@article{latif_dieffenderfer_tanneeru_lee_misra_bozkurt_2021, title={Evaluation of Environmental Enclosures for Effective Ambient Ozone Sensing in Wrist-worn Health and Exposure Trackers}, ISSN={["1930-0395"]}, DOI={10.1109/SENSORS47087.2021.9639530}, abstractNote={The ambient environmental conditions, most notably ozone concentration, play a critical role in exacerbating asthma related symptoms. Wearable devices offer a great potential for asthma care and management by tracking health and environmental status. Wearable devices in the form factor of a wristband using ultra-low power ozone sensors can provide a localized, real-time, and vigilant monitoring of users’ ambient environment. This work presents a preliminary investigation of environmental enclosures for such a custom designed wrist-worn wearable device for asthma. Enclosure design plays an important role in ensuring optimal environmental and gas sensor operation. In this study, we studied openings along the sidewall of the wrist-worn device covered with commercially available expanded polytetrafluoroethylene-based membranes to provide the required air flow while ensuring resistance to water.}, journal={2021 IEEE SENSORS}, author={Latif, Tahmid and Dieffenderfer, James and Tanneeru, Akhilesh and Lee, Bongmook and Misra, Veena and Bozkurt, Alper}, year={2021} } @article{mohaddes_silva_akbulut_zhou_tanneeru_lobaton_lee_misra_2020, title={A Pipeline for Adaptive Filtering and Transformation of Noisy Left-Arm ECG to Its Surrogate Chest Signal}, volume={9}, url={https://www.mdpi.com/2079-9292/9/5/866}, DOI={10.3390/electronics9050866}, abstractNote={The performance of a low-power single-lead armband in generating electrocardiogram (ECG) signals from the chest and left arm was validated against a BIOPAC MP160 benchtop system in real-time. The filtering performance of three adaptive filtering algorithms, namely least mean squares (LMS), recursive least squares (RLS), and extended kernel RLS (EKRLS) in removing white (W), power line interference (PLI), electrode movement (EM), muscle artifact (MA), and baseline wandering (BLW) noises from the chest and left-arm ECG was evaluated with respect to the mean squared error (MSE). Filter parameters of the used algorithms were adjusted to ensure optimal filtering performance. LMS was found to be the most effective adaptive filtering algorithm in removing all noises with minimum MSE. However, for removing PLI with a maximal signal-to-noise ratio (SNR), RLS showed lower MSE values than LMS when the step size was set to 1 × 10−5. We proposed a transformation framework to convert the denoised left-arm and chest ECG signals to their low-MSE and high-SNR surrogate chest signals. With wide applications in wearable technologies, the proposed pipeline was found to be capable of establishing a baseline for comparing left-arm signals with original chest signals, getting one step closer to making use of the left-arm ECG in clinical cardiac evaluations.}, number={5}, journal={Electronics}, publisher={MDPI AG}, author={Mohaddes, Farzad and Silva, Rafael Luiz and Akbulut, Fatma Patlar and Zhou, Yilu and TANNEERU, AKHILESH and Lobaton, Edgar and Lee, Bongmook and Misra, Veena}, year={2020}, month={May}, pages={866} } @article{azam_tanneeru_lee_misra_2020, title={Engineering a Unified Dielectric Solution for AlGaN/GaN MOS-HFET Gate and Access Regions}, volume={67}, ISSN={["1557-9646"]}, url={https://doi.org/10.1109/TED.2020.2969394}, DOI={10.1109/TED.2020.2969394}, abstractNote={Typically GaN metal-oxide-semiconductor heterojunction-field-effect transistors (MOS-HFETs) have used two separate dielectrics for the gate and access regions. However, as this article shows, with proper gate-stack engineering, a unified dielectric solution can be achieved for the transistor. HfO₂ dielectrics were deposited by atomic layer deposition (ALD). Two types of oxidants were investigated, namely, water (H₂O) and ozone (O₃). It was found that MOS-HFETs with O₃ oxidant yielded lower threshold voltage (

${V}_{\text {TH}}$

) shifts, higher maximum drain current (

${I}_{\text {DS,max}}$

) of 340 mA/mm, 20% lower ON-resistance (

${R}_{ {\mathrm {\scriptscriptstyle {ON}}}}$

), higher peak transconductance at 112.66 mS/mm, lower hysteresis, and lower gate leakage (

${5.4} \times {10}^{-{6}}$

A/cm²) compared to water oxidant based MOS-HFETs with

${I}_{\text {DS},\text {max}}$

of 240 mA/mm, 81.38 mS/mm peak transconductance, and

${1.7} \times {10}^{-{4}}$

A/cm² gate leakage. DC/RF dispersion tests showed MOS-HFETs with O₃ oxidant had ~200

$\times $

better current collapse recovery. Temperature characterization and reliability test results, such as high-temperature reverse bias (HTRB), are published for the first time on ALD-HfO₂/AlGaN/GaN MOS-HFETs using tetrakis(dimethylamino)hafnium (TDMAH) and O₃ precursor. Using an ozone oxidant provided more stability (i.e., less variability in

${R}_{ {\mathrm {\scriptscriptstyle {ON}}}}$

and

${V}_{\text {TH}}$

) as a function of temperature. Finally, when devices were electrically stressed in the OFF-state, the HTRB test showed minimal

${V}_{\text {TH}}$

drift (<0.5 V) in the case of O₃ oxidant versus much larger

${V}_{\text {TH}}$

drift (2.5 V) in the case of H₂O oxidant.}, number={3}, journal={IEEE TRANSACTIONS ON ELECTRON DEVICES}, publisher={Institute of Electrical and Electronics Engineers (IEEE)}, author={Azam, Faisal and Tanneeru, Akhilesh and Lee, Bongmook and Misra, Veena}, year={2020}, month={Mar}, pages={881–887} } @inproceedings{tanneeru_mills_lim_mahmud_dieffenderfer_bozkurt_nagle_lee_misra_2016, title={Room temperature sensing of VOCS by atomic layer deposition of metal oxide}, DOI={10.1109/icsens.2016.7808786}, abstractNote={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.}, booktitle={2016 ieee sensors}, author={TANNEERU, AKHILESH and Mills, S. and Lim, M. and Mahmud, M. M. and Dieffenderfer, J. and Bozkurt, A. and Nagle, T. and Lee, B. and Misra, V.}, year={2016} }