Photoluminescence of R-Lines in Alexandrite under High Magnetic Field and High Pressure(Magnetooptics)

The photoluminescence of R-lines due to the (CrO_6)^ center in alexandrite has been measured under pressures up to 15 GPa at room temperature and 77 K. The results show that the symmetry of the effective crystalline field, being orthorhombic at 1 atm, tends to become trigonal as pressure increases. To examine the influences of this symmetry change on the magnetic properties, the Zeeman spectrum has been measured under magnetic fields up to 15 T at 77 K. The Paschen-Back effect is found to develop under pressures near 8 GPa if the field is applied parallel to the b- and c-axes. This finding demonstrates that the character of the spins of the excited states involved in the R-lines changes as if it is transformed from the Heisenberg-type to the Ising-type. Some structural instability is suggested to occur above about 8 GPa at 77 K and about 11 GPa at room temperature

Diminution of the activity of B atoms by H-induced defects in H

Diborane and hydrogen ions were co-implanted into silicon using an implanter without an ion analyzer. The samples were annealed at 1000 °C for 30 min in argon atmosphere. Regions containing carriers became narrower with an increasing fraction of H2 gas in the source mixed gas: for example, carriers were limited only in a narrow region from the surface to $0.3\;\mu$m on silicon implanted with a mixed gas of 57% H2–43% B2H6. The width of the region containing carriers was approximately double that ($\sim 0.6\;\mu$m) on B-implanted silicon. On the other hand, the width of the region containing B atoms on the H2 and B2H6 co-implanted silicon were slightly narrower than that on B-implanted silicon. The region containing inactivated B atoms had a large number of defects and small crystallites