Performance of mass analyzed, low-energy, dual ion beam system for materials research

Abstract

Mass analyzed low-energy ion beams delivered into a UHV growth chamber have enormous potential for novel materials studies. However, there are significant practical problems in the production of useful ion fluxes at energies down to a few electron volts. Many of these problems have been investigated during the testing of a unique new instrument. This instrument consists of a dual source, mass analyzed, low-energy, ion beam system attached to an ultrahigh-vacuum (UHV) deposition chamber which houses equipment for in situ Auger electron spectroscopy and reflection high-energy electron diffraction analysis of the deposited material. A second UHV chamber, connected to the deposition chamber by means of a vacuum lock and sample transfer device, houses equipment for in situ low-energy electron diffraction and time-of-flight scattering and recoiling spectrometry. The instrument is briefly described herein and data are presented to illustrate the effects of various parameters on the performance of the ion beam. The parameters considered are beam line pressure, field penetration, electromagnetic fringing fields, retarding lens configuration, and ion arrival energy at the target (from 5 eV to 10 keV). The effects of these parameters on the energy spread and profile of the beam, ion-beam flux on target for various species, high-energy neutral atom content and electron content of the beam, and target chamber pressure are discussed. Examples showing the utilization of the instrument for (1) synthesis of the metastable binary compound carbon nitride, (2) deposition of ultrathin Al/Si multilayers, and (3) studying the growth mechanism of Si thin films, are presented. The prospects for materials research, film deposition, surface modification, and ion/surface chemistry studies using such an instrument are assessed.