Pr Thin Films Research Articles

Time-dependent electrical and electroluminescence properties of In-substituted CaSnO3 and CaSnO3:Pr thin films prepared by a chemical solution deposition method

CaSnO3, CaSn0.9In0.1O3−δ, and Ca0.995Pr0.005Sn0.9In0.1O3−δ thin films sandwiched between (In0.975Sn0.025)2O3−δ thin-film electrodes were prepared by a chemical solution deposition method. The electric and electroluminescence properties were investigated by applying dc (direct current) voltages to the films. No appreciable current was detected for the CaSnO3 thin film. When constant dc voltage was applied to the CaSn0.9In0.1O3−δ and the Ca0.995Pr0.005Sn0.9In0.1O3−δ thin films, current was close to zero just after applying the voltage, increased with increasing time at the beginning, reached a maximum at a certain time, and then decreased with increasing time. The current increased by annealing at 673 K in air and decreased reversibly by quenching from 1323 K. Ca0.995Pr0.005Sn0.9In0.1O3−δ thin film showed reddish white electroluminescence due to f-f transitions of Pr3+ ions. The time dependence of the luminance was similar to that of the current. The results were discussed in relation to oxygen absorption and desorption at high temperatures and electromigration of oxygen vacancies at room temperature.

Nebulizer-assisted spray pyrolysis development of rare earth (Pr3+) doped In2S3 thin films for an intense ultraviolet photocurrent response

Developing In2S3nanolayers using the cost-effective approach for light-current conversion has grown last decades. In this work, we report the high photo-current of indium sulfide (In2S3) thin films having different praseodymium (Pr) contents (0, 1, 2, 3, 4, and 5 wt %) using high-purity indium chloride and thiourea as the sources. The optical absorption, crystal structure, surface appearance, defect-related emission, and photoconductivity of the prepared In2S3: Pr thin films were examined by several characterization techniques. X-ray Diffraction (XRD) measurements demonstrate a cubic structure of the polycrystalline nature of the synthesized films with a preferential (220) growth orientation. The selected Pr dopant enhances the grain size of the In2S3 thin film from 46 to 65 nm and hence, benefits the photosensor properties. Field emission scanning electron microscope (FESEM) images confirms the development of interconnected ball-shaped nanograins. The room temperature photoluminescence (PL) spectra exemplify the presence of violet and green emission at 470 and 521 nm. The developed In2S3:Pr thin films exhibited good absorption in the UV region. Pr addition helped in narrowing the bandgap values from 2.91 to 2.83 eV. Among the different doping yields, the 3%Pr doped In2S3 film shows excellent I–V characteristics and offered a satisfactory external quantum efficiency (495%), pronounced photo responsivity (2.12 A/W) and impressive detectivity (1.54 × 1011 Jones) due to the enhanced light-matter interactions. The present results provide a new platform for future photosensor applications.

Enhancing the optoelectronic properties of low-cost nebulizer spray pyrolysis (NSP) prepared ZnS thin film through praseodymium doping for photodetector applications

In this report, ZnS and ZnS:Pr (1, 3, and 5 wt% of Pr) thin films were coated onto the glass substrates by using the low-cost nebulizer spray pyrolysis (NSP) technique. Various characterization techniques were employed to analyze the structural, morphological, optical, and photosensing properties of the prepared samples. The X-ray diffraction results show that the ZnS and ZnS:Pr samples exhibit hexagonal wurtzite structure having preferential growth along the (002) plane which belongs to the P63mc space group. No secondary phases were detected in all the coated thin film samples. The maximum crystallite size of 36 nm was observed for ZnS:Pr1% sample. The SEM analysis revealed that the samples exhibit agglomerated grains and the EDX spectrum of the ZnS:Pr(1 %) sample showed the presence of Zn, S, and Pr elements. The UV–vis absorption spectrum of the ZnS:Pr1% sample revealed that it has higher absorption in the UV region and a decrease in bandgap is noticed among the fabricated samples. The PL spectra showed a highly intense emission line of around 489 nm and a weak UV emission of around 385 nm for all the films. The I-V characteristics of the prepared thin films show that the ZnS:Pr1% sample has higher photosensing properties of responsivity, photoresponse, External Quantum Efficiency (EQE), and the detectivity values of 5.30 × 10-3 AW−1, 5.27, 1.70 %, and 3.76 × 109 Jones, respectively suggesting the sample might be well suited for the UV photodetector applications.

Magneto-optical property and magnetic anisotropy of (100) oriented R0.5Bi2.5Fe5O12 (R = Eu, Sm, and Pr) thin films prepared by metal–organic decomposition

Bi-substituted rare-earth iron garnets, R3−xBixFe5O12 (Bi:RIG), where R represents one of the rare-earth elements, exhibit the excellent magneto-optical (MO) properties that increase with Bi content x. In addition, magnetic properties of Bi:RIGs, such as the magnetization, the magnetic anisotropy, and the magnetostriction, could be controlled by choosing rare-earth elements. In this paper, we report on R0.5Bi2.5Fe5O12 (Bi2.5:RIG, R = Pr, Sm, and Eu) thin films on Gd3Ga5O12 (GGG) (100) single crystal substrates prepared by the metal–organic decomposition method. XRD analysis reveals that Bi2.5:RIG thin films are grown along the same orientation with GGG substrates, and their lattice constants are dependent on the ionic radii of the rare-earth ions. MO measurements show that Faraday spectra of the Bi2.5:RIG thin films have a typical spectral structure observed for Bi:RIGs. The magnetic anisotropy constants, the uniaxial magnetic anisotropy energy Ku, and the magnetocrystalline anisotropy energy K1 of Bi2.5:RIG (R = Y, Pr, Nd, Sm, and Eu) thin films are investigated by using the ferromagnetic resonance measurement.

Evaluation of alkoxide β-diketonates Ce(III), Er(III), Ln(III) complexes as precursors for the photo-deposition of CeO2:Er/Ln amorphous thin films and their influence on the luminescent properties (where Ln = Pr or Yb)

We propose the use of alkoxide β-diketonates of Ce(III), Er(III), Pr(III) and Yb(III) as precursors for photochemical deposition of CeO2:Er and CeO2:Er/Ln (Ln = Pr or Yb) thin films, followed by subsequent annealing at 950 °C. The measurements of luminescent properties revealed that CeO2:Er samples under excitation at 980 nm exhibit up-conversion emissions at 540 nm and near infrared emissions centered at 1550 nm. When co-doping is performed on the CeO2 films, CeO2:Er/Pr reduces its up-conversion characteristics and the NIR emissions increase. However, the CeO2:Er/Yb samples significantly increase the up-conversion properties and inhibit NIR emissions. Different mechanisms based on energy transfer processes are proposed to explain these differences in the degree of intensity of these emissions.

Effect of film thickness on electrical and magneto-transport properties in Pr0.5Sr0.5MnO3 thin films grown on LaAlO3 (0 1 1)

Thin films of Pr0.5Sr0.5MnO3 of various thickness (16 nm, 25 nm, 40 nm and 70 nm) have been deposited on LaAlO3 (011). The 16 nm, 25 nm, and 70 nm films show semiconducting-insulating behaviour at 0 T and 5 T magnetic fields. The 40 nm film shows melting of charge ordering and occurrence of metal to insulator transition at temperature 178 (230) K at 0 (5) T. The magnetic field reduces the resistivity showing a significant magnetoresistance (MR). The high-temperature semiconducting resistivity is governed by variable range hopping (VRH) transport mechanism, whereas the metallic region in 40 nm film follows empirical relation of a third-order polynomial. The insulating electrical behaviour and metal–insulator transition are observed to depend on the nature of substrate-induced strain that is experienced by the film.

Disentangling transient charge order from structural dynamics contributions during coherent atomic motion studied by ultrafast resonant x-ray diffraction

We report on the ultrafast dynamics of charge order and structural response during the photoinduced suppression of charge and orbital order in a mixed-valence manganite. Employing femtosecond time-resolved resonant x-ray diffraction below and at the Mn K absorption edge, we present a method to disentangle the transient charge order and structural dynamics in thin films of Pr0.5Ca0.5MnO3. Based on the static resonant scattering spectra, we extract the dispersion correction of charge ordered Mn3+ and Mn4+ ions, allowing us to separate the transient contributions of purely charge order from structural contributions to the scattering amplitude after optical excitation. Our finding of a coherent structural mode at around 2.3 THz, which primarily modulates the lattice, but does not strongly affect the charge order, confirms the picture of the charge order being the driving force of the combined charge, orbital and structural transition.

Development of a nanostructured Ce(III)-Pr(III) film for excellently corrosion resistance improvement of epoxy/polyamide coating on carbon steel

Chemical treatment of carbon steel (CS) specimens was done by an eco-friendly Ce (III)-Pr(III) composite nanofilm. The impact of composite film deposition on CS on the epoxy coating (EP) capability for reduction of CS corrosion and delamination rates was examined. The Ce (III)-Pr (III) thin film morphology was studied by field emission-scanning electron microscopy (FE-SEM) and energy dispersive spectroscopy (EDS) methods. The EP anti-corrosion capacity promotion on CS by deposition of Ce(III)-Pr(III) composite film was investigated by electrochemical impedance spectroscopy (EIS) and salt spray test. Cathodic delamination (CD) rate of EP/Ce (III)-Pr (III) system was also examined. Furthermore, molecular dynamics (MD) simulations were applied to get microscopic-level insights into the aminoamide hardener/epoxy coating interaction mechanism with Ce (III)-Pr (III) film. It was shown that the film uniformly deposited is mainly composed of oxide/hydroxide of cerium (III) and praseodymium (III) and without crack and defect. Results revealed that the Ce (III)-Pr (III) composite thin film significantly promoted the EP anti-corrosion capability and decreased the CD rate. The computational results proved that the curing agent and crosslinked EP resin adsorbed to praseodymium and cerium oxide surfaces mostly through electrostatic interactions of N and O heteroatoms with surface metal atoms.

Transport properties of resistive switching in Ag/Pr0.6Ca0.4MnO3/Al thin film structures

Thin films of Pr0.6Ca0.4MnO3 were prepared by pulsed laser deposition with an asymmetric pair of Ag and Al metal electrodes in order to study their resistive switching properties. The devices exhibited stable voltage controlled bipolar switching which proved to be reliable and non-volatile. The resistive states show a well-defined dependence on the write voltage, which was used to achieve several intermediate states, indicating that the devices could be utilized in hardware implementations of neuromorphic computing. The switching mechanism was attributed to the electric-field assisted migration of oxygen vacancies at the Al-electrode interface, resulting in a formation and modulation of a rectifying interfacial AlOx layer. The current-voltage characteristics were analyzed by means of the power exponent representation, which hinted to a device state dependent interplay of bulk-limited Poole-Frenkel conduction and interface-limited Schottky conduction. A deeper understanding of resistive switching characteristics in Ag/Pr0.6Ca0.4MnO3/Al will lead towards further advances in manganite-based neuromorphic circuits.

Effects of doping by aluminum or lanthanum on the electrical and electroluminescence properties of Ca0.6Sr0.4TiO3:Pr thin films

Thin-film electroluminescent devices containing Ca0.6Sr0.4TiO3:Pr, Al-doped Ca0.6Sr0.4TiO3:Pr, or La-doped Ca0.6Sr0.4TiO3:Pr phosphors were prepared by a conventional sol–gel and firing method. Doping by Al improved the performance of the device markedly, in that its current-starting voltage and emission-starting voltage decreased, its luminance response became more rapid, and its relative quantum efficiency increased. Almost all the effects of doping with La were opposite to those of doping with Al. On stacking thin films of Al-doped Ca0.6Sr0.4TiO3:Pr and La-doped Ca0.6Sr0.4TiO3:Pr, the current-starting voltage and the emission-starting voltages decreased further and the relative quantum efficiency increased further in comparison with the Al-doped film. The effects of doping by Al and La can be understood by assuming that Ca0.6Sr0.4TiO3:Pr separates into n-type and p-type semiconducting regions as a result of the electromigration of oxygen vacancies, and that the oxygen-vacancy density increases or decreases on doping by Al and La, respectively.

Photoluminescence and Electroluminescence Properties of La2Ti2O7:Pr

La2Ti2O7:Pr powder was prepared by a solid-state reaction method. Photoluminescence due to f-f transitions of Pr3+was induced by band-gap excitation of La2Ti2O7. La2Ti2O7:Pr thin film was prepared by sol-gel and spin-coating methods. The thin film showed visible electroluminescence due to f-f transition of Pr3+by applying ac voltages.

Nanoindentation and nanoscratch behavior of ZnO:Pr thin films deposited by DC sputtering

Abstract

Visible and near-infrared luminescent properties of Pr3+ doped strontium molybdate thin films by a facile polymer-assisted deposition process

Quartz substrate supported Praseodymium (Pr) doped strontium molybdate (SrMoO4) thin films with good uniformity and outstanding fluorescent properties are successfully fabricated via a facile polymer-assisted deposition (PAD) method. In combination with the strong chelating effect of water-soluble polymer on metal cations, the free cations without chelating are effectively ruled out but the remaining chelating metal cations are employed for the highly uniform and accurate stoichiometry luminescent SrMoO4: Pr thin films, layer-by-layer mounting on the common quartz substrates. More importantly, the excellent release of stress from polymer during the growth process of epitaxial thin film can effectively overcome the mismatch between thin film and common quartz substrate and then guarantee the quality of thin film. Under the ultraviolet (UV) light excitation, the samples show high luminescence intensity both in visible and near-infrared (NIR) regions peaked at 646 nm and 1037 nm, mainly ascribing to the transitions of 3P0 → 3F2 and 1G4 → 3H4 of Pr3+ ions. The luminescent properties can be tailored by optimizing the number of spin-coated layers and doping concentrations. The maximum emission occurs at 4 mol% of Pr3+ dopant, and it exhibits an impressive high photoluminescence quantum yield (QY) of up to 86.12%. These results evidently demonstrate the present PAD method is a useful prototype for preparing high performance luminescent thin films even on the cheap quartz substrate.

Competing orders and topology in the global phase diagram of pyrochlore iridates

Strong electronic interactions and spin orbit coupling can be conducive for realizing novel broken symmetry phases supporting quasiparticles with nontrivial band topology. 227 pyrochlore iridates provide a suitable material platform for studying such emergent phenomena where both topology and competing orders play important roles. In contrast to the most members of this material class, which are thought to display "all-in all-out" (AIAO) type magnetically ordered low-temperature insulating ground states, Pr$_2$Ir$_2$O$_7$ remains metallic while exhibiting "spin ice" (SI) correlations at low temperatures. Additionally, this is the only 227 iridate compound, which exhibits a large anomalous Hall effect (AHE) along [1,1,1] direction below 1.5 K, without possessing any measurable magnetic moment. By focusing on the normal state of 227 iridates, described by a parabolic semimetal with quadratic band touching, we use renormalization group analysis, mean-field theory, and phenomenological Landau theory as three complementary methods to construct a global phase diagram in the presence of generic local interactions among itinerant electrons of Ir ions. While the global phase diagram supports several competing multipolar orders, motivated by the phenomenology of 227 iridates we particularly emphasize the competition between AIAO and SI orders and how it can cause a mixed phase with "three-in one-out" (3I1O) spin configurations. In terms of topological properties of Weyl quasiparticles of the 3I1O state, we provide an explanation for the magnitude and the direction of the observed AHE in Pr$_2$Ir$_2$O$_7$. We propose a strain induced enhancement of the onset temperature for AHE in thin films of Pr$_2$Ir$_2$O$_7$ and additional experiments for studying competing orders in the vicinity of the metal-insulator transition.

Structural, optical and photoluminescence properties of Pr-doped β-Ga2O3 thin films

(2¯01) oriented Pr-doped β-Ga2O3 (Ga2O3:Pr) thin films have been grown on (000l) α-Al2O3 substrates using radio frequency magnetron sputtering method. The influences of the dopant contents on the structural and optical properties of the Ga2O3:Pr thin films have been systematically studied. With the increase of Pr concentration, the c-axis lattice parameter of β-Ga2O3 are elongated, with the energy band gap shrinks. The Ga2O3:Pr films show a broad-band blue (∼490 nm) and a pronounced red (∼615 nm) photoluminescence under 255 nm light illumination. The obtained photoluminescence results are related to the energy transfer of cross relaxation process within the 4f2 configuration of the Pr3+. This work may provide a prominent candidate for further developing advanced composite materials incorporated with luminescent ions.

Strain-Enhanced Colossal Magnetoresistance in Pr0.6Sr0.4MnO3 Thin Films

Thin films of Pr0.6Sr0.4MnO3 have been prepared on (100)-oriented single crystalline SrTiO3 and LaAlO3 substrates using pulsed laser deposition. X-ray diffraction analysis reveals formation of thin films with c-axis orientation. The magnetotransport properties of the thin films have been studied in comparison to the polycrystalline bulk sample. Thin films exhibit substantially larger colossal magnetoresistance than the bulk, and the effect is observed to be more pronounced in the film which experiences a larger strain. The resistivity behavior above the metal-insulator transition temperature for the bulk as well as thin films samples follows adiabatic small polaron hopping mechanism for conduction. On the other hand, resistivity in the low-temperature metallic region could be explained considering the electron-magnon and electron-electron scattering contributions to resistivity.

Catalytic Dynamics and Oxygen Diffusion in Doped PrBaCo2O(5.5+δ) Thin Films.

The Sr and Fe codoped double perovskites PrBaCo2O5.5+δ (PrBCO) thin films of Pr(Ba0.5Sr0.5)(Co1.5Fe0.5)O5.5+δ (PBSCFO) were epitaxially grown for chemical catalytic studies. The resistance behavior of PBSCFO epitaxial films was monitored under the switching flow of reducing and oxidizing gases as a function of the gas flow time, t, using an electrical conductivity relaxation (ECR) experimental setup. The R(t) vs t relationships determined at various temperatures show the occurrence of two oxidation processes, Co(2+)/Co(3+) ↔ Co(3+) and Co(3+) ↔ Co(3+)/Co(4+). Mathematical fitting of the observed R(t) vs t relationships was carried out using Fick's second law for one-dimensional diffusion of charge carriers to derive the diffusivity D(T) and τ(T) for the two processes at various temperatures, T. The D(T) vs T relationships were analyzed in terms of the Arrhenius relationship to find the activation energies Ea for each process. Oscillations in the dR(t)/dt plots, observed under oxidation reactions, were discussed in terms of a layer-by-layer oxygen vacancy exchange diffusion mechanism. Our work suggests that thin films of LnBCO (Ln = lanthanide) with their A and B sites doped as in PBSCFO are excellent candidates for the development of low or intermediate temperature energy conversion devices and gas sensor applications.

Synthesis, characterization and optical properties of ATiO3–Pr thin films prepared by a photochemical method (where A = Ba and Ca)

This article reports the characterization and optical properties of (Ba,Ca)TiO3 thin films doped with Pr at different proportions (0–15mol%). The films were deposited on Si (100) and quartz substrates using a photochemical method and post-annealed at 900°C. The evaluation of photo-reactivity of the precursor complexes was monitored by UV–vis and FT-IR spectroscopy. The obtained films were characterized by X-ray diffraction and X-ray photoelectron spectroscopy. The results indicate that Ba, Ca, Ti, O and Pr are present in the form of perovskite. Under UV light excitation (375nm) the (Ba,Ca)TiO3–Pr films show the characteristic emissions ascribed to 1D2→3H4 transition of Pr3+ ion. The optical measurements show the presence of intermediate energy levels in the band gap which influence the emission processes.

Pr and Gd co-doped bismuth ferrite thin films with enhanced multiferroic properties

Pr and Gd co-modified Bi 0⋅95−xPr x Gd 0⋅05FeO 3 (x = 0⋅00, 0⋅05, 0 ⋅10) (BPGFO) thin films on Pt(111) / Ti /SiO 2 /Si(100) substrates were prepared by a sol-gel together with spin coating technique. A detailed study of electrical and magnetic properties of these thin films is reported. X-ray diffraction analysis shows that, with an increase in Pr content, the crystal structures of BPGFO thin films retain rhombohedral (R3c) symmetry accompanied by structure distortion. Polarization-electric field hysteresis loops of these thin films demonstrate that the incorporation of Pr and Gd into the Bi site of BiFeO 3 thin film could enhance the ferroelectric performance. Compared to other thin films, the optimal ferroelectric behaviours in Bi 0⋅85Pr 0⋅1Gd 0⋅05FeO 3 thin film are ascribed to its large dielectric constant, low dissipation factor and low leakage current density. Room temperature magnetization-magnetic field curves of these thin films indicate that all the samples are of paramagnetic behaviours and the enhanced saturation magnetic properties can be found.

Effects of γ-ray irradiation on ferroelectric properties of Pr and Mn co-substituted BiFeO3 thin films

γ-ray irradiation effects on ferroelectric properties of (Bi0.85Pr0.15)(Fe0.95Mn0.05)O3 (BPFMO) thin films are investigated by pizeoresponse force microscopy and polarization–voltage hysteresis measurements. The irradiated BPFMO thin-film capacitors show reduced polarizations and imprinted hysteresis loops. The loss of nonvolatile polarization increases with the decrease of polarization values prior to the irradiation and the imprint of hysteresis loops depends on the direction of polarization. These are discussed in terms of separation of γ-ray-excited electron–hole pairs by the depolarization field and subsequent charge trapping and aggregation on charged domain walls in BPFMO thin films.