Projectile and target excitation in He^(+)+He collisions at intermediate energies

We present ab initio calculations of cross sections for projectile and target excitation occurring in the course of He^(+)+He collisions using a threeactive-electron semiclassical nonperturbative approach.Intermediate impact energies ranging from 1 keV to 225 keV/u are considered.The results of our calculations agree well with available measurements for both projectile and target excitation in the respective overlapping energy regions.A comparison of our results with those of other theoretical calculations further demonstrates the importance of a nonperturbative approach that includes a sufficient number of channels.Furthermore,it is found that the cross sections for target excitation into singlet states show a valley centered at about 25 keV/u,resulting from competition with electron transfer to singlet projectile states.By contrast,the cross sections for target excitation into triplet states do not exhibit any such structures.

Optical performance, structure and thermal stability of Al（lwt.-%Si）//Zr and Al（pure）//Zr multilayers designed for the 17-19 nm range

We report on the optical performance, structure and thermal stability of periodic multilayer films con- taining Zr and Al（lwt.-%Si） or Al（pure） layers designed for the use as extreme ultraviolet （EUV） high reflective mirrors in the range of 1~19 am. The comparison of A1/Zr （Al（lwt.-%Si）/Zr and Al（pure）/Zr） multilayers fabricated by direct-current magnetron sputtering shows that the optical and structural per- formances of two systems have much difference because of Si doped in A1. From the results of grazing incidence X-ray reflection （GIXR）, X-ray diffraction （XRD）, and EUV, the Si can disfavor the crystalliza- tion of AI and smooth the interface, consequently increase the reflectance of EUV in the Al（lwt.-%Si）/Zr systems. For the thermal stability of two systems, the first significant structural changes appear at 250 ~C. The interlayers are transformed from symmetrical to asymmetrical, where the Zr-on-A1 interlayers are thicker than Al-on-Zr interlayers. At 295 ~C for Al（pure）/Zr and 298 ~C for Al（lwt.-%Si）/Zr, the interfaces consist of amorphous Al-Zr alloy transform to polycrystalline Al-Zr alloy which can decrease the surface roughness and smooth the interfaces. Above 300 ~C, the interdiffusion becomes larger, which can enlarge the differences between Zr-on-Al and Al-on-Zr interlayers. Based on the analyses, the Si doped in Al cannot only influence the optical and structural performances of Al/Zr systems, but also impact the reaction temperatures in the annealing process.

Characterization of multilayers and their interlayers： applicationto Co-based systems

We use complementary analysis techniques to determine the structure of nanometric periodic multilayers and particularly their interfaces. We focus on Co-based multilayer which can be used as efficient optical component in the extreme ultraviolet （EUV） range. The samples are characterized using reflectivity measurements in order to determine the thickness and roughness of the various layers, X-ray emission and nuclear magnetic resonance （NMR） spectroscopies to identify the chemical state of the atoms present within the stack and know if they interdiffuse. Results are validated through the use of destructive techniques such as transmission electron microscopy or secondary ion mass spectrometry.