Controlling the polarity of ScAlN via formation of cation/anion vacancy

先前，我们已经证实，添加元素如Si或Ge可以将ScAlN的极性从Al极性反转为N极性。然而，添加碳（C）不能反转ScAlN的极化方向，这被怀疑是由于氮空位（Vn）的存在。在本年度，通过添加镁（Mg）、锌（Zn）等理论上能够产生氮空位的元素，确认了Vn对极性的作用。结果表明，在ScAlN中加入Mg或Zn，薄膜的极性均为Al极性，这意味着加入任何一种元素都不能使ScAlN的极性从Al极性转变为N极性。添加到ScAlN中的Mg或Zn浓度的增加仅导致纤锌矿相稳定性的降低，从而导致较低的压电d33响应。这些结果进一步证实了氮空位的存在不会引起氮化物的极性反转。此外，我们在2023年JSAP春季会议上的演讲也被提名获得最佳海报奖。

Previously, we have confirmed that the addition of element such as Si or Ge could inverse the polarity of ScAlN from Al-polar to N-polar. However, addition of Carbon (C) could not inverse the polarization direction of ScAlN, which is suspected to be due to the presence of nitrogen vacancy (Vn). The role of Vn on polarity is confirmed in this fiscal year by addition of element that theoretically can generate nitrogen vacancy such as magnesium (Mg) or zinc (Zn). It was found that addition of Mg or addition of Zn into ScAlN yielded in thin films with Al-polarity, which means that addition of either element was unable to inverse the polarity of ScAlN from Al-polar to N-polar. Increase in concentration of Mg or Zn added into ScAlN was only resulted in a decrease in wurtzite phase stability which led to lower piezoelectric d33 response. These results further confirm that the presence of nitrogen vacancy could not induce polarity inversion in nitride. Also, our presentation in JSAP Spring meeting 2023 was also nominated to receive best poster award.