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

2023 Fiscal Year Final Research Report

• Project/Area Number: 21K04168
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 21050:Electric and electronic materials-related
• Research Institution: National Institute of Advanced Industrial Science and Technology
• Principal Investigator: Anggraini Sri Ayu 国立研究開発法人産業技術総合研究所, エレクトロニクス・製造領域, 主任研究員 (80784123)
• Project Period (FY): 2021-04-01 – 2024-03-31
• Keywords: piezoelectric / polarity inversion / thin films / sputtering / nitride

Outline of Final Research Achievements

The polarity of scandium aluminum nitride (ScAlN) piezoelectric thin film was inversedby addition of either silicon (Si), germanium (Ge) or tin (Sn). Addition of 10 at.% Si or Ge inversed the polarity of ScAlN from Al-polar to N-polar, without significantly affect the piezoelectric response d33.However, polarity inversion in ScAlN via Si or Ge was observed when scandium (Sc) concentration was below 40 at.%.The inability of Si or Ge addition to inverse Sc0.4Al0.6N was found to correlate with phase transition occuring at higher Sc concentration. Aside from Si or Ge, addition of carbon (C) into ScAlN yielded in thin films with Al-polarity suggesting that addition of C could not inversed the polarity of ScAlN. In this study, we found that polarity inversion corresponds with the ability of Si or Ge to from aluminum vacancy (cation vacancy), while addition of C seems to tend to form nitrogen vacancy (anion vacancy)which could not cause polarity inversion.

Free Research Field

piezoelectric thin films

Academic Significance and Societal Importance of the Research Achievements

This study has successfully develop N-polar ScAlN-based thin films, including elucidate polarity control mechanism, which is expected to accelerate the realization of next-generation of radio frequency (RF) filter that will be useful for future telecommunication.