矽晶片上之硒化鎘與金奈米粒子感光元件設計與製程

Abstract

在這篇論文中，我們運用5 nm粒徑之硒化鎘奈米粒子及15 nm粒徑之金奈米粒子，透過庫倫吸引力，建構奈米感光元件於矽晶片上。為了產生庫倫吸引力於矽晶片奈米粒子之間，我們在矽晶片上之二氧化矽表面產成一層化學物質，N-[3-(trimethoxysilyl)propyl]-ethylene diamine (TMSPED)。這樣的化學分子一端與二氧化矽產生穩定的分子鍵 (covalent bond)，另外一端有氨基 (amino groups)，經過質子化 (protonation) 後可帶正電。將黏有TMSPED的矽晶片浸泡在含有金奈米粒子的水溶液中，TMSPED的正電會吸引金奈米粒子表面的正電，進而將金奈米粒子黏在晶片上。接下來我們將黏有金奈米粒子的矽晶片浸泡在表面含有帶正電之硒化鎘奈米粒子溶液。同樣地，透過庫倫吸引力將硒化鎘奈米粒子黏金奈米粒子表面上。為了要使硒化鎘奈米粒子帶正電，我們在它表面上在生成4-(2-Aminoethyl)phenol (Tyramine) 分子。理論上，經過一次次重複的組裝過程，我們能形成含有多層硒化鎘奈米粒子及金奈米粒子的奈米結構在矽晶片上。接著我們在矽晶片上之電極兩端加上電壓，並在有照375 nm光線或是完全黑的情況下，量測流過奈米感光元件的電流。實踐結果發現，在照光後，在各種電壓下有固定約2 nA的電流增加。這樣的特性主要來自於硒化鎘奈米粒子與金奈米粒子間之 “nano-Schottky-diode” 結構。除此之外，在同樣的寬度，越長的電極能量到越大的電流變化。

In this work, we used approximately 5 nm diameter CdSe NPs and 15 nm diameter Au NPs to fabricate the photo-sensing nanodevice on silicon oxide substrate by ionic interaction, where Au NPs serve as bridges to connect between CdSe NPs. To introduce Coulombic attraction between NPs and substrate, the silicon oxide surface is modified by N-[3-(trimethoxysilyl)propyl]-ethylene diamine (TMSPED), which provides positive charged amino (-NH3+) groups to attract negative (-COO-) charged Au NPs. Then, the Tyramine (4-(2-Aminoethyl)phenol)-modified CdSe NPs that have positive charged amino groups on the particle surface are assembled onto Au NPs. Theoretically, the assembly process can be repeated for several times to form multi-layers structure of Au and CdSe NPs. The overall fabrication process is observed by SEM. Finally, the nanodevice is fabricated on silicon oxide surface between Al electrodes of TSMC 0.35 □m chip. By applying voltage bias across the electrodes, we measured the photocurrent flowing through the nanodevice after illumination of 375 nm laser diode. The experimental results showed that after illumination, there was constantly about 2 nA increment to the current measured in dark for each voltage bias. This I-V behavior mainly results from the “nano-Schottky-diode” structure between CdSe and Au NPs. Besides, with the same width, the electrodes with longer length will have larger variation of photocurrent after illumination.