Thermally Stimulated Electron–Hole and Ionic Processes in Zinc Oxide Crystals

The principal results of the investigation of thermally stimulated electron–hole and ionic processes in hydrothermal and gas-phase ZnO single crystals preexcited at low temperatures, based on simultaneous study of photo-EPR and thermoluminescence (TL), are presented. The nature of the traps determining the TL peaks at 17, 24, 40, 53, 90–110, 140–150, and 160–200 K is discussed. In particular, it has been established that the lithium paramagnetic centers (Li_Zn ⁺–O^I) play the role of hole traps in ZnO giving green and red TL in the temperature range 160–200 K and, in the case of association with small-sized donors, also TL in the temperature range 90–110 K. The other traps are electronic in character, and in the presence of acceptor lithium in the crystals, they form yellow-orange TL. Optical quenching of TL has been evaluated, and it has been found that there is a difference E 0.75 eV between the thermal and optical energies of ionization of lithium acceptors. Irreversible ionic processes associated with the healing of cationic vacancies at T 360–420 K have been revealed.     

Organic light emitting devices

The purpose of this paper is to provide general information about basic physical processes involved in organic electroluminescence and to present the main parameters and advantages of organic light emitting devices (OLEDs).     

Single-molecule tethered particle motion to study protein-DNA interaction

Single-molecule techniques have been demonstrated as powerful tools to investigate individual protein-DNA interactions that are difficult to access by conventional biochemical techniques. These methods are popularly used to obtain valuable and detailed molecular mechanisms of enzyme functions. Currently, we have used single-molecule tethered particle motion to investigate protein-DNA interactions, including homologous recombination, site-specific recombination, DNA package, and the nucleosome remodeling process, and useful information was obtained. Here, we will describe the experimental designs and present the information obtained.     

壁面催化对再入飞行器等离子体鞘套及电磁参数的影响

针对超高声速流动中的高温真实气体效应,采用数值模拟求解考虑化学非平衡的三维Navier-Stokes(N-S)方程,研究了壁面催化对典型再入飞行器等离子体鞘套及电磁参数的影响规律.研究发现:(1)完全催化壁条件下等离子体密度计算结果与飞行试验符合较好;(2)完全催化壁条件下,离解原子在壁面的复合导致波后气体可压缩性增强...     

用非相干光时间延迟四波混频测量TiO_2超微粒子的扩散系数及载流子复合时间

本文报导了用非相干光时间延迟四波混频方法测得Ti_2O超微粒子的扩散系数和载流子复合时间分别为0.016cm~2/s和1.08ns.两个光栅衰减时间分别是1.07ns和0.56ns.讨论了引起两个光橱衰减时间不同的原因.     

On the existence of a homologous series of BamCum+nOy oxides with the cubic structure of the BaCuO2 oxide

Phase relations have been studied in the BaO–CuO_x system in the range of 42.0–83.0 mol.% CuO at P(O₂) = 21 kPa (air) by visual polythermal analysis (VPA), powder X-ray diffraction (XRD), differential thermal analysis (DTA), thermogravimetric analysis (TGA), chemical analysis (CA), and electron diffraction (ED) with simultaneous elemental analysis (EA) in a transmission electron microscope (TEM). The existence of discrete crystallization fields of barium–copper oxides of cation compositions Ba₄Cu₅O_y, Ba₅Cu₆O_y, Ba₇Cu₈O_y, Ba₁₂Cu₁₃O_y, and Ba₂₄Cu₂₅O_y, which have the cubic structure of the BaCuO₂ oxide, is revealed in the studied region of the system. The oxides may be represented as members of a Ba_mCu_m+nO_y homologous series. The BaCuO₂ oxide does not exist in the subsolidus region and does not have its own crystallization field. The oxygen-deficient oxide BaCuO_1.78 of the cation composition (Ba:Cu) 1:1 with the BaCuO₂ cubic structure is found in melted samples of the 50.0 mol.% CuO composition quenched at 1020–1060 °С.     

Correlation between Energy and Spatial Distribution of Intragap Trap States in the TiO2 Photoanode of Dye‐Sensitized Solar Cells

The energy and spatial distribution of intragap trap states of the TiO₂ photoanode of dye‐sensitized solar cells and their impact on charge recombination were investigated by means of time‐resolved charge extraction (TRCE) and transient photovoltage (TPV). The photoanodes were built from TiO₂ nanospheroids with different aspect ratios, and the TRCE results allowed differentiation of two different types of trap states, that is, deep and shallow ones at the surface and in the bulk of the TiO₂ particles, respectively. These trap states exhibit distinctly different characteristic energy with only a slight variation in the particle size, as derived from the results of the density of states. Analyses of the size‐dependent TPV kinetics revealed that in a moderate photovoltage regime of about 375–625 mV, the dynamics of electron recombination are dominated by shallow trap states in the bulk, which can be well accounted for by the mechanism of multiple‐trap‐limited charge transport.     

Crafting Core/Graded Shell–Shell Quantum Dots with Suppressed Re‐absorption and Tunable Stokes Shift as High Optical Gain Materials

The key to utilizing quantum dots (QDs) as lasing media is to effectively reduce non‐radiative processes, such as Auger recombination and surface trapping. A robust strategy to craft a set of CdSe/Cd_1?xZn_xSe_1?yS_y/ZnS core/graded shell–shell QDs with suppressed re‐absorption, reduced Auger recombination rate, and tunable Stokes shift is presented. In sharp contrast to conventional CdSe/ZnS QDs, which have a large energy level mismatch between CdSe and ZnS and thus show strong re‐absorption and a constrained Stokes shift, the as‐synthesized CdSe/Cd_1?xZn_xSe_1?yS_y/ZnS QDs exhibited the suppressed re‐absorption of CdSe core and tunable Stokes shift as a direct consequence of the delocalization of the electron wavefunction over the entire QD. Such Stokes shift‐engineered QDs with suppressed re‐absorption may represent an important class of building blocks for use in lasers, light emitting diodes, solar concentrators, and parity‐time symmetry materials and devices.     

类氖氙离子LMn双电子复合模拟谱

在双电子复合过程发生的能量范围内,发射X光子的原子过程除双电子复合过程外还有辐射复合、共振激发、共振复合以及直接激发原子过程.本文使用相对论组态相互作用方法计算了这些过程的截面,比较了在双电子复合过程发生的能量范围内这些原子过程的截面与双电子复合过程截面,探讨了这些过程对双电子复合过程的影响.研究结果表明,辐射复合截面随入射电子束能量的增大迅速减小,在双电子复合能量范围内几乎为一常数,可以作为本底来处理;共振激发和共振复合过程对双电子复合过程的影响可以忽略不计;当入射电子束能量高于靶离子的第一激发能时,电子碰撞直接激发截面与高Rydberg态的截面连成一片,随着入射电子束能量的增加,电子碰撞直接激发截面越来越大,这时必须考虑直接激发过程.使用相对论组态相互作用方法计算了类氖氙离子的双电子复合截面,其结果与已有的部分实验和理论结果很吻合.     

镁铝类氢类氦类锂离子双电子复合速率研究

镁铝类氢类氦类锂离子经中间双激发态进行的双电子复合过程在用双示踪元素谱线强度比研究ICF电子温度中占有很重要的地位。计算了双电子复合经不同Rydberg态跃迁通道的复合速率系数,并给出不同离化度的总的双电子复合速率系数的变化规律,比较了它们在不同电子温度和不同跃迁通道的异同,对研究X射线激光、等离子体温度诊断等诸多应用领域提供了有价值的原子数据。