Zhinong Yu

Influence of Ag thickness on structural, optical, and electrical properties of ZnS/Ag/ZnS multilayers prepared by ion beam assisted deposition

The structural, optical, and electrical characteristics of zinc sulfide (ZnS)/Ag/ZnS (ZAZ) multilayer films prepared by ion beam assisted deposition on k9 glass have been investigated as a function of Ag layer thickness. The characteristics of ZAZ multilayer are significantly improved up insertion of optimal Ag thickness between ZnS layers. The results show that due to bombardment of Ar ion beam, distinct Ag islands evolve into continuous Ag films at a thin Ag thickness of about 4 nm. The thinner Ag film as a thickness of 2 nm leads to high sheet resistance and low transmittance for the interface scattering induced by the Ag islands or noncontinuous films; and when the Ag thickness is over 4 nm, the ZAZ multilayer exhibits a remarkably reduced sheet resistance between 7–80 Ω/sq for the increase in carrier concentration and mobility of Ag layer, and a high transmittance over 90% for the interference phenomena of multilayers and low absorption and surface scattering of Ag layer. The ZAZ multilayer with 14 n...

The electrolytic polishing study of the stainless steel foil (SUS 304)

Flexible flat panel display (FPD) is considered to be one of the most optimal and flourishing display technologies in the 21st century, and the processing and exploitation of flexible substrate is one of the key techniques of flexible display. Until now there have been three choices of flexible substrate materials: (1) ultra-thin glass; (2) polymer materials; (3) metal foils. The flexible substrates of electroluminescence display must endure high-temperature annealing from 400°C to 700°C for doping activation, and have good flexibility and can obstruct oxygen and water penetration. Based on above considerations, to adopt the stainless steel foil for the FPD is the most suitable. In this paper, the electrolytic polishing process of stainless steel foil is investigated, and the results of the experiment show that the polishing time, current density, distance of cathode and anode panel, and other technical parameters affect the electrolytic polishing process, and then induce the best technical parameters. The surface roughness of stainless steel sheet decreases from 0.12μm to 0.044μm, but the dongas appear after the steel surface being polished. The dongas patterns are investigated, and this provides a more scientific basis for the experiments in the future.

Research on Blue Emitting BaAl2S4: Eu Phosphor Layers of TFEL

Europium-doped barium thioaluminate based on BaAl2S4: Eu is currently the most efficient blue phosphor for inorganic thin film electroluminescence. Many researchers and experts have been investigating on this material and have also got great achievements. The phosphors exhibit EL luminescence up to 900cd/m2, peak efficiency over 1 lm/W, and long life time of 30 thousand hours, which is sufficient to TV display application. In this work we will review the experimental research process of the fabrication on the BaAl2S4:Eu phosphor layers, introduce the four main methods of fabricating the blue emitting phosphors: two targets pulse electron beam evaporation; four targets pulse electron beam evaporation; two targets sputter deposition and one target sputter deposition. Finally we will also summarize the principal conclusions drawn from those experiments mentioned above, which will be beneficial to our research in the future.

Recovery behaviors in n-channel LTPS-TFTs under DC stress

Abstract In this paper, the degradation and recovery behaviors of polycrystalline silicon (poly-Si) thin film transistor (TFT) under direct current (dc) stress were investigated. Under positive or negative gate stress with a drain bias stress, the similar degradation and recovery behaviors were observed. The similar recovery is a limited one compared to the degradation before removing the bias stress. It is determined that hot-carrier effect is the key degradation mechanism under the positive or negative gate stress condition. The devices without drain bias stress appear no recovery behavior after removing the stress, which implies that the hot-carrier degradation is mainly because of the lateral electrical field rather than the vertical electrical field. In contrast to the degradation caused by hot-carrier effect, the degradation caused by the vertical gate electrical field cannot be recovered after removing the stress.

Research and analysis on the thin films sputtered by the Ba-Al-S:Eu target fabricated by powder sintering

Europium-doped barium thioaluminate (BaAl2S4:Eu) is currently the most efficient blue phosphor for inorganic thin film electroluminescent (iEL) device. To produce the full-color EL device, several kinds of blue-emitting layer were attempted and tested. As a key point of blue-emitting layer fabrication, single target sputtering deposition is an effective method. In this work, new structural target is introduced and the fabricated process is expatiated. The PL spectra of as fabricated targets show that both of two, 3mol% and 5mol% europium-doped, have blue emitting property. According to the PL spectra excited by 290nm, 300nm and 320nm ultraviolet, emission peaks located in the region near 470nm. So the as-fabricated targets can be used in single target sputtering deposition on thin film of BaAl2S4:Eu. XRD pattern indicates that there are 4 different phases, barium tetraaluminum sulfide (BaAl4S7), barium sulfide (BaS), europium sulfide (EuS) and barium aluminum oxide (BaAl2O4), in target 1. Besides these four compounds, other two phases, aluminum sulfide (Al2S3) and barium thioaluminate (BaAl2S4), are detected in target 2. Considering the analysis results, especially the hydrolyzation of Al2S3, target 1 is more suitable for sputtering deposition of BaAl2S4:Eu thin film. XPS and X-ray Fluorescence patterns describe the precise molar ratio of each element. In target 1 the relative atom concentration of barium, aluminum, sulfur and oxygen can be calculated from the pattern and molar ratio is about 9:33:41:17. Molar ratio of barium and europium is about 1:0.03. In short, the barium thioaluminate doped by europium sputtering target 1 is better to be applied in the fabrication of blue-emitting layer in inorganic electro-luminescent devices.

BaAl2S4:Eu thin films sputtered by complex target with spark plasma sintering BaS:Eu pellets

Europium doping barium thioaluminates thin films are sputtered by Al complex target embedded with BaS:Eu pellets sintered by spark plasma sintering (SPS). Thin films are deposited by RF-sputtering with complex target. BaAl2S4 is found in each thin film sample while BaAl4S7 appears in the samples only if the amount of BaS:Eu pellets is more than 3. Oxidizing products are BaAl2O4, BaSO4 and Al2O3. The amounts of barium thioaluminates including BaAl2S4 and BaAl4S7 will increase while the one of Al2O3 and BaS decrease if more BaS:Eu pellets are embedded in the target during sputtering. Elements analysis is carried out by EDS. The Al/Ba ratio in thin films will approach 2.0 with more pellets existing in target. PL spectra of thin films are measured and analyzed. The most obvious emission peak in each spectrum is located at about 470nm which corresponds to the 4f65d1→4f7 transition of Eu2+ in BaAl2S4 lattice. The emission peak will approach 470nm as more pellets are embedded in complex target. As a result, it can be concluded that increasing the amounts of BaS:Eu pellets in complex target is an efficient way to achieve better Eu doping barium thioaluminates thin film.

Vibronic coupling parameters and luminescent properties of Eu2+ doped complex alkaline earth thioaluminates

The luminescent properties of different MII xMII 1-xAl2S4:Eu and MIIAl2S4:Eu are researched in this paper. A novel assessment method is used to evaluate these materials base on the configuration coordinates model. Vibronic coupling parameters of these phosphor materials can be calculated by the formula. With the calculation of characteristic energy and unitless factors, performances of MII xMII 1-xAl2S4:Eu and MIIAl2S4:Eu are evaluated. We then concluded that BaAl2S4:Eu shows highest Φ value comparing with other single or complex thioaluminates. With increasing amounts of Ba and Ca ions in the BaxMg1-xAl2S4:Eu and Ca1-ySryAl2S4:Eu respectively, the complex thioaluminates gives better luminescent performance and a broad tunable emission color can be achieved.

The effect of structure perturbation on PBG of one-dimensional photonic crystals

By introducing structure perturbation coefficients with different levels, relevant effects on PBG and density of mode (DOM) in 1D photonic crystal had been detailedly discussed under specifying numbers of bilayer and contrast of refractive index in this paper. Numerical simulation indicates that there are remarkable influences on optical properties of 1D photonic crystal resulted by structure perturbation, especially for PBG location and DOM at band edge. Generally, both PBG shifting and shrinking occurs due to disruptive periodicity. In specific case, especially along with perturbation coefficient increasing, it is found that PBG is extended obviously and the higher DOM at the band edge also can be obtained. According to this, some conclusions had been drawn which are significant to developing omnidirectional reflectors, band edge lasers and other devices based 1D photonic crystals.