Study on microstructure and mechanical properties of He and H ion irradiated 6H-SiC

6H-SiC single crystal wafers were irradiated by 200 keV He ions, 100 keV H ions, and 200 keV He ions followed by 100 keV H ions, with the radiation fluences in the range of 10¹⁶ ions cm⁻², respectively. After ion irradiation, the samples were annealed at 1273 K in N₂ atmosphere. XRD, RBS/C, and nano-indentation measurements were carried out to evaluate the damage of the irradiated samples. XRD results show that new diffraction peaks from radiation damage appear at lower angles next to the main diffraction peaks, which indicates that radiation process caused the increase of lattice parameter in the damage region. RBS/C results show that complete amorphization does not occur even under 6 × 10¹⁶ cm⁻² He ions followed by 8 × 10¹⁶ cm⁻² H ions irradiation indicated by χ_min = 17.63%. Damage produced by He ion irradiation at a fluence of 6 × 10¹⁶ ions cm⁻² is greater than that produced by 3 × 10¹⁶ cm⁻² He ions and followed by 4 × 10¹⁶ cm⁻² H ions irradiation, which implied that He ions irradiation effect plays a dominant role in the process of damage producing. The nano-indentation measurements show that hardness variation depends on the irradiation fluences: high fluence radiation leads to the decrease of the hardness while low fluence radiation leads to the increase of the hardness. After annealing, the hardness of all the irradiated samples increases. Possible mechanisms are discussed for explaining these phenomena.