Control of grain size in sublimation-grown CdTe, and the improvement in performance of devices with systematically increased grain size

A method to control the grain size of CdTe thin films deposited by close space sublimation using chamber pressure is demonstrated. Grain diameter is shown to increase in the pressure range 2–200 Torr, following the linear relationship D (?m)=0.027×P (Torr)+0.90. A mechanism is proposed to explain the dominance of the 111 preferred orientation in the small-grained, but not the large-grained films. For a series of CdTe/CdS solar cells in which the only variable was grain size, the performance parameters were seen to increase from 0.54% (0.94 ?m grains) up to a plateau of 11.3% (?3.6 ?m grains). This corresponds to the point at which the series resistance is no longer dominated by grain boundaries, but by the contacts

Interaction corrections to the Hall coefficient at intermediate temperatures

We investigate the effect of electron-electron interaction on the temperature dependence of the Hall coefficient of 2D electron gas at arbitrary relation between the temperature $T$ and the elastic mean-free time $\tau$. At small temperature $T\tau \ll \hbar$ we reproduce the known relation between the logarithmic temperature dependences of the Hall coefficient and of the longitudinal conductivity. At higher temperatures, this relation is violated quite rapidly; correction to the Hall coefficient becomes $\propto 1/T$ whereas the longitudinal conductivity becomes linear in temperature.Comment: 4 pages, 3 .eps figure

Room temperature coherent spin alignment of silicon vacancies in 4H- and 6H-SiC

We report the realization of the optically induced inverse population of the ground-state spin sublevels of the silicon vacancies ($V_{\mathrm{Si}}$) in silicon carbide (SiC) at room temperature. The data show that the probed silicon vacancy spin ensemble can be prepared in a coherent superposition of the spin states. Rabi nutations persist for more than 80 $\mu$s. Two opposite schemes of the optical alignment of the populations between the ground-state spin sublevels of the silicon vacancy upon illumination with unpolarized light are realized in 4H- and 6H-SiC at room temperature. These altogether make the silicon vacancy in SiC a very favorable defect for spintronics, quantum information processing, and magnetometry.Comment: 4 pages, 3 picture

The multiplicity and the spectra of secondaries correlated with the leading particle energy

The spectra of leading particles of different nature in pp-collisions at E sub 0 = 33 GeV are obtained. The multiplicities and the spectra of secondaries, mesons, gamma-quanta, lambda and lambda-hyperons and protons for different leading particle energy ranges are determined

Admittance spectroscopy of CdTe/CdS solar cells subjected to varied nitric-phosphoric etching conditions

In this work we investigate the electric and structural properties of CdTe/CdS solar cells subjected to a nitric-phosphoric (NP) acid etching procedure, employed for the formation of a Te-rich layer before back contacting. The etching time is used as the only variable parameter in the study, while admittance spectroscopy is employed for the characterization of the cells' electric properties as well as for the analysis of the defect energy levels. Particular attention was also given to the characteristics of unetched devices and it is shown that despite the larger height of back-contact barrier such samples show well defined admittance spectra, as well as allow for extraction of as much as five defect levels in the range of 0.08-0.9 eV above the valence band. In contrast, admittance characteristics of the etched samples show a decrease of the number of the detectable trap levels with increasing etching time. (Hence it is usual for only one or two trap levels to be reported in the literature for finished devices.) The latter leads to the anomalous Arrhenius energy plots as well as the breakdown of low-frequency capacitance characteristics for samples etched with times larger than 30 s. The observed effects are attributed to physical thinning of the cells, the etching out of grain boundaries, and the tellurium enrichment of the CdTe surface by NP etching. We also perform analysis of the back-contact barrier height as extracted from dark I-V measurements at different temperatures. The dependence of this barrier height on NP etching time is compared with that of conversion efficiency, from which conclusions are drawn about both positive and negative effects of the nitric-phosphoric etch

Light-induced structural changes in photosynthetic reaction centres studied by ESEEM of spin-correlated D+QA− radical pairs

AbstractZn-substituted Rhodobacter sphaeroides R26 reaction centres (RCs) frozen in the dark and under illumination exhibit quite different recombination kinetics of the D+QA− radical pairs [Kleinfeld et al., Biochemistry, 23 (1984) 5780]. We have applied electron spin echo envelope modulation (ESEEM) of the spin-correlated D+QA− radical pairs to assess a possible light-induced change in the distance between the D and QA cofactors. The recombination kinetics and the field-swept spin-polarized EPR signal for the two preparations have been monitored by time-resolved EPR spectroscopy. For the samples frozen under illumination, a slight increase in the distance, 0.4±0.2 Å, has been detected

Математические начала ранней Вселенной и живой материи

We suppose that our Universe sprang according to the Cayley algebra. The Great Nothing is described by this algebra (no having any representation). But it may be enclosed into the Heisenberg algebra (the enclosing is not homomorphism). A new physical substance, called pre-matter (or bi-Hamiltonian matter), is underlain the latter. Our Universe has consisted of this kind of matter in its zero cycle. After the Big Bang that is identified with the total irreversible quantum transition, taking place in the bi-Hamiltonian matter, the fundamental particles were arisen. It is shown that after the so called de Sitter’s stage of Universe extension our space was in phase of the Bohr compact (space firm). Formation of alive cells were connected with this phase state of our space.Было ли у Вселенной начало, которое можно принять за акт творения, или она как causa sui существует сама по себе вечно и бесконечно? Этот вопрос, весьма актуальный в современной космологии, до сих пор не имел однозначного ответа. В данной статье начало Вселенной (Великое Ничто) отождествляется с алгеброй Кэли. Исходя из нее, дается последовательное построение физической картины мира, которая включает в себя: 1) материализацию Ничто — возникновение праматерии , 2) появление конфигурационного пространства — носителя праматерии, способного находиться в трех различных фазовых состояниях, 3) возникновение наблюдаемой материи вследствие конденсации и взрыва праматерии — тотального квантового перехода, происходящего в праматерии, и, в частности, образование живой клетки, которое происходит в той фазе пространства, которая называется боровским компактом. Важную роль играют квантовые корреляции, определяющие топологию конфигурационного пространства праматерии

Interactions in high-mobility 2D electron and hole systems

Electron-electron interactions mediated by impurities are studied in several high-mobility two-dimensional (electron and hole) systems where the parameter $k_BT\tau /\hbar$ changes from 0.1 to 10 ($\tau$ is the momentum relaxation time). This range corresponds to the \textit{intermediate} and \textit {ballistic} regimes where only a few impurities are involved in electron-electron interactions. The interaction correction to the Drude conductivity is detected in the temperature dependence of the resistance and in the magnetoresistance in parallel and perpendicular magnetic fields. The effects are analysed in terms of the recent theories of electron interactions developed for the ballistic regime. It is shown that the character of the fluctuation potential (short-range or long-range) is an important factor in the manifestation of electron-electron interactions in high-mobility 2D systems.Comment: 22 pages, 11 figures; to appear in proceedings of conference "Fundamental Problems of Mesoscopic Physics", Granada, Spain, 6-11 September, 200