Exciton-polaritons in lattices: A non-linear photonic simulator

Microcavity polaritons are mixed light–matter quasiparticles with extraordinary nonlinear properties, which can be easily accessed in photoluminescence experiments. Thanks to the possibility of designing the potential landscape of polaritons, this system provides a versatile photonic platform to emulate 1D and 2D Hamiltonians. Polaritons allow transposing to the photonic world some of the properties of electrons in solid-state systems, and to engineer Hamiltonians for photons with novel transport properties. Here we review some experimental implementations of polariton Hamiltonians using lattice geometries.     

高性能Bi3+掺杂改性PbO2电极的制备及表征

采用电沉积法制备了金属Bi3+改性PbO2(Bi-PbO2)电极,并通过扫描电镜(SEM)、X射线能谱(EDS)、X射线光电子能谱(XPS)、X射线衍射(XRD)、紫外-可见漫反射(UV-VisDRS)、荧光光谱(FP)、莫特-肖特基(Mott-Schottky)曲线、电化学阻抗谱(EIS)和线性极化扫描(LSV)等方法表征了其微结构和电化学性能.SEM、EDS和XPS结果表明,Bi3+以Bi2O3的形式掺杂进入PbO2镀层,同时其掺杂改性可明显改善PbO2镀层的微结构,使电极表面颗粒细化;XRD和UV-VisDRS分析结果显示Bi3+掺杂改性后,PbO2晶体的晶胞参数发生变化,同时禁带宽度(Eg)变小;荧光光谱分析表明Bi-PbO2电极可促进羟基自由基的产生,增强电极降解有机物的催化活性;电化学性能测试显示,Bi3+改性PbO2电极电催化活性的提升与电极的平带电势(Efb)负移、活性表面积增大、电化学反应电阻减小和析氧电位提高有关.     

Photocatalytic and photoelectrochemical properties of titania–chloroplatinate(IV)

Rutile (Ald), anatase (TH), and the mixed anatase/rutile powder (P25) were surface modified by chemisorption of H₂[PtCl₆] from aqueous solution. The resulting materials photocatalyzed the degradation and mineralization of 4-chlorophenol with visible light. Ald adsorbed only traces and was inactive, P25 adsorbed 1.1 wt.% and exhibited medium activity, whereas TH adsorbed 4.0% and was six times more active than P25. In neutral water 4.0%Pt(IV)/TH is stable towards thermal and photochemical desorption of platinate, even in the presence of strongly adsorbing fluoride ions. Contrary to this, complete photodesorption occurred in 0.1 M hydrogen chloride solution. It is postulated that adsorption affords a surface tetrachloroplatinate(IV) complex covalently linked to the titania surface through a [Ti]O---Pt bond. The flatband potential of 4.0%Pt(IV)/TH at pH 7 is determined as −0.28±0.02 V (vs. NHE), which is more anodic by 260 mV as compared with unmodified TH. Solar experiments revealed that 4.0%Pt(IV)/TH is a much better photocatalyst than 1.1%Pt(IV)/P25, P25, and TH. It catalyzed the photodegradation also in diffuse indoor daylight, conditions under which all other tested materials were inactive. Upon UV excitation 4.0%Pt(IV)/TH is even more active than P25.     

电容测量研究铬表面氧化膜的半导体性能

利用电容测量技术,基于Mott-Sckottky分析,研究了在0.5 mol•L－1 H2SO4溶液中铬表面氧化膜的半导体性质,以及膜形成条件的影响.结果表明,铬在钝化电位区内所形成的表面氧化膜具有p-型半导体特性,膜的厚度约(1.2±0.3) nm.膜的阻抗响应表现出低频弥散行为,可以用介电弛豫普适定律来描述.膜的掺杂浓度NA随成膜电位及极化时间的延长而增大,溶液pH值则通过改变膜的表面电荷而影响膜的平带电位EFB.     

铁钝化膜半导体特性的光电化学研究

近年来,光电化学作为金属钝化膜的“现场”(insltu)研究方法越来越受到重视。本文研究了铁钝化膜在硼酸/硼酸钠溶液中的光电化学行为,通过钝化膜的光电流响应与入射光强、波长及电极电位关系研究,说明铁钝化膜的非晶态n型半导体特性。实验部分研究电极由99.99%的纯铁制成(购自上海冶金所),受光面积为0.5cm~2,对电极为1cm~2的铂片,饱和甘汞电极作参比电极。溶液的组成为Na_2B_4O_7(0.075mol·L~(-1))+H_3BO_3(0.3mol·L(-1)),试剂均为分折纯,用二次蒸馏水配制。灯源为400W溴钨灯,光强用JG-Ⅰ型绝对功率计(长春真空器件厂)测量,电极电位用DH-Ⅱ型双恒电位仪(延边电化学仪器厂)控制,测量光电流-电位及光电流-光强关系时,用脉冲白光作光源,脉冲光的频率用斩光器调节。测量光电流-波长关系时,用WDG-Ⅰ型强光单色仪(四平光学仪器厂)产生单色光,并用PAR-5202型锁相放大器测量光电流,     

Insight into the influence of high temperature annealing on the onset potential of Ti-doped hematite photoanodes for solar water splitting

The unfavorable onset potential shift of Ti:Fe₂O₃ photoanode induced by high temperature post-annealing was studied. The underlying mechanism is the surface Ti/Fe atomic ratio increase, leading to adsorption capacity change of surface hydroxide ions and the positive shift of flatband potential (i.e., theoretical onset potential).     

Study on the anisotropic photonic band gaps in three-dimensional tunable photonic crystals containing the epsilon-negative materials and uniaxial materials

In this paper, the properties of anisotropic photonic band gaps (PBGs) for three-dimensional (3D) photonic crystals (PCs) composed of the anisotropic positive-index materials (the uniaxial materials) and the epsilon-negative (ENG) materials with body-centered-cubic (bcc) lattices are theoretically studied by a modified plane wave expansion (PWE) method, which are the uniaxial materials spheres inserted in the epsilon-negative materials background. The anisotropic photonic band gaps (PBGs) and one flatbands region can be achieved in first irreducible Brillouin zone. The influences of the ordinary-refractive index, extraordinary-refractive index, filling factor, the electronic plasma frequency, the dielectric constant of ENG materials and the damping factor on the properties of anisotropic PBGs for such 3D PCs are studied in detail, respectively, and some corresponding physical explanations are also given. The numerical results show that the anisotropy can open partial band gaps in such 3D PCs with bcc lattices composed of the ENG materials and uniaxial materials, and the complete PBGs can be obtained compared to the conventional 3D PCs containing the isotropic materials. The calculated results also show that the anisotropic PBGs can be manipulated by the parameters as mentioned above except for the damping factor. Introducing the uniaxial materials into 3D PCs containing the ENG materials can obtain the larger complete PBGs as such 3D PCs with high symmetry, and also provides a way to design the tunable devices.     

The protectivity of aluminum and its alloys with transition metals

The mechanism of the protectivity of aluminum and supersaturated aluminum alloys containing W, Mo, Ta and Cu has been investigated in chloride environments. The potential of zero charge (PZC) of the passive film was evaluated by a method based on impedance spectroscopy. The chloride ion adsorption on the passive film was measured by means of an in situ radiotracer technique. Constituents of the passive film as a function of depth were investigated by means of ex situ spectroscopic techniques including XPS, ISS and SIMS. The PZCs of the passive films of Al and Al alloys were calculated from the flatband potentials. A linear correlation between pitting potential and the PZC was found. Adsorption of the chloride ion on the Al-Ta surface starts at more anodic potentials than those of pure Al, and this shift is in agreement with the anodic shift of the PZC. A constant surface concentration of chloride ion was observed during the induction time for breakdown. A significant de crease of OH⁻ concentration in the passive film of Al and its alloys has been found after the passive film has undergone breakdown. The mole fraction of the alloying elements in the surface region of the passive film is ca. 1–8%. The adsorption of the chloride ion on the surface of the passive film is influenced by the anodic PZC shift, which varies with the alloying element. However, retardation of the chloride penetration into the passive film by blocking of the entry site by oxide ions of the alloying element controls the rate of breakdown. Received: 18 November 1996 / Accepted: 17 February 1996     

铁钝化膜半导体特性的光电化学研究

The photoelectrochemical behavior of the passive film on iron in pH=8.4 borate buffer solution was investigated. The mechanism considered for the generation of the photocurrent in the passive film, and the principle of the measurement of photocurrent were discussed. The band model of noncrytalline semiconductor was used to demonstrate the depedence of photocurrent on electrode potential and light wavelength. Results indicate that the passive film formed on iron in pH=8.4 borate solution is a noncrystalline semiconductor, its flatband potential (φ_(fb)) is -0.30 V(SCE), band gap energy (E_g) is affected by measuring potential (φ_m), When +0.30 V<φ_m<+0.80 V (SCE), E_g is 1.9 eV.     

Effect of poly silicon thickness on the formation of Ni-FUSI gate by using atomic layer deposited nickel film

The effect of poly-Si thickness on silicidation of Ni film was investigated by using X-ray diffraction, auger electron spectroscopy, cross-sectional scanning transmission electron microscopy, resistivity, I–V, and C–V measurements. The poly-Si films with various thickness of 30–200 nm were deposited by LPCVD on thermally grown 50 nm thick SiO₂, followed by deposition of Ni film right after removing the native oxide. The Ni film was prepared by using atomic layer deposition with a N²-hydroxyhexafluoroisopropyl-N¹ (Bis-Ni) precursor. Rapid thermal process was then applied for a formation of fully silicide (FUSI) gate at temperature of 500 °C in N₂ ambient during 30 s. The resultant phase of Ni-silicide was strongly dependent on the thickness of poly-Si layer, continuously changing its phase from Ni-rich (Ni₃Si₂) to Si-rich (NiSi₂) with increasing the thickness of the poly-Si layer, which is believed to be responsible for the observed flat band voltage shift, ΔV_FB, in C–V curves.