2023年ノーベル化学賞：量子ドットの発見と合成 Nobel Prize in Chemistry 2023 | 日本語の記事：量子ドット：化学物理工学の魅力と可能性
2023/5 大学のプレスリリース (pdf @ tuat.ac.jp) and riken.jp. Nature Communications (Open Access) or DOI or Forging a dream material with semiconductor q | EurekAlert!
高移動度の半導体コロイド量子ドット超格子を実現 ーエピタキシャル接合により、高性能化に成功ー Enabling metallic behaviour in two-dimensional superlattice of semiconductor colloidal quantum dots
理化学研究所（理研）創発物性科学研究センター創発デバイス研究チームの岩佐義宏チームリーダー、サトリア・ビスリ上級研究員（研究当時、現客員研究員、東京農工大学大学院工学研究院准教授）らの共同研究グループは、半導体コロイド量子ドット[1]の高秩序な超格子[2]薄膜を作製した結果、移動度[3]の大幅な増強に成功し、キャリアドープ[4]による金属的伝導性を初めて実現しました。
本研究成果は、将来の光電デバイス[5]開発のための新たな基盤になるものと期待できます。これまで、コロイド量子ドットからなる材料を光電デバイスへ展開する場合、特に移動度の低さが障害となっていました。
今回、共同研究グループは、有機配位子[6]によって安定化された硫化鉛（PbS）コロイド量子ドットを有機溶媒表面上で集積させました。そして、量子ドットの表面を形成するいくつかの結晶面から選択的に有機配位子を除去することで、量子ドット同士をエピタキシャル接合[7]させ、結晶の向きをそろえて広い面積に配列させた「量子ドット超格子」とも呼ぶべき薄膜をシリコン基板上に写し取ることに成功しました。この超格子薄膜の電気伝導特性を電界効果トランジスタ[8]デバイスにより調べたところ、従来の商用コロイド量子ドット薄膜よりも1,000～100万倍以上も大きな移動度を観測しました。また低温での電気抵抗測定から、この薄膜はキャリアドープによって金属的伝導性を示すことも明らかになりました。
本研究は、科学雑誌 Nature Communications (Open Access)（5月26日付）に掲載されます。
Press release file: pdf (tuat.ac.jp) and at RIKEN.jp
Bisri准教授のコメント：「この種の材料でさらなる研究を行う予定であり、量子ドット超格子の能力の大幅な向上につながる可能性があると考えています。現在のデバイスの改善に加えて、真の全「量子ドット」直接エレクトロルミネセンスデバイス、電気駆動レーザー、熱電デバイス、高感度検出器やセンサーなど、これまで量子ドット材料の範囲を超えていた新しい用途につながる可能性があります」
A team of researchers have succeeded in creating a “superlattice” of semiconductor quantum dots that can behave like a metal, potentially imparting exciting new properties to this popular class of materials.
Semiconducting colloidal quantum dots have garnered tremendous research interest due to their special optical properties, which arise from the quantum confinement effect. They are used in solar cells, where they can improve the efficiency of energy conversion, biological imaging, where they can be used as fluorescent probes, electronic displays, and even quantum computing, where their ability to trap and manipulate individual electrons can be exploited.
However, getting semiconductor quantum dots to efficiently conduct electricity has been a major challenge, impeding their full use. This is primarily due to their lack of orientational order in assemblies. According to Satria Zulkarnaen Bisri, lead researcher on the project, who carried out the research at RIKEN and is now at Tokyo University of Agriculture and Technology, “making them metallic would enable, for example, quantum dot displays that are brighter yet use less energy than current devices.”
Now, the group has published a study in Nature Communications that could make a major contribution to reaching that goal. The group, led by Satria Bisri and Yoshihiro Iwasa of RIKEN CEMS, has created a superlattice of lead sulfide semiconducting colloidal quantum dots that displays the electrical conducting properties of a metal.
The key to achieving this was to get the individual quantum dots in the lattice to attach to one another directly, “epitaxially,” without ligands, and to do this with their facets oriented in a precise way.
The researchers tested the conductivity of the material they created, and as they increased the carrier density using a electric-double-layer transistor, they found that at a certain point it became one million times more conductive than what is currently available from quantum dot displays. Importantly, the quantum confinement of the individual quantum dots was still maintained, meaning that they don’t lose their functionality despite the high conductivity.
“Semiconductor quantum dots have always shown promise for their optical properties, but their electronic mobility has been a challenge,” says Iwasa. “Our research has demonstrated that precise orientation control of the quantum dots in the assembly can lead to high electronic mobility and metallic behavior. This breakthrough could open up new avenues for using semiconductor quantum dots in emerging technologies.”
According to Bisri, “We plan to carry out further studies with this class of materials, and believe it could lead to vast improvements in the capabilities of quantum dot superlattices. In addition to improving current devices, it could lead to new applications such as true all-QD direct electroluminescence devices, electrically driven lasers, thermoelectric devices, and highly sensitive detectors and sensors, which previously were beyond the scope of quantum dot materials.”
The team included researchers from RIKEN, Tokyo Institute of Technology, the University of Tokyo, SPring-8, and the Tokyo University of Agriculture and Technology.
From: Forging a dream material with semiconductor quantum dots | RIKEN
Also, featured at:
Lined-up quantum dots become highly conductive – Physics World
高移動度の半導体コロイド量子ドット超格子を実現：移動度は従来の1000～100万倍 – EE Times Japan (itmedia.co.jp)
Metallic Magic: Forging a Dream Material With Semiconductor Quantum Dots (scitechdaily.com)
Creating a “Superlattice” of Semiconductor Quantum Dots With Metallic Behavior (azom.com)