Photoluminescence doping effects

Zinc sulfide, with its wide band gap of 3.66 eV, has been considered as an excellent electroluminescent (EL) material. The electroluminescence of ZnS has been used as a probe for unraveling the energetics at the ZnS/electrolyte interface and for possible application to display devices. Fan and Bard [127] examined the effect of temperature on EL of Al-doped self-activated ZnS single crystals in a persulfate-butyronitrile solution, as well as the time-resolved photoluminescence (PL) of the compound. Further [128], they investigated the PL and EL from single-crystal Mn-doped ZnS (ZnS Mn) centered at 580 nm. The PL was quenched by surface modification with U-treated poly(vinylferrocene). The effect of pH and temperature on the EL of ZnS Mn in aqueous and butyronitrile solutions upon reduction of per-oxydisulfate ion was also studied. EL of polycrystalline chemical vapor deposited (CVD) ZnS doped with Al, Cu-Al, and Mn was also observed with peaks at 430, 475, and 565 nm, respectively. High EL efficiency, comparable to that of singlecrystal ZnS, was found for the doped CVD polycrystalline ZnS. In all cases, the EL efficiency was about 0.2-0.3%. 

It is reported that the band structure of ZnS doped with transition metal ions is remarkably different from that of pure ZnS crystal. Due to the effect of the doped ions, the quantum yield for the photoluminescence of samples can be increased. The fact is that because more and more electron-holes are excited and irradiative recombination is enhanced. Our calculation is in good correspondence with this explanation. When the ZnS (110) surface is doped with metal ions, these ions will produce surface state to occupy the valence band and the conduction band. These surface states can also accept or donate electrons from bulk ZnS. Thus, it will lead to the improvements of the photoluminescence property and surface reactivity of ZnS. 

P PAE PD PDS PEC PL PLE PMBE PPC PPPW PR PV PWP PWPP pi-MODFET precipitate power added efficiency photodetector photothermal deflection spectroscopy photoelectrochemical photoluminescence photoluminescence excitation spectroscopy plasma-assisted molecular beam epitaxy persistent photoconductivity pseudo-potential plane-wave photoreflectance photovoltage plane-wave pseudo-potential plane-wave pseudo-potential piezoelectric modulation doped field effect transistor... 

Figure 59 shows the effect of Li doping on the relative intensity of the newly observed photoluminescence. When the amount of Li increases, the intensity of this photoluminescence increases, passing through a maximum at approximately 3 mol% of Li. A parallel relationship between the intensity... 

The major attention is given to the conqjensated GaAs superlattices with the layer thickness of 40 nm and concentration of donors and acceptors of 10 cm. The superlattice named No. 4i contains i-layers n-i-p-I stracture) and No. 4 means no i-layers n-p-n-p stmcture). Both structures belong to the long-period doping superlattices and their photoluminescence properties were measured in a wide temperature range. Pronounced effects of a-irradiation were observed [7]. 

Redistribution of the space-charge of the excited carriers is presented in Fig. 1. Therewith at low temperatures, as seen in Fig. 2, the tunable photoluminescence band maximum coincides with the difference of the quasi-Fermi levels AF, which in turn is close to the effective energy gap Eg of the doped superlattice. At... 

Optical properties of dielectrics can be modified by incorporating nanosize clusters of foreign materials. Recently Si nanoclusters were shown to excite rare-earth element Er in the silica glass host [1,2]. The favorable effect of Si nanoclusters on the photoluminescence of Er in oxidized porous silicon (OPS) was also demonstrated [3], In silica hosts doped with Si nanoclusters it was shown that the excitation energy can be transferred from nanoclusters to Er ions located in a silicalike environment near the clusters. Nowadays, there is a principal interest to incorporate Er ions inside clusters due to influence on the excitation process. 

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