for Fudan nuclear microprobe

Abstract With the help of modern personal computer (PC) and object oriented programming (OOP) technology, we have recently developed a compact, integrated, user-friendly computer system for Fudan nuclear microprobe, which was originally modeled after the SUNY/Albany system. The system software has been thoroughly rewritten so as to take advantage of todays high-performance PC and facilitate easy upgrading and expansion in the case of future development of both hardware and software. Most functions of this system such as sample searching, scanning control, data acquisition, image processing and displaying, are based on a single 80386 IBM style PC with a 1-MB DRAM TVGA high-resolution monitor. Data from up to 4 ADCs, 4 sensors and a CCD camera can be acquired simultaneously. Two stepper motors are employed to move the target; a CCD camera system is also included to locate the area of interest on the sample; the secondary electron image could act as a reference to fine adjustment. Rectangular raster scanning or irregular scanning is facilitated with beam motion triggered either by a timer or by pulses from a current integrator. A variety of built-in image displaying, processing and printing methods have also been implemented in order to make the maps easier to interpret for the eyes. All of these functions are administrated by an integrated, completely menu-driven software package-MBSYS.

Study on ion beam-assisted deposition of thin Au films by molecular dynamics simulation

Abstract The ion beam-assisted deposition (IBAD) of thin Au films with a very low ion energy was simulated by molecular dynamics methods with the atom interaction potential of embedded atom methods. IBAD results are compared with the film growth without ion-assistance and the film growth with energetic atom deposition. The effects of the arrival ratio of ion-to-atom, the energy of ions, and off-normal ion incidence on the film growth are discussed. Simulation results show that a low ion energy and high arrival ratio of ion-to-atom can result in film growth in the layer-by-layer mode.

Collision cascades induced by aluminum clusters impacting on gold thin films

Abstract The collision cascades of 0.2keV/atom aluminum clusters impacting on gold thin films were investigated. The energy spectra and the number density as a function of time were calculated by molecular dynamics simulation. The results were compared with monatomic bombardments for the same energy per atom. Aluminum atoms with energies larger than their initial energy were found. The highest energy of gold recoils is about 5 times that allowed in an isolated two-body collision. Craters were found on the target surfaces. Multiple successive collisions and collisions between moving atoms are considered to be important in producing such high energy atoms. The dependence of the energy transfer on the mass ratio and the scattering geometry of two colliding atoms are also discussed.