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Nanoscratch Characterization of GaN Epilayers Reveals Shear Resistance Variations on Sapphire Substrates

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— 1 min read

Researchers at National Chung Hsing University in Taichung, Taiwan, have conducted a study to analyze the nanotribological behavior and deformation characteristics of gallium nitride (GaN) epilayers grown on c- and a-axis sapphire substrates. The team used metal organic chemical vapor deposition to form the GaN epilayers and the nanoscratch technique and atomic force microscopy (AFM) to determine the nanotribological behavior and deformation characteristics of the GaN epilayers, respectively. The results showed that the GaN epilayers grown on c-axis sapphire have higher shear resistances than those formed on a-axis sapphire.

Key Takeaways:

  • The researchers used metal organic chemical vapor deposition to form GaN epilayers on c- and a-axis sapphire substrates.
  • The nanoscratch technique and atomic force microscopy (AFM) were used to determine the nanotribological behavior and deformation characteristics of the GaN epilayers.
  • The AFM morphological studies revealed that pile-up phenomena occurred on both sides of the scratches formed on the GaN epilayers.
  • The coefficient of friction (μ) and penetration of scratches were higher on the GaN a-axis sapphire sample than on the c-axis substrate.
  • The study suggests that cracking dominates in the case of GaN epilayers, while ploughing occurs during scratching.
  • The appearances of the scratched surfaces were significantly different for the GaN epilayers on c- and a-axis sapphire substrates.

Statistics:

  • The researchers used a ramped force of 4,000 μN to measure the coefficient of friction (μ) and penetration of scratches.
  • The study found that the GaN epilayers grown on c-axis sapphire had higher shearing resistances than those formed on a-axis sapphire.
  • The coefficient of friction (μ) was higher on the GaN a-axis sapphire sample than on the c-axis substrate.
  • The penetration of scratches was deeper on the GaN a-axis sapphire sample than on the c-axis substrate.

Sources:

  • Lin, M. H., et al. (2010). Nanoscratch Characterization of GaN Epilayers on c- and a-Axis Sapphire Substrates. Nanoscale Research Letters, 5(11), 1812-1816.
  • National Chung Hsing University, Department of Materials Science & Engineering, Taichung 40227, Taiwan.
  • H.C. Wen, National Chung Hsing University, Dept. of Materials Science & Engineering, Taichung 40227, Taiwan.
  • Springer, 233 Spring St., New York, NY 10013, USA.

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