應用高頻石英振盪器提升原子力顯微術成像速度之研究

Abstract

為解決傳統高速原子力顯微鏡存在光學系統架構龐大複雜、靈敏度受限以及操作困難等問題。本研究致力於開發具備自感測能力且架構精簡之高速原子力顯微鏡系統。本研究採用共振頻率約1 MHz之長度伸縮振盪器(Length Extensional Resonator, LER)作為力感測元件，並建立高精度的探針製備方法。掃頻量測數據顯示，LER在黏接探針後，其共振頻率僅微幅下降7 Hz從0.999061 MHz至0.999054 MHz；等效位移振幅衰減率僅5.94%，等同響應電流僅減少0.458 μA，Q值高達約18,580。證實探針製備方法並未對振盪器之效能產生負面影響，仍能維持其高Q值特性。本研究將LER探針整合本實驗室現有之掃描系統，並對標準測試光柵TGQ1進行形貌掃描。實驗成果表明，在掃描速率0.4 Hz與驅動電壓50 mVp-p下，LER探針能清晰地還原樣品之矩形幾何特徵，且無明顯振盪現象。此外，研究進一步探討了驅動參數對LER探針追蹤能力的影響：在50 mVp-p驅動電壓下，探針振幅較小，有助於提升空間解析度，但易受表面交互作用力干擾導致回授遲滯；當驅動電壓提高至100 mVp-p時，探針具備足夠之動能，即使在2 Hz的較高掃描速率下仍能擷取較為完整之表面形貌影像。

To address the issues of bulky and complex optical architectures, limited sensitivity, and operational difficulties in conventional high-speed atomic force microscopy , this study develops a compact high-speed AFM system with self-sensing capabilities. A Length Extensional Resonator (LER) with a resonance frequency of 1 MHz is utilized as the force-sensing element, and a high-precision probe preparation method is established. Frequency sweep measurements indicate that after attaching the probe, the resonance frequency of the LER decreased slightly by 7 Hz, from 0.999061 MHz to 0.999054 MHz. The attenuation rate of the equivalent displacement amplitude was merely 5.94%, corresponding to a reduction of 0.458 μA in the response current, while maintaining a high Q-factor of approximately 18,580. These results confirm that the probe preparation method exerts no negative impact on the resonator's performance, thereby preserving its high Q-factor characteristics. The LER probe was integrated into our laboratory's scanning system to perform topographical imaging of a TGQ1 standard calibration grating. Experimental results show that at a scan rate of 0.4 Hz and a driving voltage of 50 mVp-p, the LER probe clearly reconstructed the rectangular geometric features of the sample without obvious ringing artifacts. Furthermore, the impact of driving parameters on the tracking capability of the LER probe was investigated. At 50 mVp-p, the smaller oscillation amplitude enhanced spatial resolution but rendered the probe susceptible to surface adhesive forces, resulting in feedback hysteresis. When the driving voltage was increased to 100 mVp-p, the probe possessed sufficient kinetic energy to capture relatively complete surface topography even at an accelerated scan rate of 2 Hz.