Tag: silicon

Nanoislands on silicon with switchable topological textures

Nanoislands on silicon with switchable topological textures

Nanostructures with specific electromagnetic patterns promise applications in nanoelectronics and future information technologies. However, it is very challenging to control those patterns. Now, a team at HZB examined a specific class of nanoislands on silicon with interesting chiral, swirling polar textures, which can be stabilised and even reversibly switched by an external electric field.

Ferroelectrics at the nanoscale exhibit a wealth of polar and sometimes swirling (chiral) electromagnetic textures that not only represent fascinating physics, but also promise applications in future nanoelectronics. For example, ultra-high-density data storage or extremely energy-efficient field-effect transistors. However, a sticking point has been the stability of these topological textures and how they can be controlled and steered by an external electrical or optical stimulus.

New perspectives:

A team led by Prof. Catherine Dubourdieu (HZB and FU Berlin) has now published a paper in Nature Communications that opens up new perspectives. Together with partners from the CEMES-CNRS in Toulouse, the University of Picardie in Amiens and the Jozef Stefan Institute in Ljubljana, they have thoroughly investigated a particularly interesting class of nanoislands on silicon and explored their suitability for electrical manipulation.

Nanoislands on silicon

“We have produced BaTiO3 nanostructures that form tiny islands on a silicon substrate,” explains Dubourdieu. The nano-islands are trapezoidal in shape, with dimensions of 30–60 nm (on top), and have stable polarisation domains. “By fine tuning the first step of the silicon wafer passivation, we could induce the nucleation of these nanoislands,” says Dong-Jik Kim, a scientist in Dubourdieu’s team.

Read more on HZB website

Image: Artistic representation of the center down-convergent polarization field. It results from the compression of the polarization flux by the sidewalls of the nanoislands. The texture in each nanoisland resembles a swirling vortex of liquid flowing into a narrowing funnel.

Credit: Laura Canil /HZB

Quantum computers in silicon

Quantum computers in silicon

Development of a new European quantum technology begins

The EQUSPACE consortium (Enabling New Quantum Frontiers with Spin Acoustics in Silicon) has received 3.2 million euros from the European Innovation Council’s (EIC) Pathfinder Open funding program to advance the development of silicon-based quantum technologies. In addition to the Helmholtz-Zentrum Dresden-Rossendorf (HZDR), the project brings together four other partners from three EU countries and convenes experts from the fields of spin qubits, optomechanics and atomic silicon modifications to develop a novel silicon-based quantum platform.

Although silicon is the central material for classic computers, it does not play a key role in the currently favored quantum computer concepts. However, it would make a lot of sense to use the multi-billion euro silicon infrastructure already developed with semiconductor technology to process qubits – the quantum mechanical information units. Researchers have shown that so-called donor spin qubits are actually particularly well suited for this endeavor. These qubits use a property of impurity atoms, their spin, to process information. Compared to other quantum systems, they are characterized by long periods of time over which they remain stable in order to perform quantum mechanical computing operations. Currently, however, they are not the workhorse of commercial quantum computers, as there are no suitable coupling and readout mechanisms that could be used to scale them up to a practically usable level.

EQUSPACE now aims to create a long-term future for silicon-based donor spin qubits in Europe. The platform makes an effort to connect the qubits, which are based on tiny atomic spins, via sound waves in vibrating structures. Lasers and single-electron transistors will also be used to electrically read out the result at the end of the quantum mechanical calculation. The project seeks to provide a scalable solution for all important aspects of a quantum platform: the control and readout of the result, the spin-spin coupling between qubits, and the transmission of quantum information between computing units on the chip. The final outcome could be a complete quantum information platform that includes qubits, interconnects and scalable control and readout electronics.

HZDR expertise in silicon quantum technology

A team from the Institute of Ion Beam Physics and Materials Research at HZDR will contribute its expertise in the atomic modification of silicon for quantum applications and further develop the materials science methods required as a basis for the project. The team will use a focused ion beam to locally enrich ultra-pure silicon with the isotope silicon-28. Compared to many other materials, silicon-28 has the advantage that its atomic nuclei have no spin that could interact with magnetic fields or the spin of other particles and thus interfere with the calculations. “Through the targeted enrichment with special isotopes, the quantum state remains stable for longer timespans. This allows more complex quantum operations, and the platform could thus outperform classical computers and other quantum computer systems in the future,” says HZDR project manager Dr. Nico Klingner.

In addition to isotope purification, the team is developing the single-ion implantation of donor atoms. The aim is to implant individual bismuth atoms whose spin forms a two-state system that can point either “up” or “down”. The special feature of qubits is that at very low temperatures, both states can exist simultaneously in superpositions: the spin can be in a combination of the “up” and “down” states at the same time. This allows quantum computers to perform many calculations in parallel, which can drastically increase their computing power.

One of the main advantages of donor spin qubits is their relative stability compared to other types of qubits, for example those based on superconducting circuits. The spin in a donor atom is less susceptible to perturbations from the environment, so the quantum state can be maintained over longer periods of time. This stability is essential for scaling quantum computers to a larger number of qubits without losing coherence or precision of computations. “These contributions from HZDR, especially in the areas of isotope purification, implantation and strain engineering in semiconductors, are fundamental to the success of the EQUSPACE project,” states Professor Juha Muhonen, the coordinator of the project.

Read more on HZDR website

Image: In the single ion implanter TIBUSSII (Triple Ion Beam UHV System for Single Ion Implantation), individual dopants can be implanted atom by atom into a material, for example to generate qubits.

Credit: B. Schröder / HZDR

Ultrafast all-optical spin injection in silicon revealed at FERMI

Ultrafast all-optical spin injection in silicon revealed at FERMI

A revolutionary and energy-efficient information technology encoding digital data in electron spin (spintronics) by combining semiconductors and ferromagnets is being developed worldwide. Merging of memory and logic computing of magnetic based storage devices and silicon-based logic transistors is expected to ultimately lead to new computing paradigms and novel spin-based multifunctional devices. The advantages of this new technology would be non-volatility, increased data processing speed, reduced electric power consumption. All of them are essential steps towards next generation quantum computers.

To create spin-based electronics with potential to revolutionize information technology, silicon, the predominant semiconductor, needs to be integrated with spin functionality. Although silicon is non-magnetic at equilibrium, spin polarized currents can be established in Si by a variety of approaches such as the use of polarized light, hot electrons spin injection, tunnel spin injection, Seebeck spin tunneling and dynamical spin pumping methods, as had been demonstrated recently. In general, spin polarized currents refer to the preferential alignment of the spin angular momentum of the electrons in a particular direction.

Read more on the Elettra website

Image: Figure 1: a) the optical generation of spin polarized superdiffusive currents across a ferromagnetic/semiconductor interface is illustrated. b) the principles of TR-MOKE experiment are illustrated  together with a cross-section TEM image describing the quality of the Ni/Si interface.

Researchers resolve decades-long debate about shock-compressed silicon with unprecedented detail

Researchers resolve decades-long debate about shock-compressed silicon with unprecedented detail

They saw how the material finds a path to contorting and flexing to avoid being irreversibly crushed.

BY ALI SUNDERMIER

Silicon, an element abundant in Earth’s crust, is currently the most widely used semiconductor material and is important in fields like engineering, geophysics and plasma physics. But despite decades of studies, how the material transforms when hit with powerful shockwaves has been a topic of longstanding debate.

“One might assume that because we have already studied silicon in so many ways there is nothing left to discover,” said Silvia Pandolfi, a researcher at the Department of Energy’s SLAC National Accelerator Laboratory. “But there are still some important aspects of its behavior that are not clear.”

Now, researchers at SLAC have finally put this controversy to rest, providing the first direct, high-fidelity view of how a single silicon crystal deforms during shock compression on nanosecond timescales. To do so, they studied the crystal with X-rays from SLAC’s Linac Coherent Light Source (LCLS) X-ray laser. The team published their results in Nature Communications on September 21st. What they learned could lead to more accurate models that better predict what will happen to certain materials in extreme conditions.

“This is a great example of an experiment that’s necessary to better understand certain materials,” said SLAC scientist Arianna Gleason, who was the principal investigator. “You have to start simple, with single crystals, to know what you’re tracking and understand it in really detailed ways before you can build up complexity to give way to, say, the next semiconductor of the 21st Century that will allow the electronics industry to continue the remarkable progress seen in the past 50 years.”

Read more on the SLAC website