提升像散式原子力顯微鏡靈敏度之研究

Abstract

原子力顯微鏡(Atomic Force Microscope, AFM)具有奈米級解析度、不受真空環境限制等優點，因此經常被應用於生醫領域。高速原子力顯微鏡(High-Speed AFM, HS-AFM)為了對動態生物樣品進行成像，必須具備可量測高共振頻率之超小型微懸臂探針的微懸臂感測系統。商用像散式光學讀取頭因具有光點小、頻寬高等優點，可用於高速原子力顯微鏡量測超小型微懸臂。由於微懸臂感測系統之量測靈敏度對成像解析度至關重要，本研究透過改變藍光讀取頭內部之準直鏡位置、以及替換紅光讀取頭光源為穩定的氦氖雷射等不同方式進行靈敏度性能比較。其中在使用氦氖雷射替換紅光讀取頭光源，並使用鍍金微懸臂探針FMAuD時可得到較佳之靈敏度0.65 mV/nm，系統雜訊峰對峰值2.7 mV，雜訊對應位移量4.2 nm，其位移解析度可高於原商用紅光讀取頭。

Atomic Force Microscope (AFM) has nanoscale resolution and can be operated in ambient, liquid and vacuum environments. These advantages make AFM widely used in the field of biomedicine. In order to image dynamic biomedical phenomena, high-speed AFM (HS-AFM) requires a cantilever detection system which can measure ultra-small cantilever with high resonance frequency. Commercial astigmatic optical pickup head has advantages of small laser spot size and high bandwidth, which is suitable for measuring ultra-small cantilever in HS-AFM. The sensitivity of the cantilever detection system is crucial for achieving high imaging resolution. In this study, different optical configurations including changing the position of the collimator inside the blue-ray pickup head and replacing the light source of the red-light pickup head with a stable He-Ne laser were tested for optimizing the sensitivity. The experimental results show that using the red-light pickup head with the He-Ne laser to measure a gold-coated cantilever tip FMAuD had a highest sensitivity of 0.65 mV/nm. The peak-to-peak noise of the system was 2.72 mV, which corresponded to 4.2 nm in displacement. The displacement resolution of the modified optical configuration was higher than the original red-light pickup head.