High Temperature Behavior of a Gel-Derived SiOC Glass: Elasticity and Viscosity

The high temperature behavior of a sol-gel derived silicon oxycarbide glass containing 12 at.% carbon has been characterized by means of creep and in-situ ultrasonic echography measurements. Temperature induced changes include structural relaxation and densification from 1000 to 1200°C, and crystallization to form a fine and homogeneous -SiC/glass-matrix nanocomposite with 2.5 nm large crystals above 1200°C. Young's modulus measurements clearly reveal a consolidation of the material upon annealing below 1200°C. Crystallization is almost complete after few hours at 1300°C and results in a significant increase in Young's modulus. The viscosity of the oxycarbide glass is much higher than that of fused silica, with two orders of magnitude difference at 1200°C, and the glass transition temperature ranges from 1320 to 1370°C.     

Ion beam mixing of silicon-tin multilayers

Silicon and tin multilayers of total thickness 200 nm have been deposited at room temperature on beryllium and glass plate substrates under high vacuum (<5. 10^?7 mbar). The average atomic tin fraction of the whole layer varied from 0.12 to 0.60. The samples were irradiated at room temperature with Xe⁺ ions of 900 keV energy with fluences of 1.10¹⁵ to 2.10¹⁶ ions. cm^?2. Rutherford backscattering spectrometry (RBS) was used to check overall composition before irradiation. After irradiation, a substitutional Sn site was evidenced by means of¹¹⁹Sn conversion electron Mössbauer spectroscopy (CEMS), the relative population of which depends on composition and irradiation fluence. Transmission electron microscopy (TEM) was used to monitor the evolution of the samples with irradiation fluence. Electrical measurements show semiconductor behaviour of the mixed multilayers with electrical resistivity ranging from 10² to 10^?3 Ω.cm as a function of composition.