應用磁域陣列建構之無線圈式奈米級電磁鐵於記憶體及奈/微米機電系統之研究

Abstract

本研究提出一磁域陣列建構之無線圈式奈米電磁致動技術，利用半導體製程製作奈米級電磁鐵，此元件由壓電材料(鋯鈦酸鉛薄膜)與磁致伸縮材料(呈現單一磁域之鎳奈米結構)所組成。為了提升此元件在資料儲存與奈/微米機電系統的應用性，本研究提出一能量疊加之設計概念，使鎳奈米結構陣列中之某一特定鎳奈米結構之單一磁域可被此結構陣列中的其他磁域陣列所產生之磁場影響並以電場控制磁域之翻轉(即旋轉180度)。

針對奈米級電磁鐵之設計概念，本研究在鋯鈦酸鉛薄膜上製作鎳單一磁域陣列，對此特定鎳單一磁域提供一微弱磁場，造成單一磁域之能量變化；接著對元件施加電場，電場透過逆磁電效應(即電場使壓電材料因壓電效應產生應變，應變透過機械耦合傳遞至磁致伸縮材料，使磁致伸縮材料因逆磁致伸縮效應改變磁化狀態)進一步造成單一磁域之能量變化，將磁場及電場對單一磁域造成的能量變化做結合，單一磁域即可被磁域陣列之磁場輔助並以電場控制翻轉，此即為本研究提出的能量疊加設計概念。

根據設計概念，本研究透過製程參數的校正成功製作出奈米級電磁鐵。奈米級電磁鐵之材料性質檢測則證實了製作的鋯鈦酸鉛薄膜具有優良的品質， 鎳奈米結構陣列亦成功地被磁力顯微鏡檢測出以單一磁域所建構之磁域陣列。成功地製作出這些特定薄膜與奈米結構並確認這些薄膜與奈米結構具備我們所期望之特定材料性質之後，本研究則進一步對奈米級電磁鐵進行性能測試，測試結果則驗證了本研究提出的能量疊加設計概念。亦即透過磁場輔助以及電場控制，使鎳奈米結構單一磁域之長軸磁化方向旋轉180°。基於上述實驗結果，本研究成功證實，透過能量疊加(磁場加電場)之方式，奈米級電磁鐵不僅成功地展現無線圈式奈米電磁致動技術，也因此提升了奈米級電磁鐵在資料儲存與奈微米機電系統領域的應用性。

In this thesis, a magnetic domain-array configured coil-less nano-electromagnetic actuating technique is reported. We use the semi-conductor processing technology to fabricate the nano-electromagnet consisting of a piezoelectric material (PZT thin film) and magnetostrictive material (Ni nanostructures exhibiting magnetic single-domain). To create diverse applications of the electromagnet and corresponding electromagnetic-actuating for data storage and NEMS/MEMS systems, the nano-electromagnet utilizes a design concept combing the energy provide by an electric field and a magnetic field to rotate the magnetic single-domain of the Ni nanostructures of the nano-electromagnet from 0° to 180°.

Regarding the design concept of the nano-electromagnet, the Ni-nanobar arrays are fabricated on the piezoelectric PZT film to generate an “on-chip” weak magnetic field to a specific Ni-nanobar in the arrays in order to produce a magnetic-field-enhanced domain transformation to the single-domain of the specific Ni-nanobar. Furthermore, through the converse magnetoelectric effect (i.e., the electric field is applied to the piezoelectric PZT thin film to develop in-plane strains. Due to mechanical coupling between the piezoelectric PZT thin film and magnetostrictive Ni nanobar array, the strains are transmitted to the Ni nanobar array. Due to the converse magnetostriction, the domains and corresponding magnetization of the Ni nanobar array are transformed), the energy of the magnetic single-domain can be changed. Combining the transformations which magnetic-field enhances and electric-field induces, the single-domain’s magnetization-direction is rotated from 0° to 180°.

Based on the design concept, a nano-electromagnet is fabricated. After the fabrication, the piezoelectric PZT thin film and Ni nanobar array of the nano-electromagnet is characterized by corresponding equipment. The characterization results show the film and array exhibit a decent ferroelectric property and correct magnetic-domain patterns, respectively. After characterization, the nano-electromagnet is tested by modified MFM system. The testing results show the magnetization of specific single-domain in the domain array is rotated from 0° to 180° by the energy provided from the electric field together with the magnetic field. That is, the design concept of the nano-electromagnet is proved. Due to these results, the nano-electromagnet successfully demonstrates the coil-less nano-electromagnetic actuating and consequently creates more diverse applications to the future electromagnetic data storage and NEMS/MEMS systems.