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【科技部新聞稿】跳脫百年框架引領量子黑科技,台灣研究團隊雕塑石墨烯嶄新電子結構 / Enter quantum electronics via patterned strain engineering

跳脫百年框架引領量子黑科技

台灣研究團隊雕塑石墨烯嶄新電子結構

日期:2021年3月31日

發稿單位:自然科學及永續研究發展司

聯絡人:郭廷洋助理研究員

電話:(02)2737-7465

 Email:tykuo@most.gov.tw

人類能否藉由人造方式調整物質材料的原子間距離與排列,並進而賦予它全新的物理特性呢?在科技部計畫的長期支持下,成功大學物理系暨前沿量子科技研究中心張景皓助理教授及陳則銘教授組成的研究團隊,成功開發出利用半導體產業常用的蝕刻技術來調控原子排列,將原本單純的石墨烯轉變為擁有奇異量子特性的嶄新電子元件,不僅有助於探索量子傳輸的基礎物理科學問題,未來將有機會應用在量子科技之中。卓越的研究成果於今(2021)年2月刊登於國際頂尖學術期刊《自然電子》(Nature Electronics)。

近年來科學家透過類似積木的概念,將石墨烯以錯位或扭角方式堆疊起來,藉此將石墨烯從零能隙半導體轉變成超導體、絕緣體,或將其變成像磁鐵般具有鐵磁性。這方法看似簡單,但因需將薄到僅有單原子層厚度的二維材料在特定精確角度扭角堆疊,其實際操作及未來產業應用都有著不小的難度與挑戰。

研究團隊何昇晉博士(論文第一作者)與陳則銘教授試著另闢蹊徑,構想出利用半導體蝕刻技術來雕塑氮化硼基板表面,進行具有三維結構變化的堆疊,並與謝予強等團隊成員開發出能進行原子級尺度雕刻的新穎技術。有別於以往只是單純將二維材料一層一層疊上去。這個新技術能將二維材料的晶格結構(原子排列)依照被雕刻氮化硼人造超晶格基板的結構進行拉伸或扭曲變形,以此操控其對稱性破壞及電子運動等基本物理機制,進而改變物質材料之物理特性。

研究團隊另一項重要發現,在於確立了兩種新型態霍爾效應的發現(註)。過去一百多年來,科學界普遍認為磁場是霍爾效應生成的必要條件,研究團隊在具有人造晶格結構的石墨烯量子元件上,跳脫原有框架、推翻了此一論點,結合實驗及理論證實新的霍爾效應其存在完全不需任何磁場。其中帶領團隊進行理論模型建構及數值模擬的,是另一名論文第一作者同時亦是玉山青年學者的張景皓助理教授。此突破除了理解量子傳輸的基礎科學問題外,對日後應用於量子電子元件及晶片也有著莫大的幫助。

科技部持續積極耕耘基礎科學研究,以作為台灣科技創新與發展的強力後盾。未來在量子科學技術研發上也投入資源規劃整合,秉持著世界頂尖的科技研發能力與人才培養,對於台灣量子科技發展建立良好的競爭力,並與全球科技研發完美接軌。

論文名稱及連結:〈Hall effects in artificially corrugated bilayer graphene without breaking time-reversal symmetry〉
https://www.nature.com/articles/s41928-021-00537-5

 

研究成果聯絡人

陳則銘 教授

國立成功大學物理學系(所)

電話:06-2757575 ext. 65240

Email:tmchen@phys.ncku.edu.tw

張景皓 助理教授

國立成功大學物理學系(所)

電話:06-2757575 ext. 65223

Email:cutygo@phys.ncku.edu.tw

 

Enter quantum electronics via patterned strain engineering

Diamond is hard and transparent and is also a good insulator. The graphite, by contrast, is soft and dark and easy to conduct electricity. These two seemingly distant substances are actually composed of the same atom, i.e. carbon. The reason why they have completely different physical properties is that their atomic arrangement, i.e., the so-called lattice structure, is different. In nature, the difference is caused by different growth environment and conditions. So, can we artificially adjust the distance and arrangement of atoms to deform the lattice structure so as to change, or even to create, new physical properties?

With the long-term support from the Ministry of Science and Technology (MOST) and the Higher Education Sprout Project at the National Cheng Kung University (NCKU), a joint research team led by Professor Ching-Hao Chang and Professor Tse-Ming Chen at the Department of Physics and the Center for Quantum Frontiers of Research & Technology (QFort) has successfully developed new techniques to achieve the artificial lattice deformation via patterned strain engineering in two-dimensional (2D) materials. They use this means to bring bilayer graphene into an exotic quantum state and demonstrate novel quantum electronics properties, with implications in future quantum technologies. This research work was published in the premier research journal "Nature Electronics" in February 2021.

In recent years, research scientists and engineers are crazy about building nanoscale constructions by stacking layers and layers of graphene (or other atomic thin 2D materials) on top of each other, one by one, like playing with the LEGO building blocks. By twisting these atomic LEGO blocks with the formation of moiré pattern – a phenomenon that is commonly seen in our daily life – physicists was able to modulate the lattice structure (or more specifically, create a superlattice) and hence the electronic properties, transforming graphene from a zero-gap semiconductor to a superconductor, an insulator, or turning it into a ferromagnetism. This concept looks simple and, of course, very beautiful. However, due to the need to stack 2D materials that are as thin as a single atomic layer at a specific and precise angle, it is actually very challenging and pose difficulties for future industrial applications from the technological perspective. Dr. Sheng-Chin Ho, the first author of this work, and Prof. Tse-Ming Chen tried to ‘Think Different’: can we artificially and easily create a superlattice or structure in which the lattice has been distorted and/or misorientated to achieve a similar goal, or even something better?

Driven by this motivation, they came up with an idea and a device design, to artificially create the superlattice in bilayer graphene via nanofabrication. The research team develops new techniques to etch the surface of hexagonal boron nitride (hBN) substrates, then enabling the graphene placed upon it to conform to the surface topography and be lattice deformed accordingly. With these techniques, the substrate topography can be arbitrarily defined via nanolithography with the potential to approach 2.5D and 3D patterning, thereby opening up more possibilities.

In addition to the experimental realizations, Prof. Ching-Hao Chang, who is also the first author of this paper and a receipt of the Yushan Young Scholar Award, has developed the theory and performed the calculations with assistance from his colleagues to lay down the foundation for this research work. The theory completes the last piece of the puzzle, demonstrating the existence of two novel Hall effects at zero magnetic fields (or more accurately, without breaking time-reversal symmetry). For nearly 140 years since the discovery of the classical Hall effect, the magnetic field is generally considered to be a necessary condition for the Hall effect, or more accurately, a nonzero Hall conductivity. And these two Hall effects challenge this general belief. In addition to opening a new avenue for fundamental research into quantum geometrical and topological phenomena, their approach to band engineering will also be of great help to the future applications in 2D materials and quantum electronics.

With the support of the Ministry of Science and Technology, National Cheng Kung University has been very active in fundamental research in recent years, being the cornerstone for Taiwan's technological innovation and development. This kind of spirit casts the light of knowledge and gives birth to the QFort. Apart from the devotement to the research and development, QFort has also made great efforts in cultivating outstanding talents for Taiwan; for example, Dr. Sheng-Chin Ho, who led this breakthrough, has now been recruited to Harvard University as a postdoctoral researcher. All these have made the quantum technology research and development in Taiwan more competitive and integrated with the global network.

 

Media Contact:

Professor Tse-Ming Chen

Department of Physics, National Cheng Kung University

+886-6-2757575 ext. 65240

tmchen@phys.ncku.edu.tw

 

Assistant Professor Ching-Hao Chang  

Department of Physics, National Cheng Kung University

+886-6-2757575 ext. 65223

cutygo@phys.ncku.edu.tw

 

Dr. Ting-Yang Kuo

Program Manager/Assistant Research Fellow,

Department of Natural Sciences and Sustainable Development,

Ministry of Science and Technology

+886-2-2737-7465

tykuo@most.gov.tw

 

 

更新日期 : 2021/04/05