[10a-PA4-1~10] 9.1 Dielectrics, ferroelectrics

▲ [10a-PA4-10] Effect of different divalent cations on the piezoelectric and mechanical properties of MTiAlN-based thin films (M = Mg or Zn)

〇Sri Ayu Anggraini¹, Masato Uehara¹, Kenji Hirata¹, Hiroshi Yamada¹, Morito Akiyama¹ (1.AIST)

Keywords:piezoelectric, AlN, thin films

Wurtzite-structured aluminum nitride (AlN) is an attractive functional thin film due to its promising potentials in MEMS applications as well as its wide implementation in bulk-acoustic resonator (BAR) and solidly mounted resonator (SMR) applications. However, despite the dramatically high piezoelectric response of Sc_xAl_1-xN thin films [1], the expensive cost of scandium (Sc) has inhibited further commercialization of Sc_xAl_1-xN, while simultaneously has also inspired endeavors in finding alternative dopants for AlN that have relatively reasonable cost. Theoretically, magnesium (Mg)-based codopants has been touted as the potential codopants that may enhance the piezoelectric response of AlN [2]. Experimentally, MgNb has been proven to capable of generating similarly high piezoelectric response as Sc [3]. Recently, our group has also proposed the use MgTi as one of the Mg-based codopants that could also enhance the d₃₃ of AlN [4]. However, the fact that Mg is prone to oxidation has caused hesitancy in the utilization of Mg-based-codopants to improve the piezoelectric response of AlN thin films. On the other hand, there is little study regarding the use of Zn, which has relatively lower reactivity toward oxidation when compared with Mg, as divalent cation of the codopant for AlN. Therefore, in this study, we investigated the effect of Zn as the divalent cation to substitute Mg in MgTi codopants for AlN (Fig. 1 (a)) on the piezoelectricity and the mechanical properties (i.e. stiffness and hardness).