Ma Hong-Ji

Comparison of Secondary Ion Emissions from Carbon Nanotubes under Bombardments of MeV Si and Si2Clusters

The emission yields of H, H2, H3 and heavy ions from carbon nanotubes under bombardments of Si and Si2 clusters in an energy range of 0.3–3 MeV per atom are measured by using the time-of-flight technique (TOF). The emission yields of the secondary ions increase with increasing energy of Si and the electronic stopping processes play an important role. The enhanced emission yields of secondary ions induced by Si2 clusters at the low energies are clearly seen and attributed to the vicinage effect of the nuclear collision processes of cluster constituents and the secondary ion emissions are still dominated by electronic stopping processes at high energies.

Ion-Implanted Waveguides in a Nd3+-Doped Silicate Glass

Monomode enhanced-index Nd3+-doped silicate glass waveguides fabricated by ion implantation are reported. The Nd3+-doped silicate glass was implanted by 3.0 MeV B+ ions, 3.0 MeV O+ ions and 4.5 MeV Ni2+ ions, respectively. A prism-coupling method was carried out to measure dark modes in the Nd3+-doped silicate glass using a model 2010 prism coupler. The moving fibre method was applied to measure the waveguide propagation loss. After a moderate annealing, the 3.0-MeV B+-ion implanted waveguide loss is about 3.54 dB/cm; the 3.0-MeV O+-ion implanted waveguide loss is about 5.36 dB/cm; and the 4.5-MeV the Ni2+-implanted waveguide loss is about 7.55 dB/cm. The results show that with the increasing ion mass, the loss in implanted waveguide is increased.

Modal Characterization of a Planar Waveguide in Bismuth Borate Crystal

We report on the fabrication and modal property studies of planar waveguide structure in x-cut bismuth borate biaxial crystal formed by He ion implantation with triple energies. The prism coupling method is used to measure the effective refractive indices of this waveguide. We reconstruct the refractive index distribution of this waveguide by the reflectivity calculation method. Our results indicate that a broadened optical barrier is produced by the multiple He ion implantations. The so-called tunneling effect of the non-stationary mode in this type of barrier waveguide is presented by the well-known finite difference beam propagation method.

Influence of Mn-Doped Content on Ferromagnetism of Ga1−xMnxN Film Grown by LP-MOVPE

The diluted magnetic semiconductor Ga1−xMnxN was achieved by low-pressure metal organic vapour-phase epitaxy (LP-MOVPE). Proton-induced x-ray emission was employed non-destructively, quickly and accurately to determine the Mn-doped content. The magnetic property was measured by a superconducting-quantum-interference-device (SQID) magnetometer. Apparent ferromagnetic hysteresis loops measured at or above room temperature are presented. No ferromagnetic secondary phases were detected by high-resolution x-ray diffraction. The experimental results show that the ferromagnetic signal firstly decreases and then increases with the increasing Mn-doped content from 0.23% to 4.69% and it is the weakest when Mn content is 0.51%. The annealing treatment could make the ferromagnetic property stronger.

Formation of Optical Waveguide and Annealing Behaviour of LiNbO3Implanted by 3.0-MeV Nickel Ions

The optically polished LiNbO3 crystal was implanted with 3.0 MeV nickel ions to a dose of 8×1014 ions/cm2. The implanted sample was orderly annealed at different temperatures for different times in air ambient. The waveguide properties before and after annealing were investigated. Dark modes were observed by the prism coupling technique. The reconstructed refractive index profiles were obtained with the reflectivity calculation method. With the fibre probe technique, the attenuation of the Ni-implanted barrier-confined waveguide was measured for the first time. The waveguide loss was reduced from 1.65 dB/cm to 1.19 dB/cm when annealing was at 300 degrees C for 30 min. With the annealing temperature increasing to 370 degrees C, only fewer broad dark modes were found. It is indicated that the lattice damage by implantation began to resume under this annealing condition. After annealing at 380 degrees C for 60 min, all the dark modes disappeared.

Measurements of the 2P3/2 Vacancy State Alignment of Au Induced by Proton, Lithium and Boron Ion Impact

In this paper, the degree of alignment of 2P3/2 vacancy state in Au induced by proton, lithium and boron ion impact was measured using a Si(Li) detector. Also the projectile-energy dependence of the degree of alignment was investigated over the projectile energy range from 0.2 MeV/amu to 2.0MeV/amu. The de-alignment phenomenon was observed for small relative impact velocities.