摘要
理想上利用奈米結構產生表面增強拉曼散射 (SERS) 應用以應用於分子檢測等，除須具備高訊號增強能力外，其結構分佈面積亦須夠大、均勻，才可達到實際應用之需求。本研究提出利用一簡單、精確且高產率之製程以製作出具有可精準控制奈米間距之雙奈米殼層金屬粒子陣列，同時具備高拉曼訊號增強效果、製造成本低、適用於水溶液環境及大面積均勻分佈等優點。
透過垂直性蒸鍍金屬層，可於雙奈米殼層金屬粒子底端產生環狀奈米間隙，大幅增加熱點分佈面積。而藉由原子層化學氣相沈積法可精確沈積僅一奈米厚之二氧化鉿層，並可有效控制雙奈米殼層金屬粒子的奈米間隙大小，使其距離縮小至五奈米以內，提供更強的耦合電場強度。透過穿透式電子顯微鏡檢視剖面可發現環狀奈米間隙之寬度隨著二氧化鉿層厚度減少而變窄，而SERS效果亦隨之增加。
本研究建構兩種金屬結構：雙奈米殼層金/金粒子及雙奈米殼層金/銀粒子，主要差別在於第二層金屬層的材料選擇。雙奈米殼層金/金粒子已提供相當高的訊號提升能力，然而當沈積銀層為第二層金屬層時，奈米殼層金/銀粒子則又能將其SERS效果大幅提高，其訊號提升倍率高達130倍，呈現完整的待測分子拉曼光譜。

Abstract
An ideal surface-enhanced Raman scattering (SERS) nanostructure for sensing and imaging applications should provide a high signal enhancement and can be obtained by easy fabrication process with large hot spot numbers/areas. In this paper, we present a simple, precise, and high-throughput technique for producing double-nanoshelled Au nanoparticles (DNS Au NPs) arrays with well-controlled nanogap of several nanometers by employing ALD HfO2 as the dielectric layer. This DNS Au NPs structure provides respectable SERS by inducing stronger plasmon electric field from the tunable nanogap structure ranging between 10 and 1 nm and large hot-spot areas as a nanoring instead of a spot. The SERS enhancement is inversely proportional to the thickness of HfO2 and a maximum of 20 folds enhancement is found at 1nm nanogap. Moreover, we also employed Ag as second layer instead of Au forming DNS Ag NPs structures, and it significant improved the SERS performance more than an order to the DNS Au NPs.

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