Showing papers on "Cathodoluminescence published in 2007"
TL;DR: In this paper, high-purity cubic boron nitride (cBN) and hexagonal Boron Nitride (hBN) single crystals were synthesized at 4.5 GPa and 1500 C using barium BORON nitride as a solvent, and their band edge optical properties were measured by cathodoluminescence spectroscopy.
512 citations
TL;DR: From the observed patterns, the spatial and spectral properties of the wire eigenmodes are derived and the dispersion relation for plasmonic Au nanowire modes are determined.
Abstract: We use cathodoluminescence imaging spectroscopy to excite and investigate plasmonic eigenmodes of Au nanowires with lengths of 500−1200 nm and ∼100 nm width. We observe emission patterns along the Au nanowire axis that are symmetric and strongly wavelength dependent. Different patterns correspond to different resonant modes of the nanowire. From the observed patterns, we derive the spatial and spectral properties of the wire eigenmodes and determine the dispersion relation for plasmonic Au nanowire modes.
279 citations
TL;DR: In this paper, a large-scale and facile solvothermal method followed by a subsequent heat treatment was used to extract 3 µm-diameter Eu3+ microspheres, with an average diameter of 3 μm.
Abstract: Y2O3 : Eu3+ microspheres, with an average diameter of 3 μm, were successfully prepared through a large-scale and facile solvothermal method followed by a subsequent heat treatment. X-ray diffraction, Fourier transform infrared spectroscopy, energy-dispersive X-ray spectra, thermogravimetric and differential thermal analysis, inductive coupled plasma atomic absorption spectrometric analysis, scanning electron microscopy, transmission electron microscopy, photoluminescence spectra, as well kinetic decays, and cathodoluminescence spectra were used to characterize the samples. These microspheres were actually composed of randomly aggregated nanoparticles. The formation mechanisms for the Y2O3 : Eu3+ microspheres have been proposed on an isotropic growth mechanism. The Y2O3 : Eu3+ microspheres show a strong red emission corresponding to 5D0 → 7F2 transition (610 nm) of Eu3+ under ultraviolet excitation (259 nm) and low-voltage electron beams excitation (1−5 kV), which have potential applications in fluoresc...
206 citations
TL;DR: In this article, the luminescence mechanism for Eu3+ in CaIn2O4 has been elucidated, and the emission lines correspond to D0,1,2,35-FJ7 transitions from 400to700nm with comparable intensity, resulting in a white light emission with a quantum efficiency near 10%.
Abstract: CaIn2O4:xEu3+ (x=0.5%,1.0%,1.5%) phosphors were prepared by the Pechini sol-gel process [U.S. Patent No. 3,330,697 (1967)] and characterized by x-ray diffraction and photoluminescence and cathodoluminescence spectra as well as lifetimes. Under the excitation of 397nm ultraviolet light and low voltage electron beams, these phosphors show the emission lines of Eu3+ corresponding to D0,1,2,35-FJ7 (J=0,1,2,3,4) transitions from 400to700nm (whole visible spectral region) with comparable intensity, resulting in a white light emission with a quantum efficiency near 10%. The luminescence mechanism for Eu3+ in CaIn2O4 has been elucidated.
190 citations
TL;DR: In this article, nearly monodisperse and well-defined one-dimensional (1D) Gd2O3:Eu3+ nanorods and microrods were successfully prepared through a large-scale and facile hydrothermal method followed by a subsequent heat treatment process, without using any catalyst or template.
Abstract: Nearly monodisperse and well-defined one-dimensional (1D) Gd2O3:Eu3+ nanorods and microrods were successfully prepared through a large-scale and facile hydrothermal method followed by a subsequent heat treatment process, without using any catalyst or template. X-ray diffraction (XRD), thermogravimetric analysis and differential scanning calorimetry (TGA−DSC), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), photoluminescence (PL) and cathodoluminescence (CL) spectra as well as kinetic decays were used to characterize the samples. The size of the Gd2O3:Eu3+ rods could be modulated from micro- to nanoscale with the increase of pH value using ammonia solution. The as-formed product via the hydrothermal process, Gd(OH)3:Eu3+, could transform to cubic Gd2O3:Eu3+ with the same morphology and a slight shrinking in size after a postannealing process. The formation mechanism for the Gd(OH...
184 citations
TL;DR: In this article, an Eu2+-activated AlN phosphor was synthesized by firing the powder mixture of AlN, α-Si3N4, and Eu 2O3 at 2050°C for 4h under 1.0MPa N2.
Abstract: An Eu2+-activated AlN phosphor was synthesized by firing the powder mixture of AlN, α-Si3N4, and Eu2O3 at 2050°C for 4h under 1.0MPa N2. This nitride phosphor emits a strong blue color with the chromaticity coordinates of x=0.139 and y=0.106 at an accelerating voltage of 3kV. The cathodoluminescence properties of AlN:Eu2+ was evaluated by utilizing it in the Spindt-type field emission display panel. It shows that the nitride phosphor exhibits higher brightness, higher color purity, lower saturation, and longer lifetime than the currently used Y2SiO5:Ce3+, indicative of the suitability of the AlN:Eu2+ blue phosphor in field emission displays.
160 citations
TL;DR: Cathodoluminescence spectroscopy is used to address the ultraviolet (UV) luminescence of a single pencil-like ZnO nanowire whose diameter gradually reduces from bottom to top in the range of 700-50 nm and it is found that the UV emission energy evidently shifts to the high energy.
Abstract: Cathodoluminescence spectroscopy is used to address the ultraviolet (UV) luminescence of a single pencil-like ZnO nanowire whose diameter gradually reduces from bottom to top in the range of 700-50 nm. It is found that the UV emission energy evidently shifts to the high energy with the ZnO nanowire's diameter decreasing and the blue-shift of 90 meV is observed when the nanowire diameter reduces to 50 from 700 nm. The physical mechanism of the UV blue-shift of the ZnO nanowire is attributed to the Burstein-Moss effect under the high carrier concentration.
158 citations
TL;DR: In this paper, a Pechini so-gel process was used to produce CaIn2O4:Eu3+ phosphors, which were then used for X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), photoluminescence (PL), cathodolumine (CL) spectra as well as lifetimes were utilized to characterize the samples.
Abstract: CaIn2O4:Eu3+ phosphors were prepared by a Pechini so-gel process. X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), photoluminescence (PL), cathodoluminescence (CL) spectra as well as lifetimes were utilized to characterize the samples. The XRD results reveal that the samples begin to crystallize at 800 degrees C, and the crystallinity increases upon raising the annealing temperature. The FE-SEM images indicate that the CaIn2O4:Eu3+ samples consist of fine and spherical grains with size around 200-400 nm. Under the excitation of ultraviolet light and low-voltage electron beams, the CaIn2O4:Eu3+ phosphors show the characteristic emissions of Eu3+ ((DJ-7FJ ')-D-5 J, J ' = 0, 1, 2, 3 transitions). The luminescence color can be tuned from white to orange to red by adjusting the doping concentration of EU3+. The corresponding luminescence mechanisms have been proposed.
138 citations
TL;DR: In this paper, the effect of doping after annealing on the structural and optical properties has been investigated by means of X-ray diffraction (XRD), cathodoluminescence (CL) spectrum, scanning electron microscopy (SEM) and atomic force microscopy.
Abstract: Thin films of ZnO were grown by the sol–gel method using spin-coating technique on (0001) sapphire substrates. The effect of doping after annealing on the structural and optical properties has been investigated by means of X-ray diffraction (XRD), cathodoluminescence (CL) spectrum, scanning electron microscopy (SEM) and atomic force microscopy (AFM). The films that were dried at 623 K and then post annealed at 873 K showed (0002) as the predominant orientation. Two emission bands have been observed from CL spectrum. Lithium doped film shows shift in the near band edge UltraViolet emission peak and suppressed defect level emission peak in the visible range. SEM analysis of the films exhibits many spherical shaped nanoparticles. Roughness of the films determined using atomic force microscopy.
132 citations
TL;DR: In this paper, a two-step electrochemical/chemical process on a transparent, conductive substrate from an aqueous solution at 85°C was used to produce as-grown ZnO nanotubes.
113 citations
TL;DR: In this paper, a high-pressure pulsed-laser deposition process using phosphorus pentoxide as the dopant source was used to prep phosphorus-doped ZnO:P nanowires for cathodoluminescence.
Abstract: Phosphorus-doped ZnO (ZnO:P) nanowires were successfully prepared by a novel high-pressure pulsed-laser deposition process using phosphorus pentoxide as the dopant source. Detailed cathodoluminescence studies of single ZnO:P nanowires revealed characteristic phosphorus acceptor-related peaks: neutral acceptor-bound exciton emission (A0, X, 3.356 eV), free-to-neutral-acceptor emission (e, A0, 3.314 eV), and donor-to-acceptor pair emission (DAP, ~3.24 and ~3.04 eV). This means that stable acceptor levels with a binding energy of about 122 meV have been induced in the nanowires by phosphorus doping. Moreover, the induced acceptors are distributed homogeneously along the doped nanowires.
TL;DR: In this article, low temperature spatially resolved cathodoluminescence was carried out on GaN films grown by the epitaxial-lateral-overgrowth (ELO) technique with the nonpolar (11-20) and the semipolar (11 -22) orientations on R- and M-sapphires, respectively.
Abstract: Low temperature spatially resolved cathodoluminescence was carried out on GaN films grown by the epitaxial-lateral-overgrowth (ELO) technique with the nonpolar (11-20) and the semipolar (11-22) orientations on R- and M-sapphires, respectively. Defect related optical transitions were identified and their localization was correlated to different regions of ELO. The sample microstructure was further investigated by plan-view and cross-section transmission electron microscopies. It is shown that the defect related emissions are mainly localized in the seed of the samples, but different defects occur as well in the wings, especially in the case of nonpolar GaN. The structural defect densities are lowest in the overgrown wings of semipolar GaN. In particular, the [0001] wing region of semipolar ELO-GaN is almost defect-free with a cathodoluminescence spectrum dominated by the GaN band-edge emission at 3.476eV.
TL;DR: In this article, the photoluminescent and cathodolumininescent spectra are described by the well-known 5 D 0 → 7 F J transition (J = 0, 1, 2, etc.).
TL;DR: In this paper, the excitonic recombinations in hexagonal boron nitride (hBN) were investigated with spatially resolved cathodoluminescence spectroscopy in the UV range.
Abstract: The excitonic recombinations in hexagonal boron nitride (hBN) are investigated with spatially resolved cathodoluminescence spectroscopy in the UV range. Cathodoluminescence images of an individual hBN crystallite reveals that the 215 nm free excitonic line is quite homogeneously emitted along the crystallite whereas the 220 nm and 227 nm excitonic emissions are located in specific regions of the crystallite. Transmission electron microscopy images show that these regions contain a high density of crystalline defects. This suggests that both the 220 nm and 227 nm emissions are produced by the recombination of excitons bound to structural defects.
TL;DR: The results of XRD, FE-SEM, and TEM indicate that the 800 degrees C annealed sample consists of crystalline YBO3 shells and amorphous SiO2 cores, in spherical shape with a narrow size distribution, pointing out the great potential for these particles applied in displaying and lightening fields.
Abstract: Y0.9Eu0.1BO3 phosphor layers were deposited on monodisperse SiO2 particles of different sizes (300, 570, 900, and 1200 nm) via a sol−gel process, resulting in the formation of core−shell-structured SiO2@Y0.9Eu0.1BO3 particles. X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), photoluminescence (PL), and cathodoluminescence (CL) spectra as well as lifetimes were employed to characterize the resulting composite particles. The results of XRD, FE-SEM, and TEM indicate that the 800 °C annealed sample consists of crystalline YBO3 shells and amorphous SiO2 cores, in spherical shape with a narrow size distribution. Under UV (240 nm) and VUV (172 nm) light or electron beam (1−6 kV) excitation, these particles show the characteristic 5D0−7F1-4 orange-red emission lines of Eu3+ with a quantum yield ranging from 36% (one-layer Y0.9Eu0.1BO3 on SiO2) to 54% (four-layer Y0.9Eu0.1BO3 on SiO2). The luminescence properties (emission intensity and color co...
TL;DR: In this article, a model based on first-principles calculations of the surface oxygen vacancies in the different crystallographic directions is proposed for corroborating the existence of surface state bands localized at energy values compatible with the found cathodoluminescence bands and with the gas sensing mechanisms.
Abstract: Defects in SnO 2 nanowires have been studied by cathodoluminescence, and the obtained spectra have been compared with those measured on SnO 2 nanocrystals of different sizes in order to reveal information about point defects not determined by other characterization techniques. Dependence of the luminescence bands on the thermal treatment temperatures and pre-treatment conditions have been determined pointing out their possible relation, due to the used treatment conditions, with the oxygen vacancy concentration. To explain these cathodoluminescence spectra and their behavior, a model based on first-principles calculations of the surface oxygen vacancies in the different crystallographic directions is proposed for corroborating the existence of surface state bands localized at energy values compatible with the found cathodoluminescence bands and with the gas sensing mechanisms. CL bands centered at 1.90 and 2.20 eV are attributed to the surface oxygen vacancies 100° coordinated with tin atoms, whereas CL bands centered at 2.37 and 2.75 eV are related to the surface oxygen vacancies 130° coordinated. This combined process of cathodoluminescence and ab initio calculations is shown to be a powerful tool for nanowire defect analysis.
TL;DR: In this article, the excitonic recombinations in hexagonal boron nitride (hBN) were investigated with spatially resolved cathodoluminescence spectroscopy in the UV range.
Abstract: The excitonic recombinations in hexagonal boron nitride (hBN) are investigated with spatially resolved cathodoluminescence spectroscopy in the UV range. Cathodoluminescence images of an individual hBN crystallite reveals that the 215 nm free excitonic line is quite homogeneously emitted along the crystallite whereas the 220 nm and 227 nm excitonic emissions are located in specific regions of the crystallite. Transmission electron microscopy images show that these regions contain a high density of crystalline defects. This suggests that both the 220 nm and 227 nm emissions are produced by the recombination of excitons bound to structural defects.
TL;DR: In this article, the cathodoluminescence properties of rare-earth (RE = Ce, Eu, Tb) doped nanocrystalline phosphors (Y2O3, Y3Al5O12) were investigated.
Abstract: The cathodoluminescence properties of rare-earth (RE = Ce, Eu, Tb) doped nanocrystalline phosphors (Y2O3, Y3Al5O12) were investigated. Their structure and morphology were determined and correlated with optical properties. The effect of grain sizes on emission yield of RE doped nanophosphors has been investigated. A possibility of application of RE doped nanophosphors for efficient field emission display (FED) devices has been discussed.
TL;DR: This work reports the observation of plasmonic modes of annular resonators in nanofabricated Ag and Au surfaces that are imaged by spectrally resolved cathodoluminescence and demonstrates unprecedented resolution of plAsmonic mode excitation.
Abstract: We report the observation of plasmonic modes of annular resonators in nanofabricated Ag and Au surfaces that are imaged by spectrally resolved cathodoluminescence. A highly focused 30 keV electron beam is used to excite localized surface plasmons that couple to collective resonant modes of the nanoresonators. We demonstrate unprecedented resolution of plasmonic mode excitation and by combining these observations with full-field simulations find that cathodoluminescence in plasmonic nanostructures is most efficiently excited at positions corresponding to antinodes in the modal electric field intensity.
TL;DR: In this paper, the appearance of room temperature ferromagnetism in Mn-doped ZnO nanorods was investigated. But the results showed that oxygen vacancies played an important role in their appearance.
Abstract: Mn-doped ZnO nanorods are prepared by a chemical vapor deposition method using zinc and MnO2 powders as source materials of Zn and Mn, respectively. Cathodoluminescence (CL) characterization indicates that the Mn-doped ZnO nanorods grown at different growth temperatures have different oxygen vacancy concentrations. Room temperature ferromagnetism with a saturation magnetization of 0.87μB∕Mn has been observed in Mn-doped ZnO nanorods grown at 650°C, in which moderate oxygen vacancy concentration is observed by CL characterization. It is also found that oxygen vacancies play an important role in the appearance of room temperature ferromagnetism in Mn-doped ZnO nanorods.
TL;DR: In this article, the effect of erbium dopant on structural, morphological, luminescent and nonlinear optical properties was studied using spray pyrolysis technique.
TL;DR: In this paper, large gallium nitride (GaN) crystals were grown using a hydride vapor phase epitaxy (HVPE) technique and were processed into substrates for device applications.
TL;DR: In this paper, a tapered ZnO nanorod was grown on a silicon substrate by a hydrothermal downward growth process, which exhibited very strong ultraviolet emission from band gap transition and almost no green emission attributed to singly ionized oxygen vacancies.
Abstract: Tapered ZnO nanorod, herein called nanoneedle, arrays have been grown on ZnO-coated silicon substrate by a hydrothermal downward growth process. The ZnO seed layer facilitated the growth of aligned nanorods. The nanoneedles were grown with the substrate placed flush with the surface of the reaction solution and facing downward. The correlation between the depletion of solution and reaction temperature was exploited to control the length of the tapered portion of ZnO nanoneedles for the same solution. The vertical ZnO nanoneedle arrays exhibit very strong and sharp ultraviolet emission from band gap transition and almost no green emission attributed to singly ionized oxygen vacancies in the cathdoluminescence spectrum. The enhancement in optical properties will be advantageous in applications for nanoscale light-emitting devices.
TL;DR: In this article, the growth of N- and Al-polar AlN layers on c-plane sapphire by flow-modulation MOCVD (FM-MOCVD) with some flow sequence modifications was reported.
TL;DR: In this paper, the optical bandgap of amorphous AlN is about 210nm, so that the film is transparent in the ultraviolet, allowing the Gd emission to excite the Pr3+ ions.
Abstract: Sputter deposited thin film amorphous AlN:Pr (1at.%) emits in the blue-green (490–530nm) and red (∼650nm) regions of the visible spectrum under electron excitation. The addition of Gd 1at.% in the film enhances the blue emission by an order of magnitude. The enhancement in the blue region is a result of cathodoluminescence from Gd3+ at 313nm. The optical bandgap of amorphous AlN is about 210nm, so that the film is transparent in the ultraviolet, allowing the Gd emission to excite the Pr3+ ions. No significant quenching of the Gd emission is observed when the Gd and Pr ions are mixed. The blue enhancement is observed even with the two films containing each of the ions that are separated by a 500μm thick quartz spacer, showing that the enhancement is due entirely to UV radiation.
TL;DR: In this paper, high-crystalline CaMoO4:Tb3+ phosphor layers were grown on monodisperse SiO2 particles through a simple sol-gel method, resulting in formation of core-shell structured siO2@CaMoOO4+ submicrospheres, which were fully characterized by powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FESEM), energy-dispersive Xray spectra (EDS), transmission
Abstract: Highly crystalline CaMoO4:Tb3+ phosphor layers were grown on monodisperse SiO2 particles through a simple sol-gel method, resulting in formation of core-shell structured SiO2@CaMoO4:Tb3+ submicrospheres. The resulting SiO2@CaMoO4: Tb3+ core-shell particles were fully characterized by powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectra (EDS), transmission electron microscopy (TEM), photoluminescence (PL), low-voltage cathodoluminescence (CL), and kinetic decays. The XRD results demonstrate that the CaMoO4:Tb3+ layers begin to crystallize on the SiO2 spheres after annealing at 400 degrees C and the crystallinity increases with raising the annealing temperature. SEM and TEM analysis indicates that the obtained submicrospheres have a uniform size distribution and obvious core-shell structure. SiO2@CaMoO4:Tb3+ submicrospheres show strong green emission under short ultraviolet (260 nm) and low-voltage electron beam (1-3 kV) excitation, and the emission spectra are dominated by a D-5(4) -F-7(5) transition of Tb3+(544 nm, green) from the CaMoO4:Tb3+ shells.
TL;DR: In this paper, the intensity ratios of deep cathodoluminescence (CL) bands at 4.6, 3.8, and 3.1eV were correlated with the change in the S parameter of positron annihilation measurement, which represents the concentration or size of Al vacancies (VAl).
Abstract: Intensity ratios of characteristic deep cathodoluminescence (CL) bands at 4.6, 3.8, and 3.1eV to the near-band-edge emissions at 11K of AlN epilayers grown by NH3-source molecular beam epitaxy were correlated with the change in the S parameter of positron annihilation measurement, which represents the concentration or size of Al vacancies (VAl). Since the relative intensities of 3.1 and 3.8eV bands increased remarkably with lowering supply ratio of NH3 to Al (V/III ratio) and growth temperature (Tg), they were assigned to originate from VAl-O complexes. The VAl concentration could be decreased by adjusting V/III ratio and Tg, resulting in observation of fine excitonic features in the CL spectra. From the energy separation between the ground and first excited states, the binding energy of A exciton was determined to be 48meV.
TL;DR: In this article, the emission spectrum of the GdNbO4:Bi3+ powder phosphors for field emission displays were prepared by a solid state reaction and both photoluminescence and cathodolumine properties of the materials were investigated.
TL;DR: In this paper, the optical properties of multi-wall boron nitride nanotubes are investigated by means of luminescence and absorption spectroscopies, and it is shown that the luminecence is located all along the nanotube.
Abstract: Optical properties of multiwall boron nitride nanotubes are investigated by means of luminescence and absorption spectroscopies. Cathodoluminescence imaging shows that boron nitride nanotubes are highly UV luminescent materials and that the luminescence is located all along the nanotube. In comparison with the related bulk material, hexagonal boron nitride, luminescence and absorption experiments point out the role of excitonic effects in this nanoobject.