Investigation of the implantation of laser-produced Ge ions injected by high-energy low-intensity laser pulses into Si and SiO2 substrates

The development of implantation techniques requires investigation of laser plasma as a potential source of multiply charged ions. The laser ion source delivers ions with kinetic energy and charge state dependent on the irradiated target material and the parameters of the used laser radiation. By focusing the laser beam on the solid target, higher ion current densities can be produced than by using other currently available ion sources. The crucial issue for efficiency of laser ion implantation technology is selection of the proper laser beam characteristics. Implantation of different kinds of laser-produced ions into metals and organic materials was performed recently at the PALS Research Center in Prague, in cooperative experiments using 0.4-ns iodine laser pulses having energies up to 750 J at a wavelength of 1315 nm or up to 250 J at a wavelength of 438 nm. In this contribution we describe the characterization and optimization of laser-produced Ge ion fluxes as well as analysis of the direct implantation of these ions into Si and SiO2 substrates. The Ge target was irradiated using laser pulses of energy up to 50 J at radiation intensities of ∼1011 W/cm2 and ∼2x1013 W/cm2. The implanted samples were placed along the target normal at distances of 17, 31 and 83 cm from the target surface. The ion flux parameters were measured using the time-of-fight method. The depth of ion implantation was determined by Rutherford backscattering (RBS). The maximum depth of implantation of Ge ions was ∼450 nm. These investigations were carried out to optimize implantation of low and medium energy laser-generated ion fluxes as part of the project PALS000929. Some of the results will also be useful for a specific application, fabrication of semiconductor nanostructures within the SRAP 'SEMINANO' project. (author)