Heat treatment of ion-irradiated silica-based thin films

The microstructural relaxation caused by heat treatment of ion-irradiated silica-based thin films was investigated. Hybrid organic-inorganic silica-based thin films were synthesized via a sol-gel process and were irradiated with 125 keV H⁺ or 250 keV N²⁺ ions with fluences of 10¹⁵ or 10¹⁶ ions/cm². Ion irradiation was followed by heat treatment at 1100 °C or 1350 °C in an inert Ar atmosphere. The microstructure of the irradiated films before and after heat treatment was studied with a combination of Raman and infrared spectroscopies. The results indicated that while ion irradiation led to a defective structure of silica and graphitic C nanodomains, subsequent heat treatment led to structural relaxation and atomic reconfiguration of both silica and C. After heat treatment at 1100 °C, the microstructure of the films consisted of nanocrystalline graphite and structurally relaxed silica. After secondary heat treatment at 1350 °C, most of the C within the films vanished and the film microstructure only consisted of α-cristobalite silica.