Helium implantation into 4H‐SiC

Abstract

The paper provides the properties of single crystalline 4H-SiC under helium implantation at temperatures of implantation up to 750 ◦C and fluences in the range 5×1015-1×1017 cm−2. The microstructure evolution was studied by transmission electron microscopy cross- section and X-ray diffraction experiments. The mechanical property changes were investigated by using nanoindentation tests followed by atomic force microscopy observations and by using tribological tests. At elevated temperature of implantation and/or in the low fluence regime at room temperature where only the strained state of SiC is obtained, SiC becomes more resistant to crack formation but no significant change in mechanical properties is seen. At room temperature with increasing fluence the damage accumulation leads to the amorphous state for which a strong degradation of the mechanical properties is observed. At elevated temperature of implantation, amorphization is avoided and a thermally activated saturation of the strain is observed in the near surface region whereas defect accumulation occurs near the maximum of damage. Upon annealing subsequent to room temperature implantation, the near surface strain progressively relaxes while the helium ions agglomerate into platelets around the maximum of strain. These platelets evolve into bubble clusters at temperatures where the vacancies become mobile. Under particular conditions of implantation (high fluence and elevated temperature) the swelling of the surface increases during annealing due to the growth of bubbles and the formation of stacking faults resulting from the migration of interstitials towards the maximum of damage. © 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinhei

Lattice damage and nanohardness in 6H–SiC implanted with multiple-energy Xe ions

“…For the specimens implanted to 30 (0.44 dpa) and 150 (2.2 dpa) at. ppm Xe, the absence of a plateau or peak at low angle beside the main peak indicates that the implant region has been amorphized [7]. It is in agreement with previous results [15,16] which demonstrate amorphization of SiC is achieved at $0.25-0.4 dpa.…”

“…Previous studies have shown that the strain induced by He ion implantation in SiC is strongly localized along the direction perpendicular to the implanted surface [5], causing the lattice to expand. For elevated temperature He ion implants, amorphization of the crystal can be avoided due to dynamical annealing, and the strain profiles show thermally activated saturation in the near-surface region indicating that a threshold concentration of defects is reached [6,7], whereas the strain profiles also show that defect accumulation occurs near the damage peak [7]. Recently it has been demonstrated that in extended surface region both the accumulation of interstitial atoms drifted to the deeper damaged region and the recombination of point defects are enhanced by strain gradient and temperature, resulting in the nearly constant strain that levels off at sufficient fluence [8].…”

A HRXRD and nano-indentation study on Ne-implanted 6H–SiC

“…Previous studies on inert gas atoms in silicon carbide were mainly focused on microstructural evolution after helium implantation [4][5][6][7][8][9][10], but fewer efforts were paid on effects of implantation with heavier inert gas ions. Compared with helium implantation, more displacements of lattice atoms can be produced in one collision cascade by an incident heavier inert-gas ion.…”

Nanoscale investigation of deformation characteristics in a polycrystalline silicon carbide

“…Ion implantation technique is an alternative method to study irradiation damage in materials within a relatively short period of time. Helium ions were implanted into 4H-SiC in the work of Barbot et al [10], and amorphous layers were observed beneath the surface exposed to helium ions. Such irradiation-induced amorphization was reported to cause an increase in fracture toughness due to the formation of microcracks which dissipate the strain energy.…”