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The donor/acceptor heterojunction plays an important role in organic solar cells. An investigation of band bending in the donor/acceptor heterojunction is helpful in analysis of the charge transport behavior and for the improvement of the device performance. In this work, we report an approach for detection of band bending in a donor/acceptor heterojunction that has been prepared on a small and sharp tungsten tip. In situ field emission measurements are performed after the deposition process, and a linear Fowler-Nordheim plot is obtained from the fresh organic film surface. The thickness-dependent work function is then measured in the layer-by-layer deposited heterojunction. Several different types of heterojunction (zinc phthalocyanine (ZnPc)/C60, copper phthalocyanine (CuPc)/3,4,9,10-perylenetetracarboxylic bisbenzimidazole, and CuPc/C60) are fabricated and analyzed. The different charge transfer directions in the heterojunctions are distinguished by field emission measurements. The calculation method used to determine the band bending is then discussed in detail. A triple layer heterojunction (C60/ZnPc/CuPc) is also analyzed using this method. A small amount of band bending is measured in the outer CuPc layer. This method provides an independent reference method for determination of the band bending in an organic heterojunction that will complement photoemission spectroscopy and current-voltage measurement methods. [ABSTRACT FROM AUTHOR]

For matching the high energy excitation by the low voltage electron beams, the phosphors with stable crystal structure and high energy level excitation band is necessary. In this work, it is interesting to find a suitable phosphor of Na2TiGeO5 with self‐light emitting property. The tight crystal structure of Na2TiGeO5 formed by edge‐shared NaO6 and TO5 polyhedrons corresponds to its good thermal stability and degradation resistance property. The results indicate that the PL and CL intensity can still remain beyond 80% and 90% at 150°C and after 1 hour electron beams bombardment, respectively. Under the 254 nm excitation, the bright blue light peaked at 460 nm can be detected and the light control has been realized with the Cr3+ doped, which changes blue light to cyan light. The high energy excitation is attributed to the charge transfer band (CTB) of Ti4+–O2−, which matches the electron beams. The bright CL emission light centered at 450 nm with good degradation resistance property has been detected. The results indicate its potential application in field emission display (FED)s. [ABSTRACT FROM AUTHOR]

Pure Sm2O3 and Gd3+ doped Sm2O3 nanocrystalline powders were synthesized using the combustion method. The structural analysis from the Powder X-ray Diffraction revealed that pure and Gd3+ doped Sm2O3 nanocrystals of cubic phase with Ia3¯ as the space group were produced. The High Resolution Transmission Electron Microscopy results confirmed that monodisperse nanocrystals having spherical shape were formed. The results of the Energy-Dispersive X-ray analysis confirmed that the samples were free from impurities. The UV-Vis-IR absorption and photoluminescence studies, carried out to study their optical properties, showed that these materials could be used for solid state lighting devices, particularly for UV/n-UV (near-ultraviolet) excited white light-emitting diodes. The charge density and photoluminescent behaviour in the chosen system were correlated using the MEM/Rietveld analysis. [ABSTRACT FROM AUTHOR]

Abstract: A new borate phosphor NaBaY(BO3)2: Ce3+, Tb3+ (NBY:Ce3+, Tb3+) was successfully synthesized under low temperature designed to put into application in the fields of ultraviolet (UV)‐excited light emitting diodes (LEDs) and field emission displays (FEDs). The structure distortion between Ce3+, Tb3+ single‐ and co‐doping NBY was discussed by X‐ray powder diffraction Rietveld refinement, high‐resolution transmission electron microscopy (HRTEM) and spectra. NBY: Ce3+, Tb3+ presents a wide absorption band ranging from 310 to 400 nm and efficient green emission (λmax = 542 nm) with a full‐width at half‐maximum of 3.3 nm. The remarkable thermal stability has also been tested, indicating that the intensity at 200°C is still beyond 70% of the original intensity. In addition, a white LED device was manufactured by connecting a 370 nm UV chip with a blend of BaMaAl10O17: Eu2+ (BAM: Eu2+), NBY: Ce3+, Tb3+ and CaAlSiN3: Eu2+. The color coordinate, correlated color temperature and color rendering index of the manufactured LED device were (0.335, 0.347), 5511 K and 80.16, respectively. Meanwhile, the cathodoluminescence (CL) spectra under the various conditions of probe currents and accelerating voltages were also analyzed. Through successive excitation of low‐voltage electron‐beam, the wonderful performances of degradation property and color stability were obtained. These results suggest that the green‐emitting NBY: Ce3+, Tb3+ phosphor has the prospect of becoming applications in white UV LEDs and FEDs. [ABSTRACT FROM AUTHOR]

Electron field emission was investigated from multi-walled carbon nanotubes (MWCNT)/polyethylene oxide (PEO) composites with (5, 15, 25, 33, 40 and 50wt.% of MWCNTs). The resulted samples were characterized using Raman spectroscopy to estimate The MWCNTs-PEO (Nanotubes-Polymer) interaction through the shifting or width alteration of the peaks. The SEM micrographs were issued to investigate the surface morphology of the samples. In addition, and in order to gain additional understanding of the filler content and the samples thermal stability; the TGA technique was applied. The current density versus applied electric field J(E) and current stability of the prepared composites were measured using a range of voltages. Here, the 33wt.% composite displayed the lowest turn on field of 6.51V/μm, whereas the highest current density achieved was 1.17mA/cm2 by the 40wt.% composite. [ABSTRACT FROM AUTHOR]

Fluorescence intensity ratio (FIR)-based optical thermometry has attracted a great deal of attention because it allows accurate and reliable temperature measurements with high spatial resolution and real-time monitoring. Herein, we report the novel Sr 2 Gd 8 (SiO 4 ) 6 O 2 :Er 3+ (SGSO:Er 3+ ) phosphor as an optical thermometry material. The sol-gel method is used to synthesize the oxyapatite structured SGSO:Er 3+ phosphors, which exhibits a rod-like morphology. The photoluminescence spectra of SGSO:Er 3+ phosphors displays two distinct green emission bands corresponding to the electronic transitions 2 H 11/2  →  4 I 15/2 and 4 S 3/2  →  4 I 15/2 . The temperature-induced variations in the FIR result in a maximum sensitivity of 3.4 × 10 −3  K −1  at 463 K. Further, the CIE chromaticity coordinates do not shift from the green region when the temperature is increased from 303 to 483 K and the color purity only decreasing from 77.6 to 71.4%. The SGSO:2Er 3+ phosphor exhibits the color-purity of 93.5% when excited with low-energy electron beam. These results suggest that the SGSO:2Er 3+ phosphor is a promising material for optical temperature sensors and display devices. [ABSTRACT FROM AUTHOR]

The progress in field emission theory from its initial Fowler-Nordheim form is centred on the transmission coefficient. For the supply (of electrons) function one still uses the constant value due to a supply of plane-waves states. However, for emitting tips of apex radius of 1-5nm this is highly questionable. To address this issue, we have solved the Schrödinger equation in a sharp paraboloidally shaped quantum box. The Schrödinger equation is separable in the rotationally parabolic coordinate system and we hence obtain the exact eigenstates of the system. Significant differences from the usual Cartesian geometry are obtained. (1) Both the normally incident and parallel electron fluxes are functions of the angle to the emitter axis and affect the emission angle. (2) The WKB approximation fails for this system. (3) The eigenfunctions of the nanoemitter form a continuum only in one dimension while complete discretization occurs in the other two directions. (4) The parallel electron velocity vanishes at the apex which may explain the recent spot-size measurements in nearfield scanning electron microscopy. (5) Competing effects are found as the tip radius decreases to 1 nm: The electric field increases but the total supply function decreases so that possibly an optimum radius exists. [ABSTRACT FROM AUTHOR]

A series of novel Eu 3+ -activated NaBiF 4 nanoparticles were synthesized by an ultra-fast chemical precipitate method at room temperature. Under the excitation of 394 nm, all the compounds emitted glaring red emissions originating from the intra-4f transitions of Eu 3+ ions. The optimal doping concentration was found to be 40 mol% and the concentration quenching mechanism was dominated by dipole–dipole interaction. The temperature-dependent photoluminescence emission spectra revealed that the resultant nanoparticles possessed admirable thermal stability with an activation energy of 0.237 eV. The internal quantum efficiency of the synthesized nanoparticles was estimated to be as high as 73.1%. Furthermore, the optical transition parameters of Eu 3+ ions were calculated using a facile method based on the Judd-Ofelt theory to explore the local structure environment around the Eu 3+ ions in the NaBiF 4 host lattice. Additionally, the packaged light-emitting diode (LED) device, which was composed of a near-ultraviolet LED chip, synthesized nanoparticles and commercial blue-emitting/green-emitting phosphors, exhibited brightly white light with high color rendering index of 88.2 and proper correlated color temperature of 6851 K. Ultimately, the studied nanoparticles also had splendid cathodoluminescence properties. These results suggest that the Eu 3+ -activated NaBiF 4 nanoparticles were promising bifunctional materials for simultaneous white LEDs and field emission displays. [ABSTRACT FROM AUTHOR]

Bi-activated LaAlO:Ho Phosphor, was prepared by Polyol method, and its photoluminescent properties were investigated under (UV) light excitation. Luminescence studies indicated that optimum concentration of Bi and Ho in LaAlO was found to be 1 and 1.5 at.%. The luminescent intensity of Ho emission lines was remarkably enhanced on exciting with 272 nm, which suggested that efficient energy transfer from Bi ions to Ho ions takes place. There is significant energy overlap between the emission band of Bi ions and the excitation band of Ho ions.The ET efficiency has been calculated and found to be 69%. The critical ET distance has been calculated by the concentration-quenching method. The enhanced intensity and tuned luminous color of LaAlO: Bi/Ho phosphors from blue to cyan provides a promising material for field emission display devices. [ABSTRACT FROM AUTHOR]

In the present study, the willemite-based Zn 2-2x Mn 2x SiO 4 solid solution has been produced by the high-temperature solid-state reaction. The powder samples were characterized by X-ray diffraction, UV–vis spectroscopy and optical emission spectroscopy. A monotonic increase in the luminescence intensity is observed with a growth of the Mn content, but not exceeding x = 0.13. The absence of concentration quenching of luminescence below this limit is explained by stochastic arrangement of the dopant atoms, which is confirmed by crystallographic data. Basic trends in distribution of Mn ions within the willemite lattice and electronic properties were validated by means of DFT calculations. Homogenous distribution of photoactive substituent ion is a key feature in the design of luminescent materials. [ABSTRACT FROM AUTHOR]

Spectroscopic properties of K 3 Gd(PO 4 ) 2 : Tm 3+ -Dy 3+ under ultraviolet (UV) light and low-voltage electron beam excitations were investigated. Upon direct excitation Tm 3+ from its 6 F 6 level to 1 D 2 level, the decrease of emission intensity and lifetime of Tm 3+ 1 D 2 - 3 F 4 emission with increasing concentration of Dy 3+ in K 3 Gd(PO 4 ) 2 : Dy 3+ , Tm 3+ confirmed the occurrence of energy transfer from Tm 3+ to Dy 3+ . Besides, K 3 Gd(PO 4 ) 2 : Dy 3+ , Tm 3+ could be efficiently excited by 358 nm UV light and its emission color could be tuned from blue to yellow by codoping Tm 3+ . When 1% Tm 3+ and 8% Dy 3+ were codoped in the K 3 Gd(PO 4 ) 2 , intensive white emitting light with CIE of (0.338, 0.347) was achieved upon 358 nm excitation. The cathodoluminescence spectra of K 3 Gd(PO 4 ): Tm 3+ , Dy 3+ phosphors as a function of accelerating voltage and filament current were also measured. Under low-voltage electron-beam excitation, K 3 Gd(PO 4 ) 2 : Tm 3+ , Dy 3+ phosphors exhibit excellent tunable emitting property. All of the above results reveal that the as-prepared K 3 Gd(PO 4 ) 2 : Tm 3+ , Dy 3+ phosphors have potential applications in white LEDs and FEDs. [ABSTRACT FROM AUTHOR]

ZnO thin film and nanorods array have been synthesized by RF magnetron sputtering and low temperature wet chemical method, respectively. It is followed by deposition of Cu nanosheet using DC magnetron sputtering, which was oxidized subsequently to form 2D and 3D ZnO/CuO heterointerfaces. A successful fabrication of heteroepitaxial ZnO-CuO thin film was presented to improve the interface quality, crystallinity and conformal characteristic of CuO sheet. ZnO/CuO thin film revealed higher absorption efficiency in the visible region in comparison to pure ZnO. The rectifying behavior of n-ZnO/p-CuO junction could be useful in photoactive and photoconductive devices, while the uni-polar transport of p-CuO/n-ZnO thin film is beneficial for optical switching. This photoactivity attributed to extended light absorption and effective transfer of photogenerated carriers. The as-synthesized ZnO-Cu composite was determined to be a hierarchical heterostructure consisting of ZnO nanorods and Cu nanosheets with intimate hetero-interfaces. The formation of n-Cu/n-ZnO heterointerface cause to electrostatic field which facilitates electron emission. [ABSTRACT FROM AUTHOR]

The image-charge potential plays a key role in field emission by lowering the potential barrier, thereby leading to an increase in current density by orders of magnitude. The classical imagecharge potential is however strictly applicable to planar emitters rather than the curved protrusions characteristic of field emission sites. Using recent results [Jensen et al., J. Vac. Sci. Technol. B 35, 02C101 (2017)] for a hyperboloid emitting surface, we show that for a charge close to the emitter surface, the image charge magnitude and location are well approximated by replacing the surface locally by a sphere having the same radius of curvature. Corrections to the image-charge potential under this approximation are calculated and found to be significant for field emission when the radius of curvature is in the nanometer regime. In such cases, there is reduced electron emission and the effect is more pronounced at lower external field strengths. Published by AIP Publishing. [ABSTRACT FROM AUTHOR]

A white-emitting novel AlSi C N: Mn carbidonitride phosphor was synthesized by introducing SiC into AlN: Mnat the temperature as low as 1500 °C. The influence of Mn and SiC doping concentration on the structure, morphology and luminescent properties was systematically investigated by XRD, EDS, solid state NMR, FESEM, and PL. The relatively low calcination temperature endows AlN: Mn with different luminescent properties. Under 254 nm UV excitation, it not only exhibits a characteristic red emission from Mn but also covers a broad violet-blue-green emission from defects. The CIE coordinates (0.2999, 0.2510) precisely locate in the white region. With the introduction of SiC, an increasing of the red emission from Mn is observed, while no variation occurs for the defect emission. The maximum red luminescence is attained for the composition of x = 0.05 that has an improved thermal stability by 20%. Finally, a low-voltage FED device was fabricated by using AlSiCN: 0.7% Mn carbidonitride phosphor. Under low-voltage excitation, it exhibits a high brightness, low saturation, and good color stability, which makes AlSiCN: Mn carbidonitride phosphor have a great potential for full color FEDs. [ABSTRACT FROM AUTHOR]

Two scheelite-type rare-earth tungstates LiLn(WO 4 ) 2 (Ln = Sm, Eu) have been prepared using a high temperature molten salt method and structurally characterized by single crystal X-ray diffraction (SC-XRD) analyses. The structure features a three-dimensional (3D) network that is composed of two-direction packing of isolated WO 4 tetrahedra interconnected by Li|Ln atoms. The photoluminescence (PL) properties of LiLn(WO 4 ) 2 (Ln = Sm, Eu) show the characteristic spectra of Sm 3+ and Eu 3+ ions. The emission spectra of the LiSm(WO 4 ) 2 consisted of some sharp emission peaks of Sm 3+ ions centred at 562 nm, 600 nm, 645 nm, 705 nm, in which the strongest one is 645 nm due to 4 G 5/2 → 6 H 7/2 transition of Sm 3+ . For phosphor LiEu(WO 4 ) 2 , the emission spectra recorded for excitation wavelength at 393 or 464 nm exhibit a strong emission peak at 613 nm, corresponding to the 5 D 0 → 7 F 2 transition of Eu 3+ . The commission international Del’Eclairage (CIE) chromaticity coordinates of the phosphors were about (0.5166, 0.4657) for LiSm(WO 4 ) 2 and (0.6240, 0.3701) for LiEu(WO 4 ) 2 . [ABSTRACT FROM AUTHOR]

Na 2 Y 2 B 2 O 7 :Er 3+ /Yb 3+ crystalline phosphors with single monoclinic phase have been synthesized by urea assisted solution combustion method and characterized through X-ray diffraction and Field emission scanning electron microscopy analysis. Frequency upconversion (UC) emission study has been carried out upon 980 nm laser diode excitation and maximum enhancement of about ∼1433 times for the UC emission intensity of the green band in the codoped phosphor compared to that of the singly Er 3+ doped phosphor has been reported. Optical temperature sensing study performed in the developed codoped phosphor reveals that the material can be used temperature sensing application within 300–613 K temperature range with maximum sensitivity ∼7.9 × 10 −3 K −1 at 300 K. The low-voltage cathodoluminescence measurements have been performed for Na 2 Y 2 B 2 O 7 :Er 3+ -Yb 3+ phosphors as a function of accelerating voltage and filament current. The developed phosphors exhibit highly intense green emission with some weak emission bands in violet, blue and red regions upon electron beam excitation. [ABSTRACT FROM AUTHOR]

A novel nano-porous 12CaO·7Al 2 O 3 :Sm 3+ conductive phosphor with red emissions has been prepared by a self-propagating combustion method in combination with subsequent treatments under different conditions. Upon 404 nm excitation, the phosphor shows four dominating red emission peaks at 564, 601, 648 and 709 nm, which are attributed to the 4 G 5/2 → 6 H 5/2 , 6 H 7/2 , 6 H 9/2 , 6 H 11/2 transitions of Sm 3+ , respectively. The concentration-dependent luminescence of the phosphor shows that the dipole–dipole interaction is the major mechanism for the concentration quenching of red emissions of Sm 3+ ions in the phosphor. Absorption and electron spin resonance spectra indicate that the existence of encaged electrons in the phosphor plays a key role in the contribution to its conductive performance. Under electron beam excitation, the conductive phosphor exhibits the enhanced cathodoluminescence and the improved chromaticity coordinate compared to the insulating phosphor. [ABSTRACT FROM AUTHOR]

A series of Eu2+ doped BaSi2O5 phosphors were prepared using a traditional high temperature solid state reaction method. The structure, morphology, photoluminescence and cathodoluminescence properties as well as the thermal quenching properties were investigated in detail. A green emission band centered at about 500 nm can be obtained. The phosphors exhibit high current saturation and high resistance under low voltage electron bombardment. The chromaticity coordinates reveal that the phosphors can evidently enlarge the gamut compared with commercial tricolor phosphors. The results show that BaSi2O5:Eu2+ could be a potential candidate for both white light emitting diodes and field emission displays. [ABSTRACT FROM AUTHOR]

A generalized protocol for solution-based seeding and self-assembly of a wide range of cupric oxide (CuO) nanostructures is developed. Parameters of KMnO4 activation are found to play a crucial role in chemical seeding and vis-à-vis in evolution of various morphologies. To demonstrate the devised two-stage seeding and self-assembly protocol, various types of CuO nanostructure films are fabricated on flexible carbon fabric. Such systems are found to retain the native substrate's innate flexibility and the structural integrity of the grown nanostructures showed no deterioration upon rolling up or even twisting to a large degree. Among the various CuO morphologies, the nanoneedles exhibited excellent field-emitting traits such as a lower turn-on field of 0.9 V μm−1 and an appreciably good current density of 1.65 mA cm−2 at an applied macroscopic field of 1.25 V μm−1 as well as high stability under large applied fields. Theoretical estimation of the local electric field distribution supported the experimental outcomes and indicated that the field emission enhancement stems from the emitters' geometry as well as the spatial separation. The devised growth protocol is efficient, economic and high-throughput, thus it lays a promising path for exploiting CuO (and possibly other) nanostructures for flexible field emission electronics/displays as well as in vacuum nano-electronic devices. [ABSTRACT FROM AUTHOR]

High aspect ratio, conductive sharp tips have geometrical advantages in sensing and actuation. Developing these structures on soft, stretchable and bendable materials would provide distinct advantages, such as conformable sensors for biosignals, morphable displays, profilometers for curved surfaces, and so on. A major challenge in using soft materials as substrates is that the fabrication technique should be conducted in close to ambient conditions, particularly at low temperature. In this paper, the fabrication of high aspect ratio conductive sharp tips on elastomers is discussed. Without using fine feature molds, a capillary bridge is created by containing and separating a conductive viscous gel between two plates. The capillary pressure experienced by the capillary bridge shapes the gel to a sharp tip ( $\sim 100$ nm) before it solidifies. The process flow is quantified by measuring the mechanical force needed for tip creation and extracting the coefficients of the standard linear solid model for the viscoelastic gel. Electron emission is demonstrated at 22 $\mu $ bar and 1 mbar, and appears to be determined by Fowler–Nordheim tunneling for most cases. Elastomeric field emission displays and profilometers are demonstrated. [ABSTRACT FROM AUTHOR]

New low work function conductive ceramic materials have been developed by using multi‐sputtering method to realize reliable and low voltage operation display devices such as quantum dots light‐emitting diodes (QLEDs), organic light‐emitting diodes (OLEDs), field emission displays (FEDs) and so on. The work function of conductive ceramic materials exhibits as low as 1.8 eV, which were evaluated by using an ultraviolet photoelectron spectroscopy, that is the lowest work function among display materials, ever reported, being compared with 1.9 eV, 2.6 eV and 2.9 eV of Cs, LiF and Ca. Conventional low work function materials such as Cs, LiF and Ca, are highly reactive chemicals, so that those electrical properties are strongly degraded. However, regarding to experimental results, the low work function ceramic materials have the chemical stability. The extremely stable, ruggedized and low work function conductive ceramic materials are expected to be useful for realizing highly reliable and efficient QLEDs, OLEDs and FEDs. [ABSTRACT FROM AUTHOR]

A large area carbon nanotube field emission backlight that is built with a new cathode structure is reported. The approach involves unique gate insulator formation by glass etching, highly populated multi wall nanotube tips, and gate electrode assembly by anodic bonding. Impressive lamping performances are noted through dynamic control of the built in fine 4320 local dimming blocks as small as 1 cm 2 . The liquid crystal display lit by the backlight demonstrates superior luminance uniformity 97%, and a native contrast ratio 400,000:1, whilst showing less than 10% decay in emission current of the sealed panel during continuous operation over 8000 h. [ABSTRACT FROM AUTHOR]

A series of SrSiAl2O3N2:Eu2+ (0.005 ≤x≤ 0.05) phosphors were successfully synthesized through a pressureless, facile, and efficient solid state route. The crystal structure, band structure, and their photoluminescence and cathodoluminescence properties were investigated in detail. The phosphors exhibit rod shape morphology with a uniform Eu2+ distribution. Under n-UV excitation the emission spectra shift from 477 to 497 nm with an increase of Eu2+ concentration. The concentration quenching mechanism of Eu2+ emission was dominated by the dipole–dipole interaction. The thermal stability is comparable to that of the commercial Ba2SiO4:Eu2+ phosphor. The phosphor also exhibits high current saturation and high resistance under low voltage electron bombardment. All the results indicate that the SrSiAl2O3N2:Eu2+ phosphors can be considered as candidates for application in both white LEDs and FEDs. [ABSTRACT FROM AUTHOR]

In this work, a detailed field emission study of multi-walled carbon nanotubes (MWCNTs) grown on Si and Al coated Si substrates is reported. Morphological and microstructural studies of the films show higher entanglement of CNTs in the case of CNT/Si film as compared to CNT/Al/Si film. Raman studies show that the defect mediated peak (D) is substantially suppressed as compared to graphitic peak (G) resulting in significant reduction in ID/IG value in CNT/Al/Si film. Field emission (FE) current density of CNT/Al/Si film (~25 mA/cm²) is significantly higher as compared to that of CNT/Si film (~1.6 mA/cm2). A substantial improvement in temporal stability is also observed in CNT/Al/Si film. This enhancement in field emission current is attributed to strong adhesion between substrate and CNTs, low work function, high local field enhancement factor at the CNT tips and less entanglement of CNTs grown on Al/Si. The temporally stable CNT/Al/Si cold cathode can be a potential candidate to replace conventional electron sources in prototype devices. [ABSTRACT FROM AUTHOR]

A series of Mn 2+ doped Ba 2 MgSi 2 O 7 phosphors with a nominal formula Ba 2 Mg 1− x Mn x Si 2 O 7 ( x = 0.01–0.13) were prepared by a high-temperature solid-state reaction technique. Their VUV–vis photoluminescence spectra, fluorescence decay curves, and low-voltage cathodoluminescence spectra were measured and discussed in detail. The results confirm that the Mn 2+ ions enter into the four-coordinated Mg 2+ site in Ba 2 MgSi 2 O 7 host lattice. The main electron-vibrational interaction (EVI) parameters (such as Huang–Rhys factor, effective phonon energy and position of the zero-phonon line) were evaluated from the experimental spectra. Furthermore, the concentration and the temperature dependence of the emission intensity and the luminescence decays of Ba 2 MgSi 2 O 7 :Mn 2+ were investigated, accordingly the schematic energy levels for Mn 2+ in Ba 2 MgSi 2 O 7 were proposed. Due to the high emission intensity under low-voltage electron beam excitation, a further optimized sample Ba 2 Mg 0.95 Mn 0.05 Si 2 O 7 can be considered as a promising green phosphor for field emission displays (FEDs). [ABSTRACT FROM AUTHOR]

Transparent and flexible carbon doped ZnO (C:ZnO) field emission device was successfully fabricated on an arylite substrate. Excellent adhesion of deposited C:ZnO on the flexible substrate was achieved with low sputtering power and Ar flow rate. In the fabricated device, nanostructured C:ZnO and as-deposited thin films were used as field emitter and phosphor screen, respectively. The C:ZnO thin film showed a transparency of about 80% at 550 nm wavelength and average sheet resistance of 1.96 kΩ/□. The C:ZnO phosphor screen emitted red light during the field emission measurement, correlating the dominant cathodoluminescence peak at 646 nm. Thus, a promising transparent and flexible field emission display can be realized with C:ZnO based material. [ABSTRACT FROM AUTHOR]

In the paper, (1− x )Bi 0.5 Na 0.5 TiO 3 − x K 0.5 Na 0.5 NbO 3 ((1− x )BNT− x KNN, (0≤ x ≤0.08) powders with perovskite structure were firstly synthesized by the hydrothermal method, then the highly dense piezoelectric ceramics exhibiting lower coercive field were prepared by sintering (1− x )BNT− x KNN powders at 1150 °C for 2 h, followed by polarizing it in silicon oil at 80 °C for 5 min. The phase compositions and micro-morphology of (1− x )BNT− x KNN powders and ceramics were characterized by X-ray diffraction and field emission scanning electron microscope. The results showed that (1− x )BNT– x KNN (0≤ x ≤0.09) powders and ceramics dispersibility and crystal morphology could be successfully synthesized at 210 °C for 24 h by the hydrothermal method with KOH/NaOH=1:7 (molar ratio) in precursor when Ti(OC 4 H 9 ) 4 was used as titanium source. With the addition of KNN, the grain size of prepared powders became smaller and more disperse. The crystal structure of (1− x )BNT– x KNN ceramics was found to be changed from rhombohedral to pseudo-cubic phase combined with morphology change from regular round shape to cubic or rectangular shape. When the actual KNN content was in the range of 0.04–0.05, abrupt changes in both the phase and morphology of the ceramics were observed. This would be indicative of the formation of a rhombohedral and pseudo-cubic morphtropic phase boundary (MPB). The piezoelectric constant d 33 gradually reached its highest value of 96 pC/N at x =0.04, with the coercive field Ec of ceramics as 28 KV/cm. This result was much lower than that of pure BNT (45 KV/cm), indicating that the doping of KNN successfully decreases coercive field Ec of BNT ceramics. [ABSTRACT FROM AUTHOR]

Purpose: An life cycle assessment (LCA) study of a field emission display (FED) television device was established. The first objective of this study was to get an up-to-date and comprehensive picture by applying the latest developments in the area of LCA, especially concerning the use of nanoparticles. In its second part, the study shows a comparison with today's display technologies (i.e. CRT, LCD, plasma) and the timely development of the assessment of a FED television device. Methods: This LCA study covers the complete life cycle of a FED television device in accordance with the ISO 14040 standard, from the extraction of raw materials until the final end-of-life treatment in a European WEEE recycling system. Two different functional units were applied in this study: For the in-depth analysis of the FED television device, an entire device along its complete life cycle was considered as functional unit-for the subsequent comparison with today's display technologies, 'one square-inch of display during 1 h of active use' was used as an appropriate functional unit. Main data source for the FED device was patent information; ecoinvent was used as default background database. Results and discussion: The in-depth analysis of this FED television device shows a clear dominance of the production phase (independently of the impact category). Within the production of such a device, the electronics part (i.e. the printed wiring boards) shows the highest contribution-while, even when focussing on the glass and its various coating layers only, the carbon nanotubes (CNTs) production has a very minor influence. The releases of CNTs during the End-of-Life treatment do not contribute in a relevant manner to the overall impact neither-even when focussing on the 'ecotoxicity potential' by using conservative CFs reported for this type of releases. Last but not least, the comparison with the existing television display technologies shows that an FED device has an environmental advantage over all three other technologies using the above stated functional unit of 'one square-inch of display during 1 h of active use'. Conclusions: Traditional impact categories as well as the ecotoxicity factor results in clear environmental advantages for an FED television device when comparing it to the three display technologies used today. Concerning the general issue of evaluating applications of manufactured nanomaterials in LCA studies, this case study shows the high relevance of an adequate integration of nanoparticle releases into LCA studies in order to achieve an actually comprehensive evaluation. [ABSTRACT FROM AUTHOR]

A novel red emitting phosphor of Eu 3+ doped Ca 2 Ge 7 O 16 was prepared through the solid state reaction. The luminescence properties were studied in detail by photoluminescence excitation (PLE), emission (PL) spectra and cathodoluminescence (CL). Under the excitation of ultraviolet light, Ca 2 Ge 7 O 16 :Eu 3+ phosphor shows the characteristic 5 D 0 - 7 F J ( J = 1, 2, 3, 4) transition of Eu 3+ with two different emissions due to the two kinds of Eu 3+ ions. The luminescent intensity could be improved by co-doping with the charge compensators R + (Li, Na, K) which partially substitute for Ca 2+ crystal sites. CL spectra show that Eu 3+ ions were excited by the plasma produced by the incident electrons and the CL properties of Ca 2 Ge 7 O 16 :Eu 3+ , Li + as a function of accelerating voltage and probe current were investigated. Ca 2 Ge 7 O 16 :Eu 3+ phosphor offers higher thermal stability compared with the commercial red phosphor Y 2 O 3 :Eu 3+ . The results indicate that Ca 2 Ge 7 O 16 :Eu 3+ can be a suitable red-emitting phosphor candidate for FEDs and w-LEDs. [ABSTRACT FROM AUTHOR]

Nowadays there are several technologies used for flat panel displays (FPDs) and the development of FPDs with enhanced energy efficiency and improved display quality is strongly required. Field emission displays (FEDs) have been considered as one of the most promising next generation flat panel display technologies due to their excellent display performance and low energy consumption. For the development of FEDs, phosphors are irreplaceable components. In the past decade, the study of highly efficient low-voltage cathodoluminescent materials, namely FED phosphors, has become the focus of enhancing energy efficiency and realizing high-quality displays. This review summaries the recent progress in the chemical synthesis and improvement of novel, rare-earth and transition metal ions activated inorganic cathodoluminescent materials in powder and thin film forms. The discussion is focused on the modification of morphology, size, surface, composition and conductivity of phosphors and the corresponding effects on their cathodoluminescent properties. Special emphases are given to the selection of host and luminescent centers, the adjustment of emission colors through doping concentration optimization, energy transfer and mono- or co-doping activator ions, the improvement of chromaticity, color stability and color gamut as well as the saturation behavior and the degradation behavior of phosphors under the excitation of a low-voltage electron beam. Finally, the research prospects and future directions of FED phosphors are discussed with recommendations to facilitate the further study of new and highly efficient low-voltage cathodoluminescent materials. [ABSTRACT FROM AUTHOR]

Highly crystalline and uniform TiO2:Eu3+ spindlelike nanorods have been successfully synthesized through a facile hydrothermal route with citric acid (H3Cit) and ethanediamine (en) as the assistant agents for the first time. X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected-area electron diffraction (SAED), and photoluminescence (PL) spectroscopy were utilized to characterize the samples. In the synthetic process, the dosages of ethanediamine and citric acid are important parameters that affect the morphology and size of the final products. A possible formation process of the samples has been proposed in detail. The existence of Eu3+ sites in the TiO2 nanorods was proved by site-selective spectroscopy. Furthermore, the TiO2:Eu3+ spindlelike nanorods exhibit bright red (Eu3+, 5D0→7F2) luminescence under ultraviolet (UV) excitation; therefore, they may find potential applications in fluorescent lamps and field-emission displays (FEDs). [ABSTRACT FROM AUTHOR]

Abstract: Owing to enormous growing interest regarding the graphene based field emission display device, we have reported a very simple route to synthesis amorphous graphene (a-Gs) by ultra-sonication assisted unzipping of low-temperature synthesized amorphous carbon nanotubes. Also different hybrid systems have been developed by spinning assisted coating of the as prepared a-Gs on plasma enhanced chemical vapor deposited carbon nanoparticles or chemically synthesized vertically aligned silicon nanowires in order to develop hybrid cold cathode materials. Also the as synthesized a-Gs have been deposited in carbon cloth substrate by electrophoretic deposition process and thus making it usable as flexible field emitter. It has been seen that all the, pure and hybrid samples give good field emission characteristics and the best result comes from the a-Gs deposited on carbon cloth. The turn field in this case becomes as low as 0.52V/μm thus comparable or even better than the existing graphene based materials. So there should be a possibility of substituting some graphene based devices with this a-Gs having further advantage of its simple synthesis procedure as well as gram level higher yield. [Copyright &y& Elsevier]

Mn2+ doped-AlN red phosphors were prepared by the solid-state reaction method. X-ray diffraction, SEM-EDS, photoluminescence and cathodoluminescence were utilized to characterize the prepared phosphor. Under UV light or electron beam excitation, the AlN:Mn2+ phosphors exhibit a strong red emission centered at 600 nm, which is ascribed to the characteristic 4T1(4G)–6A1(6S) transition of Mn2+. Energy level diagrams were constructed to discuss the photoluminescence and cathodoluminescence processes of the AlN:1% Mn2+ phosphor. The oxygen-related defects in AlN have great influence on the photoluminescence and cathodoluminescence properties of the AlN:1% Mn2+ phosphor. The dependence of brightness on accelerating voltage or electric current, the decay behavior of CL intensity under the electron bombardment, and the stability of CIE chromaticity coordinates were investigated in detail. The results indicate that the AlN:Mn2+ phosphor exhibits a higher brightness, higher color purity, and lower saturation compared to the red Y2O3:Eu3+ phosphor, which gives the AlN:Mn2+ phosphor great potential as a red phosphor for full color FEDs. [ABSTRACT FROM AUTHOR]

The enhanced emission performance of a graphene/Mo hybrid gate electrode integrated into a nanocarbon field emission micro-triode electron source is presented. Highly electron transparent gate electrodes are fabricated from chemical vapor deposited bilayer graphene transferred to Mo grids with experimental and simulated data, showing that liberated electrons efficiently traverse multi-layer graphene membranes with transparencies in excess of 50-68%. The graphene hybrid gates are shown to reduce the gate driving voltage by 1.1 kV, whilst increasing the electron transmission efficiency of the gate electrode significantly. Integrated intensity maps show that the electron beam angular dispersion is dramatically improved (87.9°) coupled with a 63% reduction in beam diameter. Impressive temporal stability is noted (<1.0%) with surprising negligible long-term damage to the graphene. A 34% increase in triode perveance and an amplification factor 7.6 times that of conventional refractory metal grid gate electrode-based triodes are noted, thus demonstrating the excellent stability and suitability of graphene gates in micro-triode electron sources. [ABSTRACT FROM AUTHOR]

Carbon nanotube (CNT) field emission displays (FEDs) are currently in the product development stage and are expected to be commercialized in the near future because they offer image quality and viewing angles comparable to a cathode ray tube (CRT) while using a thinner structure, similar to a liquid crystal display (LCD), and enable more efficient power consumption during use. To address concerns regarding the environmental performance of CNT-FEDs, a screening-level, cradle-to-grave life cycle assessment (LCA) was conducted based on a functional unit of 10?000 viewing hours, the viewing lifespan of a CNT-FED. Contribution analysis suggests the impacts for material acquisition and manufacturing are greater than the combined impacts for use and end-of-life. A scenario analysis of the CNT paste composition identifies the metal components used in the paste are key contributors to the impacts of the upstream stages due to the impacts associated with metal preparation. Further improvement of the manufacturing impacts is possible by considering the use of plant-based oils, such as rapeseed oil, as alternatives to organic solvents for dispersion of CNTs. Given the differences in viewing lifespan, the impacts of the CNT-FED were compared with a LCD and a CRT display to provide more insight on how to improve the CNT-FED to make it a viable product alternative. When compared with CRT technology, CNT-FEDs show better environmental performance, whereas a comparison with LCD technology indicates the environmental impacts are roughly the same. Based on the results, the enhanced viewing capabilities of CNT-FEDs will be a more viable display option if manufacturers can increase the product's expected viewing lifespan. [ABSTRACT FROM AUTHOR]

Highly-luminescent nanophosphors have a decisive role in solid-state lighting (SSL) as well as in field emission display (FED) applications due to their potential use in fabrication of nanophosphor based FED and solid state display devices. Herein, the red emitting highly-luminescent Eu3+–Li+ co-doped magnesium aluminate (MgAl2O4) nanophosphors were synthesized by a customized sol–gel route with an average particle size of 18 nm, which can be easily scaled up in a large quantity. The resulting nanophosphor exhibits hypersensitive red emission, peaking at 615 nm upon 394 nm excitation. Furthermore, comparative photoluminescence (PL) studies have been carried out for Eu3+ doped and Eu3+ doped-Li+ co-doped magnesium aluminate (Li+ co-doped MgAl2O4:Eu3+) nanophosphors, which indicated that Li+ co-doping significantly improves luminescence intensity along with good crystallinity. Moreover, the charge compensation by addition of Li+ co-activator in MgAl2O4:Eu3+ lattice led to the two fold enhancement of PL intensity. The obtained results suggest that this nanophosphor could be an ultimate choice for next generation advanced luminescent nanomaterials for solid state lighting and portable FED devices. [ABSTRACT FROM AUTHOR]

A reddish-orange-emitting SnO2:Eu3+ phosphor for field emission displays ( FEDs) was successfully synthesized via a homogeneous precipitation route using urea as a precipitant. The influences of the dopant concentration of Eu3+ and calcination temperature on optical properties were investigated. The low-voltage field emission properties of the FED device prepared using the synthesized SnO2:Eu3+ phosphors were reported. Under the UV light, SnO2:Eu3+ phosphors display the strong orange-red emission peaked at 587, 591, and 597 nm due to the 5 D0→7 F1 magnetic dipole transition of Eu3+. The phosphor doped with 1.0 mol% Eu3+ possesses the highest photoluminescent ( PL) intensity. Under the low-voltage excitation of 300 V, the fabricated FED device exhibits the bright orange-red emission, high-voltage brightness saturation, and high color purity, which has a potential application in low-voltage full color FEDs. [ABSTRACT FROM AUTHOR]

Carbon nanotube field emission backlight (CNT-BLU) is promising to replace traditional backlighting devices in liquid crystal display (LCD) industry. This study reports a laser irradiation process to enhance field emission properties of buckypaper, a thin sheet of high-loading carbon nanotube network. The scanning laser treated the selected region of buckypaper to activate CNT emitters. The improvement of phosphorescence luminance intensity, uniformity, and the reduction of turn-on field were achieved by adjusting machining parameters of laser power, laser lens motion speed, laser resolution, laser beam size, and pattern orientation. Design of experiment and response surface methodology provided ways to rapidly search the feasible laser parameter setting for processing buckypaper field emitters and improving field emission properties within fewer experimental runs. 25−1 Fractional fracotrial design presented the initial models of five repsponses. In addition, the face-centered central composite design is applied since the 25−1 factional factorial design showed curvature significance. It assisted to give the scientifical insight of the following conclusions. High-energy laser treatment damages and burns the CNTs into carbon oxide materials; furthermore, it loses the effective CNTs. Low-energy laser treatment performs CNT activation and produced low field emission performance. In this study, we succeeded to apply statistical analysis methods to understand the physics and mechanics of laser-activated buckypaper field emission and, furthermore, improve, optimize, and demonstrate performance by material selection, process development, and characterization. [ABSTRACT FROM AUTHOR]

Sharp, uniform, stable, and environment-hard field-emitter arrays (FEAs) have been fabricated by Transfer-Mold fabrication method. These FEAs have potential for realizing stable and low operation voltage field-emission displays and field-emission lamps that are resistant to highly oxidizing atmospheres during the fabrication process. The extremely sharp and uniform Transfer-Mold FEAs, which have the average tip radius of 2.6-3.5 nm, have been developed by using the Transfer-Mold fabrication method. These tip shapes including height are extremely uniform being different from CNTs' nonuniform tip radii, height and pitch. Also, these tip radii are similar to the diameter of the singlewalled CNTs, 0.4-6 nm, or less than the diameter of the multiwalled CNTs, 5-10 nm. The low operation voltage Transfer-Mold FEAs has turn-on fields of 17.5-21.8 V/μm at the short distance between anode and emitter, less than 30 μm. However, other conventional FEAs such as Spindt-type FEAs, Gray-type FEAs and CNTs FEAs have the approximated turn-on fields of 50-600 V/μm. Therefore, those values of the turn-on voltages are lower than those of other conventional FEAs and can be applicable for vacuum nanoelectronic devices such as FEDs and FELs. The current fluctuations of FEAs without resistive layer are the lowest value ever reported, ±1.6%, compared with 5-several hundred % of the conventional FEAs. Also, the Transfer-Mold Mo FEAs having the base lengths of 36-1570 nm without resistive layer, exhibited extremely stable current fluctuations of as low as ±1.6-3.3% due to the extremely uniform geometric factors. Moreover, those of the environment-hard Transfer-Mold FEAs even under the oxygen radical or plasma treatments are as low as ±5.0-7.5%. However, for conventional FEAs with and without resistive layers, those are usually 5-100% and more than 100%, respectively. Therefore, the extremely sharp, uniform, stable, and environment-hard Transfer-Mold FEAs are useful for the stable and reliable vacuum nanodevices such as FEDs and FELs to a great extent. [ABSTRACT FROM AUTHOR]

Field emission display (FED) was fabricated with resist-assisted patterning (RAP) process grown carbon nanotube (CNT) emitters. Electron emission current uniformity was strongly improved by homogenizing process with silicon-on glass (SOG). The length of CNT emitters was homogenized with SOG coating and selective CNT etching process. Uniform CNT emitters were fabricated with the post-growth homogenizing process. We fabricated 3 inch FED display with 32 μm sub-pixel size with the CNT emitters. Electron emission current shows possible operation of the FED with 5 V/μm gate field. The electron emission characteristics and display performance were discussed. [ABSTRACT FROM AUTHOR]

Abstract: MSi2O2−δ N2+2/3δ :Eu2+ (M=Sr, Ba) phosphors were prepared through a two-step solid state reaction. XRD results reveal that the samples are nitrogen-rich phase. The photoluminescence results show that the MSi2O2−δ N2+2/3δ :Eu (M=Sr, Ba) phosphors can be excited by UV and blue light. The critical concentrations of Eu2+ are 5mol% and 4mol% for MSi2O2−δ N2+2/3δ :Eu (M=Sr, Ba), respectively. With an increase of the Eu2+-concentration, the emission color of SrSi2O2−δ N2+2/3δ :Eu can be tuned from green to yellow. Under the excitation of low voltage electron beams (1–3kV), the MSi2O2−δ N2+2/3δ :Eu (M=Sr, Ba) phosphors exhibit green and cyan emission, respectively. The emission intensity increases with the increasing of accelerating voltage and filament current. Due to the excellent stability, good CIE chromaticity and high color purity, MSi2O2−δ N2+2/3δ :Eu (M=Sr, Ba) phosphors may have potential application in the field emission displays. [Copyright &y& Elsevier]

Abstract: This study uses a low temperature thermal chemical vapor deposition with an applied external magnetic field to grow carbon nanotubes (CNTs) on Ni/Ag-printed glass substrates. A mixture of C2H2 and H2 gas was used for the growth of the CNTs. A Ni catalyst layer was deposited on the Ag-printed glass substrate by pulse electroplating. Scanning electron micrographs as well as the presence of two sharp peaks at 1320cm−1 (D band) and 1590cm−1 (G band) in the Raman spectra indicate that the graphitized structure of CNTs synthesized under a magnetic field has higher quality (i.e., a D-band to G-band intensity ratio of 0.303) than CNTs synthesized without a magnetic field. Transmission electron micrographs show a fine Ni catalyst at the tip of the tube for CNTs synthesized under a magnetic field, exhibiting a CNT “tip-growth” model. The synthesis of CNTs in the presence of a magnetic field also generates better field emission properties and better lighting morphology than without a magnetic field. [Copyright &y& Elsevier]

Abstract: In this paper, spherical Pr3+-doped CaTiO3 phosphor particles were fabricated through a two-step spray pyrolysis process, using citric acid and polyethylene glycol (PEG) as additives. X-ray diffraction (XRD), scanning electron microscopy (SEM), High-resolution transmission electron microscopy (HRTEM), thermogravimetric and differential thermal analysis (TG–DTA), X-ray photoelectron spectra (XPS), photoluminescence (PL), cathodoluminescence (CL) spectroscopy, and lifetime measurements were employed to characterize these samples. The results reveal that the as-prepared CaTiO3:Pr3+ phosphors are spherical with submicron particle size. The particles show a strong red emission corresponding to 1D2–3H4 (612nm) of Pr3+ under the ultraviolet excitation (325nm) and low voltage electron beams (1–5kV). Furthermore, the morphology, PL and CL intensities of the CaTiO3:Pr3+ phosphors can be tuned by altering the concentration of PEG, annealing temperature, and acceleration voltage. These phosphors show potential applications in the field of field emission displays (FEDs). [Copyright &y& Elsevier]

This paper presents new equations that describe ellipsoidal field emitters in both ellipsoidal and Cartesian coordinates. Expressions are found for the potential, electric field, and field enhancement at any point in space. For both ellipsoidal and spheroidal emitters, equations are given to determine field emission current density and total current. It is also shown that the field enhancement at the surface of a spheroidal emitter is purely dependent on the surface location and the emitter's height to radius aspect ratio. Furthermore, simplified equations are given to approximate the field enhancement and total current for prolate spheroidal emitters of height to radius ratios greater than 100. [ABSTRACT FROM AUTHOR]

Abstract: LaInO3: Sm3+, LaInO3: Pr3+ and LaInO3: Tb3+ phosphors were prepared through a Pechini-type sol–gel process. X-ray diffraction, field emission scanning electron microscopy, photoluminescence, and cathodoluminescence (CL) spectra were utilized to characterize the synthesized phosphors. XRD results reveal that the pure LaInO3 phase can also be obtained at 700°C. FE-SEM images indicate that the LaInO3: Sm3+, LaInO3: Pr3+ and LaInO3: Tb3+ phosphors are composed of aggregated spherical particles with sizes around 80–120nm. Under the excitation of ultraviolet light and low voltage electron beams (1–5kV), the LaInO3: Sm3+, LaInO3: Pr3+ and LaInO3: Tb3+ phosphors show the characteristic emissions of Sm3+ (4G5/2–6H5/2,7/2,9/2 transitions, yellow), Pr3+ (3P0–3H4, 3P1–3H5, 1D2–3H4 and 3P0–3F2 transitions, blue–green) and Tb3+ (5D4–7F6,5,4,3 transitions, green) respectively. The corresponding luminescence mechanisms are discussed. These phosphors have potential applications in field emission displays. [Copyright &y& Elsevier]

The tapered macrogate (TMG) structure is proposed to overcome the difficulties in carbon nanotube (CNT) based field emission display (FED) with high-voltage phosphors used in cathode ray tube screens. In order to achieve an ideal triode operation for field emission devices, the TMG was designed to have a very thick gate insulator with the inclined gate holes compared with the CNT emitters. The inclined gate holes with a narrower outlet than the bottom of the hole were shown to protect the CNT emitters from the anode field perfectly, enabling the authors to apply a high anode voltage over 10 kV needed for high-voltage FED. Also, the TMG structure had additional useful functions such as an electron-beam self-focusing and high durability against electrical damage. The authors successfully fabricated and demonstrated a 5 in. active-matrix CNT-FED panel with the TMG, showing color moving images with a low addressing voltage of about 15 V using amorphous silicon thin-film transistor as a switching device. [ABSTRACT FROM AUTHOR]