Evolution of helium bubbles in nickel-based alloy by post-implantation annealing

Nickel-based alloys have been considered as candidate structural materials used in generation IV nuclear reactors serving at high temperatures. In the present study, alloy 617 was irradiated with 180-keV helium ions to a fluence of 3.6×10¹⁷ ions/cm² at room temperature. Throughout the cross-section transmission electron microscopy (TEM) image, numerous over-pressurized helium bubbles in spherical shape are observed with the actual concentration profile a little deeper than the SRIM predicted result. Post-implantation annealing was conducted at 700 ℃ for 2 h to investigate the bubble evolution. The long-range migration of helium bubbles occurred during the annealing process, which makes the bubbles of the peak region transform into a faceted shape as well. Then the coarsening mechanism of helium bubbles at different depths is discussed and related to the migration and coalescence (MC) mechanism. With the diffusion of nickel atoms slowed down by the alloy elements, the migration and coalescence of bubbles are suppressed in alloy 617, leading to a better helium irradiation resistance.     

Thermal desorption characteristic of helium ion irradiated nickel-base alloy

The nickel-base alloy is one of the leading candidate materials for generation IV nuclear reactor pressure vessel.To evaluate its stability of helium damage and retention,helium ions with different energy of 80 keV and 180 keV were introduced by ion implantation to a certain dose(peak displacement damage 1-10 dpa).Then thermal desorption spectroscopy(TDS)of helium atoms was performed to discuss the helium desorption characteristic and trapping sites.The desorption peaks shift to a lower temperature with increasing dpa for both 80 keV and 180 keV irradiation,reflecting the reduced diffusion activation energy and faster diffusion within the alloy.The main release peak temperature of 180 keV helium injection is relatively higher than that of 80 keV at the same influence,which is because the irradiation damage of 180 keV,helium formation and entrapment occur deeper.The broadening of the spectra corresponds to different helium trapping sites(He-vacancies,grain boundary)and desorption mechanisms(different Hen Vm size).The helium retention amount of 80 keV is lower than that of 180 keV,and a saturation limit associated with the irradiation of 80 keV has been reached.The relatively low helium retention proves the better resistance to helium bubbles formation and helium brittleness.     

室温生长AZO/Al_2O_3叠层薄膜晶体管性能研究

针对目前大多数氧化物薄膜晶体管都需要采用热退火工艺来提高其性能不利于其在柔性显示器件中应用这一问题,提出了一种采用室温工艺制备的新型TFT器件,无需退火处理即可获得较好的器件性能。该器件采用脉冲激光沉积技术制备的AZO/Al_2O_3叠层结构作为沟道层。与单层AZO-TFT器件相比,叠层TFT器件具有更优异的性能,其迁移率为2.27 cm2·V-1·s-1,开关比为1.43×106。通过对AZO/Al_2O_3叠层薄膜的厚度、密度、粗糙度、物相、界面特性及能带结构等进行分析,发现这种叠层结构能够使电子的运动被限制在AZO薄膜平面内,即形成了二维电子传输,从而提升TFT器件的性能。     

Defect characterization and magnetic properties in un-doped ZnO thin film annealed in a strong magnetic field

Highly c-axis oriented un-doped zinc oxide（Zn O） thin films, each with a thickness of ～ 100 nm, are deposited on Si（001） substrates by pulsed electron beam deposition at a temperature of ～ 320℃, followed by annealing at 650℃ in argon in a strong magnetic field. X-ray photoelectron spectroscopy（XPS）, positron annihilation analysis（PAS）, and electron paramagnetic resonance（EPR） characterizations suggest that the major defects generated in these Zn O films are oxygen vacancies. Photoluminescence（PL） and magnetic property measurements indicate that the room-temperature ferromagnetism in the un-doped Zn O film originates from the singly ionized oxygen vacancies whose number depends on the strength of the magnetic field applied in the thermal annealing process. The effects of the magnetic field on the defect generation in the Zn O films are also discussed.