1,720,991 research outputs found
Conductive filament evolution in HfO2 resistive RAM device during constant voltage stress
No full textThe resistance evolution under constant voltage stress of the low resistive state and the high resistive state of HfO2 based RRAM cells is studied from an experimental and theoretical point of view. A filamentary model based on ions hopping and oxygen vacancies generation phenomena is used to interpret the behavior of the cells. The gap between the tip of the filament and the metal electrode is the parameter governing the device resistance. The current experiments are simulated in terms of the time evolution of the gap length during the electrical stress. The impact of the stress voltage amplitude and the parameter variability on the degradation dynamics is emphasized
Forming kinetics in HfO2-Based RRAM cells
No full textIn this paper, key aspects of the electroforming in resistive-RAM cells with HfO2 are addressed. Specifically, transient measurements were performed on extremely short timescales to characterize systematically the forming time as a function of the voltage pulse amplitude, temperature, electrode materials, and device area. An analytical model was developed, accounting for the investigated experimental parameters. Impact of the forming (and SET) waveform on read disturb is also investigated. © 1963-2012 IEEE
Reliable and robust detection of freezing of gait episodes with wearable electronic devices
Full text linkA wearable wireless sensing system for assisting patients affected by Parkinson's disease is proposed. It uses integrated micro-electro-mechanical inertial sensors able to recognize the episodes of involuntary gait freezing. The system operates in real time and is designed for outdoor and indoor applications. Standard tests were performed on a noticeable number of patients and healthy persons and the algorithm demonstrated its reliability and robustness respect to individual specific gait and postural behaviors. The overall performances of the system are excellent with a specificity higher than 97%
Electron-Related Phenomena at the TaN/Al2O3 Interface
No full textThe goal of this work is to study the transient electrical features of metal/high-k interface in MOS stacks. To this aim, electrons are injected from the gate of TaN/Al2O3/SiO2/p-Si capacitors in pulsed regime. The displacement current flowing during the pulse front is detected, and the capacitance is extracted. As a result, for the first time, a flat-band instability related to electron trapping in states near the metal/high-k interface is measured on a millisecond timescale. A picture of the time evolution of the charge density inside the oxide bulk is drawn, with the aid of a finite-element simulator. Reliability of the metal/high-k interface is also investigated by performing stress experiments in pulsed conditions. It is shown that after a certain number of pulses, the creation of new traps at the top interface of the MOS stack becomes relevant
Impact of the forming conditions and electrode metals on read disturb in HfO2-based RRAM
No full textAn experiment of read disturb is performed on HfO2 based MIM devices designed for resistive memories (RRAM). The experiment elucidates the role of the forming conditions and the electrode materials on the robustness of the low resistance state against electrical disturb. It is performed in three steps: (1) two sets of samples with different electrodes (TiN and Pt) are formed using voltage pulses with different amplitudes; (2) formed samples are subject to constant voltage stress of different entities; (3) the current flowing through the MIM during stress is monitored and processed. © 2013 Elsevier Ltd. All rights reserved
Mobile devices for the real-time detection of specific human motion disorders
No full textWe propose a wearable wireless sensing system for monitoring human motion disorders. The system is designed to be used at home or outdoor, as a mobile healthcare device assisting the person during the daily activity. It provides in real time an early detection of specific motion disorders at their outset, with excellent performance in terms of sensitivity and precision. The system is composed of inertial measurement units, a station for the real-time processing (smartphone/tablet/PC), dedicated algorithms and, eventually, a headphone for auditory feedback. An auditory feedback can warn the patient about particularly dangerous situations as the freezing of gait in the case of Parkinsonian patients, and timely provide rhythmic auditory stimulations to release the gait block. Two different hard and soft implementations of the system are discussed in this paper. The first has just one sensor in a headset. This solution features a fine detection of body motion and in particular of trunk oscillations, easy wearability, through auditory feedback. It is particularly compact and energy efficient, since no wired/wireless connection is required to give the audio-feedback (which reflects on the battery life). However, the headset suffers of the presence of a joint (the neck), which can hide important features of very disordered gaits, as in the case of the Parkinson's disease or other neurodegenerative diseases. The second implementation has two sensors on the shins. It allows fine detection of gait features, and guarantees the best performance presented in the literature to date in terms of sensitivity, specificity, precision, and accuracy in detection of the gait freezing. As a drawback, it requires an additional device in the ear for the audio-feedback, which implies higher power consumption respect to the headset device, for the wireless communication to the microphone. Different recognition algorithms were implemented in the same board, using fusion of raw signals from accelerometers and gyroscopes. The two solutions, their implementations, and experimental results will be discussed in detail, outlining strengths and deficiencies of the twos
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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