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  1. Abstract Silicon telluride (Si 2 Te 3 ) has emerged as one of the many contenders for 2D materials ideal for the fabrication of atomically thin devices. Despite the progress which has been made in the electric and optical properties of silicon telluride, much work is still needed to better understand this material. We report here on the Raman study of Si 2 Te 3 degradation under both annealing and in situ heating with a laser. Both processes caused pristine Si 2 Te 3 to degrade into tellurium and silicon oxide in air in the absence of a protective coating.more »A previously unreported Raman peak at ∼140 cm −1 was observed from the degraded samples and is found to be associated with pure tellurium. This peak was previously unresolved with the peak at 144 cm −1 for pristine Si 2 Te 3 in the literature and has been erroneously assigned as a signature Raman peak of pure Si 2 Te 3 , which has caused incorrect interpretations of experimental data. Our study has led to a fundamental understanding of the Raman peaks in Si 2 Te 3 , and helps resolve the inconsistent issues in the literature. This study is not only important for fundamental understanding but also vital for material characterization and applications.« less
    Free, publicly-accessible full text available April 7, 2023
  2. Free, publicly-accessible full text available October 1, 2022
  3. Abstract We report a combined experimental and computational study of the optical properties of individual silicon telluride (Si 2 Te 3 ) nanoplates. The p-type semiconductor Si 2 Te 3 has a unique layered crystal structure with hexagonal closed-packed Te sublattices and Si–Si dimers occupying octahedral intercalation sites. The orientation of the silicon dimers leads to unique optical and electronic properties. Two-dimensional Si 2 Te 3 nanoplates with thicknesses of hundreds of nanometers and lateral sizes of tens of micrometers are synthesized by a chemical vapor deposition technique. At temperatures below 150 K, the Si 2 Te 3 nanoplates exhibit amore »direct band structure with a band gap energy of 2.394 eV at 7 K and an estimated free exciton binding energy of 150 meV. Polarized reflection measurements at different temperatures show anisotropy in the absorption coefficient due to an anisotropic orientation of the silicon dimers, which is in excellent agreement with theoretical calculations of the dielectric functions. Polarized Raman measurements of single Si 2 Te 3 nanoplates at different temperatures reveal various vibrational modes, which agree with density functional perturbation theory calculations. The unique structural and optical properties of nanostructured Si 2 Te 3 hold great potential applications in optoelectronics and chemical sensing.« less
  4. ABSTRACT Silicon telluride (Si2Te3) is a silicon-based 2D chalcogenide with potential applications in optoelectronics. It has a unique crystal structure where Si atoms form Si-Si dimers to occupy the “metal” sites. In this paper, we report an ab initio computational study of its optical dielectric properties using the GW approximation and the Bethe-Salpeter equation (BSE). Strong in-plane optical anisotropy is discovered. The imaginary part of the dielectric constant in the direction parallel to the Si-Si dimers is found to be much lower than that perpendicular to the dimers. The optical measurement of the absorption spectra of 2D Si2Te3 nanoplates showsmore »modulation of the absorption coefficient under 90-degree rotation, confirming the computational results. We show the optical anisotropy originates from the particular compositions of the wavefunctions in the valence and conduction bands. Because it is associated with the Si dimer orientation, the in-plane optical anisotropy can potentially be dynamically controlled by electrical field and strain, which may be useful for new device design. In addition, BSE calculations reduce GW quasiparticle band gap by 0.3 eV in bulk and 0.6 eV in monolayer, indicating a large excitonic effect in Si2Te3. Furthermore, including electron-hole interaction in bulk calculations significantly reduces the imaginary part of the dielectric constant in the out-of-plane direction, suggesting strong interlayer exciton effect in Si2Te3 multilayers.« less
  5. The Unmanned aerial vehicles (UAVs) sector is fast-expanding. Protection of real-time UAV applications against malicious attacks has become an urgent problem that needs to be solved. Denial-of-service (DoS) attack aims to exhaust system resources and cause important tasks to miss deadlines. DoS attack may be one of the common problems of UAV systems, due to its simple implementation. In this paper, we present a software framework that offers DoS attack-resilient control for real-time UAV systems using containers: Container Drone. The framework provides defense mechanisms for three critical system resources: CPU, memory, and communication channel. We restrict the attacker's access tomore »the CPU core set and utilization. Memory bandwidth throttling limits the attacker's memory usage. By simulating sensors and drivers in the container, a security monitor constantly checks DoS attacks over communication channels. Upon the detection of a security rule violation, the framework switches to the safety controller to mitigate the attack. We implemented a prototype quadcopter with commercially off-the-shelf (COTS) hardware and open-source software. Our experimental results demonstrated the effectiveness of the proposed framework defending against various DoS attacks.« less