ION-BEAM DEPOSITION WITH POSITIVE AND NEGATIVE-IONS

Recently, we have developed a new apparatus for low-energy, mass-analy sed, dual-ion-beam direct deposition, The facility has two sets of ion sources, sector-type 90 degrees mass analysing magnets and beam lines including deceleration lenses for the positive and negative ions. Pos itive and negative ions merge at the substrate surface with incident a ngles of 30 degrees and -30 degrees with respect to the surface normal . The ion-beam energy can be varied between 10 eV and 20 keV. Because of this wide energy range of about three orders of magnitude, the appa ratus allows ion-beam deposition and ion implantation experiments to b e conducted under ultrahigh vacuum (UHV) conditions. A typical ion-bea m current is 10 mu A or more depending on the ion species and energy; the beam size is 10 mm or more in diameter. The base pressure of the d eposition chamber is of the order of 10(-8) Pa and the pressure during operation is about 10(-6) Pa. The machine enables positively and nega tively charged ions to be deposited simultaneously or separately. In s uch a way, it is possible to form high-purity binary compound films on conducting and insulating substrates. Furthermore, the facility is us eful for studying the fundamental processes of ion-beam deposition and /or ion-surface interactions. The machine is called TAOTRON; its nickn ame is PANDA which stands for positive and negative ion deposition app aratus. In this paper, the construction and characteristics of the fac ility are reported, together with a concise historical view of its bac kground. Preliminary results obtained by this new technique are presen ted.