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In this paper, the tension-tension fatigue behavior of unidirectional SiC/Si 3 N 4 ceramic-matrix composite with strong and weak interface bonding at room temperature has been investigated using a micromechanical approach. The hysteresis loops models considering different interface slip cases have been developed to establish the relationships between fatigue hysteresis loops, hysteresis dissipated energy, hysteresis modulus, and the interface shear stress. The damage evolution process under tension-tension fatigue loading has been analyzed using hysteresis loops. By comparing experimental fatigue hysteresis dissipated energy with theoretical computational values, the interface shear stresses of SiC/Si 3 N 4 composite with weak and strong interface bonding were obtained for different cycle numbers. The fatigue life S‒N curves and broken fibers fraction versus cycle number curves corresponding to different fatigue peak stresses have been predicted. For SiC/Si 3 N 4 with strong interface bonding, the fatigue limit stress approaches to 75% tensile strength, which is much higher than that of composite with weak interface bonding, i.e., 58% tensile strength, due to the higher interface shear stress degradation rate for weak bonding interface. [ABSTRACT FROM AUTHOR]

The atomic structure of Si(110)/SiC(0001) heterojunctions prepared on 6H-SiC(0001) was characterized by transmission electron microscopy and X-ray diffraction. An FCC-on-HCP parallel epitaxy is achieved for the Si(110)/SiC(0001) heterostructure with a growth temperature of 1050 °C and the in-plane orientation relationship is Si[1-10]//6H-SiC[11-20]. The pure edge misfit dislocations with a Burgers vector of 1 3 <11-20> SiC parallel to the interface are observed to accommodate the extreme lattice mismatch. Along the in-plane orientation Si[1-10]SiC[11-20], the Si/6H-SiC interface has a 4:5 Si-to-SiC matching mode with a residual lattice-mismatch of 0.26%. The misfit dislocation density at the Si/SiC interface is calculated as 1.217×10 14 cm −2 . [ABSTRACT FROM AUTHOR]

Abstract: Si films with <111> preferred orientation have been prepared on 6H–SiC(000−1) C-face. HRTEM and SAED results indicate that the Si film has epitaxial connection with the 6H–SiC substrate and the parallel-plane relationship of the Si/6H–SiC heterostructure is (111)Si//(000−1)6H–SiC. Using fast Fourier transform and Fourier mask filtering technique, misfit dislocations are clearly observed at the Si/6H–SiC interface, which accommodate the most of lattice mismatch strain. Every four Si (111) lattice planes are registered with five 6H–SiC(000−1) lattice planes along the interface. Based on the 4:5 lattice matching mode, the lattice structure of the Si/6H–SiC interface and its stability were energetically investigated by molecular dynamics simulations. When the Si films grow preferentially along <111> orientation on 6H–SiC(000−1) C-face, the misfit strain in Si layer significantly reduces due to the relaxation of C atoms in SiC layer near the Si/6H–SiC interface, and thus the Si/6H–SiC heterostructure has a stable interface with a small interface formation energy of −14.24eV. [Copyright &y& Elsevier]

Abstract: SiCGe/SiC heterojunction structure is required in development of SiC optoelectronic devices and light-activated switching devices. We present in this paper a primary attempt to grow the ternary alloy SiCGe on SiC substrates under varied growth conditions in a conventional hot-wall CVD system. SiH4, GeH4 and C3H8 were employed as silicon, germanium and carbon sources, respectively. The samples were measured by means of SEM, XPS, XRD, optical absorption, etc. Two different growth modes i.e., island growth and porous growth were observed. It has been shown that germanium atoms can be effectively incorporated into the ternary alloys, which makes their optical gaps to be narrowed with increasing Ge content. However, incorporation of Ge induces a heavy lattice mismatch, which limits the film thickness by the formation of mismatch defects. It has been shown that use of a buffer layer can effectively improve the growth quality of the ternary alloy. [Copyright &y& Elsevier]