Thermal conductivity of sputtered oxide films

Abstract

The thermal conductivity of oxide thin films deposited using dc, rf, and ion-beam sputtering is measured in the temperature range 80--400 K using the 3\ensuremath{\omega} method. Thermal conductivity data for amorphous thin films of ${\mathrm{SiO}}_{2}$ are nearly identical to bulk a-${\mathrm{SiO}}_{2}$. Data for amorphous ${\mathrm{Al}}_{2}$${\mathrm{O}}_{3}$, while having a magnitude and temperature dependence similar to bulk amorphous oxides, show a dependence on deposition method; rf sputtering of an ${\mathrm{Al}}_{2}$${\mathrm{O}}_{3}$ target produces films with a thermal conductivity 35% smaller than films prepared by ion-beam sputtering. Microcrystalline thin films show a rich variety of behavior: the conductivity of ${\mathrm{TiO}}_{2}$ films depends on the substrate tempreature ${\mathit{T}}_{\mathit{s}}$ and approaches the thermal conductivity of bulk ${\mathrm{TiO}}_{2}$ ceramics when ${\mathit{T}}_{\mathit{s}}$\ensuremath{\simeq}400 \ifmmode^\circ\else\textdegree\fi{}C; ${\mathrm{HfO}}_{2}$ films show glasslike thermal conductivity independent of annealing temperature up to 900 \ifmmode^\circ\else\textdegree\fi{}C; and MgO films display a crystalline thermal conductivity that is greatly reduced relative bulk values.