Be:B Amorphous Coatings and Order-Disorder Transitions

Be:B films were explored as a possible ablator material for use in inertial confinement fusion target capsules. It was found that Be:B forms an amorphous structure near the eutectic composition of 11 to 12 at. % B. It is believed that having an amorphous ablator should be useful in suppressing Rayleigh-Taylor instabilities during compression of the target. As the composition is moved away from the eutectic, an amorphous-to–columnar structure transition was more likely to be observed after some finite thickness of amorphous material had been deposited. Microstructural analysis indicated that this transition involved the nucleation of nanocrystal structures within the amorphous matrix. This nanocrystal nucleation is believed to be due to supersaturation of the dopant atom in the host. An efficient packing analysis is also presented in an effort to explain the most favorable amorphous composition of 11 to 12 at. % B doping observed.