以單一磁域建構可應用於資料儲存及奈/微米機電系統之奈米級電磁致動技術

Abstract

本論文提出一創新的單一磁域所建構之奈米電磁致動技術，其中，奈米電磁致動元件由鎳奈米結構及具有上下電極之鋯鈦酸鉛薄膜依序沉積於矽基板上所組成。設計概念為藉由能量疊加使單一磁域可被磁場輔助並以電場控制翻轉(即旋轉180度)，首先，使用自製小型電磁致動技術產生一微弱小磁場，此磁場造成單一磁域之狀態變化，接著，對元件施加電場，電場因為逆磁電效應(即電場使鋯鈦酸鉛因壓電效應產生應變，應變透過機械耦合傳遞至鎳奈米結構，並且使鎳奈米結構因逆磁致伸縮效應產生磁化狀態變化)進一步提升單一磁域之狀態變化，透過結合磁場及電場對單一磁域造成之狀態變化，單一磁域即可被磁場輔助並以電場控制翻轉，此即能量疊加之設計概念。 據上述設計，透過製程參數控制，我們成功地製造出奈米電磁致動元件，並透過各式材料性質檢測方法，我們證實了所製造元件之鋯鈦酸鉛壓電薄膜具有良好的品質，並且元件之鎳磁致伸縮層亦成功地形成具有可以被磁力顯微鏡所檢測之單一磁域。在元件所用之關鍵特殊材料皆具備我們所預期之特殊性質後，我們則進一步測試元件之性能，元件性能測試之結果則證實了所提出之能量疊加設計概念，亦即鎳奈米結構單一磁域之磁化方向被磁場輔助並以電場控制從結構長軸的某一方向翻轉至結構長軸的另一個方向(即旋轉180度)。此外，透過施加不同方向之輔助磁場(前面測試乃是施加平行鎳奈米結構長軸方向之磁場，此處測試則是施加平行鎳奈米結構短軸方向之磁場)，鎳奈米結構單一磁域之磁化方向亦可被磁場輔助並以電場控制翻轉至短軸方向(即旋轉90度)，根據上述實驗結果，我們證實了透過外加不同方向之磁場可使奈米電磁致動元件所呈現之電控磁域變化具備多樣性。

In this thesis, a novel nano-electromagnetic actuating using engineered magnetic single-domain technology is proposed. According to the proposed actuating design/approach, a nano-electromagnetic actuating device is fabricated. The nano-electromagnetic actuating device consists of Ni nanostructures (exhibiting magnetic single-domain) deposited on a piezoelectric PZT film with top and bottom electrodes fabricated on a 4-inch Si substrate. The design concept is that the magnetic single domain’s magnetization-direction can be flipped (i.e., rotate from 0-degree to 180-degree) by coupling the energy enhanced from a magnetic field and controlled from an electric field. The home-made electromagnet is used to generate a small magnetic field. The magnetic field produces the state transformation of the single domain. After this, an electric field is applied to the device and further produces the state transformation of the single domain due to the converse magnetoelectric effect (i.e., strains from PZT film are developed by the electric field through the piezoelectreic effect and subsequently transmitted into the Ni nanostructures by mechanical coupling. The Ni nanostructures subjected to the strains produce the state transformation of the single domain due to the magnetostriction). By superposing the state transformation of the single domain enhanced by the magnetic field and manipulated through the electric field, the magnetic single-domain is successfully flipped. That is, the design concept of the energy coupling is validated. According to the design concept, the nano-electromagnetic actuating device is successfully fabricated by NEMS/MEMS processing technology with precise control of the process parameters. The characterization of functional material properties utilized by the device shows that the fabricated piezoelectric PZT film and Ni magnetostrictive nanostructure exhibit excellent properties and magnetic single-domain, respectively. After the functional characterization of the specific material properties, the device under various magnetic and/or electric field is tested with a modified magnetic force microscope. The testing results show that the magnetization-direction of the magnetic single domain of the device can be irreversibly flipped or reversibly switched (i.e., irreversibly rotated from 0-degree to 180-degree or reversibly rotated from 0-degree to 90-degree) through the domain-transformation enhanced by the magnetic field and controlled by the electric field (i.e., through the energy coupling approach we proposed in the design section). That is, the device successfully demonstrates the nano-electromagnetic actuating and consequently is able to be applied to the future electromagnetic data storage and NEMS/MEMS systems.