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Abstract This work reports on the correlation between structure, surface/interface morphology and mechanical properties of pulsed laser deposited (PLD)β-Ga2O3films on transparent quartz substrates. By varying the deposition temperature in the range of 25 °C–700 °C, ∼200 nm thick Ga2O3films with variable microstructure and amorphous-to-nanocrystalline nature were produced onto quartz substrates by PLD. The Ga2O3films deposited at room temperature were amorphous; nanocrystalline Ga2O3films 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 Ga2O3films. At 700 °C, for nanocrystalline Ga2O3films, the dense grain packing reduces the elastic modulus Erwhile improving the hardness. The improved crystallinity at elevated temperatures coupled with nanocrystallinity, theβ-phase stabilization is accounted for the observed enhancement in the mechanical properties of PLD Ga2O3films. The structure-morphology-mechanical property correlation in nanocrystalline PLDβ-Ga2O3films deposited on quartz substrates is discussed in detail.
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Effect of Thermal Oxidation on the Structure, Surface Texturing, and Microstructure Evolution in Nanocrystalline Ga─O─N Films
Abstract An extensive examination of the nanoscale, crystallographic growth dynamics of the system, which is impacted by the thermal energy given to the GaN, is carried out to derive a deeper understanding of the growth kinetics, morphology and microstructure evolution, chemical bonding, and optical properties of Ga─O─N films. Thermal annealing of GaN films is performed in the temperature range of 900–1200 °C. Crystal structure, phase formation, chemical composition, surface morphology, and microstructure evolution of Ga─O─N films are investigated as a function of temperature. Increasing temperature induces surface oxidation, which results in the formation of stable β‐Ga2O3phase in the GaN matrix, where the overall film composition evolves from nitride (GaN) to oxynitride (Ga─O─N). While GaN surfaces are smooth, planar, and featureless, oxidation induced granular‐to‐rod shaped morphology evolution is seen with increasing temperature to 1200 °C. The considerable texturing and stability of the nanocrystalline Ga─O─N on Si substrates can be attributed to the surface and interface driven modification because of thermal treatment. Corroborating with structure and chemical changes, Raman spectroscopic analyses also indicate that the chemical bonding evolution progresses from fully Ga─N bonds to Ga─O─N. While the GaN oxidation process starts with the formation of β‐Ga2O3at an annealing temperature of 1000 °C, higher annealing temperatures induce structural distortion with the potential formation of Ga─O─N bonds. The structure‐phase‐chemical composition correlation, which will be useful for nanocrystalline materials for selective optoelectronic applications, is established in Ga─O─N films made by thermal treatment of GaN.
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- Award ID(s):
- 1827745
- PAR ID:
- 10566739
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Advanced Materials Interfaces
- Volume:
- 12
- Issue:
- 5
- ISSN:
- 2196-7350
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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