A study published in the journal Advanced Functional Materials reports a scalable platform developed by a combination of microtomy and vapor-liquid-solid growth of III/V nanowires (NWs). The platform can transfer large sets of single and fused nanocrystals deterministically, allowing for free preference of the target substrate and single-unit control.
Study: Scalable Platform for Nanocrystal-Based Quantum Electronics. Image Credit: wacomka/Shutterstock.com
Pros and Cons of Different Approaches for Processing of Nanocrystals
Nanocrystals (NCs) must be processed in deterministic and scalable ways before they can be used in research areas spanning from novel kinds of transistors to biosensing, optoelectronic devices, and advanced quantum machines.
In general, two main approaches can be used for scalable NC processing. One of these approaches relies on the substrate; in this case, the nanocrystals are either etched or grown from particular substrates, facilitating subsequent production stages (e.g., circuit manufacturing). The other approach is primarily transference-based; the nanocrystals are fabricated first and then transferred to a dedicated substrate.
For substrate-specified strategies, vapor-liquid-solid growth (VLS), anisotropic etching, selective area epitaxy, flame transport synthesizing, Stranski–Krastanov growth, or metalorganic vapor-phase epitaxy are preferred techniques.
These approaches produce remarkable crystal quality and positional control. Still, because the systems are built on growth substrates, system functionality might deteriorate from strains caused by the substrate, substrate/nanocrystal displacements, short-circuits, or dissatisfactory heterostructure growing settings.
Langmuir–Blodgett depositing, capillary force assembly, dry transfer printing, and nanocombed depositing are potential transference-based techniques that enable exact positioning and excellent output. Nonetheless, they are frequently solution-based and rely on target substrate processing, impacting device designs and limiting single unit monitoring.
Nanoskiving – An Approach that Offers the Best of Both Worlds
Nanoskiving –infusing components in a polymer and slicing very thin specimens using an ultramicrotome – is an alternate strategy that seeks to merge the benefits of both approaches. Previous research has produced a number of appealing and scalable nanomaterials for utilization in electrical and optical systems.
For instance, the manufacturing of sophisticated optically active nanomaterials encompassing many mm2 has been shown, and nanoskiving was coupled with etching of core–shell nanowires to generate configurable AlGaAs nanocylinders for optical systems. Despite this, nanoscale structures created by nanoskiving have yet to be used in quantum electronics.
Focus of the Study
In this work, the researchers coupled two well-known techniques – nanowire growth and microtomy – to create a scalable framework for manufacturing electrical quantum systems. The framework was universal in the sense that it could be adapted to different growing or etching-based procedures, enabling the framework to utilize a wide variety of materials.
It was demonstrated how the framework could be applied to nanocrystal networks of unusual geometries and integrated with semiconductive/superconductive technology to produce sophisticated superconducting quantum systems depending on the positioning of catalytic particles and regulated crystal overgrowth. The nanocrystal transfer technology should be perfect for creating vast grids of quantum dots with precisely adjusted tunneling barriers.
This is a fascinating new direction for quantum information systems and fundamental research, such as creating lattice-based quantum computers and cordless single-electron logic regulated by AC-fields.
During device development, chosen lamellas may be utilized as specimens for quality control, such as SEM, AFM, and TEM, which is projected to become a desired feature as systems shift from prototypes to high-throughput production.
Avenues for Future Work
The orientation of the microtomy knife slice plane and the NW high symmetry crystal axes can be optimized in the future to enhance crystal cleavage and NC architectures. Furthermore, other methods for increasing transportation patterns should be investigated, including atomic layer depositing of high-dielectric substances before microtomy, polymer removal or change, and on-site deposited connections.
Other techniques not studied in this study include the construction of radial heterostructure p–n nanocrystals implanted in a transparent polymer to optoelectronic fabric systems. Layering several lamellae having nanocrystals with carefully regulated p–n junctions might also be employed for highly efficient tandem photovoltaic cells. This technique may even be taken further to allow excessive downscaling of inter-pixel pitch among RGB sub-units in high-resolution displays.
The designed framework offers a unique approach for nanoscale system engineering with the potential for scalable synthesis. It provides new ways for integrating nanomaterials into upcoming technologies related to optics, electronics, optoelectronics, and quantum devices.
Sestoft, J. E., Gejl, A. N. et al. (2022). Scalable Platform for Nanocrystal-Based Quantum Electronics. Advanced Functional Materials. Available at: https://onlinelibrary.wiley.com/doi/10.1002/adfm.202112941