C3i Sites Research Articles

Solid-solution Er:(Sc,Y)2O3 transparent ceramics: Optical spectroscopy, inhomogeneous line broadening, C3i sites and mid-infrared laser operation

Rare-earth-doped transparent sesquioxide laser ceramics enable engineering of their gain bandwidths via solid-solution compositions exhibiting a strong inhomogeneous spectral line broadening. We report on a detailed spectroscopic study and the first mid-infrared laser operation of Erbium-doped yttria-scandia, (ScxY1−x)2O3, ceramics fabricated by vacuum sintering at 1750 °C from laser-ablated nanoparticles. The effect of the Sc fraction on the spectral and kinetic properties of Er3+ emission around 2.8 μm owing to the 4I11/2 → 4I13/2 is revealed. The inhomogeneous spectral line broadening leading to merging of individual Stark sub-levels of Er3+ multiplets is evidenced by low-temperature spectroscopy. An original method of quantifying the distribution of dopant Er3+ ions over C2 and C3i symmetry sites in the cubic bixbyite structure is suggested based on the transition probabilities derived by the Judd-Ofelt theory. In the parent Er:Y2O3 ceramic, the Er3+ ions nearly follow the ideal distribution with 3/4 of ions residing in C2 sites, and Sc addition skews it in favor of C3i sites. A continuous-wave Er:(Sc,Y)2O3 ceramic laser generated 312 mW at 2716 nm with a slope efficiency of 18.6% and a laser threshold of 128 mW.

Spectroscopy of thulium ions in solid-solution sesquioxide laser ceramics: Inhomogeneous spectral line broadening, crystal-field engineering and C3i sites

We present a detailed spectroscopic study of Tm3+ ions in stoichiometric and “mixed” (solid-solution) cubic (C-type, sp. gr. Ia3‾) sesquioxides R2O3 (RY, Lu, Sc or their mixture), with the goal of developing broadband-emitting gain media for ultrafast lasers at ∼2 μm. Evidence of a linear variation (increase) of the crystal-field strength when decreasing the ionic radius of the host-forming cation R3+ in the isostructrural R2O3 series is presented. The crystal-field splitting of Tm3+ multiplets is determined for C2 sites and justified using a barycenter plot, and the first evidence of C3i Tm3+ species is presented. A remarkable inhomogeneous spectral broadening for compositionally “mixed” sesquioxides (in particular with Sc3+) with respect to the parent compounds is revealed at low temperatures. It is proven that binary and ternary “mixed” R2O3 compounds form substitutional solid-solutions with a mixing of the host-forming cations at the atomic level. The stimulated-emission and gain cross-sections for the 3F4 → 3H6 Tm3+ transition are determined. Guidelines for material engineering of Tm3+-doped gain media for mode-locked 2-μm lasers are also provided.

Selective Laser Spectroscopy of the Bixbyite-Type Yttrium Scandate Doped by Rare-Earth Ions.

Yttrium scandate crystals doped by Nd3+ and Tm3+ ions have been successfully grown in the form of fibers using the laser-heated pedestal growth (LHPG) technique. The selective laser spectroscopy methods have identified and distinguished three distinct types of optically active centers associated with Nd3+ and Tm3+ ions. The substitution of Y3+ and Sc3+ for rare-earth ions in the C2 structural site leads to the formation of two distinct basic long-time centers. In Nd3+:YScO3, another type of center (a short-lifetime one) is formed known as the Nd3+-Nd3+ aggregate pair. This center arises from the substitution of Y3+ or Sc3+ for Nd3+ cation in the adjacent MO6 polyhedra that share an edge. In Tm3+:YScO3, the third optical center is formed as a result of the substitution of Y3+ or Sc3+ for Tm3+ in the MO6 octahedra with the C3i site symmetry. The fluorescence decay lifetimes of Nd3+ and Tm3+ ions in the YScO3 crystal structure have been accurately measured and estimated. A Stark level diagram illustrating the splitting of 4F3/2, 4I11/2, and 4I9/2 multiplets of Nd3+ ions has been constructed to show features of the active optical centers with the C2 site symmetry.

Implementation Science to Improve Tobacco Cessation Services in Oncology Care.

Every patient with cancer deserves access to evidence-based tobacco cessation interventions as part of their routine oncology care. The NCI Cancer Moonshot funded the Cancer Center Cessation Initiative (C3I) to help establish and/or expand tobacco treatment programs at 52 NCI-designated Cancer Centers. Although this initiative has broadened the availability of tobacco treatment services across US cancer centers, the reach and utilization of these services remains low among patients. To help address the remaining gap between the availability and utilization of evidence-based treatments for tobacco use in the oncologic context, staff and investigators at C3I sites and the C3I Coordinating Center formed the C3I Implementation Science Working Group. The mission of this working group is to bring together clinicians, scientists, and policymakers who share a common interest in implementation science and treating tobacco use in the oncologic context to collaborate on projects aimed at shrinking the practice gap in this area. Through case study examples, we describe how the C3I Implementation Science Working Group is supporting efforts to identify effective ways to increase the utilization of evidence-based tobacco treatments within cancer treatment settings and promote the broader impact and long-term sustainability of C3I.

Integrating Diversity, Equity, and Inclusion Approaches Into Treatment of Commercial Tobacco Use for Optimal Cancer Care Delivery.

Tobacco-related cancer incidence and mortality and commercial tobacco use have decreased steadily in recent decades, but improvements have not been equitably experienced across population subgroups. A complex interaction across socioecological domains of individual, interpersonal, community/organization, and societal/policy factors influence disparities in tobacco use, treatment, and related health outcomes. NCI's Cancer Center Cessation Initiative (C3I) provides an ideal platform to examine and intervene on multilevel influences across the cancer control continuum to reduce any disproportionate tobacco-related burden and eliminate tobacco-related disparities. The C3I Diversity, Equity, and Inclusion (DEI) Working Group encourages cancer centers to develop, evaluate, and adopt evidence-based practices regarding DEI for prevention and treatment of commercial tobacco use across the cancer control continuum. This paper highlights how 3 C3I sites intervene to address socioecological influences on tobacco use among racially, ethnically, socioeconomically, and geographically diverse patient subgroups. It then outlines ways in which DEI considerations could be integrated into research with patients with cancer who use tobacco and practices related to standards of cancer care. Incorporating DEI considerations in the pursuit of optimal tobacco treatment could facilitate elimination of inequities in population-level cancer outcomes, spanning the full continuum of cancer care from prevention to survivorship.

ZnO – Yb2O3 composite optical ceramics: Synthesis, structure and spectral-luminescent properties

Zinc oxide optical ceramics containing 0–2 wt% ytterbium are prepared by uniaxial hot pressing of commercial oxides at 1150 and 1180 °C. The ceramics have the main crystalline phase of hexagonal wurtzite-type ZnO. Ytterbium ions do not enter the ZnO crystals but form a cubic sesquioxide phase of Yb2O3 located at the ZnO grain boundaries. Yb acts as an inhibitor for the ZnO grain growth. The ceramics exhibit transmittance up to 60 % in the visible. Their transmission in the infrared is determined by the free charge carrier absorption. The Yb3+ ions are found in C2 and C3i sites in Yb2O3 crystals. Under X-ray excitation, the ceramics exhibit intense luminescence bands in the blue (near-band-edge emission) and green (defect emission) whose positions, intensities and decay times depend on the Yb content. Yb2O3 causes a redistribution of luminescence intensity in favor of the near-band-edge emission and fastens the emission decay.

Radio-, Thermo- and Photoluminescence Properties of Lu2O3:Eu and Lu2O3:Tb Nanopowder and Film Scintillators

This work is dedicated to the preparation and characterization of the radio-, thermo-, and photoluminescent properties of Lu2O3:Eu and Lu2O3:Tb nanopowder (NPs) scintillators, prepared by means of hydrothermal processing, and their film analogues made of these NPs by the spin coating method. The luminescent properties of NPs and films were characterized by cathodoluminescence (CL), photoluminescence (PL), X-ray excited radioluminescence (RL), and thermoluminescence (TL) at low and high temperatures. In Lu2O3:Eu NPs and films, mostly the luminescence of Eu3+ ions occupying the C2 site of the host, with the most intensive peaks at 611.6 nm and a decay time of 1.5 ms, was observed. On the contrary, two types of Tb3+ centers in the C2 and C3i sites with the main emission lines at 542.4 and 544.0 nm and the corresponding 4f→5d excitation bands at 270 and 305 nm and decay times of t1/e = 2.17 and 3.96 ms were observed in the case of Lu2O3:Tb NPs and films. Indications were noted that Tb3+ in the C3i symmetry position was most active in the CL spectra of Lu2O3:Tb NPs and a respective film. Thermoluminescent peaks at 110 °C and 170 °C for Lu2O3:Eu NPs and at 75 °C and 120 °C in Lu2O3:Tb NPs were observed corresponding to the hole and electron traps, respectively. Significantly different onsets of temperature quenching of Eu3+ and Tb3+ luminescence in Lu2O3:Eu and Lu2O3:Tb NPs were found at ~90 °C and ~320 °C, respectively.

Assignment of the vibrational spectra of the parent polysilsesquioxane (POSS): Octahydridosilasequioxane, H8Si8O12

Polysilsesquioxanes (POSS) are molecules with the empirical formula (RSiO1.5)n where R is a hydrogen atom or hydroxyl or an organic moiety such as an alkyl, alkene, acrylate or epoxide. The silicon atoms occupy the corners of a cube and oxygen atoms are located on the edges, the versatility of silsesquioxanes arises from the vacant fourth position of silicon. The choice of substituent enables a wide variety of properties to be engineered in a straightforward manner. The parent POSS is octasilsesquioxane, H8Si8O12, with R=H and n=8. The present work employs periodic density functional theory calculations in conjunction with all the available vibrational (infrared, Raman and inelastic neutron scattering) spectra to generate a complete assignment of all the modes of the parent POSS octasilsesquioxane and some of its isotopomers for both the free, (Oh), molecule and the solid state material (C3i site symmetry) including the forbidden and very weak modes. The latter are of interest because in less symmetrical silsesquioxanes, these modes will be activated.

Molecular dynamics simulation and crystal field calculations of the Eu2O3-PbO-SiO2 glassy system submitted to long annealing time

The Eu2O3-PbO-SiO2 glassy system submitted to a long annealing time (100ps) has been obtained by molecular dynamics calculations. The average of 87/86 sites of the Eu3+ ion with six/seven nearest neighbours are used to discuss the number of lines and the local symmetry of the luminescent site through the crystal field parameters, using the simple overlap model in the frame of the method of equivalent nearest neighbours. The magnitude of the Bq2(q=0, 1, 2) and the non-negligible B44 and B46(B34, B36 and B66) lead to the indication of distorted C4h and C3i site symmetries of the six and seven nearest neighbours, respectively. We have then compared very satisfactorily our 7F1 sublevels calculations with those observed in the emission spectra of an Eu-borate glass annealed for 30min and 17h. This comparison is justified because the emission behaviour of europium ions in different glassy systems are honestly very similar. Further, the decrease observed in the 5D0→7F2/5D0→7F1 transition intensity ratio is a clear indication that the Eu3+ ion are nucleating a crystalline phase. Such satisfactory comparisons indicate that we have obtained a transparent glass-ceramics.

Advances in luminescence of lanthanide doped Y_2O_3: case of S_6 sites

Although the emission of lanthanide (Ln) ions doped cubic sesquioxides has been subject of extensive studies, there are fundamental issues still to be elucidated. Specifically, compared to the well-understood emission of Ln at C2 sites, the emission at the inversion S6 (C3i) sites, representing ¼ of the total sites, has been identified only for Pr, Nd, Eu, Sm and Yb. Here, we present a first report and improved identification of the emission, excitation and decay properties of Tb, Dy and Pr at S6 sites in Y2O3 by use of time-gated luminescence spectroscopy. The green emission of Tb at S6 sites is characterized by an intensity ratio relative to the cyan band at 490 nm of 10 compared to 2 measured for Tb at C2 sites. Dy at S6 sites displays a relatively intense, near-infrared emission at 765 nm which is red-shifted by ca. 200 nm relative to yellow peaked emission of Dy at C2 sites. The emission lifetimes of 9.4 and 4.8 ms, associated with Tb and Dy at S6 sites, exceed by a factor of 5 and 10 those of C2 counterparts. It is also found that Dy may be regarded as a sensitive probe for the inversion symmetry, comparable with the more recognized Eu. The participation of Ln at S6 sites to the up-conversion emission is revealed for the first time in Sm doped Y2O3 and Eu /Tb, Yb co-doped Y2O3 and explained in terms of successive ground state and excited state absorptions and cooperative energy transfer, respectively.

Spectroscopy of C3i and C2 sites of Nd3+-doped Lu2O3 sesquioxide either as ceramics or crystal

C3i, C2 sites and also pairs of Nd3+ in Lu2O3 ceramics and crystal as laser potential sesquioxides are analyzed.

Symmetry-Related Transitions in the Photoluminescence and Cathodoluminescence Spectra of Nanosized Cubic Y2O3:Tb3+

Herein the photoluminescence spectra of nanosized cubic Y2O3:Tb3+ having Tb3+ concentrations varying between 0.1 and 10 Mol% are described. Low temperature cathodoluminescence spectra from these materials recorded in a scanning transmission electron microscope are presented and discussed. By studying the photoluminescence-spectra recorded at room temperature and focused on the 5D4→7F5 (C2) and 5D4→7F5 (C3i) transitions, at 542.8 and 544.4 nm respectively, it was found that the critical distance for energy transfer from Tb3+ ions at C3i lattice sites to Tb3+ ions at C2 lattice sites was 1.7 nm; at distances >1.7 nm, which prevail at low Tb3+ concentration, this energy transfer virtually stops. The gradual change of the excitation spectra upon increasing the Tb3+ concentration is also explained in terms of energy transfer from Tb3+ at C3i sites to Tb3+ at C2 sites. Cathodoluminescence spectra recorded at low temperatures with the scanning transmission electron microscope provided additional evidence for this radiationless energy transfer.

Nd3+-doped Lu2O3 transparent sesquioxide ceramics elaborated by the Spark Plasma Sintering (SPS) method. Part 1: Structural, thermal conductivity and spectroscopic characterization

We report the detailed analysis of both structural characterization by SEM, thermal conductivity of high value and high resolution spectroscopic properties of Nd3+-doped Lu2O3 transparent ceramics fabricated by the non-conventional SPS method. The emission spectra of the main C2 site shows two close 4F3/2→4I11/2 laser lines at 1076.3 and 1080.5nm, respectively. The optical properties of the two C2 and C3i sites and of C2–C3i and C2–C2 Nd3+ pairs have especially been analyzed.

Photoluminescence properties and energy transfer in Y2O3:Eu3+ nanophosphors

The photoluminescence (PL) properties of Y2O3:Eu3+ nanophosphors were systematically investigated with the goal of improving the color quality and quantum efficiency of Y2O3:Eu3+ nanophosphors for potential applications in nanoscale devices. The emission spectra, excitation spectra and fluorescence decay curves were employed to trace the energy transfer process from Eu3+ at C3i site to Eu3+ at C2 site. The experimental results show that the energy transfer process becomes more and more efficient with the increase in the Eu3+ concentration. The emission of Eu3+ at C2 site is favorable because it has high radiative efficiency and better color quality. The successful suppress of the emission Eu3+ at C3i is especially important for its applications in general illumination or display technology. The quantum efficiency and color quality of Y2O3:Eu3+ can be improved by controlling the energy transfer between the Eu3+ at S6 site and Eu3+ at C2 site.

Er:Lu_2O_3 – Laser-related spectroscopy

The spectra of Er:Lu2O3 have been studied between 7 K and room temperature, particularly for transitions between the 4I13/2 and 4I15/2 manifolds. This includes the determination of energy levels for Er in the C2 site and some levels for the C3i site, as well as absorption and stimulated emission cross sections and radiative lifetimes. At cryogenic temperatures, the emission lines at 1576 and 1601 nm are promising for laser operation, and the unusual breadth of the 1535-nm zero line makes it attractive for diode laser pumping, thus providing the potential for very small quantum defect lasing.

Optical spectroscopy of Sm3+ in C2 and C3i sites of Y2O3 ceramics

The Sm3+ optical spectra in Y2O3 translucent ceramics are dominated by electric-dipole transitions connected to the centers of C2 symmetry, similar to those reported for single crystals. However, quasi-selective time-resolved excitation and emission spectroscopy investigation evidenced, for the first time, additional lines in the magnetic dipole allowed 6H5/2 → 4G5/2, 4F5/2 and 4G5/2 → 6H5/2, 7/2 transitions, associated with the centrosymmetric C3i centers. An energy level scheme for C3i and an improved one for C2 centers are proposed. The 4G5/2 emission lifetimes of these two structural centers (1.48 ms for C2 and 8.4 ms for C3i at 300 K) as well as the emission quenching are quite distinct, whereas Sm3+ ions in C2 centers are involved both in intra-center C2 → C2 cross-relaxation on intermediate levels and inter-center C2 ↔ C3i energy transfers (that imply only Stark levels of the ground 6H5/2 and metastable 4G5/2 manifolds), Sm3+ ions in C3i sites can participate only in the last processes. The spectroscopic data determined in this work (energy level structures, absorption and emission cross-sections, de-excitation processes parameters) suggest the prospect of Sm-doped Y2O3 ceramics as phosphor or four-level laser active materials on the highest intensity line at 608 nm in the 4G5/2 → 6H7/2 transition under GaN diode laser (~405 nm) pumping or as suppressors of amplified one-micron spontaneous emission for the Nd:Y2O3 lasers.

Energy Transfers between Er3+Ions Located at the Two Crystalographic Sites of Er2O3Grown on Si(111)

Films of Er2O3 grown on Si(111) substrates by rf-magnetron sputtering were characterized by synchrotron radiation X-ray diffraction and photoluminescence spectroscopy in spectral and time domains. We measured the photoluminescence and the intensity ratio of the peaks in the photoluminesence as a function of temperature at the excitation wavelength of 800 nm. We determined the energy levels of Er3+ ions in poly crystal Er2O3 and revealed energy transfers from C2 to C3i sites in the Er2O3 on the basis of a simple theory.

Energy Transfers between Er3+ Ions Located at the Two Crystalographic Sites of Er2O3 Grown on Si(111)

Films of Er2O3 grown on Si(111) substrates by rf-magnetron sputtering were characterized by synchrotron radiation X-ray diffraction and photoluminescence spectroscopy in spectral and time domains. We measured the photoluminescence and the intensity ratio of the peaks in the photoluminesence as a function of temperature at the excitation wavelength of 800 nm. We determined the energy levels of Er3+ ions in poly crystal Er2O3 and revealed energy transfers from C2 to C3i sites in the Er2O3 on the basis of a simple theory.

Synthesis, structure and magnetic properties of the Lu 2O 3–CoO mixed system

Polycrystalline samples of the cubic Lu 2− x Co x O 3 solid solutions ( x = 0.1, 0.3, 0.5) were prepared and analyzed by the XRD Raman spectroscopy and magnetic susceptibility measurements. The samples crystallize in the space group Ia-3 with a byxbyite structure type. The structure refinement have shown that Co 3+ is preferentially distributed in C3i sites in Lu 2O 3 host. Replacing Lu 3+ by Co 3+ introduces slight changes in the atomic coordinates leading to decrease of the mean cation–anion distances. The ability of Raman spectroscopy to detect changes in local co-ordination is utilized. The susceptibility data was analyzed within 2–50 K range according to the second-order perturbation (Van Vleck equation). The differences in χ −1( T) are mainly caused by the difference in the crystal field strength and less by exchange interaction. The concentration dependence of the magnetic susceptibility is caused by the concentration dependence of effective crystal field.

Optimization of photoluminescence ofY2O3:Eu andGd2O3:Eu phosphors synthesized by thermolysis of 2,4-pentanedione complexes

Spherical shaped nanoparticles of seriesY2 − xEuxO3 (x = 0.06, 0.10, 0.20, and 2)and Gd2 − xEuxO3 (x = 0.06, 0.10)were prepared by thermolysis of 2,4-pentanedione complexes of Y, Gd, and Eu. The bixbyite phase ofGd2 − xEuxO3 samples wasformed at 500 °C, whereas the thermal decomposition of Y and Eu complexes’ mixtures occurredat higher temperatures. Linearity in the concentration dependence on latticeparameter confirmed the formation of solid solutions. The distribution ofEu3 + inGd2 − xEuxO3 was changed with thermal annealing: in the as-prepared sample (x = 0.10) the distribution waspreferential at C3i sites whilein the annealed samples, Eu3 + were distributed at both C2 and C3i sites. Rietveld refinement of site occupancies as well as emission spectra showed a random distribution ofcations in Y2 − xEuxO3. The photoluminescence (PL) measurements of the sample showed red emission with the main peak at614 nm (5D0–7F2). The PL intensity increased with increasing concentration ofEu3 + in both series. Infrared excitation was required to obtain good Raman spectra. The lineardependence of the main Raman peak wavenumber offers a non-destructive methodfor monitoring the substitution level and its homogeneity at the micron scale.