轉印缺陷對石墨烯電性的影響

Effect of Transfer-induced Defectiveness on Graphene's Electronic Performance

江博穗(Chiang Bo Suei)

指導教授 ： 謝雅萍

國立中正大學/工學院/光機電整合工程研究所/碩士(2014年)

摘要

石墨烯應用於電晶體和透明導電電極等等電子應用產品是日趨漸增，提升本身石墨烯特性對於應用產品是一大利，我們想藉由轉印步驟來提升石墨烯特性，進而增加電子商品化的可能性。
對於轉印步驟我們是使用不同的聚合物去支撐石墨烯，再將其除去。一般使用的聚合物是PMMA，其有殘留物和較多氧鍵結，使其石墨烯特性降低。為了transfer 便利性，我們使用Parafilm封口膜來做轉印材料。
因為Parafilm是首度被用在transfer graphene，我們嘗試極佳化(optimization)其transfer 參數(包括adhere溫度、removing solvent、removing 溫度)。目標為得到更完整的轉印。我們的衡量標準為om(完整度)及四點霍爾電性量測。若graphene轉印的很好，我們預期om沒有破洞，且其電性應較佳。我們意外發現利用Parafilm轉印時，會得到較高載子遷移率之石墨烯(相對於PMMA轉印)。(由四點量測及FET)使用氯仿去除的Parafilm的平均載子遷移率是1531cm2/VS，而使用二甲苯去除Parafilm的平均載子遷移率是2543 cm2/VS。然而，表面的乾淨度確有所侷限(猜測是因為有其他增加黏性的參雜物)，不過大致上可以跟PMMA差不多，運氣好的話可以很乾淨。
為了瞭解高mobility的原因及增進表面乾淨度。我們找出其主要純成分paraffin(我們選用alkane C20H42, 純度99%)。XPS分析顯示出相對於PMMA而言，Parafilm & Paraffin wax均有較低的氧鍵結訊號，我們懷疑高載子遷移率是因為這是沒有化學鍵與graphene bond所致(有還原石墨烯高載子遷移率的現象)。
而AFM OM也顯示Parafilm使用Xylene的石墨烯較PMMA及Paraffin wax有乾淨的表面。其Raman也顯示較低的Id/Ig ，Raman的G 與2D 位置分析也顯示其doping concentration 較低。可以見得Paraffin wax與graphene較無化學作用產生。
然而Paraffin wax轉印較容易有破洞，導致電性無法有代表性的結果。懷疑是transfer 抓力不好。
將來會由TEM驗證其無化學鍵之完美轉印。成功證實高載子遷移率的原理假設；從G-FET量測得到的Vgs-Ids圖很明顯的斜率高於PMMA-Transferred，種種分析明顯說明了使用Paraffin Wax材料作為轉印材料，可以得到特性較好且完整的石墨烯。

關鍵字

石墨烯場效電晶體 ； 轉印 ； 石墨烯

並列摘要

Graphene used in transistors and transparent conductive electrode and so on electronic applications is increasing day by day. Enhance the properties of graphene itself is a boon for applications. We want to improve graphene properties by transferring, thus increasing the electronic commercialization possibilities.
Now the transfer step is the use of different polymers to support graphene, and then removed it. The polymer is generally used PMMA, and it has more residues and oxygen bonding to deteriorate the graphene characteristics. To the convenience of transferring, we use Parafilm as the transfer material.
Because Parafilm is the first to be used in the transfer graphene, we try to excellent technology (optimization) whose transfer parameters (including adhere temperature, removing solvent, removing the temperature). The objective is to obtain a more complete transfer from om (integrity) and a four-point Hall electrical measurements. If graphene transfer is very good, we expect no holes in om picture, and should be better in electrical properties. We accidentally found the use of parafilm to transfer graphene grown CVD, you will get a higher carrier mobility of graphene (relative to PMMA-transferred). (Measured by the four point hall effect andG- FET). However, the cleanliness of surface really have limitations (guess is because there are other parameters to increase the viscosity of debris), but generally it’s similar with PMMA-transferred or more cleaner.
In order to understand the reasons for the high mobility and enhance surface cleanliness. We identify the principal ingredient of pure paraffin (we chose alkane C20H42, 99% purity). Xps display parafilm & Paraffin were lower relative to PMMA oxide peak, we suspect that the high mobility because it is not caused by chemical bond with graphene bond (reduced graphene's high mobility)
The AFM and OM images also show that compared to PMMA,Parafilm, and Paraffin wax – transferred have a clean surface. It also shows the Raman G and 2D position analysis and lower Id/Ig in Raman .It’s also showed lower doping concentration .It’s also showed a narrower full width at half maximum. There is no chemical work in paraffin wax with graphene.
However, paraffin wax transfer is more likely to have holes. It causes no electrical representative results. Suspect the bad grip in transfer.
In the future, no bond perfection verify its transfer from the TEM. Successfully demonstrate the principle of high carrier mobility assumptions. From the G-FET measurements obtained Vgs-Ids figure. The other lines show obviously higher than the slope of PMMA-Transferred. The use of a variety of Paraffin Wax material as a transfer material can be obtained better performance and complete graphene.

並列關鍵字

transfer ； graphene ； GFET

參考文獻

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