Shingo Houzumi

Scanning Tunneling Microscopy Observation of Graphite Surfaces Irradiated with Size-Selected Ar Cluster Ion Beams

A cluster ion irradiation system with cluster size selection has been developed to study the effects of the cluster size in surface processing using cluster ions. A permanent magnet with a magnetic field of 1.2 T was installed for size separation of large cluster ions. Traces formed on a graphite surface by the impact with Ar cluster ions under an acceleration energy of 30 keV were investigated by scanning tunneling microscopy. The nature of the traces is strongly affected by the number of constituent atoms of the irradiating cluster ion. When the cluster ion is composed of 100–3000 atoms, crater like traces are observed on the irradiated surfaces. In contrast, such traces are not observed at all with the irradiation of the cluster ions composed of over 5000 atoms. This behavior is discussed on the basis of the kinetic energy per constituent atom of the cluster ion.

Low-Damage Sputtering of GaAs and GaP Using Size-Selected Ar Cluster Ion Beams

We have investigated the irradiation damage depths produced by an Ar gas cluster ion beam (GCIB) and an Ar monomer ion beam (MIB) on GaAs and GaP, in a comparison of the cathode luminescence (CL) spectra of ion-irradiated and nonirradiated areas. The depths of irradiation damage in both substrates were estimated from the relationship between the CL intensity and the electron beam acceleration voltage.

High rate etching of GaAs and GaP by gas cluster ion beams

Gas cluster ion beam (GCIB) techniques have recently been proposed as new processing methods. We have been investigating the characteristics of GCIB techniques through sputtering GaAs and GaP by Ar gas cluster ion beams as a function of cluster size and acceleration energy. The Ar cluster size was selected by a magnetic spectrometer, and was obtained from the mass spectra measured by a time of flight mass spectrometer. The average sputtering yields of GaAs and GaP were 0–47 and 0–66 atoms/ion for 5–30 k V, respectively. The sputtering yields of GaAs and GaP were higher than those of an Ar monomer ion.

EXPRIMENTAL STUDY OF CLUSTER SIZE EFFECT WITH SIZE-SELECTED CLUSTER ION BEAM

A size-selected gas cluster ion beam (GCIB) system has been developed to study the size effects of energetic large cluster ion bombardments on a solid surface for the first time. This system equipped a permanent magnet with a magnetic flux density of 1.2 T. There is a sliding detector and sample holder on a guiding rail perpendicular to the incoming cluster beam axis. By locating a sample at a certain position, particular size of cluster ion can be irradiated continuously with affordable ion current density. When the total acceleration energy of Ar-GCIB was 5keV, both amorphous and oxide thickness on Si substrate increased with decreasing cluster size. This result showed good agreement with that obtained from molecular dynamics simulations.