Investigation Of Plasma Produced By High-Energy Low-Intensity Laser Pulses For Implantation Of Ge Ions Into Si And Sio2 Substrates

Abstract

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 a charge state dependent on the irradiated target material and the parameters of the laser radiation used. By the focusing the laser beam on the solid target the higher current densities of ions than by using other currently available ion sources can be produced. The crucial issue for efficiency of the ion implantation technology is selection of proper laser beam characteristics. Implantation of different kinds of laser‐produced ions into metals and organic materials were 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 wavelength of 1315 nm or up to 250 J at wavelength of 438 nm. In this contribution we describe the characterization and optimization of laser‐produced Ge ion streams as well as analysis of the direct implantation of these ions into Si and SiO2 substrates. The Ge target was irradiated with the use of laser pulses of energy up to 50 J at radiation intensities of ∼1011 W/cm2 and ∼2′1013 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 stream parameters were measured using the time‐of‐fight method. The depth of ion implantation was determined by the Rutherford backscattering method (RBS). The maximum depth of implantation of Ge ions was ∼450 nm. These investigations were carried out for optimization of low and medium energy laser‐generated Ge ion streams, suitable for specific implantation technique, namely for fabrication of semiconductor nanostructures within the SRAP “SEMINANO” project.