Thermal stability of surface plasmon resonance absorption in $a$-С:Н$\langle$Ag+TiО$_{2}\rangle$ nanocomposite films

The thermal stability of surface plasmon resonance in $a$-С:Н$\langle$Ag$\rangle$ and $a$-С:Н$\langle$Ag+TiО$_{2}\rangle$ nanocomposite films is studied. The films were deposited by ion-plasma magnetron sputtering of a combined graphite-metal target in the atmosphere of the argon and methane mixture. The structure and optical properties of nanocomposite films were studied using transmission electron microscopy and optical spectroscopy, respectively. It is found that surface plasmon resonance in the $a$-С:Н$\langle$Ag+TiО$_{2}\rangle$ films persists to the annealing temperature of 450$^{\circ}$C in argon atmosphere, whereas in $a$-С:Н$\langle$Ag$\rangle$ films, surface plasmon resonance disappears at the annealing temperature of 350$^{\circ}$C. It is shown that annealing at 350$^{\circ}$C leads to the significant increase in the diameter of silver nanoparticles in the structure of the $a$-С:Н$\langle$Ag$\rangle$ films. In the $a$-С:Н$\langle$Ag+TiО$_{2}\rangle$ films, along with the appearance of silver nanoparticles with a large diameter, silver nanoparticles with a small diameter are present, which remain after annealing at this temperature. The higher thermal stability of surface plasmon resonance in the $a$-С:Н$\langle$Ag+TiО$_{2}\rangle$ films is explained by the presence of TiO$_2$ nanoparticles in the structure of films, which inhibit the coalescence of silver nanoparticles at high temperatures.