@misc{bhatnagar_zaferani_rafiefard_baraeinejad_vazifeh_mohammadpour_ghomashchi_dillersberger_tham_vashaee_2023, title={Advancing personalized healthcare and entertainment: Progress in energy harvesting materials and techniques of self-powered wearable devices}, volume={139}, ISSN={["1873-2208"]}, DOI={10.1016/j.pmatsci.2023.101184}, abstractNote={The emergence of self-powered wearable devices has revolutionized health and wellness monitoring by effortlessly integrating it into daily life. This article explores the recent advancements and challenges in energy efficiency and harvesting technologies, which have been instrumental in the development of these wearables. These self-powered systems encompass sensors, energy harvesting mechanisms, power management units, energy storage, data transmission, and processing platforms. This article emphasizes the energy harvesting aspect, providing a concise overview of core techniques, and critically analyzing their application in state-of-the-art wearable devices. Furthermore, we investigate ongoing research and industry efforts to establish networks of self-powered wearables for sustained, long-term operation. Through this analysis, the article aims to provide insights into leveraging current knowledge and technology to accelerate the growth and potential of self-powered wearable devices in healthcare and entertainment.}, journal={PROGRESS IN MATERIALS SCIENCE}, author={Bhatnagar, Prithu and Zaferani, Sadeq Hooshmand and Rafiefard, Nassim and Baraeinejad, Bardia and Vazifeh, Amir Reza and Mohammadpour, Raheleh and Ghomashchi, Reza and Dillersberger, Harald and Tham, Douglas and Vashaee, Daryoosh}, year={2023}, month={Oct} }
 @article{bhatnagar_vashaee_2022, title={Development of MEMS Process Compatible (Bi,Sb)(2)(Se,Te)(3)-Based Thin Films for Scalable Fabrication of Planar Micro-Thermoelectric Generators}, volume={13}, ISSN={["2072-666X"]}, DOI={10.3390/mi13091459}, abstractNote={Bismuth telluride-based thin films have been investigated as the active material in flexible and micro thermoelectric generators (TEGs) for near room-temperature energy harvesting applications. The latter is a class of compact printed circuit board compatible devices conceptualized for operation at low-temperature gradients to generate power for wireless sensor nodes (WSNs), the fundamental units of the Internet-of-Things (IoT). CMOS and MEMS compatible micro-TEGs require thin films that can be integrated into the fabrication flow without compromising their thermoelectric properties. We present results on the thermoelectric properties of (Bi,Sb)2(Se,Te)3 thin films deposited via thermal evaporation of ternary compound pellets on four-inch SiO2 substrates at room temperature. Thin-film compositions and post-deposition annealing parameters are optimized to achieve power factors of 2.75 mW m−1 K−2 and 0.59 mW m−1 K−2 for p-type and n-type thin films. The measurement setup is optimized to characterize the thin-film properties accurately. Thin-film adhesion is further tested and optimized on several substrates. Successful lift-off of p-type and n-type thin films is completed on the same wafer to create thermocouple patterns as per the target device design proving compatibility with the standard MEMS fabrication process.}, number={9}, journal={MICROMACHINES}, author={Bhatnagar, Prithu and Vashaee, Daryoosh}, year={2022}, month={Sep} }
 @article{bhatnagar_vashaee_2022, title={Process Considerations for selective doping of poly-Si thin films with spin-on dopants and nickel silicide formation for planar thermoelectric devices}, volume={150}, ISSN={["1873-4081"]}, DOI={10.1016/j.mssp.2022.106941}, abstractNote={The formation of highly doped p-type (boron-doped) and n-type (phosphorus-doped) poly-Si thin films with spin-on dopants on the same wafer poses unique challenges. This work evaluates the pros and cons of different approaches to dopant diffusion, residue removal, and diffusion mask selection when working with spin-on dopants. The experiments have been carried out to optimize the formation of highly doped poly-Si thin films that will form the active layers of a micro-thermoelectric generator (μ-TEG). Building upon previous work on residue removal methods, we report that the residue formation is also dependent on the oxide-silicon surface with a PECVD oxide-Si interface not requiring a post-dopant diffusion nitric acid treatment to achieve a hydrophobic surface. Furthermore, comparing the direct dispense and proximity diffusion methods verifies the existing reports of enhanced diffusion in the latter case. Besides, we observe that doping first with Boron is more conducive than doping first with phosphorus to reduce sheet resistance. We also optimize the contact formation with Ti/Ni thin films and report the mean contact resistivity. Notably, contact annealing precludes the nitric acid treatment requirement even if the surface is hydrophilic after removing dopant residue. Additionally, the sequence of silicidation is observed to be dependent on the doping of the underlying areas.}, journal={MATERIALS SCIENCE IN SEMICONDUCTOR PROCESSING}, author={Bhatnagar, Prithu and Vashaee, Daryoosh}, year={2022}, month={Nov} }