應用超快雷射對表面電漿薄膜做質量轉移與製作奈米結構之研究

Mass transfer and nano-fabrication by ultrafast laser interactions on plasmonic thin films

陳柏翰(Bo-Han Chen)

指導教授 ： 蔡定平

國立臺灣大學/理學院/應用物理所/碩士(2010年)

https://doi.org/10.6342/NTU.2010.00243

摘要

隨著元件尺寸的縮小(scaling)，電漿子學(Plasmonic)為目前奈米光學領域中熱門的議題，本論文利用雷射作為熱源發展出可製作微米及次微米級結構的系統，並選擇金薄膜作為研究對象，將其實驗結果分析討論，給予一個簡單的物理機制圖像，為研究電漿子學領域提供一個新穎、快速製作元件的方法。物理機制的推測結果在相變化材料鍺銻碲(Ge2Sb2Te5)的實驗中也觀測到類似結果，應用實驗結果，我們成功將微米級的圖檔樣貌，以次微米級的單位精準度控制，將其質量轉移至另一基板上。
系統架構利用飛秒脈衝(Femto-second pulse)雷射做為短時間高能量光源，雷射光經高倍率油鏡(100X, NA 1.4)聚焦至金奈米薄膜(Gold thin film)樣品上。樣品製作部分我們將金濺鍍(DC sputter coating)於透明基板上，稱為母板(Donor side)。並在金薄膜上方加蓋一片玻璃基板，稱為子板(Receiver side)。藉由電腦控制三軸式奈米平移台的移動，可以控制雷射光聚焦在金膜上的位置。我們調整薄膜厚度與雷射照度，並使用原子力顯微儀觀察其不同實驗條件下的微觀結構。在高雷射照度下，金可以從母板轉移質量至子板，且此特性也成功適用於其他不同金屬材質，利用雷射推進質量移轉技術我們成功從母板轉移一張由相變化材料Ge2Sb2Te5薄膜材料組成的圖檔(293x283 pixel)到子板，大小為50 um x 50 um。在低雷射照度下，金膜母板則形成最小直徑為250 nm的凸起結構，利用此結構排出Y形波導(Y-splitter)。關於雷射推進質量轉移和金膜圓柱隆起的物理機制包含在分析討論內。
實用性，雷射推進質量移轉技術可將不同的金屬轉移到同一個位置基板上，製作出微米裝置(Microdevice)，例如天線、電路。以及利用雷射光在低雷射照度下，製作奈米結構，例如電漿波導(Plasmonic waveguide)。顯示此技術具有奈米製作能力，且具有低複雜低成本的優點。

關鍵字

表面電漿 ； 飛秒雷射 ； 質量轉移 ； 鍺銻碲 ； 奈米電漿結構 ； 奈米製程

並列摘要

Laser-induced forward transfer (LIFT) is a simple, fast, one-step process technology, which utilizes the short pulse laser to remove the material from a donor thin film to a receiver substrate. In this thesis, we present a method of the deposited dots by using femto-second LIFT for the gold thin films with the thickness: 20, 30, and 40 nm. Each gold thin film was deposited on a glass substrate by a sputter in an argon chamber with the pressure 0.5 Pa. The growth rate of the gold thin film is 0.2 nm/s. The samples were mounted on a x-y-z stage that positions the sample with a resolution of 0.4 nm relative to a 100X microscope objective and is subsequently irradiated by the Ti:sapphire laser (wavelength λ= 800 nm) with pulse duration of 140 fs and 80 MHz repetition rate. The topography of sample is studied by atomic force microscopy (AFM). Through the observaed morphologies of the receiver side and donor side, the following three zones can be observed. (1) Below the first laser fluence threshold, JT1, no structure formation on the donor film and the receiver substrate was found. (2) Between JT1 and second fluence threshold, JT2, the donor film forms a cylindrical shaped bump, with the size around 18 nm (thickness) x 250 nm (diameter), and gold was transferred to the receiver substrate and formed an island-like geomorphology with nanometer grains. Their sizes are around 5 nm (thickness) x 20 nm (diameter) for LIFT 20 nm-thick donor film. We attribute this phenomenon to phase explosion occurring almost in the superheated liquid free surface of source film. (3) Above JT2, the donor film is ablated and the elevated rim structure, which diameter size is around 300 nm. In receiver substrate, the deposited dots form a disk shaped, which size is around 27 nm (thickness) x 900 nm (diameter) for LIFT 30 nm-thick donor film. Possible mechanisms leading to the observed dots form the resolution limits of this technique are also discussed. The dots of nanothickness thin films via laser pulses may provide a simple and efficient method for fabrication of nanoscale structures, e.g. plasmonic devices. Thus, LIFT technique provides a relatively simple method for the combination of the multiple dissimilar materials within a single microdevice.

並列關鍵字

Surface Plasmons ； Ultrafast laser ； Thermal effect ； Gold thin film ； Ge2Sb2Te5 ； Laser-induced forward transfer ； Plasmonic nanostructure ； Nanolithography

參考文獻

[3-1] 陳富豪，「應用光熱效應之相變化奈米微影製程」碩士論文，國立台灣大學物理學研究所(2009)。

[1-1] 邱國斌、蔡定平「金屬表面電漿簡介」，物理雙月刊，第廿八卷第二期，472-485 頁(2006)。

[1-3] M. F. Crommie, C. P. Lutz, and D. M. Eigler, "Confinement of electrons to quantum corrals on a metal surface," Science 262, 218-220 (1993).

[1-4] B. D. Gates, Q. B. Xu, M. Stewart et al., "New approaches to nanofabrication: Molding, printing, and other techniques," Chem. Rev. 105, 1171-1196 (2005).

[1-5] S. H. Hong, and C. A. Mirkin, "A nanoplotter with both parallel and serial writing capabilities," Science 288, 1808-1811 (2000).