Showing papers by "Veena Misra published in 2016"
TL;DR: The preliminary efforts to achieve a submilliwatt system ultimately powered by the energy harvested from thermal radiation and motion of the body are described with the primary contributions being an ultralow-power ozone sensor, an volatile organic compounds sensor, spirometer, and the integration of these and other sensors in a multimodal sensing platform.
Abstract: We present our efforts toward enabling a wearable sensor system that allows for the correlation of individual environmental exposures with physiologic and subsequent adverse health responses. This system will permit a better understanding of the impact of increased ozone levels and other pollutants on chronic asthma conditions. We discuss the inefficiency of existing commercial off-the-shelf components to achieve continuous monitoring and our system-level and nano-enabled efforts toward improving the wearability and power consumption. Our system consists of a wristband, a chest patch, and a handheld spirometer. We describe our preliminary efforts to achieve a submilliwatt system ultimately powered by the energy harvested from thermal radiation and motion of the body with the primary contributions being an ultralow-power ozone sensor, an volatile organic compounds sensor, spirometer, and the integration of these and other sensors in a multimodal sensing platform. The measured environmental parameters include ambient ozone concentration, temperature, and relative humidity. Our array of sensors also assesses heart rate via photoplethysmography and electrocardiography, respiratory rate via photoplethysmography, skin impedance, three-axis acceleration, wheezing via a microphone, and expiratory airflow. The sensors on the wristband, chest patch, and spirometer consume 0.83, 0.96, and 0.01 mW, respectively. The data from each sensor are continually streamed to a peripheral data aggregation device and are subsequently transferred to a dedicated server for cloud storage. Future work includes reducing the power consumption of the system-on-chip including radio to reduce the entirety of each described system in the submilliwatt range.
131 citations
TL;DR: This report explores the promise that wearable biosensors, along with integrated mobile apps, hold for improving the quality of patient care and clinical outcomes and the broad societal implications of using mobile health technologies.
Abstract: Mobile technology has become a ubiquitous part of everyday life, and the practical utility of mobile devices for improving human health is only now being realized. Wireless medical sensors, or mobile biosensors, are one such technology that is allowing the accumulation of real-time biometric data that may hold valuable clues for treating even some of the most devastating human diseases. From wearable gadgets to sophisticated implantable medical devices, the information retrieved from mobile technology has the potential to revolutionize how clinical research is conducted and how disease therapies are delivered in the coming years. Encompassing the fields of science and engineering, analytics, health care, business, and government, this report explores the promise that wearable biosensors, along with integrated mobile apps, hold for improving the quality of patient care and clinical outcomes. The discussion focuses on groundbreaking device innovation, data optimization and validation, commercial platform integration, clinical implementation and regulation, and the broad societal implications of using mobile health technologies.
85 citations
TL;DR: In this article, the properties of SiO2 gate dielectric deposited by atomic layer deposition (ALD) on Si-face of 4H silicon carbide (SiC) were systematically studied.
Abstract: Properties of SiO2 gate dielectric deposited by atomic layer deposition (ALD) on Si-face of 4H silicon carbide (SiC) were systematically studied. The interface state and effective fixed charge densities of ALD SiO2 on n-type 4H–SiC with various post deposition anneal (PDA) conditions were evaluated. It has been found that nitrous oxide (N2O) PDA not only reduces the effective fixed charge density, which includes the fixed oxide charge and charged interface states, at SiC/SiO2 interface but also decreases the gate leakage current. Negative effective fixed charge is observed at SiC/ALD SiO2 interface after N2O PDA. ALD SiO2-based lateral n-channel MOSFETs show high threshold voltage with the promising field-effect mobility and the peak field-effect mobility increases with N2O PDA temperature.
17 citations
TL;DR: In this article, a trade-off between the optimal surface trap characteristics and minimal surface leakage is presented for suppressing current collapse in AlGaN/GaN-based MOS-HFETs.
Abstract: Many passivation dielectrics are pursued for suppressing current collapse due to trapping/detrapping of access-region surface traps in AlGaN/GaN based metal oxide semiconductor heterojuction field effect transistors (MOS-HFETs). The suppression of current collapse can potentially be achieved either by reducing the interaction of surface traps with the gate via surface leakage current reduction, or by eliminating surface traps that can interact with the gate. But, the latter is undesirable since a high density of surface donor traps is required to sustain a high 2D electron gas density at the AlGaN/GaN heterointerface and provide a low ON-resistance. This presents a practical trade-off wherein a passivation dielectric with the optimal surface trap characteristics and minimal surface leakage is to be chosen. In this work, we compare MOS-HFETs fabricated with popular ALD gate/passivation dielectrics like SiO2, Al2O3, HfO2 and HfAlO along with an additional thick plasma-enhanced chemical vapor deposition SiO2 passivation. It is found that after annealing in N2 at 700 °C, the stack containing ALD HfAlO provides a combination of low surface leakage and a high density of shallow donor traps. Physics-based TCAD simulations confirm that this combination of properties helps quick de-trapping and minimal current collapse along with a low ON resistance.
7 citations
01 Oct 2016
TL;DR: In this paper, a 14nm ultrathin SnO2 thin film was deposited by ALD resulting in VOCs sensing at room temperature, and the ultra-low power consumption and the room temperature operation of these devices make them compatible with wearable devices for real-time health and environment monitoring.
Abstract: This work demonstrates room temperature sensing of volatile organic compound (VOC) — acetone via an ultrathin film metal oxide sensing layer. Atomic layer deposition (ALD) enables a high quality ultrathin film with precise thickness control. The 14nm ultrathin SnO2 thin film was deposited by ALD resulting in VOCs sensing at room temperature. The ultra-low power consumption (less than 50nW) and the room temperature operation of these devices make them compatible with wearable devices for real-time health and environment monitoring.
4 citations
TL;DR: In this paper, the resistive switching behavior in BaTiO3/La0.7Sr0.3MnO3 (BTO/LSMO) heterostructures integrated with semiconducting substrates Si (100) using MgO/TiN buffer layers by pulsed laser deposition.
Abstract: Ferroelectric materials such as BaTiO3 have been studied for emerging non-volatile memory applications. However, most of the previous work has been focused on this material when it was deposited on insulting oxide substrates such as SrTiO3. Unfortunately, this substrate is not suitable for CMOS-based microelectronics applications. This motivated us to carry out the present work. We have studied the resistive switching behavior in BaTiO3/La0.7Sr0.3MnO3 (BTO/LSMO) heterostructures integrated with semiconducting substrates Si (100) using MgO/TiN buffer layers by pulsed laser deposition. Current-Voltage (I-V) measurements were conducted on BTO (500nm)/LSMO (25nm) devices at 200K. We have observed a broad hysteresis in forward and reverse voltage sweeps which is an important property for memory applications. Secondly, the RON/ROFF ratio is estimated at ~ 150, consistent with the reported numbers (30-100) in the literature. Thirdly, the device is stable at least up to 50 cycles. However, we found that hysteretic behavior was suppressed upon oxygen annealing of the device at 1 atmospheric pressure, 200o C for 1hr, inferring the important role of oxygen vacancies in the resistive switching behavior of BTO/LSMO device. Future work will focus on investigating the correlation between ferroelectricity and resistive switching in these devices using local probe technique piezo force microscopy (PFM) technique.
1 citations
01 Oct 2016
TL;DR: In this paper, power spectral densities (PSD) of the response of each gas were calculated and found to have significant differences in magnitude for each analyte and provide evidence of selective room temperature adsorption of gases on SnO 2.
Abstract: This work demonstrates a new method for selective identification of low ppb concentrations of O 3 . Atomic layer deposited thin film SnO 2 was used as a sensing layer. SnO 2 sensitized quartz crystal microbalances (QCM) demonstrate expected mass loading behavior as well as unique frequency domain response towards synthetic air, O 3 , and NO 2 at room temperature. Power spectral densities (PSD) of the response of each gas were calculated and contain peaks at different normalized frequencies. These PSD peaks are found to have significant differences in magnitude for each analyte and provide evidence of selective room temperature adsorption of gases on SnO 2 .
1 citations