Femtosecond Laser Plasma Fabrication of Chalcogenide-Silicon Photonic Materials

The research presented in this thesis covers the modification of the crystalline silicon or thin film deposition on silicon with chalcogenide glasses (ChGs) that are un-doped or doped with rare-earth ions to obtain the spectral emission in the near-infrared (NIR) region through a femtosecond pulsed laser deposition (fs-PLD) route. Four chalcogenide glass materials; gallium lanthanum sulphide (Ga-La-S), Er3+-doped gallium lanthanum sulphide (Er-Ga-La-S), germanium selenide (GeSe4), and germanium antimony selenide (Ge20Sb15Se65) were used. The properties of the chalcogenide films were studied as a function of process parameters such as; substrate temperature, laser pulse energy, deposition time, and background gas pressure. For each glass material, thin films have been deposited, implanted or diffused directly onto/into silicon substrate using fs- PLD. The structure and various physical properties of the chalcogenide thin films prepared from these chalcogenide glasses have also been systematically investigated.
Results showed that the structural characteristics of the target chalcogenide glass changed from amorphous to crystalline on increasing substrate temperatures; no intermixing and interdiffusion behaviour were observed between the silicon substrate and the deposited Ga-La-S and Er-doped Ga- La-S layers while ion-implanted Ge-Se and diffused Ge-Sb-Se layers were detected sub-surface of the silicon substrate. Furthermore, increasing the substrate temperature resulted in an increase in the thickness of the deposited layer, while the ion-implanted and diffused layer thickness decreased. Room temperature photoluminescence and lifetimes of the 4I13/2→4I15/2 transition of Er3+ thin films are also reported in this thesis.
The results showed ChGs thin films with high homogeneity and smooth surfaces, with several droplets, were obtained in all the different configurations. It was also found that the optical properties of the thin films were strongly dependent on the preparation conditions, especially the substrate temperature.