Synthesis of Berried Nanocrystals by Heavy-Ion Implantation and Stabilized High-Efficient Luminescence

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The purpose of this work is to produce nanocrystals of 1-10 nm in diameter by heavy ion implantation and subsequent thermal annealing, to reveal the basic synthesis mechanism, to establish luminescence-related quantum states of crystalline interface and to activate the nanocrystals as quantum dots with stable luminescence property. These will contribute to the application as photo devises and to understanding of radiation-induced fundamental processes in solids1. Fabrication of Ge nanocrystals in SiO_2 was studied for a procedure of implantation and subsequent thermal annealing. A comparison between experimental and simulated changes of the depth profile of implanted Ge atoms led to effective values of solubility and diffusion coefficient of Ge atoms in the SiO_2 matrix. The mean diameter of precipitates calculated using those values are 10-15 nm, depending on ion dose and annealing duration.2. Hydrogen plays very important role in luminescence of Si nanocrystals embedded in SiO_2. Si-containing SiO_2 samples produced by ion implantation followed by thermal annealing are very complex systems having high density defects, locally concentrated Si segregates and Si nanocrystals. Hydrogen was implanted into the system which was controlled by applying an appropriate annealing procedure, and the trapping-detrapping process of hydrogen has been revealed by applying the elastic recoil detection technique. It was found for hydrogen to successfully terminate Si dangling bonds on the interface of Si nanocrystal/SiO_2 under a controlled implantation and thermal annealing condition.3. Broad photoluminescence was observed around wave lengths of 720 nm and 550 nm, respectively, for Si and Ge implanted samples of SiO_2 followed by thermal annealing in N_2 atmosphere.