The enhanced optical property of chemical passivated n type GaSb
In the paper, Te-doped n type GaSb was passivated by (NH4)2S, the optical and surface properties of passivated GaSb were investigated by PL and AFM. After passivation treatment, the luminescence intensity of GaSb was enhanced. The passivation time would also affect luminescence intensity and the surface smooth of GaSb.
Luminescence from indented Te-doped GaSb crystals
Cathodoluminescence in the scanning electron microscope has been used to investigate the effect of plastic deformation, produced by indentation, in Te-doped GaSb crystals. Deformation has been found to cause a strong quenching of the luminescence emission as well as spectral changes. In particular, the decrease of the near band edge emission is accompanied by the relative increase of the defect band A and of the 730 meV band related to the VGaGaSbTeSb centres. Annealing treatments up to 600 °C lead to partial recovery of the deformation induced defects, and reveal the existence of Te out-diffusion processes from the deformed areas.
Across the structural re-entrant transition in BaFe2(PO4)2: influence of the two-dimensional ferromagnetism.
BaFe2(PO4)2 was recently prepared by hydrothermal synthesis and identified as the first two-dimensional (2D) Ising ferromagnetic oxide, in which honeycomb layers made up of edge-sharing FeO6 octahedra containing high-spin Fe(2+) ions (S = 2) are isolated by PO4 groups and Ba(2+) cations. BaFe2(PO4)2 has a trigonal R-3 structure at room temperature but adopts a triclinic P-1 structure below 140 K due to the Jahn-Teller (JT) instability arising from the (t2g)(4)(eg)(2) configuration. The triclinic crystal structure was refined to find significantly distorted Fe(2+)O6 octahedra in the honeycomb layers while the distortion amplitude QJT was estimated to 0.019 Å. The JT stabilization energy is estimated to be ∼7 meV per formula unit by DFT calculations. Below ∼70 K, very close to the ferromagnetic transition temperature Tc = 65.5 K, the structure of BaFe2(PO4)2 returns to a trigonal R-3 structure in the presence of significant ferromagnetic domains. This rare re-entrant structural transition is accompanied by a discontinuous change in the quadrupolar splitting of Fe(2+), as determined by Mössbauer spectroscopy. EPR measurements show the presence of magnetic domains well above Tc , as expected for a ferromagnetic 2D Ising system, and support that the magnetism of BaFe2(PO4)2 is uniaxial (g⊥ = 0).