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- 2018
- electron-transparent membranes
- micropump
- field emission electron source
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- ion mobility spectrometry
- Optoelectronic Information Science and Engineering
- Wroclaw University of Science and Technology
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[IEEE 2018 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS) - Madrid, Spain (2018.10.1-2018.10.5)] 2018 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS) - Automatic Fall Risk Assessment for Challenged Users Obtained from a Rollator Equipped with Force Sensors and a RGB-D Camera
摘要： Fall risk assessments provide a useful tool to prevent morbidity and mortality provoked by falls. Nowadays, these assessments are usually performed manually by the medical staff. This approach has three main drawbacks: i) it is time consuming, so it is only performed a few times per volunteer during their rehabilitation process; ii) it requires supervision by medical staff, so assessment at home or preferred environments is not feasible; and iii) fall risk is evaluated in a global way, so imminent fall risk is not available for decision making in assistive navigation. In this paper we propose an imminent fall risk estimator for rollator's users that can be automatically obtained on the fly. Its main advantages are: i) it can be used in everyday conditions in any environment; ii) it does not require assistance of medical staff; and iii) it is suitable for a variety of users with minimal configuration changes. We have validated our estimator with a set of volunteers (n=10) presenting different physical and cognitive disabilities. Although the number of volunteer is limited, results show that our estimator is coherent to two traditional, well accepted assessments: the Tinetti Mobility Test and the walking speed.
关键词： walking speed,Tinetti Mobility Test,on-board sensors,fall risk assessment,rollator
更新于2025-09-19 17:15:36
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Eighteen functional monolayer metal oxides: wide bandgap semiconductors with superior oxidation resistance and ultrahigh carrier mobility
摘要： Layered metal oxides have emerged as an up-and-comer in the family of two-dimensional materials due to their natural abundance, intrinsic bandgap, and chemical inertness. Based on first-principles calculations, we systematically investigated the atomic structures, energetic stability, and electronic properties of 18 monolayer metal oxides. All these monolayer metal oxides are predicted to be energetically favorable with negative formation energies in the range of -4.27 to -0.47 eV per atom, suggesting good experimental feasibility for synthesis of these monolayer metal oxides. Monolayer metal oxides exhibit superior oxidation resistance, and possess modest to wide bandgaps (1.22–6.48 eV) and high carrier mobility (especially up to 8540 cm2 V?1 s?1 for the InO monolayer), thereby rendering these low-dimensional materials promising candidates for carrier transport. Also, a pronounced in-plane anisotropy for the carrier mobility with a longitudinal/horizontal ratio as large as 115 is revealed for the monolayer metal oxides. These 2D metal oxides exhibit notable absorption in the ultraviolet range with the absorption coefficient >10? cm?1. The combined novel properties of these monolayer metal oxides offer a wide range of opportunities for advanced electronic and optoelectronic applications.
关键词： two-dimensional materials,optoelectronics,monolayer metal oxides,bandgap,carrier mobility,oxidation resistance
更新于2025-09-19 17:15:36
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Correlation Between Two-Dimensional Electron Gas Mobility and Crystal Quality in AlGaN/GaN High-Electron-Mobility Transistor Structure Grown on 4H-SiC
摘要： We investigated the correlation between the crystal quality and two-dimensional electron gas (2DEG) mobility of an AlGaN/GaN high-electron-mobility transistor (HEMT) structure grown by metal-organic chemical vapor deposition. For the structure with an AlN nucleation layer grown at 1100 °C, the 2DEG mobility and sheet carrier density were 1627 cm2/V·s and 3.23 × 1013 cm?2, respectively, at room temperature. Further, it was confirmed that the edge dislocation density of the GaN buffer layer was related to the 2DEG mobility and sheet carrier density in the AlGaN/GaN HEMT.
关键词： MOCVD,2DEG,Mobility,AlGaN/GaN HEMT,Carrier Density,Edge and Screw Dislocation
更新于2025-09-19 17:15:36
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Remote Phonon Scattering in Two-Dimensional InSe FETs with High-κ Gate Stack
摘要： This work focuses on the effect of remote phonon arising from the substrate and high-κ gate dielectric on electron mobility in two-dimensional (2D) InSe field-effect transistors (FETs). The electrostatic characteristic under quantum confinement is derived by self-consistently solving the Poisson and Schr?dinger equations using the effective mass approximation. Then mobility is calculated by the Kubo–Greenwood formula accounting for the remote phonon scattering (RPS) as well as the intrinsic phonon scatterings, including the acoustic phonon, homopolar phonon, optical phonon scatterings, and Fr?hlich interaction. Using the above method, the mobility degradation due to remote phonon is comprehensively explored in single- and dual-gate InSe FETs utilizing SiO2, Al2O3, and HfO2 as gate dielectric respectively. We unveil the origin of temperature, inversion density, and thickness dependence of carrier mobility. Simulations indicate that remote phonon and Fr?hlich interaction plays a comparatively major role in determining the electron transport in InSe. Mobility is more severely degraded by remote phonon of HfO2 dielectric than Al2O3 and SiO2 dielectric, which can be effectively insulated by introducing a SiO2 interfacial layer between the high-κ dielectric and InSe. Due to its smaller in-plane and quantization effective masses, mobility begins to increase at higher density as carriers become degenerate, and mobility degradation with a reduced layer number is much stronger in InSe compared with MoS2.
关键词： two-dimensional material,indium selenide,mobility,phonon scattering,high-κ dielectric,field effect transistor
更新于2025-09-19 17:15:36
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Shallow and Undoped Germanium Quantum Wells: A Playground for Spin and Hybrid Quantum Technology
摘要： Buried-channel semiconductor heterostructures are an archetype material platform for the fabrication of gated semiconductor quantum devices. Sharp confinement potential is obtained by positioning the channel near the surface; however, nearby surface states degrade the electrical properties of the starting material. Here, a 2D hole gas of high mobility (5 × 10^5 cm^2 V^{-1} s^{-1}) is demonstrated in a very shallow strained germanium (Ge) channel, which is located only 22 nm below the surface. The top-gate of a dopant-less field effect transistor controls the channel carrier density confined in an undoped Ge/SiGe heterostructure with reduced background contamination, sharp interfaces, and high uniformity. The high mobility leads to mean free paths ≈ 6 μm, setting new benchmarks for holes in shallow field effect transistors. The high mobility, along with a percolation density of 1.2 × 10^{11} cm^{-2}, light effective mass (0.09m_e), and high effective g-factor (up to 9.2) highlight the potential of undoped Ge/SiGe as a low-disorder material platform for hybrid quantum technologies.
关键词： germanium,quantum well,quantum devices,mobility
更新于2025-09-19 17:15:36
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Dodecaborane-Based Dopants Designed to Shield Anion Electrostatics Lead to Increased Carrier Mobility in a Doped Conjugated Polymer
摘要： One of the most effective ways to tune the electronic properties of conjugated polymers is to dope them with small-molecule oxidizing agents, creating holes on the polymer and molecular anions. Undesirably, strong electrostatic attraction from the anions of most dopants localizes the holes created on the polymer, reducing their mobility. Here, a new strategy utilizing a substituted boron cluster as a molecular dopant for conjugated polymers is employed. By designing the cluster to have a high redox potential and steric protection of the core-localized electron density, highly delocalized polarons with mobilities equivalent to films doped with no anions present are obtained. AC Hall effect measurements show that P3HT films doped with these boron clusters have conductivities and polaron mobilities roughly an order of magnitude higher than films doped with F4TCNQ, even though the boron-cluster-doped films have poor crystallinity. Moreover, the number of free carriers approximately matches the number of boron clusters, yielding a doping efficiency of ≈100%. These results suggest that shielding the polaron from the anion is a critically important aspect for producing high carrier mobility, and that the high polymer crystallinity required with dopants such as F4TCNQ is primarily to keep the counterions far from the polymer backbone.
关键词： mobility,molecular dopants,Coulomb screening,semiconducting polymers,dodecaboranes
更新于2025-09-19 17:15:36
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Naphthalene and perylene diimides – better alternatives to fullerenes for organic electronics?
摘要： The LUMO levels of rylene diimides are highly comparable to those of fullerenes but this class of molecules offers tunability of both HOMO and LUMO levels and the related band gap by either simple substitution at the aromatic core or annulation to give expanded p-scaffolds. In this article we highlight the most outstanding achievements during the last decade in terms of charge carrier mobility for organic thin-film and single crystal field-effect transistors as well as photovoltaic performance for both small molecule and polymeric compounds.
关键词： fullerenes,perylene diimides,organic electronics,photovoltaic performance,naphthalene diimides,charge carrier mobility
更新于2025-09-19 17:15:36
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Chiral differentiation of <scp>d</scp> - and <scp>l</scp> -isoleucine using permethylated β-cyclodextrin: infrared multiple photon dissociation spectroscopy, ion-mobility mass spectrometry, and DFT calculations
摘要： Chiral di?erentiation of protonated isoleucine (Ile) using permethylated b-cyclodextrin (perCD) in the gas-phase was studied using infrared multiple photon dissociation (IRMPD) spectroscopy, ion-mobility, and density functional theory (DFT) calculations. The gaseous protonated non-covalent complexes of perCD and D-Ile or L-Ile produced by electrospray ionization were interrogated by laser pulses in the wavenumber region of 2650 to 3800 cm?1. The IRMPD spectra showed remarkably di?erent IR spectral features for the D-Ile or L-Ile and perCD non-covalent complexes. However, drift-tube ion-mobility experiments provided only a small di?erence in their collision cross-sections, and thus a limited separation of the D- and L-Ile complexes. DFT calculations revealed that the chiral distinction of the D- and L-complexes by IRMPD spectroscopy resulted from local interactions of the protonated Ile with perCD. Furthermore, the theoretical results showed that the IR absorption spectra of higher energy conformers (by B13.7 kcal mol?1) matched best with the experimentally observed IRMPD spectra. These conformers are speculated to be formed from kinetic-trapping of the solution-phase conformers. This study demonstrated that IRMPD spectroscopy provides an excellent platform for di?erentiating the subtle chiral di?erence of a small amino acid in a cyclodextrin-complexation environment; however, drift-tube ion-mobility did not have su?cient resolution to distinguish the chiral di?erence.
关键词： chiral differentiation,ion-mobility mass spectrometry,permethylated β-cyclodextrin,IRMPD spectroscopy,DFT calculations,isoleucine
更新于2025-09-19 17:15:36
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A novel hydrogenated boron–carbon monolayer with high stability and promising carrier mobility
摘要： Although immense research on the extension of the two-dimensional (2D) material family has been carried out, 2D materials with a satisfactory band gap, high carrier mobility, and outstanding thermodynamic stability under ambient conditions are still limited. In this work, using first principles calculations, we proposed new 2D ternary materials consisting of C, B, and H atoms, namely hexagonal-BCH (h-BCH) and tetragonal-BCH (t-BCH). Both phonon calculations and ab initio molecular dynamics simulations show that these proposed sheets are thermodynamically stable phases. The electronic structure calculations indicate that h-BCH and t-BCH sheets are semiconductors with a band gap of 2.66 and 2.22 eV, respectively. Remarkably, the h-BCH (t-BCH) sheet exhibits electron mobility as high as 7.41 × 10^3 (1.09 × 10^3) cm^2 V^{-1} s^{-1}, which is higher than that of the MoS2 monolayer, though the hole mobility is about one (two) order of magnitude lower. Equally important is the fact that the position of both the conduction and valence band edges of the h-BCH sheet matches well with the chemical reaction potential of H2/H+ and O2/H2O, giving a 2D photocatalyst as a potential candidate for overall visible-light-driven water splitting. Therefore, the designed h-BCH and t-BCH monolayers have promising applications in future electronics and photocatalysts.
关键词： 2D materials,boron-carbon-hydrogen,photocatalysis,first principles calculations,carrier mobility
更新于2025-09-19 17:15:36
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[IEEE 2019 SBFoton International Optics and Photonics Conference (SBFoton IOPC) - Sao Paulo, Brazil (2019.10.7-2019.10.9)] 2019 SBFoton International Optics and Photonics Conference (SBFoton IOPC) - A Pedestal Waveguide Coupler for Mode Division Multiplexing
摘要： Providing reliable broadband wireless communications in high mobility environments, such as high-speed railway systems, remains one of the main challenges faced by the development of the next generation wireless systems. This paper provides a systematic review of high mobility communications. We first summarize a list of key challenges and opportunities in high mobility communication systems, then provide comprehensive reviews of techniques that can address these challenges and utilize the unique opportunities. The review covers a wide spectrum of communication operations, including the accurate modeling of high mobility channels, the transceiver structures that can exploit the properties of high mobility environments, the signal processing techniques that can harvest the benefits (e.g., Doppler diversity) and mitigate the impairments (e.g., carrier frequency offset, intercarrier interference, channel estimation errors) in high mobility systems, and the mobility management and network architectures that are designed specifically for high mobility systems. The survey focuses primarily on physical layer operations, which are affected the most by the mobile environment, with some additional discussions on higher layer operations, such as handover management and control-plane/user-plane decoupling, which are essential to high mobility operations. Future research directions on high mobility communications are summarized at the end of this paper.
关键词： High mobility communications,fast time-varying fading,ICI,CFO,Doppler diversity,mobility management
更新于2025-09-19 17:13:59