自動化精密機械控制系統在掃描式穿隧電子顯微鏡與消磁機的應用

Abstract

本實驗利用低電壓操控壓電陶瓷，製作掃描式穿隧電子顯微鏡(scanning tunneling microscope, STM)，附自動步進探針系統以及避震系統。為提高掃瞄解析度，先研究STM探針，設計自動斷電系統，測試各種製針參數，並使用掃瞄電子顯微鏡觀察，測試出探針針尖達30 nm的製針參數，並設計可同時製造六根STM探針的機器。在STM機台與系統改良方面，增強機構剛性使解析度大幅提升，又將步進器重量簡化、調整步進器彈簧彈力系數，改變控制步進器的電壓波形，使步進系統更穩定。由改變放大電流來增快回饋速度，提高小尺度範圍的解析度。對於機台有電磁雜訊干擾的問題部分，設計金屬檔板達到電磁波屏蔽。測量功能方面，開發出電流-電壓量測功能，可以取得樣品特定位置區域的電性結構。 在研發永磁式消磁機方向上，研發過程分為消磁技術、機械結構設計、自動控制三個部分。消磁技術方面先測試所需磁場大小，測得磁場約7000高斯是消除硬碟磁盤上訊息的最低磁場，測試磁鐵規格與設計排列來達到所需的最低磁場，再使用磁區探測筆及磁力顯微鏡來反覆驗證消磁效果。機械結構設計方面，需克服硬碟經軌道通過磁場所需抵抗的拉力及螺桿的摩擦力，配合適當的馬達與減速機達到硬碟傳送的力量。自動控制系統方面，設計出單一按鍵即可讓硬碟盒移動通過磁場，並使用霍爾元件偵測磁場是否衰退，確認是否消磁成功。

We developed a low voltage scanning tunneling microscope (STM) equipped with an automatic stick-slip stepper and vibration damping systems. To improve the scanning resolution, we develop a STM tip maker which can automatically turn off the electric power as electrochemical etching is finished. The parameters to make sharp tips with a tip diameter of 30 nm are obtained. Additionally, we develop a tip maker to produce six tips at once. For the STM machine, we redesign and reduce the weight of the step motor, and we fix the waveform of the driving voltage to reach a stable motion of the step motor. The feedback speed is tuned and, at last, a new function of scanning tunneling spectroscopy is established. The same technology is used to make a magnetic data eraser. The development of the date eraser is divided into three parts: magnetic erasing method, mechanical architecture design, and automatic control. For the magnetic erasing method, we test out the minimum magnetic field required to erase magnetic data. We use magnetic colloid marker and magnetic force microscopy (MFM) to double confirm the magnetic erasing process. For the mechanical architecture design, we design the mechanical transportation of hard disks. The resistance force as hard disk passing through the magnets is calculated and the motor and the decelerator are selected to install in the machine. For the last part, we design an electronic system automatically controlled by a programmable chip. A hall measurement element to detect the magnetic field of the eraser is installed as well.