3d Transition Metal Doping Research Articles

Molecular Design of TiO<SUB>2</SUB> for Gigantic Red Shift via Sublattice Substitution

The effects of 3d transition metal doping in TiO2 phases have been simulated in detail. The results of modelling indicate that Mn has the biggest potential among 3d transition metals, for the reduction of energy gap and the introduction of effective intermediate bands to allow multi-band optical absorption. On the basis of theoretical formulation, we have incorporated considerable amount of Mn in nano-crystalline TiO2 materials. Mn doped samples demonstrate significant red shift in the optical absorption edge, with a secondary absorption edge corresponding to theoretically predicted intermediate bands/states. The gigantic red shift achievable in Mn-doped TiO2 is expected to extend the useful TiO2 functionalities well beyond the UV threshold via the optical absorption of both visible and infrared photon irradiance.

Effect of 3d transition metal doping on the superconductivity in quaternary fluoroarsenide CaFeAsF

We examined the doping effect of 3d transition metal (TM) elements (Cr, Mn, Co, Ni and Cu) at the Fe site of a quaternary fluoroarsenide CaFeAsF, an analogue of 1111-type parent compound LaFeAsO. The anomaly at ∼120 K observed in resistivity (ρ) versus temperature (T) plot for the parent compound is suppressed by the doping of each TM element. Furthermore, Co and Ni doping (CaFe1−xTMxAsF, TM = Co,Ni) induces superconductivity with a transition temperature maximized at the nominal x = 0.10 for Co (22 K) and at x= 0.05 for Ni (12 K). These optimal doping levels may be understood by considering that Ni2+(3d8) adds double electrons to the FeAs layers compared with Co2+ (3d7). Increased x for Co or Ni breaks the superconductivity, while metallic nature dρ/dT > 0 is still kept. These observations indicate that Co and Ni serve as electron donors. In contrast, Cr, Mn and Cu doping does not induce superconductivity, yielding dρ/dT < 0 below the ρ–T anomaly temperature, indicating that these TM ions act as scattering centers. The two different types of behavior of TM replacing the Fe site are discussed in relation to the changes in the lattice constants with doping.

3d transition metal doping of semiconducting boron carbides

The introduction metallocenes, in particular ferrocene (Fe(η 5-C 5H 5) 2), cobaltocene (Co(η 5-C 5H 5) 2), and nickelocene (Ni(η 5-C 5H 5) 2), together with the carborane source molecule closo-1,2-dicarbadodecaborane, during plasma enhanced chemical vapor deposition, will result in the transition metal doping of semiconducting boron carbides. Here we report using ferrocene to introduce Fe dopants, and a semiconducting boron-carbide homojunction has been fabricated. The diode characteristics are very similar to those fabricated with Co and Ni doping.

Effect of 3d, 4d, and 5d transition metal doping on damping in permalloy thin films

The effect of doping on the magnetic damping parameter of Ni80Fe20 is measured for 21 transition metal dopants: Ti, V, Cr, Mn, Co, Cu, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Hf, Ta, W, Re, Os, Ir, Pt, and Au. For most of the dopants, the damping parameter increases linearly with dopant concentration. The strongest effects are observed for the 5d transition metal dopants, with a maximum of 7.7×10−3 per atomic percent osmium.

Magnetoresistance in pulsed laser deposited 3d transition metal doped ZnO films

ZnO films with different 3d transition metal doping (Ti, Co, Mn) were prepared by pulsed laser deposition. The occurrence of positive magnetoresistance (MR) was studied in dependence on temperature. Large positive MR was observed in Co- and Mn-doped ZnO films at 5 K. Zn0.98Mn0.02O films show a positive MR up to ∼ 31% at 5 K. The positive MR for Co- and Mn-doped ZnO films decreases drastically from 5 K to 50 K. Positive MR was also observed in Zn0.9998Ti0.0002O films at 290 K, while negative MR was observed at 5 K. Clear stripe-like magnetic domain pattern was observed by magnetic force microscopy for the Zn0.9998Ti0.0002O films, indicating the possible ferromagnetism at room temperature due to Ti3+-ions in a polarized spin state.

Semi-Insulating InP Grown by MOCVD

ABSTRACTFe (C5H5)2 and Fe (CO)5 were used as the 3d transition metal dopants in semi-insulating InP epitaxial layer grown by MOCVD. From the bright and dark field images of the TEM analysis, many precipitates were observed. Three extra peaks of the X-ray diffraction were found. The peaks of free-exciton recombination, donor-acceptor transition and the recombination of bound exciton with phonon emission were observed in the short wavelength range. Two Fe related peaks was observed at 0.7079 eV and 0.6897 eV. For a wide range (10–600) of In/Fe mole fraction, the resistivity keeps at high values (about 108 Ω -cm) and appears the highest resistivity of 5 × 108 Ω -cm for 1 μ m layer.