Effect of high-energy electron irradiation in an electron microscope column on fluorides of alkaline earth elements (CaF, SrF, and BaF).

Nikolaichik, V.; Sobolev, B.; Zaporozhets, M.; Avilov, A.

The effect of high-energy (150 eV) electron irradiation in an electron microscope column on crystals of fluorides of alkaline earth elements CaF, SrF, and BaF is studied. During structural investigations by electron diffraction and electron microscopy, the electron irradiation causes chemical changes in MF crystals such as the desorption of fluorine and the accumulation of oxygen in the irradiated area with the formation of oxide MO. The fluorine desorption rate increases significantly when the electron-beam density exceeds the threshold value of ∼2 × 10 pA/cm). In BaF samples, the transformation of BaO into Ba(OH) was observed when irradiation stopped. The renewal of irradiation is accompanied by the inverse transformation of Ba(OH) into BaO. In the initial stage of irradiation of all MF compounds, the oxide phase is in the single-crystal state with a lattice highly matched with the MF matrix. When the irradiation dose is increased, the oxide phase passes to the polycrystalline phase. Gaseous products of MF destruction (in the form of bubbles several nanometers in diameter) form a rectangular array with a period of ∼20 nm in the sample.

ELECTRON beams; ELECTRON microscopy; FLUORIDES; ALKALINE earth metals; FORCE & energy; ELECTRON diffraction; ELECTRON distribution

Crystallography Reports, 2012, Vol 57, Issue 2, p299

1063-7745

Academic Journal

10.1134/S1063774512010087