This work reports investigation on the deposition and evaluation of an aluminum-doped zinc oxide (AZO) thin film and its novel applications to micro- and nano-devices. The AZO thin film is deposited successfully by atomic layer deposition (ALD). 50 nm-thick AZO film with high uniformity is checked by scanning electron microscopy. The element composition of the deposited film with various aluminum dopant concentration is analyzed by energy-dispersive X-ray spectroscopy. In addition, a polycrystalline feature of the deposited film is confirmed by selected area electron diffraction and high-resolution transmission electron microscopy. The lowest sheet resistance of the deposited AZO film is found at 0.7 kΩ/□ with the aluminum dopant concentration at 5 at.%. A novel method employed the ALD in combination with the sacrificial silicon structures is proposed which opens the way to create the ultra-high aspect ratio AZO structures. Moreover, based on this finding, three kinds of micro- and nano-devices employing the deposited AZO thin film have been proposed and demonstrated. Firstly, nanowalled micro-hollows with an aspect ratio of 300 and a height of 15 µm are successfully produced
. Secondly, micro- and nano-fluidics, including a hollow fluidic channel with a nanowall structure as a resonator and a fluidic capillary window as an optical modulator is proposed and demonstrated. Lastly, nanomechanical resonators consisting of a bridged nanobeam structure and a vertical nanomechanical capacitive resonator are fabricated and evaluated.
This article demonstrates a new approach using a thermoelectric generator (TEG), which converts thermal energy from ambient temperature fluctuations into electricity for the power source of portable devices. Using TEGs with heat storage material on one side of the TEG, a temperature difference can be created at both sides of the TEG from ambient temperature variations. In this work, the electric power generation and its storage to a capacitor are evaluated for the TEG-heat storage device. Two kinds of TEGs (#1 and #2) with different sizes have been evaluated. Maximum output power densities of TEGs #1 and #2 are 0.27 and 0.45 mW/cm 2 at temperature difference ΔT = 7 C, respectively. The electric power from the TEG can be stored in a capacitor via a DC-DC converter. The temperature difference dependences of the electronic conversion efficiency for the DC-DC booster are evaluated for both TEGs. A charge stored in the capacitor is 113 μAh under ΔT = 3 C. The maximum output power and the storable energy in the capacitor are 30 μW and 500 mJ, respectively, under ambient temperature fluctuations in near room temperature. The investigation in this work could possibly lead to high potential for battery-free wireless sensing systems.
K E Y W O R D Sambient temperature fluctuations, phase-change material, thermoelectric generator, wireless internet of things sensing system
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