Structural properties and dopant-modified bandgap energies of Ba0.5 Sr 0.5 TiO 3 thin films grown on LaAlO 3 substrates

Ba_0.5Sr_0.5TiO₃ thin films doped with different concentration of Ti, Mg and Al dopants were prepared by pulsed laser deposition technique on LaAlO₃ substrates. The crystalline properties of these doped thin films were studied using X-ray diffraction, micro-Raman scattering, atomic force microscopy, and transmission electron microscopy. The bandgap energies of BST thin films are determined from the transmission and absorption measurements by the ultraviolet-visible spectrophotometer. It was found out that the bandgap energies of the doped BST thin films depend strongly on the dopant concentration.     

Dielectric properties of Sm, Nd and Fe doped Bi1.5Zn0.92Nb1.5O6.92 pyrochlores

New pyrochlore ceramics have been produced by doping Sm and Nd into the Bi site and Fe into the Nb site in the Bi_1.5Zn_0.92Nb_1.5O_6.92 (BZN) pyrochlore. Doped pyrochlore ceramics were produced by conventional solid state mixing of oxides at different doping levels using the compositions of Bi_1.5−xSm_xZn_0.92Nb_1.5O_6.92, Bi_1.5−xNd_xZn_0.92Nb_1.5O_6.92 and Bi_1.5Zn_0.92Nb_1.5−xFe_xO_6.92−x. The solubility limit of cations was determined as x = 0.13, 0.18 and 0.15 for Sm, Nd and Fe, respectively. While Sm and Nd increased the dielectric constant (?), Fe doping led a decrease in ?. Dielectric constant of Sm and Nd doped BZN increased to 199 at x = 0.13 (Sm) and to 219 at x = 0.18 (Nd). At low Fe dopings (x = 0.05), the dielectric constant of BZN increased to 242 but decreased to 211 at x = 0.15. The dielectric losses were lower for Sm and Nd dopings than Fe but in all cases it was lower than 0.006. The dielectric constant of Sm, Nd and Fe doped BZN ceramics was nearly independent of frequency within the frequency range between 1 kHz and 2 MHz, but decreased considerably with temperature between 20 and 200 °C. Temperature coefficient of Sm doped BZN (−354 ppm/°C) was lower than Nd and Fe doped BZN ceramics at solubility limits (−538 ppm/°C for Nd and −565 ppm/°C for Fe).     

Energetics of NP and NB complexes in silicon

Using ab initio (Hartree–Fock and local density approximation) and semiempirical (Austin Model 1) calculations, we studied the energetics and electronic structures of NB and NP complexes. We found that these complexes are electrically inactive. The formation energies are 1.6 eV for the NB coupling and 2.4 eV for the NP pairing. The N–P and N–B interatomic equilibrium distances are about 3.5 Å for both complexes.     

Investigation of the Effects of Doping and Post‐Deposition Treatments on the Conductivity,Morphology, and Work Function of Poly(3,4‐ethylenedioxythiophene)/Poly(styrene sulfonate) Films

We investigate the influence of annealing conditions on the physical properties of thin films of poly(3,4‐ethylenedioxythiophene)/poly(styrene sulfonate) (PEDOT/PSS). In particular, we describe how annealing temperature, the ambient gas, and choice of dopant affect the conductivity, morphology, and work function of the films. Two specific dopants are considered, sorbitol and glycerol, and broad guidelines are developed for using PEDOT/PSS as a hole‐injection electrode in polymeric light‐emitting devices, solar cells, and photodetectors.     

非晶态硒碲材料中卤族元素掺杂对空穴陷阱的影响

用静电放电方法研究硒碲材料中卤族元素掺杂对空穴陷阱的影响。结果表明卤族元素掺杂增加了硒碲材料的光量子效率η和光生载流子漂移长度μτE.而体陷阱积分密度 N_(?)降低以及空穴深陷阱态分布减小,说明硒碲材料中卤族元素掺杂使得浅空穴陷阱密度增大。     

Highly Efficient p‐i‐n and Tandem Organic Light‐Emitting Devices Using an Air‐Stable and Low‐Temperature‐Evaporable Metal Azide as an n‐Dopant

Cesium azide (CsN₃) is employed as a novel n‐dopant because of its air stability and low deposition temperature. CsN₃ is easily co‐deposited with the electron transporting materials in an organic molecular beam deposition chamber so that it works well as an n‐dopant in the electron transport layer because its evaporation temperature is similar to that of common organic materials. The driving voltage of the p‐i‐n device with the CsN₃‐doped n‐type layer and a MoO₃‐doped p‐type layer is greatly reduced, and this device exhibits a very high power efficiency (57 lm W^?1). Additionally, an n‐doping mechanism study reveals that CsN₃ was decomposed into Cs and N₂ during the evaporation. The charge injection mechanism was investigated using transient electroluminescence and capacitance–voltage measurements. A very highly efficient tandem organic light‐emitting diodes (OLED; 84 cd A^?1) is also created using an n–p junction that is composed of the CsN₃‐doped n‐type organic layer/MoO₃ p‐type inorganic layer as the interconnecting unit. This work demonstrates that an air‐stable and low‐temperature‐evaporable inorganic n‐dopant can very effectively enhance the device performance in p‐i‐n and tandem OLEDs, as well as simplify the material handling for the vacuum deposition process.     

Photo-catalytic degradation of Rhodamine B on C-, S-, N-, and Fe-doped TiO2 under visible-light irradiation

C-, S-, N-, and Fe-doped TiO₂ photocatalysts were synthesized by a facile sol–gel method. The structure and properties of catalysts were characterized by N₂ desorption–adsorption, X-ray diffraction (XRD), UV–vis spectroscopy, and X-ray photoelectron spectroscopy (XPS). Results revealed that the surface area of the multi-doped TiO₂ was significantly increased and the crystallite size was smaller than the pure TiO₂ obtained by a similar route. Compared with TiO₂, the peak position in doped-TiO₂ XRD patterns was slightly shifted, which could be attributed to the distortion by the substitution of carbon, nitrogen, and sulfur dopants for some oxygen atoms and Fe³⁺ for Ti⁴⁺ in the lattice of TiO₂. These substitutions were confirmed by XPS. In addition, these dopants were responsible for narrowing the band gap of TiO₂ and shifting its optical response from ultraviolet (UV) to the visible-light region. The photocatalytic reactivities of these multi-doped TiO₂ catalysts were investigated by degrading Rhodamine B (RB) in aqueous solution under visible-light irradiation (λ > 420 nm). It was found out that the reactivity was significantly enhanced and the catalyst doped with nitrogen, carbon, sulfur, and 0.3 wt% iron had the highest photocatalytic activity.     

Interaction between implanted fluorine atoms and point defects in preamorphized silicon

We have studied, by means of B diffusion analyses, the effect of F on the point defect density in preamorphized Si. Through molecular beam epitaxy (MBE) Si samples containing a special B multi-spike were grown. These samples were amorphized to a depth of 550 nm by implanting Si at liquid nitrogen temperature and then enriched with F at different energies (65–150 keV) and fluences (0.7–5 × 10¹⁴/cm²). After solid phase epitaxy (SPE) of the samples, we induced, by thermal annealing at 850 °C, the emission of Si self-interstitials (Is) from the end-of-range (EOR) defects. We studied the diffusion of the B spikes, demonstrating that F effectively reduces the B diffusion. This reduction is shown to be caused not by a direct B–F chemical interaction, but by a F interaction with point defects. In particular, F is able to reduce the density of Is, which are responsible for the B diffusion. Still, we showed that F does not appreciably influence the Is emission from the EOR defects, but a local interaction occurs between F atoms and Is after the release of these defects from the EOR region. This interaction results in a consistent reduction of B diffusivity in F enriched regions.     

Luminescent Er3+ doped transparent alumina ceramics

We report on successful preparation of Er³⁺ doped transparent alumina (0.1–0.17 at.%) exhibiting visible light photoluminescence using wet shaping method and hot isostatic pressing. The effects of dopant amount, type of doping powder and powder pre-treatment on final microstructure, real in-line transmittance and photoluminescence characteristics were studied.The real in-line transmittance ranged between 28 and 56%, depending on processing parameters. The transparency decreased with increased amount of dopant. The decrease is dependent on the type of doping powder and its pre-treatment.The photoluminescence spectra measured in both visible and NIR region showed typical emission bands due to the presence of Er³⁺ ions. The decay profiles of the ⁴S_3/2 → ⁴I_15/2 transition were fitted with a 2-exponential function, with faster component in the range of 360–700 ns and slower component around 1.6-2.4 μs. The intensity of emissions and lifetime of the ⁴S_3/2 level decrease significantly with increasing concentration of Er³⁺ ions.