Showing papers on "Cathodoluminescence published in 2008"
Journal Article•
384 citations
TL;DR: In this paper, a combination of sol−gel process and electrospinning was used to combine one-dimensional YVO4:Ln and quasi-one-dimensional VO4-Ln nanofibers.
Abstract: One-dimensional YVO4:Ln and Y(V, P)O4:Ln nanofibers and quasi-one-dimensional YVO4:Ln microbelts (Ln = Eu3+, Sm3+, Dy3+) have been prepared by a combination method of sol−gel process and electrospinning. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric and differential thermal analysis (TG−DTA), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), photoluminescence (PL), low-voltage cathodoluminescence (CL), and time-resolved emission spectra as well as kinetic decays were used to characterize the resulting samples. Due to an efficient energy transfer from vanadate groups to dopants, YVO4:Ln phosphors showed their strong characteristic emission under ultraviolet excitation (280 nm) and low-voltage electron beam excitation (1−3 kV). The energy transfer process was further studied by the time-resolved emission spectra as well as kinetic decay curves of Eu3+ upon excitation into the VO4...
225 citations
TL;DR: In this article, a low-temperature controllable chemical bath deposition method was demonstrated to prepare one-dimensional ZnO nanorods and two-dimensional nanoplates, and their surface-related emissions were studied by temperature-dependent cathodoluminescence spectra.
Abstract: In this paper, a low-temperature controllable chemical bath deposition method was demonstrated to prepare one-dimensional ZnO nanorods and two-dimensional nanoplates, and their surface-related emissions were studied by temperature-dependent cathodoluminescence spectra. By changing the precursor concentration, the ZnO morphology evolves from nanorods to nanoplates. ZnO nanorods grow fast along the c-axis direction due to the high surface energy of the polar (0001) plane when the concentration of OH- ions is low in the precursor solution. When the OH- concentration is increased, more OH- ions preferably adsorb on the (0001) plane of ZnO, and the growth of the ZnO nanocrystallite along the c axis is partially suppressed. However, they can still grow sideways along directions. Therefore, with the OH- concentration increased, the average aspect ratio (high/width) of ZnO nanorods is decreased. Finally, two-dimensional ZnO nanoplates are formed. Low-temperature cathodoluminescence spectra of such ZnO na...
221 citations
TL;DR: This study represents a new methodology for fabricating hollow nanostructures with defined crystallinity and unique optical properties for optoelectronic applications, particularly in the ultraviolet region, such as blue lasing and light emitting diodes.
Abstract: Novel BN hollow nanoribbons (BNHNRs) were fabricated by a simple ZnS nanoribbon templating method. Such BNHNRs have a distinct structure and show unique optical properties, as demonstrated from Raman, Fourier transform infrared spectroscopy, UV−vis spectroscopy, and cathodoluminescence spectroscopy, when compared with other forms of BN nanostructures. With high crystallinity, the BNHNRs exhibit an extraordinary ultraviolet CL emission at 5.33 eV. Such a property is highly advantageous for optoelectronic applications, particularly in the ultraviolet region, such as blue lasing and light emitting diodes. This templating method has also been extended to synthesize other hollow nanostructures such as boron carbonitride. This study represents a new methodology for fabricating hollow nanostructures with defined crystallinity and unique optical properties.
197 citations
TL;DR: High-spatial resolution cathodoluminescence studies on individual heterostructure studies for the first time reveal a new ultraviolet emission peak, which is not observed in separate ZnS or ZnO nanostructures.
Abstract: We report on a controlled synthesis of two novel semiconducting heterostructures: heterocrystalline-ZnS/single-crystalline-ZnO biaxial nanobelts and side-to-side single-crystalline ZnS/ZnO biaxial nanobelts via a simple one-step thermal evaporation method. In the first heterostructure, a ZnS domain is composed of the heterocrystalline superlattice (3C-ZnS) N /(2H-ZnS) M [111]-[0001] with the atomically smooth interface between wurtzite and zinc blende ZnS fragments. High-spatial resolution cathodoluminescence studies on individual heterostructures for the first time reveal a new ultraviolet emission peak ( approximately 355 nm), which is not observed in separate ZnS or ZnO nanostructures. The present hererostructures are expected to become valuable not only with respect to fundamental research but also for a design of new broad-range ultraviolet nanoscale lasers and sensors.
188 citations
TL;DR: In this paper, phase-pure epitaxial BiFeO3 thin films grown on SrTiO3(001) substrates by ultrahigh vacuum sputtering reveal defect transitions at 2.20 and 2.45eV, of which the latter can be attributed to defect states due to oxygen vacancies.
Abstract: UV-visible absorption and cathodoluminescence spectra of phase-pure epitaxial BiFeO3 thin films grown on SrTiO3(001) substrates by ultrahigh vacuum sputtering reveal a bandgap of 2.69–2.73eV for highly strained ∼70nm thick BiFeO3 films. This bandgap value agrees with theoretical calculations and recent experimental results of epitaxial BiFeO3 films, demonstrating only minimal bandgap change with lattice distortion. Both absorption and cathodoluminescence spectra show defect transitions at 2.20 and 2.45eV, of which the latter can be attributed to defect states due to oxygen vacancies.
172 citations
Journal Article•
TL;DR: In this article, a controlled synthesis of two novel semiconducting heterostructures: heterocrystalline ZnS/ZnO biaxial nanobelts via a simple one-step thermal evaporation method is reported.
Abstract: We report on a controlled synthesis of two novel semiconducting heterostructures: heterocrystalline-ZnS/single-crystalline-ZnO biaxial nanobelts and side-to-side single-crystalline ZnS/ZnO biaxial nanobelts via a simple one-step thermal evaporation method. In the first heterostructure, a ZnS domain is composed of the heterocrystalline superlattice (3C-ZnS) N /(2H-ZnS) M [111]-[0001] with the atomically smooth interface between wurtzite and zinc blende ZnS fragments. High-spatial resolution cathodoluminescence studies on individual heterostructures for the first time reveal a new ultraviolet emission peak ( approximately 355 nm), which is not observed in separate ZnS or ZnO nanostructures. The present hererostructures are expected to become valuable not only with respect to fundamental research but also for a design of new broad-range ultraviolet nanoscale lasers and sensors.
162 citations
TL;DR: In this article, surface plasmon polaritons are excited on the gold surface by a nanoscale focused electron beam and coupled into free space radiation by gratings fabricated into the surface.
Abstract: We use cathodoluminescence imaging spectroscopy to excite surface plasmon polaritons and measure their decay length on single crystal and polycrystalline gold surfaces. The surface plasmon polaritons are excited on the gold surface by a nanoscale focused electron beam and are coupled into free space radiation by gratings fabricated into the surface. By scanning the electron beam on a line perpendicular to the gratings, the propagation length is determined. Data for single-crystal gold are in agreement with calculations based on dielectric constants. For polycrystalline films, grain boundary scattering is identified as additional loss mechanism, with a scattering coefficient SG=0.2%.
127 citations
TL;DR: The as-obtained phosphor samples present sphere-like agglomerates composed of nanosheets with highly crystallinity in spite of the moderate reaction temperature of 200 degrees C, making the materials have potential applications in fluorescent lamps for advertizing signs and other color display fields.
Abstract: Tb(1−x)BO3:xEu3+ (x = 0−1) microsphere phosphors have been successfully prepared by a simple hydrothermal process directly without further sintering treatment. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), photoluminescence (PL), low-voltage cathodoluminescence (CL), and time-resolved emission spectra as well as lifetimes were used to characterize the samples. The as-obtained phosphor samples present sphere-like agglomerates composed of nanosheets with highly crystallinity in spite of the moderate reaction temperature of 200 °C. Under ultraviolet excitation into the 4f8 → 4f75d transition of Tb3+ at 245 nm (or 284 nm) and low-voltage electron beamsʼ excitation, TbBO3 samples show the characteristic emission of Tb3+ corresponding to 5D4 → 7F6, 5, 4, 3 transitions; whereas ...
120 citations
TL;DR: In this paper, the dependence of the emission spectra on particle morphology and electron energy is explored by means of full electromagnetic calculations based on the boundary element method (BEM) for light-emission image maps obtained by using a light detection system that is incorporated into a transmission electron microscope (TEM), operated in scanning mode.
Abstract: We analyze cathodoluminescence (CL) emission from silver nanorod antennas induced by energetic electron beams. The dependence of the emission spectra on particle morphology and electron energy is explored by means of full electromagnetic calculations based on the boundary element method (BEM). We present light-emission image maps obtained by using a light detection system that is incorporated into a transmission electron microscope (TEM), operated in scanning mode. The intensity of each pixel in these maps corresponds to the photon counting rate when the electron beam is focused at that position of the sample. The maps exhibit strong dependence on the polarization of the emitted light and reveal standing-wave patterns of surface plasmons sustained by the nanorods, leading to characteristic spatial variations that correspond to the actual plasmon-mode symmetries. We thus demonstrate direct mapping of plasmon-mode symmetries by observing the variation of the CL intensity as the electron beam scans the sample. Good agreement between experimental and theoretical results is obtained, including the spatial modulation of the intensity along the direction perpendicular to the rods. In particular, plasmon modes of different azimuthal nature are resolved via their characteristic spatial dependence in our polarization-sensitive light detection system.
114 citations
TL;DR: It is proposed that the self-assembly evolution occurs by homocentric layer-by-layer growth and the tunable luminescent properties have potential applications in fluorescent lamps and field emission displays.
Abstract: Rhombohedral-calcite and hexagonal-vaterite types of LuBO:Eu3+ microparticles with various complex self-assembled 3D architectures have been prepared selectively by an efficient surfactant- and template-free hydrothermal process for the first time. X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectrometry, transmission electron microscopy, high-resolution transmission electron microscopy, selected area electron diffraction, photoluminescence, and cathodoluminescence spectra as well as kinetic decays were used to characterize the samples.
TL;DR: In this paper, focused-ion-beam milling of a single-crystal Au surface was used to fabricate a 590-nm-long linear ridge that acts as a surface plasmon nanoresonator.
Abstract: We use focused-ion-beam milling of a single-crystal Au surface to fabricate a 590-nm-long linear ridge that acts as a surface plasmon nanoresonator. Cathodoluminescence imaging spectroscopy is then used to excite and image surface plasmons on the ridge. Principal component analysis reveals distinct plasmonic modes, which proves confinement of surface plasmon oscillations to the ridge. Boundary-element-method calculations confirm that a linear ridge is able to support highly localized surface plasmon modes (mode diameter <100 nm). The results demonstrate that focused-ion-beam milling can be used in rapid prototyping of nanoscale single-crystal plasmonic components.
TL;DR: A facile and effective route toward the synthesis of ZnS multi-angular branched nanostructures with needle-shaped tips has been developed in this article, where an average width of the structurally and chemically uniform, single-crystalline, defect-free tips was found to be less than 10 nm.
Abstract: A facile and effective route toward the synthesis of ZnS multiangular branched nanostructures with needle-shaped tips has been developed. An average width of the structurally and chemically uniform, single-crystalline, defect-free tips was found to be less than 10 nm. Cathodoluminescence from individual ZnS multiangular branched nanostructures was investigated at high spatial resolution on the nanometer scale. The size-dependent optical spectra exhibit sharp ultraviolet band gap emission and broad visible emission. Field-emission measurements show a relatively low turn-on field of ∼3.77 V/μm at a current density of 10 μA/cm2 and the highest field enhancement factor β of ∼2182 ever reported for 1D ZnS nanostructures. This was attributed to the specific sharp tips and high aspect ratios. These unique nanostructures are envisaged to be highly promising for novel optoelectronic and field-emitting devices.
TL;DR: In this paper, focused-ion-beam milling of a single-crystal Au surface was used to fabricate a 590-nm-long linear ridge that acts as a surface plasmon nanoresonator.
Abstract: We use focused-ion-beam milling of a single-crystal Au surface to fabricate a 590-nm-long linear ridge that acts as a surface plasmon nanoresonator. Cathodoluminescence imaging spectroscopy is then used to excite and image surface plasmons on the ridge. Principal component analysis reveals distinct plasmonic modes, which proves confinement of surface-plasmon oscillations to the ridge. Boundary-element-method calculations confirm that a linear ridge is able to support highly-localized surface-plasmon modes (mode diameter < 100 nm). The results demonstrate that focused-ion-beam milling can be used in rapid prototyping of nanoscale single-crystal plasmonic components.
TL;DR: In this article, spherical particles of rare-earth doped LaF3 are synthesized through refluxing in glycerol/water media, and they are shown to be promising as highly efficient low-voltage cathodoluminescent phosphors.
Abstract: Spherical particles of rare-earth doped LaF3 are synthesized through refluxing in glycerol/water media. The low-voltage cathodoluminescence of LaF3:Eu due to D50→F71 and D50→F72 transitions was found to be sensitive to the site that Eu3+ ions occupied. The luminous efficiency of LaF3:Ce3+, Tb3+ with green emission is improved from 1.53 to 2.02 lm/W compared with LaF3:Tb3+, due to the energy transfer processes from Ce3+ to Tb3+ ions. Our results suggest that the obtained spherical particles of rare-earth doped LaF3 are promising as highly efficient low-voltage cathodoluminescent phosphors, which have received considerably less attention.
TL;DR: A blue-purple Luminescence at room temperature was observed in the cathodoluminescence spectrum of the synthesized single micro- and nanocube of carbon, which exhibited that this unique carbon nanomaterial is a new semiconductor with blue luminescence.
Abstract: Micro- and nanocubes of carbon have been synthesized by laser ablation in liquid. The morphology and structure analyses indicated that these micro- and nanocubes are single crystals with a body-centered cubic structure with a lattice constant of 5.46 A, which is so-called C8-like structure, and they have a slightly truncated shape bounded mainly by {200} facets. A blue-purple luminescence at room temperature was observed in the cathodoluminescence spectrum of the synthesized single micro- and nanocube of carbon, which exhibited that this unique carbon nanomaterial is a new semiconductor with blue luminescence. The physical and chemical mechanisms of the synthesis of carbon micro- and nanocubes were pursued upon laser ablation in liquid.
TL;DR: In this article, an ensemble of multilayer boron nitride nanotubes with diameters from 30 nm to 110 nm is studied and the results are compared with the related bulk material, hexagonal BN.
Abstract: Individual multiwall boron nitride nanotubes with diameters from 30 nm to 110 nm are shown to be efficient UV emitters by cathodoluminescence. Their luminescence does not evolve much in this diameter range, with dominant UV recombinations at about 230 nm. As a result, single nanotube properties can be obtained from experiments performed on ensembles of nanotubes. Such ensembles are studied by photoluminescence as a function of temperature 5 K‐300 K and by photoluminescence excitation experiments at 9 K. The results are discussed and compared with the related bulk material, hexagonal boron nitride. The strong luminescence recorded around 230 nm is attributed to excitonic effects, more precisely to excitons bound to the structural defects: dislocations, facets, which are observed along the walls.
TL;DR: In this article, spectral cathodoluminescence (CL) mapping and defect selective etching of GaN single crystal were studied by means of spectral graph analysis and defect selection.
Abstract: Dislocations in GaN single crystal were studied by means of spectral cathodoluminescence (CL) mapping and defect selective etching. We show that the c-type screw dislocations are not recombination active. The recombination strength of the a- and (a+c)-type dislocations is influenced by impurity gettering. While fresh dislocations exhibit a CL contrast of 0.01–0.05 in accordance with intrinsic dislocation states, grown in dislocations show a contrast of 0.25. From the analysis of spectral CL maps, we find that impurities such as oxygen and silicon are depleted in the surrounding of the dislocations. We explain the increased contrast by a reduced screening of the electrical field of the dislocation.
Journal Article•
TL;DR: In this paper, an ensemble of multilayer boron nitride nanotubes with diameters from 30 nm to 110 nm is studied and the results are compared with the related bulk material, hexagonal BN.
Abstract: Individual multiwall boron nitride nanotubes with diameters from 30 nm to 110 nm are shown to be efficient UV emitters by cathodoluminescence. Their luminescence does not evolve much in this diameter range, with dominant UV recombinations at about 230 nm. As a result, single nanotube properties can be obtained from experiments performed on ensembles of nanotubes. Such ensembles are studied by photoluminescence as a function of temperature 5 K‐300 K and by photoluminescence excitation experiments at 9 K. The results are discussed and compared with the related bulk material, hexagonal boron nitride. The strong luminescence recorded around 230 nm is attributed to excitonic effects, more precisely to excitons bound to the structural defects: dislocations, facets, which are observed along the walls.
TL;DR: In this article, the gap energy temperature dependence of large bulk AlN single crystals was investigated through the optical properties of high-quality large bulk single crystals grown by a sublimation-recondensation technique.
TL;DR: In this paper, the facile electrical-field-assisted laser ablation in liquid (EFLAL) was developed to controllably fabricate the mass production of GeO2 micro- and nanoparticles with various shapes.
Abstract: We have developed a unique technique, the facile electrical-field-assisted laser ablation in liquid (EFLAL) without any catalyst or organic additives, to controllably fabricate the mass production of GeO2 micro- and nanoparticles with various shapes. By adjusting the applied electrical field, we synthesized the high-index facets GeO2 micro- and nanocubes and spindles, and propose the growth mechanisms of nanostructures upon EFLAL. On the basis of the cathodoluminescence measurements of dispersive GeO2 nanoparticles, we observed a shape-dependent red-shift of emission wavelength when the shape of GeO2 nanostructures transforms into spindle from cube, and then we established the physical model to address the anomalous red-shift of emission wavelength. Accordingly, we expecte EFLAL to be a general route to synthesize the micro- and nanostructures with metastable structures or metastable shapes.
TL;DR: In this article, a comprehensive model accounts for the polarity-dependent transport properties and their correlations with carrier concentration profiles, showing that defect emissions, traps, and interface chemistry correlate with strong polarity dependence that correlates with defect emissions.
Abstract: Depth-resolved cathodoluminescence spectroscopy, current-voltage, capacitance-voltage, and deep level transient spectroscopy of ZnO (0001) Zn- and (0001¯) O-polar surfaces and metal interfaces show systematically higher Zn-face near band edge emission and lower near-surface defect emission. Even with remote plasma decreases of the 2.5 eV near-surface defect emission, (0001)-Zn face emission quality still exceeds that of (0001¯)-O face. Ultrahigh vacuum-deposited Au and Pd diodes on as-received and O2/He plasma-cleaned surfaces display a strong polarity dependence that correlates with defect emissions, traps, and interface chemistry. A comprehensive model accounts for the polarity-dependent transport properties and their correlations with carrier concentration profiles.
TL;DR: In this article, a flow-rate modulation epitaxy (FME) was used to reduce parasitic reactions and lower the optimal growth temperature of hexagonal boron nitride (h-BN).
TL;DR: In this paper, a correlation between the structural and optical properties of GaN thin films grown in the [112¯0] direction has been established using transmission electron microscopy and cathodoluminescence spectroscopy.
Abstract: A correlation between the structural and optical properties of GaN thin films grown in the [112¯0] direction has been established using transmission electron microscopy and cathodoluminescence spectroscopy. The GaN films were grown on an r-plane sapphire substrate, and epitaxial lateral overgrowth was achieved using SiO2 masks. A comparison between the properties of GaN directly grown on sapphire and GaN laterally grown over the SiO2 mask is presented. The densities and dimensions of the stacking faults vary significantly with a high density of short faults in the window region and a much lower density of longer faults in the wing region. The low-temperature luminescence spectra consist of peaks at 3.465 and 3.41eV, corresponding to emission from donor-bound excitons and basal-plane stacking faults, respectively. A correlation between the structural defects and the light emission characteristics is presented.
TL;DR: In this article, the role of pH on the growth mechanisms leading to rod and platelet formation is discussed, and it is observed that thermal treatment of ZnO grown in neutral sol affects the deep-level luminescence, reducing the yellow emission but retaining the green luminecence.
TL;DR: In this paper, the solutions of surface modes in cylindrical metallic wires and cavities are obtained within a nonlocal dielectric formalism, and energy-loss spectra due to surface-plasmon excitation are calculated with use of the nonlocal formalism both for electron trajectories near a metallic nanowire and a metallic nocavity.
Abstract: The solutions of surface modes in cylindrical metallic wires and cavities are obtained within a nonlocal dielectric formalism. We compare the results with those obtained from standard local approaches. The specular reflection model is applied to describe the nonlocal potentials in the vicinity of the wires and cavities. The external probe exciting the surface plasmons are fast electron beams traveling parallel to the wires and cavities, as those commonly used in electron microscopy and cathodoluminescence. Energy-loss spectra due to surface-plasmon excitation are calculated with use of the nonlocal formalism both for electron trajectories near a metallic nanowire and a metallic nanocavity. When nonlocal effects are considered, the intensity of the plasmon excitation is reduced, and a blueshift of the energy is observed. This effect is more pronounced for very thin wires and cavities where the cylindrical interfaces are strongly interacting. The blueshifts reported here are important for the accurate design of the plasmon response in one-dimensional metallic nanostructures.
TL;DR: One-dimensional Mn2+-doped Zn2SiO4 microbelts and microfibers were prepared by a simple and cost-effective electrospinning process as mentioned in this paper.
Abstract: One-dimensional Mn2+-doped Zn2SiO4 microbelts and microfibers were prepared by a simple and cost-effective electrospinning process. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric and differential thermal analysis (TG-DTA), scanning electron microscopy (SEM), energy-dispersive X-ray spectrum (EDS), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), photoluminescence (PL), and cathodoluminescence (CL) spectra as well as kinetic decays were used to characterize the samples. The XRD and DTA results show that the Zn2SiO4 phase begins to crystallize at 800 °C and crystallizes completely around 1000 °C. SEM results indicate that the as-prepared microbelts/fibers are smooth, whose diameters decrease with increasing the annealing temperature. The average diameter of the Zn2SiO4:Mn2+ microfibers annealed at 1000 °C is 0.32 μm, and their lengths reach up to several millimeters. The average width and thickness of the Zn2SiO4:M...
TL;DR: In this article, the authors measured the Raman and cathodoluminescence (CL) spectra of ZnO nanoparticles with different crystallite sizes and found that the frequency of the E2 phonon in these nanoparticles, which is initially high, decreases with the crystallite size.
Abstract: We have measured the Raman and cathodoluminescence (CL) spectra of ZnO nanoparticles with different crystallite sizes. The Raman spectra show that the frequency of the E2 (high) phonon in these nanoparticles, which is initially high, decreases with the crystallite size, while its linewidth increases. This result is explained by the size effect. The CL spectra show that the relative intensity ratio of the CL peak at around 500–600nm to the band-edge CL peak at approximately 360nm drastically increases as the crystallite size decreases. We use the surface recombination model to explain this result. According to this model, the relative intensity ratio increases because of an increase in the concentration of deep levels on the surface of the crystallites and/or an increase in the free-carrier concentration.
TL;DR: In this article, the possibility of white light emitting devices using carbon nitride (CNx) thin films has been studied, and it was concluded that the red peak originates from the level relating to H atom and blue peak from C-N bonds.
Abstract: The possibility for white light emitting devices using carbon nitride (CNx) thin films has been studied. Microwave electron cyclotron resonance (ECR)–plasma chemical vapor deposition (CVD) and RF-sputtering apparatuses have been used for the formation of CNx thin films. In both cases, CH4 was used as the source or sub-source of carbon in order to investigate the effect of hydrogenated carbon nitride for luminescence. The cathodoluminescence (CL) measurement of the film grown by ECR–plasma CVD method showed three peaks of red, green, and blue (R/G/B). The photoluminescence (PL) measurement of the film grown by RF-sputtering also showed the red peak, which could not be observed in the film without hydrogen. Together with the X-ray photoelectron spectroscopy (XPS) analysis data, we concluded that the red peak originates from the level relating to H atom and blue peak from C–N bonds.
TL;DR: In this paper, the growth mechanism, cathodoluminescence and field emission of dual phase ZnS tetrapod tree-like heterostructures are reported, which consist of two phases: zinc blende for the trunk and hexagonal wurtzite for the branch.
Abstract: We report the growth mechanism, cathodoluminescence and field emission of dual phase ZnS tetrapod tree-like heterostructures. This novel heterostructures consist of two phases: zinc blende for the trunk and hexagonal wurtzite for the branch. Direct evidence is presented for the polarity induced growth of tetrapod ZnS trees through high-resolution electron microscopy study, demonstrating that Zn-terminated ZnS (111)/(0001) polar surface is chemically active and S-terminated ((1) over bar(1) over bar(1) over bar)/(000 (1) over bar) polar surface is inert in the growth of tetrapod ZnS trees. Two strong UV emissions centered at 3.68 and 3.83 eV have been observed at room temperature, which are attributed to the bandgap emissions from the zinc blende trunk and hexagonal wurtzite branch, indicating that such structures can be used as unique electromechanical and optoelectronic components in potential light sources, laser and light emitting display devices. In addition, the low turn-on field (2.66 V mu m(-1)), high field-enhancement factor (over 2600), large current density (over 30 mAcm(-2) at a macroscopic field of 4.33 V mu m(-1)) and small fluctuation (similar to 1%) further indicate the availability of ZnS tetrapod tree-like heterostructures for field emission panel display. This excellent field-emission property is attributed to the specific crystallographic feature with high crystallinity and cone-shape patterned branch with nanometer-sized tips. Such a structure may optimize the FE properties and make a promising field emitter.