藉由自旋幫浦效應和自旋賽貝克效應研究在有機半導體苝四甲酸二酐中的自旋注入以及傳輸性質

Investigate Spin Injection and Transport Properties in Organic Semiconductor PTCDA by Spin Pumping and Spin Seebeck Effect

翁聖岳(Sheng-Yueh Weng)

指導教授 ： 林敏聰

國立臺灣大學/理學院/應用物理研究所/碩士(2019年)

https://doi.org/10.6342/NTU201902001

摘要

在自旋電子學中，自旋在儲存設備的控制以及偵測資訊中扮演著很重要的角色。利用導電電子以及磁子傳輸的純自旋流在金屬以及非有機材料中被廣泛地研究，但在因其弱自旋軌道耦合 (spin-orbit coupling) 而被預測有長自旋擴散長度 (spin diffusion length) 和自旋鬆弛時間 (spin relaxation time) 的有機材料中卻還沒被研究透徹。在π共軛有機半導體 (π-conjugated organic semiconductor) 中，電荷載子是藉由跳躍傳導 (hopping transport) 的但是自旋傳輸性質卻還尚未清楚。在這系列的實驗中，我們用自旋幫浦 (spin pumping effect) 和自旋賽貝克效應 (spin Seebeck effect) 這兩種機制來產生純自旋流 (pure spin current) ，並將其注入至π共軛有機半導體苝四甲酸二酐 (PTCDA) 中展示其中的自旋傳輸現象。藉由比較這兩種自旋注入實驗，我們發現其自旋流穿透深度的不同，並認為純自旋流的產生機制還有自旋流來源和能障間的介面是十分重要的。變溫自旋賽貝克效應實驗暗示孔洞效應似乎在能障太薄的時候會產生巨大的影響，但當其足夠厚實自旋流則可以流入能障苝四甲酸二酐。

關鍵字

自旋幫浦 ； 自旋賽貝克效應 ； 共軛有機半導體 ； ?四甲酸二酐 ； 自旋注入 ； 自旋傳輸

並列摘要

In spintronics, spin transport plays an important role in controlling and detecting information in storage devices. Pure spin current, carried by conduction electrons or magnons, have been investigated in a wide range of metals and inorganic semiconductors but rarely in organic materials, which have been predicted to have the long spin diffusion length and spin relaxation time due to its low spin-orbit coupling which is caused by low atomic number of composing atoms.
It has been reasoned that charge carriers in π-conjugated organic semiconductor transport by hopping but the spin transport property is not clear yet. Here we used two kinds of sources, spin pumping and the spin Seebeck effect, to inject pure spin currents into π-conjugated organic semiconductors PTCDA and demonstrate the spin transport inside. By comparing these two kinds of spin injections, we conclude that the generation mechanisms of pure spin current and the interface between source and barrier are both important since the resulting penetration lengths of spin current are different between the two methods. Temperature-dependent spin Seebeck effect measurements have also been performed and imply the pinhole issue would cause a serious impact if the thickness of PTCDA is excessively thin but spin current would flow through organic materials when PTCDA is thick enough.

並列關鍵字

Spin pumping ； spin Seebeck eff ect ； π-conjugated organic semiconductor ； PTCDA ； spin injection ； spin transport

參考文獻

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