【公開日：2024.07.25】【最終更新日：2024.06.25】
課題データ / Project Data
課題番号 / Project Issue Number
23JI0042
利用課題名 / Title
Origin of Room Temperature Ferromagnetism in Thin films of Undoped d0 Semiconducting Oxides
利用した実施機関 / Support Institute
北陸先端科学技術大学院大学 / JAIST
機関外・機関内の利用 / External or Internal Use
外部利用/External Use
技術領域 / Technology Area
【横断技術領域 / Cross-Technology Area】（主 / Main）物質・材料合成プロセス/Molecule & Material Synthesis（副 / Sub）計測・分析/Advanced Characterization
【重要技術領域 / Important Technology Area】（主 / Main）次世代ナノスケールマテリアル/Next-generation nanoscale materials（副 / Sub）高度なデバイス機能の発現を可能とするマテリアル/Materials allowing high-level device functions to be performed
キーワード / Keywords
スピントロニクスデバイス/ Spintronics device,先端半導体（超高集積回路）/ Advanced Semiconductor (Very Large Scale Integration),原子層薄膜/ Atomic layer thin film
利用者と利用形態 / User and Support Type
利用者名（課題申請者）/ User Name (Project Applicant)
NGUYEN Hoa Hong
所属名 / Affiliation
Masaryk Univ., Faculty of Science, Dept of Condensed Matter Physics
共同利用者氏名 / Names of Collaborators in Other Institutes Than Hub and Spoke Institutes
Nguyen Sy PHAM-Masaryk Univ.,Martin FRIAK-Masaryk Univ.
ARIM実施機関支援担当者 / Names of Collaborators in The Hub and Spoke Institutes
Tatsuya MURAKAMI-JAIST
利用形態 / Support Type
（主 / Main）技術代行/Technology Substitution（副 / Sub）-
利用した主な設備 / Equipment Used in This Project
報告書データ / Report
概要（目的・用途・実施内容）/ Abstract (Aim, Use Applications and Contents)
ZnO films were fabricated before by using the Pulse Laser Deposition technique. It was found (also with collaborations with JAIST) that undoped ZnO films could be room temperature ferromagnetic, and doping transition-metal (TM) should not be the main cause to induce magnetism into this type of wide band-gap semiconductor. The observed ferromagnetism (FM) was supposed to be due to defects/vacancies, but at the Zn sites, not at the O size. ZnO nano-films could be a very good candidate for spintronic devices, therefore, in this research we want to clarify the origin of FM in this family. ZnO films with different thicknesses were deposited on R-cut Al2O3 substrates by Sputtering at ARIM . We have been measuring structural and magnetic properties of those samples, as well as perform modeling , in order to make it clear, if the FM in ZnO films is due to Zn/O defects, then we can figure it out where those defects and vacancies should be located, and in details, how they contribute to magnetic moments. It will be a good guide for a new generation of potential spintronic devices, when one can manipulate well magnetic properties of the nano-scaled semiconductor.
実験 / Experimental
Films of ZnO with different thicknesses were deposited on R-cut Al2O3 substrates by Sputtering technique at ARIM-JAIST. We have been measuring XRD, VSM in Ceitec (Brno). We will expect to run XPS, PAS, MFM in the future.
結果と考察 / Results and Discussion
We have been doing experiments. The initial results are good, as expected. ZnO films made by sputtering have almost the same properties as those of ZnO films made by the PLD technique. It is surprising that films fabricated at such a low temperature (100 C ) could have such a good quality. All films of ZnO films are well crystallized as wurtzite structure, well oriented and there is no alien phase. As for magnetic properties, all pristine ZnO films are ferromagnetic at room temperature. The saturated magnetization is in the same order as that of the Pulse-Laser Ablated films. There is no big difference in magnitude of magnetization versus thickness. Or in other words, sputtered ZnO films of different thicknesses have Ms in the same order of magnitude. It is to say that if the observed FM in ZnO films originates from defects, then those defects are supposed to contribute quite thoroughly along the depth of the film, but not basically at the surface-interface as in other cases of semiconducting oxide films such as TiO2 and SnO2 films. No obvious surface-related-magnetism has been observed. We plan to measure magnetic moment versus temperature (M-T) at a high temperature scale (possible at Ceitec in Brno), in order to figure out precisely Curie temperature (TC) of the compound. We will perform modeling to determine how defects would distribute in which orientation, thus may contribute to the total magnetic moment. If possible, some PAS measurements will be done to determine the profile of defects. XPS will be done to confirm the existence of Zn and/or O vacancies in those films. We plan to write a paper in mid -2024, with Dr. Murakami at ARIM as our co-author.
図・表・数式 / Figures, Tables and Equations
Fig. 1. XRD patterns of ZnO films with different thicknesses
Fig.2. Magnetization versus magnetic field taken at 300K measured for ZnO films with different thicknesses (note: field was applied parallel to the film plane)
その他・特記事項（参考文献・謝辞等） / Remarks(References and Acknowledgements)
We would like to thank GACR for financial support (Project No. 22-21547S) and partial support from the MEYS (Project CZ.02.01.01/00/22_008/0004572). Many thanks to ARIM-JAIST for providing its facilities.
成果発表・成果利用 / Publication and Patents
論文・プロシーディング（DOIのあるもの） / DOI (Publication and Proceedings)
口頭発表、ポスター発表および、その他の論文 / Oral Presentations etc.
特許 / Patents
特許出願件数 / Number of Patent Applications：0件
特許登録件数 / Number of Registered Patents：0件