Characterization of Al2O3/ZrO2 nano multilayer thin films prepared by pulsed laser deposition

Highlights: ► Al2O3/ZrO2 nano multilayer of 40 bilayers is deposited using PLD. ► In situ HTXRD is performed on the 20/5, 15/5 and 10/5 nm samples. ► XTEM is also performed on 20/5 nm sample. ► Crystallization temperature is reduced from 873 K to RT with decrease of layer thickness. ► Thermal expansion coefficient of zirconia is calculated. ► Alumina is amorphous in the entire temperature range. - Abstract: Microstructural characterization of pulsed laser deposited Al2O3/ZrO2 multilayers on Si (1 0 0) substrates at an optimized oxygen partial pressure of 3 × 10−2 mbar and at room temperature (298 K) has been carried out. A nanolaminate structure consisting of alternate layers of ZrO2 and Al2O3 with 40 bi-layers was fabricated at different zirconia layer thicknesses (20, 15 and 10 nm). The objective of the work is to study the effect of ZrO2 layer thickness on the stabilization of tetragonal ZrO2 phase for a constant Al2O3 layer thickness of 5 nm. The Al2O3/ZrO2 multilayer films were characterized using high temperature X-ray diffraction (HTXRD) in the temperature range 298–1473 K. The studies showed that the thickness of the zirconia layer has a profound influence on the crystallization temperature for the formation of tetragonal zirconia phase. The tetragonal phase content increased with the decrease of ZrO2 layer thickness. The cross-sectional transmission electron microscope (XTEM) investigations were carried out on a multilayer thin films deposited at room temperature. The XTEM studies showed the formation of uniform thickness layers with higher fraction of monoclinic and small fraction of tetragonal phases of zirconia and amorphous alumina.