Implantation and Sputtering of Ge and Si Ions into SiO2 Substrates using Electric Fields for Acceleration and Optimisation of Laser-produced Ion Streams used for Modification of Semiconductor Materials

摘要

Laser plasma has been proved to be a potential source of multiply charged ions which could support the growing demands for high-current ion beams. To optimize the efficiency of the ion implantation technology selection of proper laser beam characteristics is very important and should be investigated. With LIS, several variables can and must be controlled. The properties of ions (current densities, the ion charge state, angular and energy distributions) depend on target material and the laser energy, pulse duration and intensity on the target surface. So, the characteristics of laser-produced ion streams should be determined with the use of precise ion diagnostic methods.Based on the preliminary results for acceleration of ions produced with the use of a repetitive laser system at IPPLM the special electrostatic-acceleration system has been designed and prepared. This device permitted to accelerate ions having charge states of 1+ to energies up to ～40 keV. The movable target holder was located inside the cylindrical box connected with a high-voltage source (up to 50 kV at 50 mA). The accelerated Ge and Si ions was implanted to SiO_2/Si substrates and analyzed.This contribution is concerned mainly on the analysis and optimization of laser-produced Ge and Si ion streams as well as on investigation of the direct implantation of these ions into SiO_2 substrates. Targets were irradiated with the use of repetitive (up to 10 Hz) laser with energy up to 700 mJ in one pulse, at radiation intensities of ～10~(11) W/cm~2. The ion stream parameters were measured using the time-of-fight method. The depth of ion implantation was determined by X-Ray Photoelectron Spectroscope (XPS). After the implantation the samples were annealed in different temperatures in range of to create nanocrystal structures and then analyzed by the means of Raman Spectroscopy, Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). The work has been performed within SEMINANO project supported by EC (within 6FP).