Dielectric Response and a Phenomenon of a Narrow Band Absorption for a Classical Rotor in a Double Well Potential

The theory of dielectric relaxation in a planar ensemble of polar molecules is presented for a model where dipoles rotate in an intermolecular conservative double well potential, having a profile U = U_0*sin^2(θ). The evolution of the wide band dielectric spectra is demonstrated when the potential depth U_0 is varied; an isotropic and anisotropic medium being taken as examples. The spectra comprise the Debye relaxation and the quasi-resonant Poley absorption region. The rigorous theory is compared with a simplified one which was called the hybrid quasi-elastic bond / extended diffusion model. This approximation is valid for a qualitative description and also for the quantitative one at the large field parameter p = (U_0/((k_B)T))^(1/2). For P >> 1 the spectrum comprises one narrow absorption band and one Debye relaxation region considerably shifted to low frequencies. It is show that in the long lifetime limit τ there exists a minimum absorption band Δν_0(p). The quantity Δν_0 becomes small if the parameter p >> 1.The dielectric relaxation in ice 1 is discussed with regards to this phenomenon

Features of the Pulsed Treatment of Silicon Layers Implanted with Erbium Ions

Abstract—The formation of thin-film solid solutions of erbium in silicon and synthesis of erbium silicides were performed using continuous implantation of silicon with erbium ions followed by pulsed ion-beam treat- ment. Structural and optical properties of formed Si:Er layers were studied by Rutherford backscattering, trans- mission electron microscopy, and low-temperature photoluminescence. The dependences of erbium redistribu- tion, the microstructure of Si:Er layers, and their photoluminescence in the near-IR region on the erbium con- centration and pulsed treatment conditions were determined

Ectoplasm & Superspace Integration Measure for 2D Supergravity with Four Spinorial Supercurrents

Building on a previous derivation of the local chiral projector for a two dimensional superspace with eight real supercharges, we provide the complete density projection formula required for locally supersymmetrical theories in this context. The derivation of this result is shown to be very efficient using techniques based on the Ectoplasmic construction of local measures in superspace.Comment: 18 pages, LaTeX; V2: minor changes, typos corrected, references added; V3: version to appear in J. Phys. A: Math. Theor., some comments and references added to address a referee reques

Температурная зависимость роста 3C-SiC при быстрой вакуумно-термической обработке кремния

The paper presents the results of a study of the structure, phase composition, and growth kinetics of silicon carbide epitaxial layers on silicon substrates during their rapid vacuum thermal treatment. Transmission electron microscopy revealed the formation of layers of the cubic polytype SiC (3C-SiC) on silicon during carbidization in the temperature range of 1000–1300 °C. It was found that the formation of SiC layers proceeds in two stages, characterized by different activation energies. In the lower temperature range from 1000 to 1150 °C, the activation energy of the SiC growth process is Ea = 0.67 eV, while in the temperature range from 1150 to 1300 °C, the activation energy increases by almost an order of magnitude (Ea = 6.3 eV), which indicates a change in the limiting physical process. It has been established that the type of conductivity and the orientation of the substrate affect the thickness of the formed SiC layers. In this case, the greatest thickness of silicon carbide layers is achieved on silicon substrates with (111) orientation of p-type conductivity.Представлены результаты исследования структуры, фазового состава и кинетики роста эпитаксиальных слоев карбида кремния на кремниевых подложках при их быстрой вакуумно-термической обработке. Методами просвечивающей электронной микроскопии установлено формирование слоев кубического политипа SiC (3C-SiC) на кремнии при карбидизации в диапазоне температур 1000–1300 °С. Обнаружено, что формирование слоев SiC проходит в два этапа, характеризующихся различными энергиями активации. В более низкотемпературном диапазоне (1000–1150 °С) энергия активации процесса роста SiC составляет Ea = 0,67 эВ, тогда как в диапазоне 1150–1300 °С она увеличивается практически на порядок (Ea = 6,3 эВ), что указывает на смену лимитирующего физического процесса. Установлено, что тип проводимости и ориентация подложки оказывают влияние на толщину формированных слоев SiC. При этом наибольшая толщина слоев карбида кремния достигается на кремниевых подложках с ориентацией (111) p-типа проводимости

On 2D N=(4,4) superspace supergravity

We review some recent results obtained in studying superspace formulations of 2D N=(4,4) matter-coupled supergravity. For a superspace geometry described by the minimal supergravity multiplet, we first describe how to reduce to components the chiral integral by using ``ectoplasm'' superform techniques as in arXiv:0907.5264 and then we review the bi-projective superspace formalism introduced in arXiv:0911.2546. After that, we elaborate on the curved bi-projective formalism providing a new result: the solution of the covariant type-I twisted multiplet constraints in terms of a weight-(-1,-1) bi-projective superfield.Comment: 18 pages, LaTeX, Contribution to the proceedings of the International Workshop "Supersymmetries and Quantum Symmetries" (SQS'09), Dubna, July 29-August 3 200

Optical detection of single non-absorbing molecules using the surface plasmon of a gold nanorod

Current optical detection schemes for single molecules require light absorption, either to produce fluorescence or direct absorption signals. This severely limits the range of molecules that can be detected, because most molecules are purely refractive. Metal nanoparticles or dielectric resonators detect non-absorbing molecules by a resonance shift in response to a local perturbation of the refractive index, but neither has reached single-protein sensitivity. The most sensitive plasmon sensors to date detect single molecules only when the plasmon shift is amplified by a highly polarizable label or by a localized precipitation reaction on the particle's surface. Without amplification, the sensitivity only allows for the statistical detection of single molecules. Here we demonstrate plasmonic detection of single molecules in realtime, without the need for labeling or amplification. We monitor the plasmon resonance of a single gold nanorod with a sensitive photothermal assay and achieve a ~ 700-fold increase in sensitivity compared to state-of-the-art plasmon sensors. We find that the sensitivity of the sensor is intrinsically limited due to spectral diffusion of the SPR. We believe this is the first optical technique that detects single molecules purely by their refractive index, without any need for photon absorption by the molecule. The small size, bio-compatibility and straightforward surface chemistry of gold nanorods may open the way to the selective and local detection of purely refractive proteins in live cells

Band-gap and sub-band-gap photoelectrochemical processes at nanocrystalline CdS grown on ZnO by successive ionic layer adsorption and reaction method

Cadmium sulfide nanoparticle (NP) deposition by the successive ionic layer adsorption and reaction (SILAR) method on the surface of mesoporous ZnO micro-platelets with a large specific surface area (110 ± 10 m2g− 1) results in the formation of ZnO/CdS heterostructures exhibiting a high incident photon-to-current conversion efficiency (Y) not only within the region of CdS fundamental absorption (Ymax = 90%; 0.1 M Na2S + 0.1 M Na2SO3), but also in the sub-band-gap (SBG) range (Ymax = 25%). The onset potentials of SBG photoelectrochemical processes are more positive than the band-gap (BG) onset potential by up to 100 mV. A maximum incident photon-to-current conversion efficiency value for SBG processes is observed at larger amount of deposited CdS in comparison with the case of BG ones. The Urbach energy (EU) of CdS NPs determined from the photocurrent spectra reaches a maximal value on an early deposition stage (EU = 93 mV at SILAR cycle number N = 5), then lowers somewhat (EU = 73 mV at N = 10) and remains steady in the range of N from 20 to 300 (EU = 67 ± 1 mV). High efficiency of the photoelectrochemical SBG processes are interpreted in terms of light scattering in the ZnO/CdS heterostructures

Формирование SiC методом вакуумной карбидизации на пористом кремнии

Planar-view TEM investigation revealed the formation of cubic silicon carbide layers on porous silicon by vacuum carbidization. The formation of cubic silicon layers in the form of a two-phase system was found. At the same time, the formed SiC layers on the mesoporous buffer layer are predominantly polycrystalline. Using the Rutherford backscattering method, it was found that the use of buffer layers of porous silicon makes it possible to obtain SiC layers of greater thickness than on a pure silicon substrate under similar conditions of vacuum carbidization. It is shown that an increase in the pore size in porous silicon layers leads to an increase in the thickness of the formed SiC layers. It has been shown by scanning electron microscopy that vacuum carbideization of porous silicon leads to formation of SiC grains in pores, partial overgrowth and sintering of pores. The dependence of the SiC grain size on the pore size was established.Методами просвечивающей электронной микроскопии установлено, что вакуумная карбидизация пористого кремния при 1100 °C приводит к формированию слоев кубического карбида кремния. Обнаружено формирование слоев кубического SiC в виде двухфазной системы. При этом сформированные слои SiC на мезопористом буферном слое являются преимущественно поликристаллическими. Методом резерфордовского обратного рассеяния установлено, что использование буферных слоев пористого кремния позволяет получать слои SiC большей толщины, чем на чистой кремниевой подложке при аналогичных условиях вакуумной карбидизации. Показано, что увеличение размера пор в слоях пористого кремния приводит к увеличению толщины формируемых слоев SiC. С помощью метода растровой электронной микроскопии показано, что вакуумная карбидизация пористого кремния приводит к формированию зерен SiC в порах, частичному зарастанию и спеканию пор. Установлена зависимость размера зерен SiC от размера пор.