Magnetron Sputtering With Helium Aluminum And Its Structure Analysis

Aimed at the helium damages in plutonium caused by α decay, a new method of incorporating helium atoms in aluminum films by magnetron sputtering in He/Ar mixed atmosphere was investigated both theoretically and experimentally to simulate the helium effects in plutonium. This paper emphasized on the influences of preparing process parameter on helium concentration and the influences of helium on the microstructure of aluminum films. The importance of this work is to gain a further understanding of physical process of incorporating helium into metal films by magnetron sputtering and the corresponding analysis techniques on the investigation.On the research of preparing process of aluminum film incorporated with helium, the relationships of helium concentration with helium partial pressure, substrate bias voltage, and deposition temperature were investigated. The C ions elastic recoil detection analysis (C-ERDA) was used to measure the helium concentration and depth profile. It was suggested that the helium depth distribution is homogeneous in the film. Helium concentration increased with the He/Ar ratio in the vacuum chamber linearly at first, and trended to 'saturated' at about 7 a.%. Helium concentration increased with increasing of substrate bias voltage in the range between 0 and -50V, but remained almost the same below -50V. When the deposition temperature increased, helium concentrations decreased. The helium concentrations can be controlled easily by adjusting the process parameter. The thermal desorption experiments (TDS) and aging experiments showed that the helium in aluminum are stable, heating under 500℃ or leaving it in room temperature by 120 days did not lead to helium desorption.In the theoretical analysis, it is considered that the helium incorporated in aluminum origined from both scatting neutrals and positive ions attracted by substrate electric field. A new theoretical model were developed to analysis the physical process. It can predict the trend of influence of several process parameter on helium concentration, but it can not be used to calculate accurate concentrations.X-ray diffraction (XRD), transmission electron microscope (TEM), scanning electron microscope (SEM) were used to investigate the microstructure of aluminum films incorporated with helium, the surface morphology, and helium form in the films. It was suggested that the helium atoms aggregated to helium bubbles with the size of about 1 nm. The stress coursed by helium bubbles resulted in broadening of XRD peaks.