Mapping Electrical Properties Using STEM-EBIC for Electric Field-Induced Resistance Changes in Amorphous Gallium Oxide

Abstract

Non-stoichiometric amorphous gallium oxide (GaOx) films exhibit unique electrical properties arising from structural disorder and ion dynamics, leading to insulator-to-metal transitions and memristive switching. The insulator-to-metal transition in GaOx follows the Anderson transition, where localized electrons in disordered materials become delocalized and enable metallic conduction as the Fermi energy crosses the mobility edge [ 1]. In contrast, memristive switching arises from oxygen ion migration, where an electric field induces oxygen concentration gradients across the film, causing uniform resistance modulation without filament formation [ 2]. While these phenomena reveal GaOx’s potential for electronic switching and memory applications, further study is required to clarify how the interplay of ion distribution, structural disorder, and electronic properties governs its resistive behavior. This study aims to elucidate these fundamental mechanisms to enhance understanding of GaOx’s electronic properties. Using 4D-STEM and EELS, we focused on capturing intricate atomic and electronic structures. 4D-STEM enabled detailed characterization of atomic arrangements, and pair distribution function (PDF) analysis allowed us to characterize short-range order and observe local atomic configurations. EELS provided information on electronic structure, particularly revealing details in the oxygen K edge, which highlighted the local electronic environment. To further investigate how these atomic and electronic structures respond to applied bias, we used in-situ biasing TEM. This enabled us to observe modifications in atomic ordering and electronic states occurring with resistance changes under applied bias. Additionally, we employed STEM-EBIC and SEEBIC for nanoscale mapping of electrical properties. STEM-EBIC generates nanoscale images by detecting the electrons and holes separated by the electric field after the generation of electron-hole pairs, while SEEBIC provided quantitative insight into conductivity changes by measuring holes escaping to ground following secondary electron release.

Authors 7

1. Sanghyo Lee corresponding

   Seoul National University

   Affiliation as printed

   Seoul National University , Department of Materials Science & Engineering , Seoul 08826 , Republic of Korea

2. Jinseok Ryu

   Seoul National University

   Affiliation as printed

   Seoul National University , Department of Materials Science & Engineering , Seoul 08826 , Republic of Korea

3. 이성훈

   Seoul National University

   Affiliation as printed

   Seoul National University , Department of Materials Science & Engineering , Seoul 08826 , Republic of Korea

4. Philipp Hein Aachen Institute of Physical Chemistry

   RWTH Aachen University

   Affiliation as printed

   RWTH Aachen University , Institute of Physical Chemistry , Aachen , North Rhine- Westphalia , Germany

5. Manfred Martin Aachen Institute of Physical Chemistry

   RWTH Aachen University

   Affiliation as printed

   RWTH Aachen University , Institute of Physical Chemistry , Aachen , North Rhine- Westphalia , Germany

6. Youngwoon Kim

   Seoul National University

   Affiliation as printed

   Seoul National University , Department of Materials Science & Engineering , Seoul 08826 , Republic of Korea

7. Miyoung Kim