Structural and mechanical properties of nanocrystalline Ga<inf>2</inf>O<inf>3</inf>films made by pulsed laser deposition onto transparent quartz substrates

This work reports on the correlation between structure, surface/interface morphology and mechanical properties of pulsed laser deposited (PLD) β-Ga2O3 films on transparent quartz substrates. By varying the deposition temperature in the range of 25 °C-700 °C, 1/4200 nm thick Ga2O3 films with variable microstructure and amorphous-to-nanocrystalline nature were produced onto quartz substrates by PLD. The Ga2O3 films deposited at room temperature were amorphous; nanocrystalline Ga2O3 films were realized at 700 °C. The interface microstructure is characterized with a typical nano-columnar morphology while the surface exhibits the uniform granular morphology. Corroborating with structure and surface/interface morphology, and with increasing deposition temperature, tunable mechanical properties were seen in PLD Ga2O3 films. At 700 °C, for nanocrystalline Ga2O3 films, the dense grain packing reduces the elastic modulus Er while improving the hardness. The improved crystallinity at elevated temperatures coupled with nanocrystallinity, the β-phase stabilization is accounted for the observed enhancement in the mechanical properties of PLD Ga2O3 films. The structure-morphology-mechanical property correlation in nanocrystalline PLD β-Ga2O3 films deposited on quartz substrates is discussed in detail.