Sunday, November 19, 2017

Nano-'hashtags' could be the key to generating the highly sought Majorana quasiparticle

Finding Majoranas
Deterministic growth of InSb nanowire networks. Credit: University of California - Santa Barbara

UC Santa Barbara scientists are on the cusp of a major advance in topological quantum computing.

In a paper that appears in the journal Nature, Chris Palmstrøm, a UCSB professor of electrical and computer engineering and of materials, and colleagues describe a method by which "hashtag"- shaped nanowires may be coaxed to generate Majorana quasiparticles. These quasiparticles are exotic states that if realized, can be used to encode information with very little risk of decoherence—one of quantum computing's biggest challenges—and thus, little need for .


"This was a really good step toward making things happen," said Palmstrøm. In 2012, Dutch scientists Leo Kouwenhoven and Erik Bakkers (also authors on the paper) from the Delft and Eindhoven Universities of Technology in the Netherlands, reported the first observation of states consistent with these quasiparticles. At the time, however, they stopped short of definitive proof that they were in fact the Majoranas, and not other phenomena.

Under the aegis of Microsoft Corporation's Research Station Q headquartered on the UCSB campus, this team of scientists is part of a greater international effort to build the first topological quantum computer.


The quasiparticles are named for Italian physicist Ettore Majorana, who predicted their existence in 1937, around the birth of quantum mechanics. They have the unique distinction of being their own antiparticles—they can annihilate one another. They also have the quality of being non-Abelian, resulting in the ability to "remember" their relative positions over time—a property that makes them central to topological quantum computation.
"If you are to move these Majoranas physically around each other, they will remember if they were moved clockwise or anticlockwise," said Mihir Pendharkar, a graduate student researcher in the Palmstrøm Group. This operation of moving one around the other, he continued, is what is referred to as "braiding." Computations could in theory be performed by braiding the Majoranas and then fusing them, releasing a poof of energy—a "digital high"—or absorbing energy—a "digital low." The information is contained and processed by the exchange of positions, and the outcome is split between the two or more Majoranas (not the quasiparticles themselves), a topological property that protects the information from the environmental perturbations (noise) that could affect the individual Majoranas.
However, before any braiding can be performed, these fragile and fleeting quasiparticles must first be generated. In this international collaboration, semiconductor wafers started their journey with patterning of gold droplets at the Delft University of Technology. With the gold droplets acting as seeds, Indium antimonide (InSb) semiconductor nanowires were then grown at the Eindhoven University of Technology. Next, the nanowires traveled across the globe to Santa Barbara, where Palmstrøm Group researchers carefully cleaned and partially covered them with a thin shell of superconducting aluminum. The nanowires were returned to the Netherlands for low temperature electrical measurements.
"The Majorana has been predicted to occur between a superconductor and a semiconductor wire," Palmstrøm explained. Some of the intersecting wires in the infinitesimal hashtag-shaped device are fused together, while others barely miss one another, leaving a very precise gap. This clever design, according to the researchers, allows for some regions of a nanowire to go without an aluminum shell coating, laying down ideal conditions for the measurement of Majoranas.
"What you should be seeing is a state at zero energy," Pendharkar said. This "zero-bias peak" is consistent with the mathematics that results in a particle being its own antiparticle and was first observed in 2012. "In 2012, they showed a tiny zero-bias blip in a sea of background," Pendharkar said. With the new approach, he continued, "now the sea has gone missing," which not only clarifies the 2012 result and takes the researchers one step closer to definitive proof of Majorana states, but also lays a more robust groundwork for the production of these quasiparticles.
Majoranas, because of their particular immunity to error, can be used to construct an ideal qubit (unit of quantum information) for , and, according to the researchers, can result in a more practicable quantum computer because its fault-tolerance will require fewer qubits for error correction.
"All quantum computers are going to be working at very low temperatures," Palmstrøm said, "because 'quantum' is a very low energy difference." Thus, said the researchers, cooling fewer fault-tolerant qubits in a  circuit would be easier, and done in a smaller footprint, than cooling more error-prone qubits plus those required to protect from error.
The final step toward conclusive proof of Majoranas will be in the braiding, an experiment the researchers hope to conduct in the near future. To that end, the scientists continue to build on this foundation with designs that may enable and measure the outcome of braiding.
"We've had the funding and the expertise of people who are experts in the measurements side of things, and experts in the theory side of things," Pendharkar said, "and it has been a great collaboration that has brought us up to this level."
Source:PHYS
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Monday, October 30, 2017

Schottky and pn junction cryogenic radiation detectors made of p-InSb compound semiconductor

Abstract

Schottky and pn junction detectors were fabricated with p-InSb. Fabrication methods, energy spectra of 241Am alpha particles and rise times are shown. We could observe pulses at operating temperatures up to 77 and 115 K for the Schottky and the pn junction detectors, respectively.

PACS


29.40.W
07.85.F

Keywords


Radiation detector;
Semiconductor;
Insb;


Source:DirectDirect

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Sunday, October 22, 2017

Growth of one-dimensional InSb nanostructures with controlled orientations on InSb substrates by MOCVD

Highlights

Single crystalline InSb nanowires with high uniformity have been obtained on InSb substrate.
We realized controllable growth orientation of InSb nanowire by MOCVD.
A vapor-solid-solid growth of mode was attributed to the InSb nanowire growth.
The prepared InSb NWs show promise for future application in nanoelectronic devices.

Abstract

We have synthesized InSb nanorods on InSb substrates by using metal-organic chemical vapor deposition (MOCVD). It is found that the crystal orientation of the substrate plays a remarkable role in controlling growth orientation of the InSb nanorods. On a [100]-oriented InSb substrate, the nanorods tend to lie on the substrate along its [1–10]-axis. In comparison, [111]-oriented InSb substrates tend to promote the vertical growth of InSb nanowires and free-standing InSb nanowires are consequently obtained. The evolutions of diameter and length of the nanowires on InSb (111) substrates as a function of growth temperatures, T, and input V/III source ratios, rV/III, provide the optimized growth condition, i.e., T = 400 °C and rV/III = 50. The orientated growth of one-dimensional InSb nanostructures is discussed and analized by employing a vapor-solid-solid (VSS) growth mechanism.
Image 1

Keywords

Nanostructures
InSb
III-V Semiconductors
Metal-organic chemical vapor deposition

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The role of impurity band conduction in the low temperature characteristics of thin InSb films grown by molecular beam epitaxy

Abstract

We report on the temperature-dependent electrical properties of high-quality undoped InSb layers of various thicknesses grown on GaAs(100) substrates by molecular beam epitaxy. The layers are found to be n-type in the measured temperature range (77–297 K). A differential Hall approach was employed to characterize the depth dependence of the electrical properties of the InSb films. The temperature variations of these data were then modelled with the inclusion of conduction through an impurity band, formed by the overlap of the wavefunctions of the dislocation-related donors. These analyses suggest that the contribution of the impurity band is dominant close to the interface even at room temperature, but its effect falls with increasing thickness, until at ~1000 nm, its contribution is only comparable to that of the conduction band at low temperatures. The dislocation donor densities deduced from this modelling follow an approximately reciprocal trend with increasing distance from the interface.
Source:IOPscience
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Monday, September 25, 2017

Heteroepitaxial growth of InSb(111) on Si(111)

Abstract

Heteroepitaxial growth of InSb( 111) films on Si( 111 ) was investigated using two-step growth: heteroepitaxial interface growth (HIG) and InSb surface growth ( ISG). An Si ( 111 ) substrate with a hydrogen-terminated surface was prepared and introduced into the deposition chamber. In and Sb were evaporated from independent Knudsen cells. In was supplied to the 300 °C substrate without Sb to grow thin In layers at the initial stage of HIG. Then Sb was supplied and InSb film was grown continuously under the supply of In and Sb. Heteroepitaxial crystallites with directions InSb[111]∥Si[111] and InSb[1̄10]∥Si[1̄10] or InSb[11̄0]∥Si[1̄10] were formed after HIG. The 25 nm thick InSb(111) heteroepitaxial film on Si(111) formed by HIG was grown further at the higher substrate temperature of 430 °C by ISG. InSb films with a total thickness of approximately 3 µm were formed after the HIG and ISG. The reflection high energy electron diffraction (RHEED) patterns of the deposited film showed clear streaks of InSb( 111) with Kikuchi patterns. A single-domain InSb film with a smooth InSb( 111) surface was grown without a buffer layer. A room temperature electron mobility of 49 300 cm2 V−1 s−1 was measured for the heteroepitaxial InSb( 111 ) /Si( 111 ) film.

Keywords

Heteroepitaxial growth
InSb

Source:ScienceDirect
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Wednesday, September 6, 2017

Quantum well band formation in Ag films on InSb(111)

Abstract

Room temperature deposition of Ag on InSb(111) is known to lead to three-dimensional clustering, without long-range crystalline order. We show by means of angle-resolved photoemission that 'two-step' growth in which the films are annealed to room temperature after low temperature deposition results in the formation of Ag films which are epitaxial, atomically flat, and display a quasi-discrete quantum well band structure. Core level analysis highlights different chemical interactions between the substrate and deposited materials for room temperature and 'two-step' Ag growth.
Source:IOPscience
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Sunday, August 13, 2017

Recent progress in InSb based quantum detectors in Israel

Abstract

InSb is a III–V binary semiconductor material with a bandgap wavelength of 5.4 μm at 77 K, well matched to the 3–5 μm MWIR atmospheric transmission window. When configured as a Focal Plane Array (FPA) detector, InSb photodiodes offer a large quantum efficiency, combined with excellent uniformity and high pixel operability. As such, InSb arrays exhibit good scalability and are an excellent choice for large format FPAs at a reasonable cost. The dark current is caused by Generation–Recombination (G–R) centres in the diode depletion region, and this leads to a typical operating temperature of ∼80 K in detectors with a planar implanted pn junction. Over the last 15 years SCD has developed and manufactured a number of different 2-dimensional planar FPA formats, with pitches in the range of 15–30 μm.
In recent years a new epi-InSb technology has been developed at SCD, in which the G–R contribution to the dark current is reduced. This enables InSb detector operation at 95–100 K, with equivalent performance to standard InSb at 80 K. In addition, using a new patented XBnn device architecture in which the G–R current is totally suppressed, epitaxial InAsSb detectors have been developed with a bandgap wavelength of 4.2 μm, which can operate in the 150–170 K range.
In this short review of the past two decades, a number of key achievements in SCD’s InSb based detector development program are described. These include High Operating Temperature (HOT) epi-InSb FPAs, large format megapixel FPAs with high functionality using a digital Read Out Integrated Circuit (ROIC), and ultra low Size, Weight and Power (SWaP) FPAs based on the HOT XBnn architecture.

Keywords

Infrared detector
Focal plane array
InSb
Bariode
InAsSb
XBn

Source:ScienceDirect
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Thursday, August 10, 2017

InAs/InSb nanowire heterostructures grown by chemical beam epitaxy

Abstract

We report the Au-assisted chemical beam epitaxy growth of defect-free zincblende InSb nanowires. The grown InSb segments are the upper sections of InAs/InSb heterostructures on InAs(111)B substrates. We show, through HRTEM analysis, that zincblende InSb can be grown without any crystal defects such as stacking faults or twinning planes. Strain-map analysis demonstrates that the InSb segment is nearly relaxed within a few nanometers from the interface. By post-growth studies we have found that the catalyst particle composition is AuIn2, and it can be varied to a AuIn alloy by cooling down the samples under TDMASb flux.
Source:IOPscience
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Tuesday, August 1, 2017

RESEARCH NOTES Strain energy of (111) and ([111 over bar]) surfaces of InSb

Abstract

The strain energies per unit area of polished (0.1 μm powder) surfaces of InSb have been computed from the observed curvature of thin wafers polished on one side and etched on the other, as being of order 1 erg cm-2. These values are much larger than those computed by others from InSb wafers treated similarly on both sides and are ascribed only indirectly to surface bonding configurations.

Source:IOPscience

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Thursday, July 27, 2017

High Resistivity InSb Crystal Growth using the Vertical Bridgman Method for Fabrication of Schottky Diodes

Abstract

Compound semiconductor InSb crystals were grown using raw materials with different purities, for application as radiation detector substrates. The electrical properties of the grown crystals were compared with those of commercial InSb wafers. The resistivity of the grown crystals prepared from 99.9999% purity raw materials showed a higher value than those of commercial crystals.
Source: Iopscience
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Wednesday, July 19, 2017

THz Wave Modulator Based on the Decay of THz Surface Plasmon along an Intrinsic InSb Surface

Abstract

THz surface plasmon are decayed exponentially when propagating along the surface of a semiconductor. A metal razor bladeis used to couple THz surface plasmon to THz waves at different position on the surface of an indium antimonide wafer. Thus the intensity of the output THz wave is modulated.
Keywords:InSb wafer,
Source: Iopscience
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Monday, July 10, 2017

Brolis Semiconductors Ltd. Receives Shipment of Veeco MBE Production System

Brolis Semiconductors Ltd. and Veeco Instruments Inc. (Nasdaq: VECO) announced today that Brolis has received shipment of a Veeco GEN200® Edge™ Molecular Beam Epitaxy (MBE) production system for installation at their new epitaxial wafer production facility in Vilnius, Lithuania.

Dominykas Vizbaras, CEO of Brolis, commented, “The mission of our company is to become a world-leading provider of complex epitaxial structures for long-wave optoelectronics, such as thermal imaging, concentrator photovoltaic and other custom devices. Veeco is the world’s leading provider of production MBE systems, so we anticipate that the GEN200 will enable us to be extremely competitive in terms of wafer quality, speed to market, and cost effectiveness of our products.”
Jim Northup, Vice President and General Manager of Veeco’s MBE Operations, commented, “We are pleased Brolis has chosen Veeco as their MBE equipment supplier as they open their new state-of-the-art epitaxial manufacturing fab. The GEN200 will support Brolis’ market penetration goals with its production-proven performance and the industry’s lowest cost of ownership.”

About the Veeco GEN200 Edge MBE System

The most cost-effective and highest-capacity multi-4" production MBE system in the market today, the Veeco GEN200 Edge MBE System delivers superior throughput, long campaigns and excellent wafer quality in growing epitaxial wafers for custom devices.

About Brolis Semiconductors Ltd
Brolis Semiconductors Ltd. manufactures type-I GaSb laser diodes for wavelength range 1800nm – 4000nm and offers high-throughput MBE service of arsenides and antimonides on GaSb, InSb, InAs, GaAs and InP substrates. Our key technologies include growth of mixed group-V antimonides and quinternary heterostructures, which is very important for most infrared optoelectronic device applications such as type-II superlattice FPAs, GaSb laser diodes, tunnel junction devices, etc.


SOURCE:LEDinside

If you need more information about InSb wafer,please visit our website:www.powerwaywafer.com/Indium-Semiconductor-wafer.html or send us email to  powerwaymaterial@gmail,com

Brolis Semiconductors Ltd. Receives Shipment of Veeco MBE Production System

Brolis Semiconductors Ltd. and Veeco Instruments Inc. (Nasdaq: VECO) announced today that Brolis has received shipment of a Veeco GEN200® Edge™ Molecular Beam Epitaxy (MBE) production system for installation at their new epitaxial wafer production facility in Vilnius, Lithuania.

Dominykas Vizbaras, CEO of Brolis, commented, “The mission of our company is to become a world-leading provider of complex epitaxial structures for long-wave optoelectronics, such as thermal imaging, concentrator photovoltaic and other custom devices. Veeco is the world’s leading provider of production MBE systems, so we anticipate that the GEN200 will enable us to be extremely competitive in terms of wafer quality, speed to market, and cost effectiveness of our products.”
Jim Northup, Vice President and General Manager of Veeco’s MBE Operations, commented, “We are pleased Brolis has chosen Veeco as their MBE equipment supplier as they open their new state-of-the-art epitaxial manufacturing fab. The GEN200 will support Brolis’ market penetration goals with its production-proven performance and the industry’s lowest cost of ownership.”

About the Veeco GEN200 Edge MBE System

The most cost-effective and highest-capacity multi-4" production MBE system in the market today, the Veeco GEN200 Edge MBE System delivers superior throughput, long campaigns and excellent wafer quality in growing epitaxial wafers for custom devices.

About Brolis Semiconductors Ltd
Brolis Semiconductors Ltd. manufactures type-I GaSb laser diodes for wavelength range 1800nm – 4000nm and offers high-throughput MBE service of arsenides and antimonides on GaSb, InSb, InAs, GaAs and InP substrates. Our key technologies include growth of mixed group-V antimonides and quinternary heterostructures, which is very important for most infrared optoelectronic device applications such as type-II superlattice FPAs, GaSb laser diodes, tunnel junction devices, etc.


SOURCE:iopscience

If you need more information about InSb wafer,please visit our website:www.powerwaywafer.com/Indium-Semiconductor-wafer.html or send us email to  powerwaymaterial@gmail,com

Friday, July 7, 2017

Diamond turning of small Fresnel lens array in single crystal InSb

Abstract

A small Fresnel lens array was diamond turned in a single crystal (0 0 1) InSb wafer using a half-radius negative rake angle (−25°) single-point diamond tool. The machined array consisted of three concave Fresnel lenses cut under different machining sequences. The Fresnel lens profiles were designed to operate in the paraxial domain having a quadratic phase distribution. The sample was examined by scanning electron microscopy and an optical profilometer. Optical profilometry was also used to measure the surface roughness of the machined surface. Ductile ribbon-like chips were observed on the cutting tool rake face. No signs of cutting edge wear was observed on the diamond tool. The machined surface presented an amorphous phase probed by micro Raman spectroscopy. A successful heat treatment of annealing was carried out to recover the crystalline phase on the machined surface. The results indicated that it is possible to perform a 'mechanical lithography' process in single crystal semiconductors.
Keywords:InSb wafer,
SOURCE:iopscience
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Tuesday, June 27, 2017

Ion irradiation-induced bimodal surface morphology changes in InSb

High-energy ion irradiation of InSb results in the formation of bimodal surface structures, namely microscale hillock-like structures fully composed of nanoscale fibers. Analysis of the surface structures by a wide range of electron microscopy techniques reveals correlations between the irradiation conditions, such as the ion energy and fluence, and changes in the surface morphology. Sputtering effects play a key role in the integrity of the surface layer with increasing ion fluence. Possible mechanisms responsible for the morphological transformation are discussed, including both irradiation-induced and mechanical effects.

Keywords:InSb;

SOURCE:iopscience

If you need more information about InSb wafer,please visit our website:www.powerwaywafer.com/Indium-Semiconductor-wafer.html or send us email to  powerwaymaterial@gmail,com