Aluminum Single Electron Transistors with Islands Isolated from a Substrate

The low-frequency noise figures of single-electron transistors (electrometers) of traditional planar and new stacked geometry were compared. We observed a correlation between the charge noise and the contact area of the transistor island with a dielectric substrate in the set of Al transistors located on the same chip and having almost similar electric parameters. We have found that the smaller the contact area the lower the noise level of the transistor. The lowest noise value 8*10E-6 e/sqrt(Hz) at f = 10 Hz. has been measured in a stacked transistor with an island which was completely isolated from a substrate. Our measurements have unambiguously indicated that the dominant source of the background charge fluctuations is associated with a dielectric substrateComment: Review paper, latex, 10 pages, 7 figures, to be publ. in JLTP, 2000; Proceeding of "Electron Transport in Mesoscopic Systems", August 12-15, 1999 Geteborg, Sweden, http://fy.chalmers.se/meso_satellite/index.html See also LT22 manuscript: http://lt22.hut.fi/cgi/view?id=S1113

Metallic single-electron transistor without traditional tunnel barriers

We report on a new type of single-electron transistor (SET) comprising two highly resistive Cr thin-film strips (~ 1um long) connecting a 1 um-long Al island to two Al outer electrodes. These resistors replace small-area oxide tunnel junctions of traditional SETs. Our transistor with a total asymptotic resistance of 110 kOhm showed a very sharp Coulomb blockade and reproducible, deep and strictly e-periodic gate modulation in wide ranges of bias currents I and gate voltages V_g. In the Coulomb blockade region (|V| < 0.5 mV), we observed a strong suppression of the cotunneling current allowing appreciable modulation curves V-V_g to be measured at currents I as low as 100 fA. The noise figure of our SET was found to be similar to that of typical Al/AlOx/Al single-electron transistors.Comment: 5 pages incl. 4 fig

Noise in Al single electron transistors of stacked design

We have fabricated and examined several Al single electron transistors whose small islands were positioned on top of a counter electrode and hence did not come into contact with a dielectric substrate. The equivalent charge noise figure of all transistors turned out to be surprisingly low, (2.5 - 7)*10E-5 e/sqrt(Hz) at f = 10 Hz. Although the lowest detected noise originates mostly from fluctuations of background charge, the noise contribution of the tunnel junction conductances was, on occasion, found to be dominant.Comment: 4 pages of text with 1 table and 5 figure

«Fragility» as a predictor of bleedings in elderly patients with atrial fibrillation taking direct oral anticoagulants

The purpose of the study is to assess the contribution of senile asthenia level to hemorrhagic complications quantity in elderly patients with atrial fibrillation (AF) taking direct oral anticoagulants (DOAC).Material and methods. Elderly patients &gt;75 y.o. with AF taking dabigatran, apixaban or rivaroxaban in full or reduced dosages and without special features of bleeding (such as double and triple antithrombotic therapy) were included in the study. If a patient was under anticoagulants before the study (but not earlier than one became 75 y.o.), this experience was also analyzed. All bleedings during the first 18 months of anticoagulating were taken in mind. Patients in different DOAC groups were comparable in age and concomitant pathology. The «fragility» index was evaluated at the stage of inclusion in the study; an adapted Rockwood scale was used.Results and discussion. 102 patients with AF &gt;75 y.o. taking dabigatran, apixaban or rivaroxaban in dosages corresponding to the instructions were included in the study. During the analyzed period, 19 small clinically significant hemorrhagic events that did not require hospitalization or cancellation of DOAC were recorded. Patients with and without bleeding in anamnesis were significantly differed only by «fragility» index score (р = 0,001). The differences between concomitant pathology level which are mentioned in scale, is also not statistically significant. The average age of patients with and without bleeding anamnesis was not also significantly different (p = 0.12). In the future, it is advisable to continue the study using several scales for assessing the severity of the «fragility» index. Thus, it is advisable to calculate the «fragility» index in patients &gt;75 years of age with AF taking DOAC

Josephson charge-phase qubit with radio frequency readout: coupling and decoherence

The charge-phase Josephson qubit based on a superconducting single charge transistor inserted in a low-inductance superconducting loop is considered. The loop is inductively coupled to a radio-frequency driven tank circuit enabling the readout of the qubit states by measuring the effective Josephson inductance of the transistor. The effect of qubit dephasing and relaxation due to electric and magnetic control lines as well as the measuring system is evaluated. Recommendations for operation of the qubit in magic points producing minimum decoherence are given.Comment: 11 pages incl. 6 fig

Quartz Reef from Gold Occurrences in Riphean Deposits of the Avzyan Ore Region (South Urals): Mineralogical and Thermocriometric Features

Жильный кварц из золотосульфидно-кварцевого месторождения Горный Прииск и золотокварцевых малосульфидных рудопроявлений Улюк-Бар и ВосточноАкташское имеет сходные температуры гомогенизации первичных флюидных включений (228–382°С) и солевой состав, в котором преобладают хлориды магния и калия. Солёность варьирует в интервале 5,4–15,8 мас. % NaCl экв. Его формирование обусловлено миграцией магматогенных флюидов в связи с тектонотермальным этапом на границе среднего и позднего рифея. Безрудный жильный кварц из вмещающих рифейских отложений характеризуется более низкими Тгом (128–238°С), преобладанием хлоридов железа в солевом составе и более высокой солёностью (12,9–22,8 мас. % NaCl экв.). В золотосульфидном проявлении Богряшка образование кварца, имеющего Тгом 152–292°С и преобладание хлоридов кальция и магния в составе солей, связаны с дорудным процессом магнезиальножелезистого метасоматоза.Quartz reefs from the gold-sulfide-quartz deposit Gorny Priisk and gold-quartz sulfide bearing ore occurrences Ulyuk-Bar and Vostochno-Aktashskoe have the similar temperatures of homogenization of primary fluid inclusions (228-382 ° C) and salt composition, in which magnesium and potassium chloride predominate. Salinity varies in the range of 5,4-15,8 wt. % NaCl equiv. Generation of gold- bearing quartz reefs was caused by the migration of magmatogene fluids connected with the tectono-thermal stage between the Middle and Late Riphean. Barren vein quartz from the host Riphean rocks is characterized by lower temperatures of homogenization (128-238 ° C), predominance of the iron chlorides in salt composition and higher salinity (12,9-22,8 wt% NaCl equiv.). The generation of quartz in the gold-sulphide ore occurrence Bogryashka, which have temperatures of homogenization of 152-292 ° C and the predominance of calcium and magnesium chlorides in the salts, is associated with the pre-ore process of magnesian-ferruginous metasomatism

Silicon nanobridge as a high quality mechanical resonator

The paper presents details of the fabricating technology of nanoscale mechanical resonators based on suspended silicon nanowires. The structures were made from silicon on insulator material, the thickness of the upper layer of silicon is 110 nm, the thickness of silicon oxide is 200 nm. Fabrication process contains standard CMOS compatible technologies only: Electron lithography with positive resist, reactive ion and liquid etching, electron beam deposition of thin films. The presented structures can be used as sensors of mass, displacement, acceleration, pressure with extremely high sensitivity

Механический резонанс в кремниевом нанопроводе с высокой добротностью

Resonance properties of nanomechanical resonators based on doubly clamped silicon nanowires, fabricated from silicon-on-insulator and coated with a thin layer of aluminum, were experimentally investigated. Resonance frequencies of the fundamental mode were measured at a temperature of $20\,\mathrm{mK}$ for nanowires of various sizes using the magnetomotive scheme. The measured values of the resonance frequency agree with the estimates obtained from the Euler-Bernoulli theory. The measured internal quality factor of the $5\,\mathrm{\mu m}$-long resonator, $3.62\times10^4$, exceeds the corresponding values of similar resonators investigated at higher temperatures. The structures presented can be used as mass sensors with an expected sensitivity $\sim 6 \times 10^{-20}\,\mathrm{g}\,\mathrm{Hz}^{-1/2}$

Sulfide mineralization, native gold and its geochemical connections in the Riphean deposits of the Avzyan ore-bearing region (the Southern Urals)

In the Avzyan ore-bearing region the sulfides from the low-sulfide gold-quartz deposits (Ulyuk-Bar, Kurgashly) are characterized by higher concentrations of As, Co, Ni, Cu, Pb in comparison with sulfides from sediments outside of ore-bearing zones. The gold is associated with As and sometimes - with S and Co. Gold-bearing sulfides are situated mostly in sandstones, where they were formed as a result of replacement of early formed ore-free pyrites by arsenopyrite and its association with arsenic pyrite during fluid movement ( Т = 250-450°С, Р = 26-360 bar) through fault zones. This process is fixed in the zonal distribution of arsenic pyrite and in varying behavior of total As in rocks. The proportion of p-type conduction pyrite increases with the depth, and zones of its development and high content of As in rocks are controlled by faults. The strong positive correlation of Au with S, Cu, Co, Pb, Ni, Zn is marked at the gold-sulfide (Bogryashka) and gold-sulfide-quartz (Gorny Priisk) occurrences. The connection of Au with As is not clear. At the Bogryashka occurrence pyrites are characterized by high concentrations of Sb, at the Vostochno-Aktashskoe occurrence - by Co and V. The gold in the Gorny Priisk ore deposit and in the Bogryashka occurrence is characterized by high ratio Au/Ag (>21) and impurity of Bi (0.4-1.2 wt %). The ratio Au/Ag is 5-8 in the gold from the Ulyuk-Bar and the Vostochno-Aktashskoe occurrences. Native gold in the Ulyuk-Bar and the Bogryashka occurences is associated with uranium-thorium minerals