異常霍爾效應應用於自旋電子散射氫氣感測器之研究

Abstract

本研究藉由量測異常霍爾效應電阻(RHall, Rxy)之變化以感測氫氣壓力。為探討材料薄膜性質對氫氣感測的影響，實驗製備[Co(t)/Pd(t)]n之試片。當t=1nm且n=10,13,17,20，可觀察試片厚度與不同堆疊數材料磁性異向性對氫氣感測能力之變化。另外分別在t=1,2,4nm，n=20,10,5，可觀察Co膜厚與介面數對於氫氣感測之影響。實驗結果發現試片厚度參數最為影響氫氣氣體感測能力，[Co(1)/Pd(1)]10試片儘管厚度僅為[Co(1)/Pd(1)]20試片的二分之一，但霍爾電阻變化量為其之近12倍。而異向性對感測能力的影響在外加磁場下，垂直異向性試片在無磁場下有最大之電阻變化量，而水平異向性試片則在外加磁場2700 Oe有最大之變化量。在最大水平異向性[Co(4)/Pd(4)]5試片產生AMR貢獻項，反使氫氣反應量降低。而與傳統電阻率(Resistivity, Rxx)變化氫氣感測器比較，Rxy約大於Rxx變化量一個級數，可證明其潛在應用價值。

In this research, hydrogen sensors were fabricated and their performance was examined by measuring Anomalous Hall Effect resistance (RHall, Rxy). We deposited two series of [Co(t)/Pd(t)]n multi-layer samples : First series is fixing the thickness of each layer but varying stacking number (t = 1nm and n=10,13,17,20). Second series is fixing total thickness to be 40 nm but varying the number of interfaces (t=1,2,4 nm for n=20,10,5, respectively).This is to observe the effects of sample thickness, magnetic anisotropy, and stacking on hydrogen sensing. The result shows that sample thickness is the primary factor for hydrogen-sensing. Though the thickness of sample [Co(1)/Pd(1)]10 is half to that of sample [Co(1)/Pd(1)]20 , the resistance response is about 12 times bigger. For magnetic anisotropy, sample with perpendicular magnetic anisotropy (PMA) has the most significant response without a magnetic field, while sample with in-plane magnetic anisotropy (IMA) becomes most sensitive in the presence of a magnetic field. However, for IMA [Co(4)/Pd(4)]5 sample, its AMR effect is significant and thus that the ability of hydrogen-sensing is reduced. In comparison with traditional resistivity-type (Rxx) sensors, the proposed sensors exhibit superior performance by a factor of ten. This thereby demonstrates its potential in sensor technology.