PolyAPT is involved in several projects centered on atomic-level studies to guide and accelerate the development of novel and enhanced functionalities relevant to a variety of applications. These applications include information technology, photonics, quantum technologies, clean energy, aerospace and transportation, metallurgy, and health and bio-integrated technologies. Below, are provided a few examples of ongoing activities.
Quantum engineering
Uncovering and harnessing quantum processes in materials has been a powerful paradigm to achieve novel or superior technologies. This research axis subscribes to this vision and to the decades-long quest for enhanced functionalities through a precise manipulation of matter at the atomic scale. The fundamental paradigm here is the capability to tailor the physical properties through a precise, atomistic-level control of structure and composition during the synthesis of materials and throughout device processing. New methods are proposed to study and control charge carrier quantum states, heat transport, spin dynamics, quantum superposition, confinement, and coherence. These methods provide a rich playground to systematically investigate some of the most exciting phenomena and problems in condensed matter physics and lay the groundwork to implement innovative and scalable quantum technologies. Our team is currently using APT in the following projects:
- • Isotopically engineered low-dimensional systems.
- • Nuclear spin engineering.
- • Spin qubits and qudits in silicon.
- • Hybrid quantum systems.
- • Hole spin in a two-dimensional gas.
Figure: Three-dimensional point cloud of a Silicon quantum well used as a Spin Qubit embedded in Silicon-Germanium as imaged by APT (left) and the maps of the top and bottom interface of the quantum well (right). The material structure was fabricated by the Scappucci group at the TU Delft.
Integrated photonics
On-chip integrated devices capable of the generation, detection, and manipulation of electromagnetic radiation within the short-wave infrared (“SWIR”, 1.7-3 µm), mid-infrared (“MIR”, 3-8 µm) to terahertz (“THz”, 30-1000 µm) range are being highly sought after for applications in medical diagnosis, environmental pollution monitoring, detection of trace gases and explosive, security screening systems, and anti-counterfeiting measures. While beyond visible radiation sensing, imaging, and communication are very powerful applications, they are currently either underutilized or alienated due to the lack of well-integrated compact platforms. One of the key challenges stems from the fact that the current devices are very costly, bulky, range-limited, and/or not fully integrated with the market-ready electronic and optoelectronic platforms. With this perspective, our team develop scalable, tunable, and compact photonic platforms based on new class of semiconductors. This includes:
- • Silicon-integrated light emitters and photodetectors.
- • SWIR and MWIR sensing and imaging.
- • Compact THz technologies.
Figure: Atom Probe Tomography result of a 1.7 µm Ge/SiGe superlattice designed for quantum cascade lasing in the THz range. The sample was grown in the Moutanabbir group at Polytechnique Montreal.
Figure: Atom Probe Tomography result of a gold catalyzed InP nanowire containing 4 InPAs quantum dots. This nanowire structure is developed for single photon sources. The nanowire was grown by the Philip Poole group at the National Research Council Canada in Ottawa.
Energy Conversion and Storage
Adopting a much broader use of renewable energy sources is inarguably one of the key strategies to face both the increasing demand for energy and the colossal challenges related to global warming. Some of the main technological hurdles towards an environment-friendly economy powered by renewable sources like solar radiation, water and wind are related to cost, scalability, efficiency, and our ability to store the harvested energy and make it readily available anywhere at any time. Improving current materials and developing new ones are part of the solution to address these challenges. With this perspective, our team and collaborators establish innovative methods to improve materials used in clean energy conversion and storage. These efforts are benefiting from APT to accelerate the optimization of their performance. The current projects focus on:
- • Monolithic multi-junction solar cells.
- • Thermoelectrics.
- • Li-ion batteries.
Structural alloys
The goal of alloying is generally to achieve compositional homogeneity. Of course, at the atomic level this is never fully achieved. Often, this is a deliberate design goal, for example when designing multi-phase microstructures. In this case, APT becomes important when the size of the phase is at or lower than the nanoscale. Even if the final phase size is at the micron level, APT is a valuable tool in observing pre-nucleation phenomena, such as atom clustering. On the other hand, if the microstructure is single phase, segregation of alloying atoms to crystallographic defects is inevitable. Such segregation can be very influential in terms of, for example, mechanical properties (segregation to dislocations) or processing (segregation to grain boundaries). In order to properly design alloys, it is very important to reveal the location of the alloying atoms at every stage of the microstructural evolution and there is a very large body of work in the literature where APT has been shown to be decisive in explaining phenomena and mechanisms in structural alloys. There are obviously a great many alloys that could benefit from APT. The current projects focus on:
- • Advanced steels with improved fatigue resistance.
- • Hydrogen embrittlement.
- • Magnesium alloys.
- • Fine scale microstructures.
Biomineralization and Biomaterials
Biomineralization in mineralized tissues from interactions amongst four categories of components: i) mineral that belongs to the Ca-P family, with multiple transitional polymorphs; ii) structural proteins (mostly fibrillar collagen); iii) regulatory noncollagenous proteins that are inherently unstructured and highly acidic to bind to mineral and regulate mineralization (e.g., the protein osteopontin), and iv) water which exists in connective tissues as bound, or structural, water. APT provides atomic resolution imaging and chemical mapping in 3D of biomineralized structures in a hydrated state, which has been heretofore unattainable by conventional electron microscopy, for the double purpose of retaining structural water and “fixing” transient rapid and rare events of biomineralization by instantaneous freezing. This will allow for a better understanding of biomineral ultrastructure, formation pathways, regulatory determinants, how mineralization is altered in disease, and bioinspired solutions for materials that effectively osseointegrate into bone. Our team investigate:
- • The nature of biomineral and its transitions.
- • Protein regulation of biomineralization in the extracellular matrix.
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