臺灣博碩士論文加值系統

分子電性量測平台以「電極-分子-電極」(metal-molecule-metal, MMM)系統為基本架構。過去以聚焦離子/電子束誘導金屬沉積法(focused ion/electron beam-induced deposition, FIBD/FEBID)製作金屬電極，但於選定的電極區域外圍會有少量金屬沉積，當兩電極外圍金屬互相重疊時，形成橋接電極間的漏電通路。本論文以熱敏式微影技術(thermal scanning probe lithography, t-SPL)為主軸，開發「鉑電極–單壁奈米碳管–鉑電極」(Pt-SWCNT-Pt)電性量測平台。T-SPL為利用加熱探針刻劃出固定形式圖案(well-defined pattern)，相較於光學微影技術(photolithography)與電子束微影技術(e-beam lithography)，具有下列三個優點：(1)無光罩微影技術、(2)常壓環境下操作、(3)解析度小於10 nm。本實驗於已沉積單壁奈米碳管之元件，以旋轉塗佈的方式將兩層特定光阻附著於元件，上下層光阻材料分別為聚鄰苯二甲醯胺(polyphthalamide, PPA)及聚二甲基戊醯胺(polydimethylglutarimide, PMGI)。當加熱探針接觸到光阻表面，PPA受熱分解成易揮發的單體化合物，藉此刻劃單壁奈米碳管兩端的電極圖案，過程迅速約1至3分鐘。接著將晶片浸泡蝕刻液將裸露的PMGI去除，再利用物理氣相沉積鉑金屬，舉離(lift-off)去除光阻後即可得到Pt-SWCNT-Pt系統。本論文聚焦於元件開發及非彈性電子穿隧能譜：(1)為使熱阻式原子力顯微鏡能在塗佈光阻的元件觀察到單壁奈米碳管，使用低濃度的PPA溶液使光阻膜厚變薄，但蝕刻過程時對需保留PMGI區域保護力下降；提高PPA濃度能保護PMGI不被侵蝕，但光阻太厚無法觀察到單壁奈米碳管。最適條件為20 nm的PMGI及20 nm PPA。(2)量測鉑導線電阻並計算電阻率為4.11 X 10–6 Ωcm，遠低於以FIBD/FEBID製作鉑導線之電阻率。(3)得到Pt-SWCNT-Pt的電阻為9.5 kΩ，符合文獻報導中奈米單壁奈米碳管的電阻。並且在4.2 K下量測非彈性電子穿隧能譜(inelastic electron tunneling spectroscopy, IETS),觀測到類石墨物質的C-C鍵振動譜峰(G band, ~1600 cm–1)。

The study on molecular electronic properties is based on Metal-Molecule-Metal (MMM) junctions. Common method for fabricating MMM junctions such as focused ion/electron beam-induced deposition (FIBD/FEBID) is not ideal due to metal-halo which may result in short circuit. Herein, Pt-SWCNT (single-walled carbon nanotube)-Pt platforms were fabricated by thermal scanning probe lithography (t-SPL). T-SPL uses heated probe to define the pattern. A dedicated t-SPL instrument is NanoFrazor which is thermal atomic force microscopy probe. First, two-layer polymers were spin coated on wafer which has been deposited SWCNTs. The base layer is polymethylglutarimide (PMGI) and top layer is polyphthalaldehyde (PPA). The probe of NanoFrazor can be heated to 1000 0C. When the hot probe is brought into contact with surface, PPA decomposes and evaporates locally. Therefore, we pattern the both ends of SWCNT for electrodes. The time of this process is about 1-3 minutes. Next, using developer to dissolve the bare PMGI. Subsequently, deposit Pt by physical vapor deposition (PVD) and then lift off unwanted region of Pt. This study focuses on fabrication of Pt-SWCNT-Pt platforms by t-SPL technique. (1) To scan the SWCNT which under the two-layer polymers by AFM, decreasing the concentration of PPA for thinner film; however, low concentration of PPA result in the PMGI being over-etching. The 20 nm PMGI and 20 nm PPA are appropriate conditions. (2) The resistivity of Pt wire is 4.11 X 10–6 Ωcm which is lower than that fabricated by FIBD/FEBID. (3) The resistance of Pt-SWCNT-Pt is 9.5 kΩ which consistent with previous work. Furthermore, the IETS (inelastic electron tunnelling spectroscopy) signal of SWCNT are detected.

口試委員會審定書 #
謝誌 i
中文摘要 ii
ABSTRACT iii
目錄 iv
圖目錄 vii
表目錄 x
第一章 緒論 1
1.1 前言 1
1.2 分子橋接系統的建構 2
1.2.1 機械式控制破裂接合法 3
1.2.2 掃描式穿隧顯微鏡破裂接合法 4
1.2.3 電遷徙誘發破裂接合法 6
1.2.4 碳電極共價鍵橋接系統 8
1.3 分子電性的量測 10
1.3.1 I(s)及I(t)技術量測法 10
1.3.2 導電原子力顯微術 12
1.3.3 觸覺感應回饋式導電原子力顯微術 13
1.3.4 非彈性電子穿隧能譜 14
1.4 單壁奈米碳管簡介 17
1.4.1 結構及分類 17
1.4.2 導電性 18
1.4.3 拉曼光譜特徵 19
1.5 研究動機 20
第二章 實驗部分 21
2.1 藥品、耗材及實驗 21
2.1.1 藥品與耗材 21
2.1.2 儀器 22
2.2 實驗原理及設備介紹 23
2.2.1 黃光微影技術 23
2.2.2 熱敏式微影技術 24
2.2.3 I-V量測及降溫系統 29
2.2.4 非彈性電子穿隧能譜量測系統 30
2.3 量測元件的製備 36
2.3.1 鉑電極設計與製程 36
2.3.2 單壁奈米碳管溶液前處理 37
2.3.3 熱敏式微影技術製作鉑接觸電極 40
2.3.4 量測元件載台製作 42
2.3.5 超音波焊線 44
第三章 結果與討論 46
3.1 光阻膜厚關係校正 46
3.2 最佳化製程條件 47
3.2.1 最佳光阻厚度 47
3.2.2 最佳蝕刻秒數 49
3.3 熱敏式微影技術製作金屬電極結果 51
3.3.1 鉑導線製作結果 51
3.3.2 鉑電極-單壁奈米碳管-鉑電極製作結果 54
3.4 鉑電極-單壁奈米碳管-鉑電極平台電性量測結果 56
3.4.1 變溫I-V量測結果 56
3.4.2 非彈性電子穿隧能譜量測結果 59
第四章 結論 63
參考文獻 64

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