Microstructure of Pb2Sr2ACu3O8 Superconductors: New Structures and Superstructures

We report a detailed study of the microstructure of the new class of high-Tc superconductors, Pb2Sr2ACu3O8, by transmission electron microscopy and diffraction. Several new structural and superstructural variants are observed for A=Eu+Sr, Dy+Ca/Sr or Dy+Sr. Approximately 50% of the individual crystals analyzed displayed weak violation of the c centering present in x-ray macroscopic structure determination, and superstructure variants with modulation vectors parallel to a and/or b were observed in 25% of Eu+Sr the crystals analyzed. In the A=Dy+Sr structures only, structure modulations were observed along [110] and [110] directions

Ion-implantation and diffusion behaviour of boron in germanium

Results are presented of implantation and diffusion study of boron (B) in germanium (Ge). B implantation was carried out in Ge with different energies and to different doses. High-resolution secondary ion mass spectroscopy was used to obtain concentration profiles after furnace annealing. The as-implanted profiles show a long tail possibly due to enhanced diffusion. A limited diffusion has been observed after furnace annealing. Using T-SUPREM, diffusivity value of 1.5(±0.3)×10-16 cm2/s at 850°C has been extracted. This value is two orders of magnitude lower than previously reported values. The results question the change in diffusion mechanism of B diffusion in Si–Ge alloys from low Ge levels to high Ge levels

Diffusion of ion-implanted boron in germanium

The diffusion of boron (B) in germanium (Ge) is studied. B was introduced in Ge wafers by ion implantation and concentration profiles after furnace annealing were obtained using secondary ion mass spectroscopy. The diffusion coefficient and solid solubility of B in Ge has been calculated to be 1.5(±0.3)x10-16 cm2/s and 5.5(±1.0)x1018/cm3, respectively at 850 ºC by fitting experimentally obtained profiles. The value of diffusion coeffient is at least two orders of magnitude lower than the minimum value reported in the literature for B diffusion in Ge. The results are significant as they question the general agreement about vacancy diffusion as the mechanism responsible for diffusion of B in Ge

Crystal Growth and Substitutional Chemistry of Pb2Sr2MCu3O8

We report the crystal growth and ceramic preparation of Pb2Sr2MCu3O8 phases containing a variety of lanthanoids and lanthanoid/alkaline-earth metal solid solutions. These recently discovered high-temperature superconductors add to our understanding of the chemical and structural features key to superconductivity in cuprates. The growth of millimeter-sized crystals from PbO-rich fluxes is described. Ceramic samples of the Pb2Sr2MCu3O8 phase are formed under low oxygen partial pressures for the majority of the lanthanoids. Systematic structural changes are observed as a function of lanthanoid size. The substitution of alkaline-earth metals on the lanthanoid site and the substitution of barium for strontium to form Pb2Ba2YCu3O8 are also described