Strain Modulation of Si Vacancy Emission from SiC Micro- and Nanoparticles.

Single-photon emitting point defects in semiconductors have emerged as strong candidates for future quantum technology devices. In the present work, we exploit crystalline particles to investigate relevant defect localizations, emission shifting, and waveguiding. Specifically, emission from 6H-SiC micro- and nanoparticles ranging from 100 nm to 5 µm in size is collected using cathodoluminescence (CL), and we monitor signals attributed to the Si vacancy (VSi) as a function of its location. Clear shifts in the emission wavelength are found for emitters localized in the particle center and at the edges. By comparing spatial CL maps with strain analysis carried out in transmission electron microscopy, we attribute the emission shifts to compressive strain of 2-3% along the particle a-direction. Thus, embedding VSi qubit defects within SiC nanoparticles offers an interesting and versatile opportunity to tune single-photon emission energies while simultaneously ensuring ease of addressability via a self-assembled SiC nanoparticle matrix.

The heterogeneous nucleation of threading dislocations on partial dislocations in III-nitride epilayers.

III-nitride compound semiconductors are breakthrough materials regarding device applications. However, their heterostructures suffer from very high threading dislocation (TD) densities that impair several aspects of their performance. The physical mechanisms leading to TD nucleation in these materials are still not fully elucidated. An overlooked but apparently important mechanism is their heterogeneous nucleation on domains of basal stacking faults (BSFs). Based on experimental observations by transmission electron microscopy, we present a concise model of this phenomenon occurring in III-nitride alloy heterostructures. Such domains comprise overlapping intrinsic I1 BSFs with parallel translation vectors. Overlapping of two BSFs annihilates most of the local elastic strain of their delimiting partial dislocations. What remains combines to yield partial dislocations that are always of screw character. As a result, TD nucleation becomes geometrically necessary, as well as energetically favorable, due to the coexistence of crystallographically equivalent prismatic facets surrounding the BSF domain. The presented model explains all observed BSF domain morphologies, and constitutes a physical mechanism that provides insight regarding dislocation nucleation in wurtzite-structured alloy epilayers.

High-quality, large-area MoSe2 and MoSe2/Bi2Se3 heterostructures on AlN(0001)/Si(111) substrates by molecular beam epitaxy.

Atomically-thin, inherently 2D semiconductors offer thickness scaling of nanoelectronic devices and excellent response to light for low-power versatile applications. Using small exfoliated flakes, advanced devices and integrated circuits have already been realized, showing great potential to impact nanoelectronics. Here, high-quality single-crystal MoSe2 is grown by molecular beam epitaxy on AlN(0001)/Si(111), showing the potential for scaling up growth to low-cost, large-area substrates for mass production. The MoSe2 layers are epitaxially aligned with the aluminum nitride (AlN) lattice, showing a uniform, smooth surface and interfaces with no reaction or intermixing, and with sufficiently high band offsets. High-quality single-layer MoSe2 is obtained, with a direct gap evidenced by angle-resolved photoemission spectroscopy and further confirmed by Raman and intense room temperature photoluminescence. The successful growth of high-quality MoSe2/Bi2Se3 multilayers on AlN shows promise for novel devices exploiting the non-trivial topological properties of Bi2Se3.

Sub-surface laser nanostructuring in stratified metal/dielectric media: a versatile platform towards flexible, durable and large-scale plasmonic writing.

Laser nanostructuring of pure ultrathin metal layers or ceramic/metal composite thin films has emerged as a promising route for the fabrication of plasmonic patterns with applications in information storage, cryptography, and security tagging. However, the environmental sensitivity of pure Ag layers and the complexity of ceramic/metal composite film growth hinder the implementation of this technology to large-scale production, as well as its combination with flexible substrates. In the present work we investigate an alternative pathway, namely, starting from non-plasmonic multilayer metal/dielectric layers, whose growth is compatible with large scale production such as in-line sputtering and roll-to-roll deposition, which are then transformed into plasmonic templates by single-shot UV-laser annealing (LA). This entirely cold, large-scale process leads to a subsurface nanoconstruction involving plasmonic Ag nanoparticles (NPs) embedded in a hard and inert dielectric matrix on top of both rigid and flexible substrates. The subsurface encapsulation of Ag NPs provides durability and long-term stability, while the cold character of LA suits the use of sensitive flexible substrates. The morphology of the final composite film depends primarily on the nanocrystalline character of the dielectric host and its thermal conductivity. We demonstrate the emergence of a localized surface plasmon resonance, and its tunability depending on the applied fluence and environmental pressure. The results are well explained by theoretical photothermal modeling. Overall, our findings qualify the proposed process as an excellent candidate for versatile, large-scale optical encoding applications.