工學院: 機械工程學研究所指導教授: 黃光裕丁仁峰Ding, Ren-FengRen-FengDing2017-03-132018-06-282017-03-132018-06-282016http://ntur.lib.ntu.edu.tw//handle/246246/278338探討真空、大氣及液體等多樣化環境中的樣品，原子力顯微術(Atomic force microscopy)已是強而有力的技術。研究生物化學的領域中，多數分子結構與特性的量測必須在水溶液環境中，以保持其原生狀態。使用動態模式原子力顯微術偵測樣品表面特徵，可以避免表面結構的損害，並且提高掃描影像的解析能力。動態模式取決於微懸臂的共振模態，如彎曲共振(Flexural resonance)，扭轉共振(Torsional resonance)以及側向彎曲共振(Lateral resonance)等。彎曲共振是微懸臂最基礎的共振模態，並且是原子力顯微術最常使用的動態模式，但該模態只能探討樣品表面縱向性質(Out-of-plane property)。為了瞭解樣品表面橫向性質(In-plane property)，則會用扭轉或側向彎曲共振模態做量測模式。此外，微懸臂的扭轉及側向共振頻率遠高於彎曲共振頻率，非常可能適用於高速原子力顯微術的發展。 原子力顯微術一般採用壓電元件激振微懸臂，但也容易造成液體擾動而影響微懸臂的動態特性，使得其激振效果不彰，無法取得樣品結構特徵的高解析影像。本研究提出直激振臂術(Direct cantilever excitation)解決此類問題，此術不但可以使微懸臂作動於微小振幅，並且其振幅訊號能維持高訊雜比(Signal-to-noise ratio)，進而提高偵測的靈敏度，得到高品質的量測結果。本研究開發的直激振臂術包括勞倫茲激力術(Lorentz force excitation)、雷射加熱術(Laser thermal excitation)以及焦耳激振術(Joule driving excitation)，其工作原理於激振效能將於本研究內所探討及驗證。勞倫茲激力術於扭轉模態有最佳的激振表現；雷射加熱術對於彎曲及扭轉模態都有優秀的激振效率；焦耳激振術則是能以最簡單的方式有效激振微懸臂。最後利用這些直激振力術取得高解析影像，如紫色細胞膜(Purple membrane) 的週期性微結構、白雲母(Muscovite mica)的原子排列以及高定向熱解石墨(Highly oriented pyrolytic graphite)上的有序氣體分子層結構。這些利用扭轉共振模態得到的量測結果，相似於彎曲共振模態所得的研究結果；這也更進一步驗證扭轉共振模態於量測應用上的可行性。Atomic force microscopy (AFM) has become a powerful technique for probing the nano-scale of a sample in various environments such as a vacuum, atmosphere, and liquid. In biochemistry research, molecular structures and the properties of living cells are measured in aqueous solutions for approximating their physiological state. In order to protect the surface structure from damage and to improve the imaging resolution, dynamic AFM is developed and utilized to investigate the surface characteristics. The dynamic mode includes flexural, torsional, lateral resonance modes, etc., which depend on the resonant modal of the AFM cantilever. Flexural resonance (FR) mode, the most fundamental mode of the cantilever, is mostly operated on dynamic AFM. This mode, however, is applied to probing out-of-plane material properties only. For acquiring surface in-plane properties, torsional resonance (TR) or lateral resonance (LR) mode should be used. Moreover, TR and LR modes have much higher resonant frequencies than does the FR mode; hence they are eligible to be developed on high-speed AFM. In TR mode, the sensitivity is also higher, and the contact point can be precisely defined without the influence of long-range force. LR mode is seldom used, since the cantilever’s motion is hardly measured by the AFM detection method. The piezoelectric element is commonly adopted to stimulate the AFM cantilever. In liquid, it is prone to cause the fluid-borne excitation to interfere with cantilever dynamics. Consequently, spurious peaks readily emerge in the frequency spectrum, and the real interaction between the tip and sample surface is difficultly indicated as well. In order to solve the problem, direct cantilever excitations are proposed and developed to vibrate the cantilever in a stable manner with small amplitudes of less than 1 nm. In this way, the signal-to-noise ratio (SNR) of the measured signal is enhanced, thus improving the detection sensitivity. For FR and TR modes, the developed direct cantilever excitations are successfully applied on MultiMode AFM, which include Lorentz force, laser thermal, and Joule driving excitations. Electromagnetic, photothermal, and electrothermal effects are elaborated in their working principles; their excitation performances are also verified experimentally. Lorentz force excitation expresses the best excitation performance for TR mode. Laser thermal excitation has excellent excitation efficiencies in both FR and TR modes. Joule driving excitation demonstrates the simplest method to stimulate the cantilever successfully. In liquid, the resonant peak in the frequency spectrum becomes pure and simple through using direct cantilever excitations. Therefore, MultiMode AFM within the homemade acoustic enclosure, which is built for isolating external influences, can obtain high-resolution images such as periodic trimer structures on purple membrane, atomic arrangement on mica, and ordered layers of gas molecules on highly oriented pyrolytic graphite. In these measurements, the results in TR mode agree with those of previous studies using FR mode.11387221 bytesapplication/pdf論文使用權限: 同意有償授權(權利金給回饋本人)原子力顯微術直激振臂術彎曲共振扭轉共振勞倫茲激力術雷射加熱術焦耳激振術Atomic force microscopyDirect cantilever excitationFlexural modeTorsional modeLorentz force excitationLaser thermal excitationJoule driving excitationthesis10.6342/NTU201600839http://ntur.lib.ntu.edu.tw/bitstream/246246/278338/1/ntu-105-D00522020-1.pdf