Guoqing Zhao

Cross sections for 165° backscattering of 2.0–9.0 MeV 4He from carbon

The relative cross sections for non-Rutherford backscattering of 4He ions from carbon atoms at the energy of 2.0–9.0 MeV were measured at a backscattering angle ϑlab = 165°. The results are presented in both graphical and numerical form with typical uncertainties less than 3%. In addition, the feature of the well-known resonance at Er = 4.262 MeV is discussed.

Cross sections for 165° backscattering of 2.0–9.0 MeV 4He ions from nitrogen

Abstract The cross sections for 165° backscattering of 4He ions from N in ZrN films with the energy ranging from 2.0 MeV to 9.0 MeV were measured, and the excitation curves were plotted. The results were used to analyse the N implanted in the steel, and a computer simulation was performed.

Excitation function and angular distribution for the 14N(α,p)17O reaction

Abstract The cross sections for 14 N(α,p) 17 O reactions at lab angle 165° and incident energies between 5.5 and 7.5 MeV were measured. Angular distribution of protons for an incident energy of 6.576 MeV, which is the energy of the resonance peak of the excitation function of the reaction 14 N(α,p) 17 O is presented. Finally, two examples for detecting nitrogen with this reaction are given.

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.

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.

Interface adhesion enhanced by MeV ions

Abstract The adhesion enhancement of Ag or Au films on Ta (with native oxide) and Ta2O5 (anodic oxidation) interfaces by bombarding with 1.5–18 MeV Si ions at both room temperature (RT) and low temperature (LT) (170 K) has been studied. The threshold doses Dth for these systems to pass the Scotch tape test at RT as a function of ion electronic stopping power d E d X were measured. The power law D th ∞ ( d E d x) n with various magnitudes and n values were observed for all these systems. SIMS measurements showed MeV ion-induced migration of silver into the tantalum substrate for the irradiated Ag/Ta and Ag/Ta2O5 systems. Significantly increased threshold doses were observed for samples irradiated at LT except for the Ag/Ta2O5 interface, which indicated that possible bonds between silver and oxygen atoms formed during MeV ion bombardment may inhibit the further migration of silver into the substrate. The preliminary results about Dth as a function of the thickness of the ultrathin silicon native oxide on Ag/SiOx/Si and Au/SiOx/Si systems showing the different behavior in adhesion enhancement between Ag and Au films are also compared and discussed.

Lifetime measurement of the 28Si compound state at 13.095 MeV by the blocking effect

Abstract The 〈110〉 axial and (111) planar blocking dips in an Al crystal are used to measure the lifetime of the state at 13.095 MeV in the compound nucleus 28Si excited by the 27Al(p, α)24Mg reaction at Ep = 1565 keV. The blocking dips for 2.12 MeV α particles from this reaction at Ep = 1183.4 keV are also measured and the radiation damage in the crystal is investigated. Monte Carlo simulations and analytical methods in the axial blocking measurement and analytical methods in the planar blocking case are used. The measured lifetime at the Ep = 1565 keV resonance, τ = 15 ± 2 as, is in good agreement with the value derived from the reaction-yield measurement.

Theoretical study on the role of bound electron in backward secondary electron emission induced by He+ incident on solid surfaces

Abstract A theoretical study on the role of bound electron in the process of backward secondary electron emission for He + incident on Al, Cu and C has been made. A Monte-Carlo computer code based on the theoretical model for the simulation of this phenomenon has been developed. The code can be used to calculate the yield, distribution statistics and other physical parameters of emitted electrons. The calculated results are compared with experimental data of other authors, and a good agreement is found. We also calculated the yield for He + incident on Al and Cu at the energy near the electronic stopping power maximum.