keV Gas Research Articles

Effects of bombardment by high energy gas cluster ion beams

We have developed a 200 keV gas cluster implantation system with a E × B mass filter (wien filter) which selects the cluster size in the range 1–4000 atoms, and studies the effects of bombarding an Si(100) surface with Ar cluster ions. Damaged layers irradiated with Ar cluster ion beams 3000 atoms in size at 150 keV were distributed between 100 Å and 200 Å. Detailed studies of the cluster size effect were achieved using Si(100) substrates which were covered with SiO 2. By changing the thickness of the SiO 2 covering, we could obtain more detailed information on the depth of the irradiation damage. The damaged layers irradiated with 100 keV cluster ion beams of size 500 and 3000 atoms were about 130 Å and 160 Å respectively. However, the depth of the damaged layer was much greater than the value expected from the cluster velocity at the energy of the constituent atoms of the cluster. These results indicate that gas cluster ion irradiation has the capability of producing shallow implantation.

Gas cluster ion beam equipments for industrial applications

30 keV and 200 keV gas cluster ion beam equipments have been developed for industrial applications. A gas cluster source with a non-cooled nozzle was used for both the equipments. Sufficient monomer ion suppression was achieved by using an E × B filter and chromatic lenses mass filter with low extraction voltage. These equipments are suitable to be used for low-damage surface treatment of metals, insulators and semiconductors without heavy metal contamination.

The Nucleus of Our Home Galaxy: A Remnant of an Active or a Starburst Galaxy?

To resolve the above dilemma, two essentially different approaches are undertaken: First, a new, detailed analysis of the entire radiation spectrum of Sgr A∗, from radio band up to gamma-rays, is reviewed, which enables us to put substantial constraints on the mass of a putative black hole. The derived upper limit turns out to be too small to allow the black hole to serve as an ‘engine’ for a Seyfert galaxy. Second, analyses of recent data on the 10 KeV gas in the central 200 pc and on star formation history at the Galactic center both make a star burst the likely episode in a recent past. Taken together, the two approaches seem to indicate that the history of the central part of our Galaxy can be better described as that of a starburst, rather than a Seyfert, galaxy.