9 research outputs found
Significant enhancement of ferromagnetism in ZnCrTe doped with iodine as an n-type dopant
The effect of additional doping of charge impurities was investigated in a
ferromagnetic semiconductor ZnCrTe. It was found that the doping
of iodine, which is expected to act as an n-type dopant in ZnTe, brought about
a drastic enhancement of the ferromagnetism in ZnCrTe while the
grown films remained electrically insulating. In particular, at a fixed Cr
composition of x = 0.05, the ferromagnetic transition temperature Tc increased
up to 300K at maximum due to the iodine doping from Tc = 30K of the undoped
counterpart, while the ferromagnetism disappeared due to the doping of nitrogen
as a p-type dopant. The observed systematic correlation of ferromagnetism with
the doping of charge impurities of both p- and n-type, suggesting a key role of
the position of Fermi level within the impurity d-state, is discussed on the
basis of the double exchange interaction as a mechanism of ferromagnetism in
this material.Comment: 5 figures, to be published in Phys. Rev. Let
Explosive crystallization starting from an amorphous-silicon surface region during long pulsed-laser irradiation
A newly developed method of backside time-resolved reflectivity measurement is useful for probing the interface between solid and transient liquid Si. Measurements indicate that explosive crystallization starts very near the Si surface from a highly undercooled liquid Si layer thinner than 3 nm for laser irradiation with long pulses ranging from 65 to 200 ns. During the laser irradiation, surface melt-in continues into fine-grained polycrystalline Si produced by explosive crystallization, followed by solidification of the surface-liquid layer
Spin relaxation in CdTe/ZnTe quantum dots
We have measured photoluminescence (PL) spectra and time-resolved PL in CdTe quantum dots (QDs) under the longitudinal magnetic field up to 10T. Circular polarization of PL increases with increasing magnetic field, while its linear polarization is absent under linearly polarized excitation. Time-resolved PL measurements clarified that this behavior is caused by the suppression of spin relaxation induced by the longitudinal magnetic field. We believe that this behavior is related to the hyperfine interaction of electron spin with magnetic momenta of lattice nuclei