Influence of Sb content on phase composition change of nanoscaled Co-Sb films deposited on heated substrate

The subject of this study is the formation of the phase composition and structure in nanoscaled CoSb$_{x}$ (30 nm) ($1.82\le x\le 4.16$) films deposited by molecular-beam epitaxy on substrates of oxidized monocrystalline silicon at 200$^\circ$ C and the following thermal treatment in vacuum from 300–700$^\circ$C. It is established that after deposition, the films are polycrystalline without texture. With increased Sb content, the formation of the phase composition in the films takes place in such a sequence as is provided by the phase diagram for the bulk state of the Co-Sb system. With annealing in vacuum at temperatures above 450–500$^\circ$ C, sublimation occurs not only for the crystalline Sb phase, but for the antimonides as well. This is reflected in the phase composition change by the following chemical reactions: CoSb$_2\overset{600^\circ\mathrm C}\longrightarrow$ Sb$\uparrow$ = CoSb, CoSb$_3\overset{600^\circ\mathrm C}\longrightarrow$ Sb$\uparrow$ = CoSb$_2$, CoSb$_3\overset{600^\circ\mathrm C}\longrightarrow$ Sb$\uparrow$ = CoSb$_3$ and leads to increases in the amounts of the CoSb and CoSb$_{2}$ phases and decreases in the amounts of CoSb$_{3}$. CoSb$_{x}$(30 nm) ($1.82\le x\le 4.16$) films are found to be thermostable up to $\approx$ 350$^\circ$ C.