scispace - formally typeset
Search or ask a question
Journal ArticleDOI

Influence of transition metal doping on the structural, optical, and magnetic properties of TiO2 films deposited on Si substrates by a sol-gel process.

19 Dec 2013-Nanoscale Research Letters (Springer)-Vol. 8, Iss: 1, pp 533-533
TL;DR: It is found that the magnetizations of the TM-doped TiO2 films decrease with increasing dopant content, which is related to electric disorder due to the ART.
Abstract: Transition metal (TM)-doped TiO2 films (TM = Co, Ni, and Fe) were deposited on Si(100) substrates by a sol–gel method. With the same dopant content, Co dopants catalyze the anatase-to-rutile transformation (ART) more obviously than Ni and Fe doping. This is attributed to the different strain energy induced by the different dopants. The optical properties of TM-doped TiO2 films were studied with spectroscopic ellipsometry data. With increasing dopant content, the optical band gap (EOBG) shifts to lower energy. With the same dopant content, the EOBG of Co-doped TiO2 film is the smallest and that of Fe-doped TiO2 film is the largest. The results are related to electric disorder due to the ART. Ferromagnetic behaviors were clearly observed for TM-doped TiO2 films except the undoped TiO2 film which is weakly magnetic. Additionally, it is found that the magnetizations of the TM-doped TiO2 films decrease with increasing dopant content.

Content maybe subject to copyright    Report

Citations
More filters
Journal ArticleDOI
TL;DR: In this paper , pristine TiO 2 nanotubes (NTs) and Fe-, Ni-, Co-and Pt co-doped TiO2 NTs are synthesized via the hydrothermal method and photodecomposition of a mixture of NH 3 , CH 4 , and CO 2 are investigated under simulated solar light irradiation.

11 citations

Journal ArticleDOI
TL;DR: It is found that prepared TiOx thin films significantly reduce the transmittance of destructive UV radiation; a feature that can be useful for the protection of photovoltaic devices.
Abstract: Transparent titanium oxide thin films attract enormous attention from the scientific community because of their prominent properties, such as low-cost, chemical stability, and optical transparency in the visible region. In this study, we developed an easy and scalable solution-based process for the deposition of transparent TiOx thin films on glass substrates. We showed that the proposed method is also suitable for the fabrication of metal-doped TiOx thin films. As proof-of-the-concept, europium Eu(III) ions were introduced into TiOx film. A photoluminescence (PL) study revealed that Eu-doped TiOx thin films showed strong red luminescence associated with 5D0→7Fj relaxation transitions in Eu (III). We found that prepared TiOx thin films significantly reduce the transmittance of destructive UV radiation; a feature that can be useful for the protection of photovoltaic devices. In addition, transparent and luminescent TiOx thin films can be utilized for potential security labeling.

10 citations


Cites background from "Influence of transition metal dopin..."

  • ...The presence of C 1s can be a tributed to the carbon contamination caused by exposure of the film surface to the atmosphere [18]....

    [...]

  • ...The presence of C 1s can be attributed to the carbon contamination caused by exposure of the film surface to the atmosphere [18]....

    [...]

  • ...The presence of 1s can be a tributed to the carbon conta ination caused by exposure of the fil surface to the at osphere [18]....

    [...]

Journal ArticleDOI
TL;DR: In this article, the Ni(II)-imidazole-anatase composites with room temperature ferromagnetism and good photocatalytic activity were prepared by a simple adsorption method using [Ni(1- Me Im) 6 ]Cl 2 ·H 2 O complex and anatase TiO 2 as starting materials in aqueous medium.

10 citations

Journal ArticleDOI
06 Mar 2018-Ionics
TL;DR: In this paper, a series of dye-sensitized solar cell (DSSC) TiO2-(SiO2)100-xNix-GO (TSN) (x 0, 2.5, 5.0, 7.5) films were successfully prepared using a sol-gel method via doctor-blade technique.
Abstract: A series of dye-sensitized solar cell (DSSC) TiO2-(SiO2)100-xNix-GO (TSN) (x = 0.0, 2.5, 5.0, 7.5) films were successfully prepared using a sol-gel method via doctor-blade technique. Tetraethyl-orthosilicate (TEOS), absolute ethanol (C2H5OH), deionized water, and acid ammonia were mixed in one solution. Nickel (II) nitrate hexahydrate (Ni(NO3)2.6H2O) and diethanolamine were added to the prepared solution to produce the precursor of (SiO2)100-xNix. This work is to determine the influence of Ni2+ in the TiO2-SiO2-GO-based DSSC performances. The films were prepared by SiO2 amorphous without Ni2+ and added with Ni2+ at 2.5, 5.0, and 7.5%, respectively. The crystal structure and morphology properties of the films were analyzed using X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), and energy dispersion X-ray. FESEM images showed the amount of Ni2+ was found to increase the grain growth of TSN2.5 and TSN7.5 films ranging from 30.14 to 40.19 nm and 48.01 to 77.04 nm, respectively. The structural characteristics of TiO2-(SiO2)100-xNix-GO are confirmed as anatase phase and belong to TiO2 with a characteristic peak of (101) as a predominant peak. The photovoltaic performances were analyzed using J–V measurement and electrochemical impedance spectroscopy (EIS) to determine the factors that influence the performance of the DSSCs. Hence, this study suggests that the TSN7.5 films exhibited the highest cell performance, presenting a Jsc, Voc, FF, and cell efficiency of 20.52 mA/cm2, 0.230 V, 0.391, and 1.843%, respectively. TiO2-(SiO2)100-xNix-GO doped with 7.5% Ni provide larger diffusion rate, low recombination effect, and longer electron lifetime, thus enhancing the performance of DSSCs.

9 citations

Journal ArticleDOI
TL;DR: In this paper, boron-doped TiO2 nano-powders were obtained by following an emulsion-based sol-gel (EBSG) route and were calcined at 550°C for 6h.

9 citations

References
More filters
01 Jan 1995

14,960 citations

Journal ArticleDOI
11 Feb 2000-Science
TL;DR: Zener's model of ferromagnetism, originally proposed for transition metals in 1950, can explain T(C) of Ga(1-)(x)Mn(x)As and that of its II-VI counterpart Zn(1)-Mn (x)Te and is used to predict materials with T (C) exceeding room temperature, an important step toward semiconductor electronics that use both charge and spin.
Abstract: Ferromagnetism in manganese compound semiconductors not only opens prospects for tailoring magnetic and spin-related phenomena in semiconductors with a precision specific to III-V compounds but also addresses a question about the origin of the magnetic interactions that lead to a Curie temperature (T(C)) as high as 110 K for a manganese concentration of just 5%. Zener's model of ferromagnetism, originally proposed for transition metals in 1950, can explain T(C) of Ga(1-)(x)Mn(x)As and that of its II-VI counterpart Zn(1-)(x)Mn(x)Te and is used to predict materials with T(C) exceeding room temperature, an important step toward semiconductor electronics that use both charge and spin.

7,062 citations


"Influence of transition metal dopin..." refers methods in this paper

  • ...Some theory models, such as the Ruderman-Kittel-Kasuya-Yosida exchange [4], super exchange [5], double exchange [6], magnetic polarons [7], and F-center exchange mechanism [8], have been used to explain ferromagnetism in transitionmetal-element-doped TiO2....

    [...]

Journal ArticleDOI
TL;DR: It is proposed thatferromagnetic exchange here, and in dilute ferromagnetic nitrides, is mediated by shallow donor electrons that form bound magnetic polarons, which overlap to create a spin-split impurity band.
Abstract: Dilute ferromagnetic oxides having Curie temperatures far in excess of 300 K and exceptionally large ordered moments per transition-metal cation challenge our understanding of magnetism in solids. These materials are high-k dielectrics with degenerate or thermally activated n-type semiconductivity. Conventional super-exchange or double-exchange interactions cannot produce long-range magnetic order at concentrations of magnetic cations of a few percent. We propose that ferromagnetic exchange here, and in dilute ferromagnetic nitrides, is mediated by shallow donor electrons that form bound magnetic polarons, which overlap to create a spin-split impurity band. The Curie temperature in the mean-field approximation varies as (xdelta)(1/2) where x and delta are the concentrations of magnetic cations and donors, respectively. High Curie temperatures arise only when empty minority-spin or majority-spin d states lie at the Fermi level in the impurity band. The magnetic phase diagram includes regions of semiconducting and metallic ferromagnetism, cluster paramagnetism, spin glass and canted antiferromagnetism.

2,743 citations

Journal ArticleDOI
S. H. Wemple1, M. DiDomenico1
TL;DR: In this article, a single effectiveoscillator fit was used to analyze refractive-index dispersion data below the interband absorption edge in more than 100 widely different solids and liquids.
Abstract: Refractive-index dispersion data below the interband absorption edge in more than 100 widely different solids and liquids are analyzed using a single-effective-oscillator fit of the form ${n}^{2}\ensuremath{-}1=\frac{{E}_{d}{E}_{0}}{({E}_{0}^{2}\ensuremath{-}{\ensuremath{\hbar}}^{2}{\ensuremath{\omega}}^{2})}$, where $\ensuremath{\hbar}\ensuremath{\omega}$ is the photon energy, ${E}_{0}$ is the single oscillator energy, and ${E}_{d}$ is the dispersion energy. The parameter ${E}_{d}$, which is a measure of the strength of interband optical transitions, is found to obey the simple empirical relationship ${E}_{d}=\ensuremath{\beta}{N}_{c}{Z}_{a}{N}_{e}$, where ${N}_{c}$ is the coordination number of the cation nearest neighbor to the anion, ${Z}_{a}$ is the formal chemical valency of the anion, ${N}_{e}$ is the effective number of valence electrons per anion (usually ${N}_{e}=8$), and $\ensuremath{\beta}$ is essentially two-valued, taking on the "ionic" value ${\ensuremath{\beta}}_{i}=0.26\ifmmode\pm\else\textpm\fi{}0.04$ eV for halides and most oxides, and the "covalent" value ${\ensuremath{\beta}}_{c}=0.37\ifmmode\pm\else\textpm\fi{}0.05$ eV for the tetrahedrally bonded ${A}^{N}{B}^{8\ensuremath{-}N}$ zinc-blende- and diamond-type structures, as well as for scheelite-structure oxides and some iodates and carbonates. Wurtzite-structure crystals form a transitional group between ionic and covalent crystal classes. Experimentally, it is also found that ${E}_{d}$ does not depend significantly on either the bandgap or the volume density of valence electrons. The experimental results are related to the fundamental ${\ensuremath{\epsilon}}_{2}$ spectrum via appropriately defined moment integrals. It is found, using relationships between moment integrals, that for a particularly simple choice of a model ${\ensuremath{\epsilon}}_{2}$ spectrum, viz., constant optical-frequency conductivity with high- and low-frequency cutoffs, the bandgap parameter ${E}_{a}$ in the high-frequency sum rule introduced by Hopfield provides the connection between the single-oscillator parameters (${E}_{0},{E}_{d}$) and the Phillips static-dielectric-constant parameters (${E}_{g},\ensuremath{\hbar}{\ensuremath{\omega}}_{p}$), i.e., ${(\ensuremath{\hbar}{\ensuremath{\omega}}_{p})}^{2}={E}_{a}{E}_{d} \mathrm{and} {E}_{g}^{2}={E}_{a}{E}_{0}$. Finally, it is suggested that the observed dependence of ${E}_{d}$ on coordination number and valency implies that an understanding of refractive-index behavior may lie in a localized molecular theory of optical transitions.

2,346 citations


"Influence of transition metal dopin..." refers background in this paper

  • ...Note that it is common to observe the development of an Urbach tail on doping transition metal oxides [45,46]....

    [...]

Journal ArticleDOI
TL;DR: In this paper, it was shown that while the states of large total spin have both the highest and lowest energies, their average energy is the same as those of low total spin.
Abstract: Zener has suggested a type of interaction between the spins of magnetic ions which he named "double exchange." This occurs indirectly by means of spin coupling to mobile electrons which travel from one ion to the next. We have calculated this interaction for a pair of ions with general spin $S$ and with general transfer integral, $b$, and internal exchange integral $J$.One result is that while the states of large total spin have both the highest and lowest energies, their average energy is the same as for the states of low total spin. This should be applicable in the high-temperature expansion of the susceptibility, and if it is, indicates that the high-temperature Curie-Weiss constant $\ensuremath{\theta}$ should be zero, and $\frac{1}{\ensuremath{\chi}}$ vs $T$ a curved line. This is surprising in view of the fact that the manganites, in which double exchange has been presumed to be the interaction mechanism, obey a fairly good Curie-Weiss law.The results can be approximated rather well by a simple semiclassical model in which the spins of the ion cores are treated classically. This model is capable of rather easy extension to the problem of the whole crystal, but the resulting mathematical problem is not easily solved except in special circumstances, e.g., periodic disturbances (spin waves).

2,086 citations


"Influence of transition metal dopin..." refers methods in this paper

  • ...Some theory models, such as the Ruderman-Kittel-Kasuya-Yosida exchange [4], super exchange [5], double exchange [6], magnetic polarons [7], and F-center exchange mechanism [8], have been used to explain ferromagnetism in transitionmetal-element-doped TiO2....

    [...]