The effect of substrate bias on the piezoelectric properties of pulse DC magnetron sputtered AlN thin films
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The effect of substrate bias on the piezoelectric properties of pulse DC magnetron sputtered AlN thin films Nguyen Quoc Kha´nh1,* , Ja´nos Rado´1, Zsolt Endre Horva´th1, Saeedeh Soleimani1, Binderiya Oyunbolor1, and Ja´nos Volk1 1
Centre for Energy Research, Institute of Technical Physics and Materials Science, Konkoly-Thege M. út 29-33, H-1121 Budapest, Hungary
Received: 27 July 2020
ABSTRACT
Accepted: 1 November 2020
Substrate bias was applied for AlN deposition on rolled Ni sheet during pulse DC reactive sputtering to overcome the difficulty caused by thermal expansion mismatch between Ni substrate and AlN upon substrate heating. It was shown by Piezoresponse Force Microscopy (PFM) that the quality of the deposited AlN layer depends strongly on the negative substrate bias, i.e., the energy transferred via the bombardment of the accelerated positive ions on the sample. As the negative substrate bias becomes larger, the so formed layer shows higher piezoresponse, and better homogeneity. A Z-cut LiNbO3 single crystal was used as a reference to correct the PFM signals. The highest average d33 piezoelectric coefficient value, achieved at - 100 V substrate bias, is 3.4 pm/V indicating the feasibility of AlN deposition on rolled Ni substrate for vibration energy harvesting applications.
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The Author(s) 2020
1 Introduction Tremendous number of sensors to be applied nowadays over the world necessitates the use of sustainable, maintenance-free, and self-powered sensor system [1]. Piezoelectric materials are promising for such purpose, being a good transducer to convert directly the stimulus into electric signal in the case of sensing, or into electrical energy as vibrational energy harvesters for sensor operation. Aluminum nitride (AlN) thin film has been widely studied for piezoelectric energy harvester Address correspondence to E-mail: [email protected]
https://doi.org/10.1007/s10854-020-04810-9
application, among others, due to its excellent properties, like piezoelectricity even at high temperature, extreme hardness, good thermal and chemical stabilities, and not least, environment friendly lead-free material. [2]. AlN films can be grown by various methods including Chemical Vapor Deposition (CVD) [3], MetalOrganic Chemical Vapor Deposition (MOCVD) [4], Molecular Beam Epitaxy (MBE) [5], Pulsed Laser Deposition (PLD) [6], and Atomic Layer Deposition (ALD) [7]. However, these methods are expensive, and high processing temperatures are required. Direct Current (DC) and Radio Frequency
J Mater Sci: Mater Electron
(RF) reactive ion sputtering, being low temperature and low-cost processes with excellent reproducibility and high output, therefore, are the most frequently applied techniques to produce AlN thin layer [8–10]. Silicon wafer (with or without top oxide) is the most commonly used substrate for AlN deposition. Depending on requirements of the device to be fabricated different metals are deposited as buried electrode prior to AlN growth [11–14]. Sometimes sapphire or glass substrate have been also used [
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