Pulsed laser-The researchers used pulsed laser deposition to design self-integrating atomic quantum wires to form nanonetworks

Quantum advances rely on the production of nanowires based on a variety of state-of-the-art nanolithography techniques, developing the wires through bottom-up synthesis. However, a key challenge is to grow uniform atomic crystal lines and construct network structures to build nanocircuits.

In a new report in Science Advances, Tomoya Asaba and a team of physics and materials science researchers from Kyoto University, the University of Tokyo in Japan, and the German Institute for Theoretical Physics have found a simple way to develop wires in the shape of nanorings, stripes, and X-/Y- knots on an atomic scale.

Using pulsed laser deposition, physicists and materials scientists have grown single crystal atomic-level wires of Mott insulators, which maintain a band gap comparable to that of wide-band gap semiconductors. The wire is as thick as a unit of battery and only a few microns long. The researchers observed the formation of atomic patterns through non-equilibrium reactor-diffusion processes, providing unprecedented insight into the phenomenon of atomic-level self-organization and thereby gaining insight into the formation of quantum structures in nanonetworks.

New methods for designing atomic-scale nanowires

As size decreases, the basic characteristics of most technical devices change. As devices are reduced to the nanoscale, the fabrication and integration of one-dimensional lineae becomes increasingly complex. Developing top-down approaches to include nanowires of less than 10 nanometers in thickness and width using large equipment such as electron beam and focused ion beam lithography is another technical challenge.

Similarly, bottom-up techniques using self-assembly processes are not effective in determining the uniformity of wires. In bottom-up engineering, nanowire array integration depends on two complex steps: first, grow randomly oriented nanowire and then arrange them into an array; Therefore, a new method is needed to make uniform atomic-scale wires and design nanopatterns.

In this work, Asaba and colleagues designed uniform and long ruthenium trichloride (RuCl 3) single crystal wires at the atomic scale by a simple deposition method. They made several characteristic patterns necessary to implement quantum nanocircuits, including atomic smooth junctions and nanorings. Ruthenium trichloride materials are interesting as Mott insulators, where electron-electron interactions open up a band gap. The team formed and integrated the nanowire pattern as part of the film growth process, thus diverging from the traditional approach behind the atomic-level wire pattern -- and promoting self-organization instead.

Engineering nanocircuit

During the experiment, the team used pulsed laser deposition to melt ruthenium trichloride on the surface of highly oriented pyrolytic graphite and observed the results using a scanning tunneling microscope. They obtained atomic resolution images of samples grown at high deposition temperatures to detect surfaces covered by unique wire patterns. Although each line is made up of periodically spaced atoms, they note the single-crystal structure. The materials scientists then studied the material forming atomic wires by extending the deposition time to grow two-dimensional monolayers and thicker films, and to verify its composition as crystalline ruthenium trichloride.

Atomic lines remain more than 3 microns in length, a unique and unprecedented feature. They also contain two or four ruthenium trichloride single crystal chains grown on the surface of the pyrolytic graphite. In its structure, wires initially consist of quadrupole chains of the material, which are later reduced to double chains as the temperature decreases, forming atomically smooth junctions and rings, free of defects and clusters, leading to the design of nanocircuits.

Characterizing nanocircuit

The materials scientist next studies the electronic structure of the material by measuring the differential tunnel conductance and comparing the results with various forms of the material and the pyrolytic graphite surface. They noted a distinct energy gap in the ruthenium trichloride, indicating the presence of a semiconductor or insulating electronic structure.

They reveal the origin of the band gap by systematically performing band calculations on variant forms of ruthenium trichloride materials, including double-stranded lines and their monolayer and block forms, to observe electron correlations and spin orbit interactions. The material eventually revealed an open gap of Fermi energy in all experimental structures used in the study to confirm that the material was a Mott insulator.

The mechanism of pattern formation

The team attributes the formation of the nanowire array to thin film growth unlike any process known to date. In addition to the striped patterns observed in the experiment, the team also discussed the underlying mechanism of pattern formation and the emergence of several different features. According to the pattern, the static interaction is not the driving force of the atom line array.

Instead, they attribute this characteristic to non-equilibrium reaction-diffusion processes. Because scanning tunneling microscopy is too slow to capture the dynamic process of film growth, the team wanted to make direct measurements of the dynamic process at the atomic scale to fully understand the growth mechanism.

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In this way, Tomoya Asaba and colleagues hypothesized that the reaction-diffusion mechanism could stimulate the origin of pattern formation in atomic lines, thereby leading to the manifestation of fringe patterns through Turing instability. This feature contributes to the spontaneous emergence of spatial periodic patterns.

Nanowires and junctions greatly improve the integration of electronic circuits and provide a physical platform for exploring non-equilibrium self-organization phenomena based on atomic scales applicable to singular electronic states and quantum advances.

Source: Laser Net