本學位論文分為兩個部分：
第一部分為採用低成本的奈米製程技術製作大面積之奈米金屬元件。我們首先利用奈米球鏡微影術（NLL）於光阻層上製作出週期性排列的奈米孔洞陣列，接著在奈米孔洞內部進行熱蒸鍍，依序沉積二氧化矽（SiO₂）與金（Au），形成具結構性之金屬奈米顆粒。藉由調整奈米球的尺寸、曝光時間與蒸鍍厚度等製程條件，可有效控制金屬奈米結構的尺寸與週期。最後透過散射光光譜的量測，分析不同尺寸的奈米金屬結構在光學性質上的差異，特別是其局部表面電漿共振（Localized Surface Plasmon Resonance, LSPR）特性之變化。
第二部分則建立一套以儀表放大器（INA121P）搭配鎖相放大器（SR830）所構成的差動電性量測系統，應用於量測AlGaN/GaN高電子遷移率電晶體（HEMT）中無閘極結構的光效應行為。實驗中透過施加光照於感測區，觀察其對源極與汲極間電流之影響，以評估光照對元件表面態與通道載子濃度的改變效應。本研究比較差動量測與傳統單端量測在訊號增益與可偵測最小光照變化的極限值上的差異。特別針對過去使用長波長雷射時無法觀測的微弱光效應，本研究驗證在差動量測條件下是否能成功捕捉到這些微小訊號，並評估其作為高訊噪光感測平台的潛力。

This thesis is divided into two parts:
The first part focuses on the fabrication of large-area nanostructured metallic devices using low-cost nanofabrication techniques. We first employed Nanosphere-Lens Lithography (NLL) to create a periodic array of nanoholes in the photoresist layer. Subsequent thermal evaporation was used to sequentially deposit silicon dioxide (SiO₂) and gold (Au) into the nanoholes, forming well-defined metallic nanoparticles. By adjusting fabrication parameters such as the size of the nanospheres, exposure time, and deposition thickness, the size and periodicity of the metallic nanostructures can be effectively controlled. Finally, optical scattering spectra were measured to analyze the differences in optical properties among nanoparticles of various sizes, particularly the variations in localized surface plasmon resonance (LSPR) characteristics.
The second part involves the development of a differential electrical measurement system composed of an instrumentation amplifier (INA121P) and a lock-in amplifier (SR830), which is applied to study the photoresponse behavior of gateless AlGaN/GaN high electron mobility transistors (HEMTs). In the experiments, light was illuminated onto the sensing region to observe changes in the current between the source and drain, aiming to evaluate the effects of photo-induced surface state modulation and the resulting variations in channel carrier concentration. This study compares differential measurements with conventional single-ended measurements in terms of signal amplification and the minimum detectable light-induced signal. In particular, it investigates whether weak photoresponses—previously undetectable under long-wavelength laser illumination—can be successfully captured using the differential measurement setup, thereby demonstrating its potential as a highly Signal-to-Noise Ratio optical sensing platform.

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