熱調制顯微與能譜技術

Abstract

本論文以懸浮式氮化矽微結構為量測平台，針對奈米線與奈米顆粒樣品，系統性研究在聚焦電子束激發下的熱調製行為。研究中採用掃描式電子顯微鏡（SEM）的電子束對樣品進行局部直流加熱，同時在樣品加熱端以ω的頻率交流電流加熱，並以鎖相放大器量測2ω與3ω訊號。此實驗設計讓我發現了電子束可以對一奈米線或微米線的熱傳導進行調製，並發現其調製機制跟樣品的二次電子與核電子躍遷的X光放射相關。此外，研究過程中亦系統性分析了不同裝置長度下熱阻、熱調製沿距離變化，以及熱輻射、X射線發射等能量耗散機制對訊號的影響。 為實現熱調製顯微術，我進一步結合資料擷取系統（DAQ）實現高解析度熱影像取得。實驗結果證實，熱調製顯微術不僅能有效改變奈米尺度下材料的局部熱傳導特性，也能對元素特徵邊界行為進行精細解析。為驗證熱調製能譜成分技術，我透過精細調控電子束加速電壓分別於Si、Ge、Pt等材料的X光特徵吸收邊（K-edge、L-edge）附近，量測到顯著的熱調製訊號變化。特別以電子探針微區分析（EPMA）作為對照，針對同一SiGe顆粒區域進行材料成分分布分析。並將其與傳統EPMA分析結果進行比較。 本研究展示了高解析度熱調製顯微術與能譜技術對於微奈米材料分析的新應用潛力，並對其機制提出具體實驗證據與理論探討。

This thesis employs suspended SiNₓ microstructures as measurement platforms to systematically investigate the thermal modulation behavior of nanowire and nanoparticle samples under focused electron beam excitation. The electron beam of a scanning electron microscopy (SEM) is used for localized DC heating of the samples, while an AC current at frequency ω is applied at the heater and lock-in amplifiers are utilized to measure the 2ω and 3ω signals. This experimental design allows me to discover that the electron beam can modulate the thermal conduction of a nanowire or microwire, and the modulation mechanism is related to the sample’s secondary electrons’ emission and X-ray emission from core-level electrons’ transitions. Additionally, I systematically analyze the effects of thermal resistance, thermal modulation variation along distance, and energy dissipation mechanisms such as thermal radiation and X-ray emission on the signal under different device lengths. To realize thermal modulation microscopy, I further integrate a data acquisition system (DAQ) to achieve high-resolution thermal imaging. The experimental results confirm that thermal modulation microscopy can effectively reveal the local thermal conduction properties of materials at the nanoscale and resolve the boundaries of samples. To validate the thermal modulation spectroscopy capabilities, I find changes in thermal modulation signals near the characteristic absorption edges (K-edge, L-edge) of materials such as Si, Ge, and Pt by fine-tuning the electron beam acceleration voltage. For comparison, electron probe microanalysis (EPMA) is used as a reference to analyze the material composition distribution in the same SiGe particle region. Overall, this work demonstrates the new application potential of high-resolution thermal modulation mapping in micro/nano material analysis, providing experimental evidence and theoretical discussions for the underlying mechanisms.