News
Alessandro Buzzi wins “Best Presentation” at WOLTE15
Alessandro Buzzi won the award for Best Presentation at WOLTE15 for his presentation entitled “Building blocks design for superconducting nanowire asynchronous logic” which took place on June 8, 2022.
Presentation Abstract:
Superconducting nanowires have emerged in recent years as a candidate for low-power electronics [1]. In particular, their inherent spiking behavior [2] and the possibility of integration with superconducting loop memory cells [3] make them an excellent candidate for asynchronous spiking computing. Although some proof-of-concept devices have been demonstrated, the lack of reliable standard cells that combine memory and logic functions has hindered the design of larger circuits.
We present an approach for digital logic based on niobium nitride superconducting nanowires, in which the information is stored in a superconducting loop and altered asynchronously by the inputs.
Additionally, we show how building blocks are designed and combined to reproduce circuits equivalent to lookup tables, flip-flops, shift registers, and linear feedback shift registers.
Fig.1 displays a destructive readout memory, our elementary building block. This device consists of a superconducting loop with two parallel branches. The constant bias current is transferred between the branches using two nanocryotrons (nTron), three-terminal components able to modulate the
switching current of a superconducting channel from a gate input [1]. This basic design allows for further functionalities by slight modifications of the structure. For example, another input on the left side can be added to obtain an OR gate, moving the inputs on the right branch will produce a NOR gate while the combination of multiple loops can be used to make sequential elements and circuits.
We simulated the above-mentioned circuits with SPICE and verified their behavioral and electrical characteristics. Moreover, we experimentally demonstrated the correct function of the destructive readout memory (Fig. 1). We plan to fabricate and characterize the single-loop gates and integrate them into multi-block structures. Our work paves the way for the realization of asynchronous superconducting logic. We aim to develop a reliable system of standard cells that would provide a basis for future integrations of ultra-low-power circuits.
EIPBN 2022 Best Electron Micrograph Award
Congratulations to Alessandro Buzzi and Matteo Castellani for winning the award for the “Best Electron Micrograph” for their image entitled “A Maze in Grace.”
New Publication “Electron Emission Regimes of Planar Nano Vacuum Emitters”
Recent advancements in nanofabrication have enabled the creation of vacuum electronic devices with nanoscale free-space gaps. These nanoelectronic devices promise the benefits of cold-field emission and transport through free space, such as high nonlinearity and relative insensitivity to temperature and ionizing radiation, all while drastically reducing the footprint, increasing the operating bandwidth, and reducing the power consumption of each device. Furthermore, planarized vacuum nanoelectronics could easily be integrated at scale similar to typical microscale and nanoscale semiconductor electronics. However, the interplay between different electron emission mechanisms from these devices is not well understood, and inconsistencies with pure Fowler-Nordheim (FN) emission have been noted by others. In this work, we systematically study the current-voltage characteristics of planar vacuum nanodevices having few-nanometer radii of curvature and free-space gaps between the emitter and the collector. By investigating the current-voltage characteristics of nearly identical devices fabricated from two different materials and under various environmental conditions, such as temperature and atmospheric pressure, we are able to clearly isolate three distinct emission regimes within a single device: Schottky, FN, and saturation. Our work will enable robust and accurate modeling of vacuum nanoelectronics, which will be critical for future applications requiring high-speed and low-power electronics capable of operation in extreme conditions.
A complete description of the work may be found here.
Honorable Mention in Poster Contest for Dip Joti Paul
Dip Joti Paul won an Honorable Mention in the DLS student poster contest held at CLEO in San Jose from May 7-12 for his poster “Infrared Refractive Index Measurement of Niobium Nitride Thin-Film via FTIR”.
See the full poster here.
New Publication “PHz Electronic Device Design and Simulation for Waveguide-Integrated Carrier-Envelope Phase Detection”
Carrier-envelope phase (CEP) detection of ultrashort optical pulses and low-energy waveform field sampling have recently been demonstrated using direct time-domain methods that exploit optical-field photoemission from plasmonic nanoantennas. These devices are compact and integratable solid-state detectors operating at optical frequencies under ambient conditions using low pulse energies (picojoule-level). Potential applications include frequency-comb stabilization, optical time-domain spectroscopy, compact tools for attosecond science and metrology, and petahertz-scale information processing. However, to date these devices have been driven by free-space optical waveforms and their implementation within integrated photonic platforms has yet to be demonstrated. In this work, we design and simulate fully-integrated plasmonic nanoantennas coupled to a SiN-core waveguide for CEP detection. We find that when coupled to realistic on-chip, few-cycle supercontinuum sources, these devices are suitable for direct time-domain CEP detection within integrated photonic platforms. We estimate a signal-to-noise ratio of 30 dB at 50 kHz resolution bandwidth, and address technical details, such as the tuning of the nanoantennas plasmonic resonance, CEP slippage in the waveguide, optical losses, and sensitivity to driving pulse characteristics such as energy and duration. Our results provide the basis for future design and fabrication of time-domain CEP detectors and allow for the development of fully-integrated attosecond science applications, frequency-comb stabilization and light-wave-based PHz electronics.
A complete description of the work may be found here.
