Showing papers by "Alexei O. Orlov published in 2014"
TL;DR: In this paper, a template-assisted combustion-based method was developed to synthesize the ultrasmall (below 5 nm) α-Fe2O3 nanoparticles, where iron and ammonium nitrate were used as oxidizers, glycine as a "fuel" and mesoporous silica (SBA-15) as a template.
Abstract: A template-assisted combustion-based method is developed to synthesize the ultrasmall (below 5 nm) α-Fe2O3 nanoparticles. The iron and ammonium nitrate are used as oxidizers, glycine as a “fuel” and mesoporous silica (SBA-15) as a template. Because of the ultralow sizes and high crystallinity, the combustion-derived α-Fe2O3 nanoparticles exhibit superparamagnetism in the temperature range of 70–300 K. The high specific surface area (132 m2/g) of α-Fe2O3 indicates the important role of surface magnetic spins resulting in remarkably high magnetization (21 emu/g) at 300 K.
104 citations
TL;DR: In this article, a shape-engineered monometallic thermocouple was constructed from a lithographically defined nanowire having one abrupt variation in width along its length and tested at room temperature; these structures exploited a change in Seebeck coefficient that is present at these size scales.
Abstract: We study the generation of thermoelectricity by nanoscale thermocouples (TCs) formed from a single layer of metal with cross-sectional discontinuity. Typically, a TC is formed when a second conductor is inserted between two sections of a first conductor forming two junctions situated at different temperatures. Here, we investigate the behavior of TCs formed not of two conductors but rather nanowires of the same metal of two cross-sectional areas. Monometallic TCs were constructed from a lithographically defined nanowire having one abrupt variation in width along its length, and tested at room temperature; these structures exploit a change in Seebeck coefficient that is present at these size scales. To investigate the thermoelectric properties of such “shape-engineered” TCs, nanoscale heaters were employed to set the local temperatures. Temperature profiles at the hot and cold junctions of the TCs were determined both by simulations and experiments. Results demonstrate that the magnitude of the open-circuit voltage, and hence the relative Seebeck coefficient, is a function of the parameters of the variations in the segment widths. The fabrication complexity of such shape-engineered monometallic nanowire TCs is greatly reduced compared to that of conventional bimetallic TCs, and could be mass-produced using simpler manufacturing techniques.
46 citations
TL;DR: In this article, the authors used a radiofrequency reflectometry technique to detect changes in the charge state of a capacitively coupled trap, in very close agreement with modeling of the trap's occupation probability.
Abstract: The continuous downscaling of transistors results in nanoscale devices which require fewer and fewer charged carriers for their operation. The ultimate charge controlled device, the single-electron transistor (SET), controls the transfer of individual electrons. It is also the most sensitive electrometer, and as a result the electron transport through it can be dramatically affected by nearby charges. Standard direct-current characterization techniques, however, are often unable to unambiguously detect and resolve the origin of the observed changes in SET behavior arising from changes in the charge state of a capacitively coupled trap. Using a radio-frequency (RF) reflectometry technique, we are able to unequivocally detect this process, in very close agreement with modeling of the trap's occupation probability.
25 citations
01 Jan 2014
TL;DR: The background and evolution of the work on magnetic implementations of Quantum-Dot Cellular Automata, first called Magnetic QCA, and now known as Nanomagnet Logic (NML), are described.
Abstract: We describe the background and evolution of our work on magnetic implementations of Quantum-Dot Cellular Automata (QCA), first called Magnetic QCA (MQCA), and now known as Nanomagnet Logic (NML).
13 citations
01 Jan 2014
TL;DR: It was Cowburn who first realized that the properties of nanoscale, single-Domain magnets - which are very different from large, multi- Domain magnets - are well suited for digital computing.
Abstract: Magnetic computing–in the broadest sense–is about using magnetic signals (nanomagnets,
domain walls) to represent and process information. Nowadays, when “information
processing” and “electronics” is synonymous, this concept sounds rather exotic. However,
before the triumphant era of CMOS logic devices, non-charge based computers were
serious candidates for information processing–for example, ingenious magnetic computing
circuits were invented by RJ Spain [1–3]. It was Cowburn [4] who first realized that the properties of nanoscale, single-Domain magnets - which are very different from large, multi-Domain magnets - are well suited for digital computing.
7 citations
Proceedings Article•
12 Mar 2014TL;DR: This paper combines previous work on antenna-coupled thermocouples with a new approach to near-??eld- coupled nano-antennas, which might open up the possibility of obtaining carrier phase a?er envelope demodulation.
Abstract: Infrared detectors for the long-wave infrared range (??LWIR) are of special interest due to their ability to detect black-body radiation of objects at room temperature. Such detectors are attractive candidates for various applications including energy harvesting, target tracking, and thermal imaging, but their applications to communication systems have been largely unexplored. In this paper, we combine our previous work on antenna-coupled thermocouples with a new approach to near-??eld-coupled nano-antennas, which might open up the possibility of obtaining carrier phase a?er envelope demodulation.
7 citations
TL;DR: Sun et al. as mentioned in this paper demonstrate that the observed phenomenon is not due to a size-dependent Seebeck effect, but is rather wire-size-dependent heat transport that causes unequal heating at the bonding pads.
Abstract: In a recent article, Sun et al. [J. Appl. Phys. 110, 083709 (2011)] claim to measure a size-dependent thermoelectric effect in a micron-scale single-metal thermocouple. In this Comment, we demonstrate that the observed phenomenon is not due to a size-dependent Seebeck effect as claimed, but is rather wire-size-dependent heat transport that causes unequal heating at the bonding pads. As a result, the bonding pads are at two different temperatures, and the observed voltage corresponds to a thermoelectric effect of a parasitic thermocouple formed between their metal structure and the bonding-pad wires. We provide simulations and suggest a control experiment based on their structure that supports our contention that the observation depends on width-dependent heat transport in the wires.
6 citations
TL;DR: In this paper, a combination of 30% H2O2 solution and an alumina based slurry in 1:3 volumetric ratio along with added sodium dodecyl sulfate and poly(vinyl pyrrolidone) was successfully used to pattern gold in a CMP Damascene process.
Abstract: In this article, the authors investigate chemical mechanical planarization (CMP) of gold. Our experiments show that the oxidizer concentration, hardness of the adhesion layer, and surfactants added to stabilize the slurry are the main factors determining the outcome of the process. A combination of 30% H2O2 solution and an alumina based slurry in 1:3 volumetric ratio along with added sodium dodecyl sulfate and poly(vinyl pyrrolidone) was successfully used to pattern gold in a CMP Damascene process. After fabricating inlaid gold structures with CMP, the authors observed that pattern density, as opposed to feature size, is the major factor in determining the amount of metal thinning in inlaid features. 10 μm lines at 5% density were thinned down by 40 nm, while 150 μm pads at 75% density were recessed by 20 nm. The authors believe that in this process, metal recess, that is a chemical effect, outweighs dishing, a feature-size dependent factor, in controlling the severity of metal thinning.
4 citations
08 Jun 2014
TL;DR: In this paper, the polarization-dependent response of antenna-coupled single-metal thermocouples for infrared (IR) detection was investigated and it was shown that the observed open-circuit voltage response changes polarity as a function of the polarization angle of the incident radiation.
Abstract: We report on the polarization-dependent response of antenna-coupled single-metal thermocouples for infrared (IR) detection. We find that for certain antenna geometries, the observed open-circuit voltage response changes polarity as a function of the polarization angle of the incident radiation. This behavior is due to a change in the location of the hot junction as the polarization of the incident IR radiation rotates from the co-polarized to the cross-polarized state.
3 citations
22 Jun 2014
TL;DR: In this article, a bi-metallic antenna-coupled infrared thermocouple was proposed for the long-wave infrared range (LWIR) with a comparison between the two types of detectors.
Abstract: Infrared detectors in the long-wave infrared range (LWIR) are of special interest since they are sensitive to blackbody radiation of objects at room temperature, with a wide range of applications. In previous work, we have reported bi-metallic antenna-coupled infrared detectors for the LWIR [1], and here we report novel mono-metallic antenna-coupled infrared detectors, as well as a comparison between the two. Such antenna-coupled thermocouples are promising candidates for various applications including energy harvesting [2], target tracking [3], and thermal imaging. These detectors operate without the need of any bias or cooling. The antenna design determines the resonant frequency, directivity, and polarization of these detectors.
3 citations
01 Dec 2014
TL;DR: Polarization-sensitive, antenna-coupled, monometallic thermocouples were designed, fabricated, and studied for long-wave infrared radiation in this paper, where the receiving nano-antenna was integrated into the thermocouple, and thermopiles comprising a series combination of ten nanoantennas were constructed.
Abstract: Polarization-sensitive, antenna-coupled, monometallic thermocouples were designed, fabricated, and studied for long-wave infrared radiation. The receiving nanoantenna was integrated into the thermocouple, and thermopiles comprising a series combination of ten nanoantennas were constructed. The response showed a cosine square polarization dependence, as expected from antenna theory.
TL;DR: In this article, a clock/logic/input structure for nanomagnetic logic (NML) was proposed that implements a two-input slant-based OR gate with both clocking and input programming through current pulses.
Abstract: We report a clock/logic/input structure for nanomagnet logic (NML) that implements a two-input slant-based OR gate with both clocking and input programming through current pulses. The clock line is a copper conductor embedded in a Si substrate with CoFe as a flux concentrator. Inputs are implemented with overlaid and dedicated bias lines. The programmability of such inputs allows us to test the same NML device for all possible input combinations. Results are determined by magnetic force microscopy. This scheme is easy to fabricate and can control thicker (20-30 nm) input nanomagnets. Close proximity of bias lines in such a structure allows us to investigate the effect of overlapping bias fields. We also report micromagnetic simulations that relate the slant in the output magnet to the dimensions of the input nanomagnets required to effect proper logic operation.
Patent•
16 May 2014TL;DR: In this paper, the authors describe a thermocouple made of a single material and shape-engineered to contain one or more variations in their width along their length, which exploit a difference in the Seebeck coefficient that is present at these size scales.
Abstract: Nanoscale thermocouples are made of a single material and are shape-engineered to contain one or more variations in their width along their length. The mono-metallic nanowire junctions resulting from the width variation(s) exploit a difference in the Seebeck coefficient that is present at these size scales. Such devices have a wide variety of uses and can be coupled with an antenna in order to serve as an infrared detector.
01 Dec 2014
TL;DR: In this paper, a dual channel reflectometry technique was used to identify charging processes in nanoscale Si single-electron transistors (SETs) by analyzing signals reflected from the drain and the gate of the SETs.
Abstract: We demonstrate a novel dual channel reflectometry technique for identification of charging processes in nanoscale Si single-electron transistors (SETs). By analyzing signals reflected from the drain and the gate of the SET we are able to pinpoint the details of single electron charging in the SET island and in the charged defects nearby.
22 Jun 2014
TL;DR: In this paper, the authors used a dual channel technique that enables spatial identification of charging processes within a single-hole transistors (SHT) to solve the problem of where the first charge carriers spatially accumulate during the formation of the conducting island.
Abstract: Si CMOS single-electron transistors (SET) fabricated using fully depleted SOI [1] enable an understanding of charging mechanisms in ultimately scaled CMOS devices down to a transport through a single dopant [2]. A schematic representation of such a device is shown in Fig 1. Radio-frequency (RF) reflectometry [3] is an effective tool for charge detection in various single-electron systems. Since it does not require any DC current flow the detection of electrons passing even through a single tunnel junction [4] is possible. When a Si SET is populated with electrons, one intriguing question need to be answered: where do the first charge carriers spatially accumulate during the formation of the conducting “island”? To address this issue we use a dual channel technique that enables spatial identification of charging processes within the device. Here we present results obtained using this technique for single-hole transistors (SHT). A micrograph of a typical studied SHT device.
08 Jun 2014
TL;DR: In this paper, the authors apply radiofrequency reflectometry (RFR) to nanowire silicon-on-insulator (SOI) single-electron transistors with a novel experimental configuration in which RFR is performed simultaneously at both the drain and gate of the device.
Abstract: We apply radio-frequency reflectometry (RFR) to nanowire Silicon-On-Insulator (SOI) single-electron transistors with a novel experimental configuration in which RFR is performed simultaneously at both the drain and gate of the device. We use this technique to investigate the effects of back-gating on the measured RFR characteristics of the SETs, and discuss possible experimental limitations of this technique.