Ultraviolet-Cathodoluminescent 330 nm light source from a 2-inch wide CNT electron-beam emission under DC electric field

We report a 2-inch wide-area AlGaN-based ultraviolet (UV) – cathodoluminescence (CL) light source emission using electron beam (EB) pumped source under DC electric field from an AlGaN/GaN multi-quantum-well grown on a sapphire substrate. The EB-pumping is achieved by wide-area carbon nanotubes (CNT) based field emitters and is arranged via a metal mesh, thereby acting as a gate to pump the electron flow. We have carried out UV–CL measurements with a turn-on field emission in the anode voltage ranging between 5 kV and 9 kV at anode current up to 1 mA. The best results are obtained at the low consumption energy of 7 W (anode current 1 mA; anode voltage 7 kV). The 330 nm UV–CL emission shows an output power of ~225 mW, with an as-calculated power efficiency of ~3.6%. The CL measurements show (5–8) % defect luminescence in the visible region.     

A Monte Carlo simulation of cathodoluminescence generated in ZnS phosphor powders

Abstract

Field emission displays (FEDs) are the possible full colour flat panel displays of the future. Studies on the FEDs include research on the applicability of wide band gap ZnS phosphors used in cathode ray tubes (CRT's) in the FED environment. Surface reactions occur on the ZnS surface during prolonged electron bombardment to form a non-luminescent ZnO layer with a consequent loss in cathodoluminescence (CL) intensity. Using a Monte Carlo algorithm, the electron energy loss within the ZnS layer of varying thickness on a ZnS substrate and determine the energy loss within the ZnS as function of the ZnO thickness. Since the oxide layer is non-luminescent, the energy loss within the ZnS in proportional to the generated CL. The results obtained correlate with experimental measurements of phosphor degradation during electron bombardment in UHV.     

Effect of radiation damage on luminescence of erbium-implanted SiO2/Si studied by slow positron beam

The effect of damage on 1.54 μm luminescence for 30 keV-Er-implanted SiO₂ films has been studied by positron annihilation and cathodoluminescence. It was found that S-parameter in the films decreased after implantation, indicating the suppression of positronium formation. The luminescence appeared with the recovery of the S-parameter after 600°C annealing. The intensity reached a maximum at 900°C annealing whereas the S-parameter did not change significantly. It seems that most damages recover at 600°C and thereafter Er ions transform to an optically active state at 900°C.     

Surface chemical changes of CaTiO3:Pr upon electron beam irradiation

Surface chemical changes of CaTiO₃:Pr³⁺ phosphor material and their effect on the red emission intensity of the ¹D₂→³H₄ transition of Pr³⁺, upon electron beam irradiation are presented. Red emission at 613 nm was obtained upon probing the surface with a 2 keV electron beam. The surface chemical changes and Pr³⁺ red emission were monitored using an Auger Electron Spectroscopy (AES) and Cathodoluminescence (CL) spectrometer, respectively. The CL intensity decreased with a decrease in O on the surface at 1×10⁻⁸ Torr base pressure and decreased with an increase in O on the surface at 1×10⁻⁶ Torr O₂. The X-ray Photoelectron Spectroscopy (XPS) revealed that CL degradation at 1×10⁻⁶ Torr O₂ is due to the formation of CaO and CaO_x as well as TiO₂/Ti₂O₃ non-luminescent species on the surface.     

Solution synthesis and optimization of ZnO nanowindmills

In this work, novel windmill-like ZnO structures were fabricated through a solution route at low reaction temperature. The as-synthesized ZnO nanowindmill has a central trunk of nanorod and six symmetrical nanorods grown epitaxially on the surface of the ZnO trunk along [0 0 0 1] direction. Each nanorod forming the windmill with a smooth top is about 6 μm in length and about 700 nm in diameter. Several control experiments were conducted to study the formation of the nanowindmills of ZnO in detail. Cathodoluminescence (CL) property of the as-obtained product was investigated, which shows there are three emission peaks centered at 384, 616 and 753 nm in CL spectrum.     

Radiation induced defects in SiO 2

The main luminescent centers in SiO 2 films are the red luminescence R (650 v nm; 1.85 v eV) of the non-bridging oxygen hole center (NBOHC) and the twofold-coordinated (divalent) silicon with a blue B (460 v nm; 2.7 v eV) and a UV band (285 v nm; 4.4 v eV). Especially the latter ones are produced under irradiation, but from existing precursors assumed as silicon related oxygen deficient centers (SiODC). Therefore, in order to prove these models we compare a direct oxygen implantation with a direct silicon implantation into SiO 2 layers. The main result is: implanting oxygen increases the red band R but does not affect the blue band B. Silicon surplus increases the amplitude of the blue (B) luminescence, but reduces the amplitude of the red (R) one. Studying the cathodoluminescence dose dependence of these blue and red bands we have established defect transformation kinetics in SiO 2 including six main defects and precursors as well as the mobile oxygen as the main transmitter between precursors and the radiation induced defects. The kinetics is described by eight rate equations which predict the dose dependence of the red (R) and blue (B) luminescence intensities and their temperature dependences very well.     

Er~(3+)、Pr~(3+)共掺杂AlN薄膜的发光特性和能量传递机理

采用离子注入的方法在氮化铝(AlN)薄膜中实现Er~(3+)和Pr~(3+)的共掺杂,以阴极荧光光谱仪为主要表征手段,对其发光特性进行研究.对于Er~(3+)单掺杂的AlN薄膜,在410nm和480nm可以观察到Er~(3+)较强的发光峰,在537nm、560nm、771nm和819nm可观察到Er~(3+)的较弱的发光峰;对于Pr~(3+)单掺杂的AlN薄膜,Pr~(3+)的最强发光峰位于528nm,在657nm和675nm可以观察到Pr~(3+)的较弱的发光峰;而对于Er~(3+)和Pr~(3+)共掺杂的AlN薄膜,在494nm观察到与Pr~(3+)相关的新跃迁峰.根据实验现象,对AlN薄膜中Er~(3+)和Pr~(3+)之间的能量传递机制进行了深入分析,结果表明Er~(3+)的4F7/2→4I15/2能级跃迁与Pr~(3+)的3P0→3H4能级跃迁之间发生了共振能量传递,从而使Pr~(3+)产生了494nm新的发光峰.     

Effects of SnO2 surface coating on the degradation of ZnS thin film phosphor

Pulsed laser deposited ZnS bare and SnO₂ coated ultra thin films were subjected to prolonged electron beam bombardment with 2 keV energy and a steady 44 mA/cm² current density, in 1 × 10⁻⁶ Torr O₂ pressure backfilled from a base pressure of 3 × 10⁻⁹ Torr at room temperature. Auger electron spectroscopy (AES) was used to monitor changes of the surface chemical composition of both the bare and coated phosphor films during electron bombardment. Degradation was manifested by the decrease of sulphur and accumulation of oxygen on the surface of the bare phosphor. However, with the SnO₂ coating this phenomenon was delayed until the protective SnO₂ was depleted on the surface through dissociation and reduction.     

Formation of multiple nanoscale twin boundaries that emit intense light in indirect-gap AlGaAs epilayers

Parallel twin boundaries arranged at similar intervals of nanometer length, that emitted an intense monochromatic light polarized parallel to the boundaries, were self-organized in an indirect-gap AlGaAs epilayer; the epilayer was grown on a rough As-deficient surface of an AlGaAs(0 0 1) substrate with any lattice constant, by conventional metal-organic chemical-vapor deposition. Most boundaries were of -type on B, and they extended from the interface between the epilayer and the substrate. There existed no compositional fluctuation around the boundaries. The formation mechanism was discussed.     

Transient excitation behavior of a donor–acceptor–acceptor Auger molecule in a semiconductor host

Under the particular situation of highly doped and almost compensated semiconductors, a new kind of bound state happens at high external excitation levels, which is formed of a close donor–acceptor molecule and a neighboring second donor or acceptor. The de-excitation behavior of such a bound state resembles characteristics known from Auger transitions and for this reason it is called an Auger molecule. The existence region of Auger molecules is determined in silicon-doped Ga_{1− x} Al _x As by electron-beam excited luminescence measurements at low temperature. The main peak position and the luminescence intensity of the donor–acceptor recombination channel turn out to be affected in a characteristic manner by the existence of Auger molecules at high excitation levels. An analysis of corresponding rate coefficients for the reproduction of experimental results is also presented. Received: 14 September 1999 / Accepted: 3 February 2000 / Published online: 21 June 2000