Dongpu Zhang

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...

Analysis of europium doped luminescent barium thioaluminate

Abstract Europium-doped barium thioaluminate sputtering target was synthesized by powder sintering method and thin film was deposited by radio frequency (RF) sputtering. X-ray diffractometer (XRD) pattern indicated that the main compound of the target was BaAl 4 S 7 . Oxygen was the main impurity which led to the formation of BaAl 2 O 4 . It was shown that both BaAl 4 S 7 and BaAl 2 S 4 were contained in the as-grown thin films and a 471.7 nm emission peak in the PL spectra appeared due to a combination of BaAl 4 S 7 :Eu 2+ and BaAl 2 S 4 :Eu 2+ . In addition, the product of oxidation in the film was BaSO 4 instead of BaAl 2 O 4 and led to an emission peak at 415.2 nm in the PL spectra assigned to the f→f transition of Eu 2+ in the BaSO 4 host.

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.