Growth, Structure, and Thermal Conductivity of Yttria-Stabilized Hafnia Thin Films

Yttria-stabilized hafnia (YSH) films of 90 nm thickness have been produced using sputter-deposition by varying the growth temperature (T-s) from room-temperature (RT) to 400 degrees C. The effect of T-s on the structure, morphology, and thermal conductivity of YSH films has been investigated. Structural studies indicate that YSH films crystallize in the cubic phase. The lattice constant decreases from 5.15 to 5.10 angstrom with increasing T-s. The average grain size (L) increases with increasing T-s; L-T-s relationship indicates the thermally activated process of the crystallization of YSH films. The analyses indicate a critical temperature to promote nanocrystalline, cubic YSH films is 300 degrees C, which is higher compare to that of pure monoclinic HfO2 films. Compared to pure nanocrystaliine hafnia, the addition of yttria lowers the effective thermal conductivity, The effect of grain size on thermal conductivity is also explored.