鑭鈣鍶錳氧穿隧磁阻元件之製作與特性研究

Abstract

利用磁控濺鍍系統製作斜坡式La-Ca-Sr-Mn-O(LCSMO)穿隧磁阻元件，為了減少蝕刻對斜面的破壞，我們使用側向離子束蝕刻的方式以改善斜面的粗糙度和減少堆積物的產生。我們製作了一系列不同絕緣層厚度的斜坡式穿隧磁阻元件，發現在絕緣層厚度6~9 nm時有明顯的TMRmax值(〖TMR〗_max%=(R_(↑↑)-R_(↑↓))/R_(↑↑) ×100%)。最大穿隧磁阻發生在絕緣層厚度7 nm時，其值有73%。絕緣層厚度8 nm的樣品有最大的低磁場磁阻(LFMR)8.38%(LFMR%=(R(H)-R(0))/(R(0))×100%)。利用Jullirer model計算元件的自旋極化率，發現樣品絕緣層厚度7 nm有最大的自旋極化率51.8%，而隨著絕緣層厚度的增加自旋極化率會降低。計算磁場敏感度(dMR/dH)時發現，絕緣層厚度6 nm的樣品在5 K時，其磁場敏感度最佳為0.061 %/Oe。並進一步討論元件的磁特性和電特性。

La-Ca-Sr-Mn-O(LCSMO)-based tunneling magnetoresistance (TMR) junctions have been fabricated on SrTiO3 substrates with artificial ramp-edge grain boundaries. The multilayer thin films were deposited using a radio-frequency magneto-sputtering system. In order to reduce the etching damage to the ramp-edge, we use a lateral-ion- beam etching to improve the roughness and reduce the production of redeposited compounds. We have fabricated a series of TMR devices with different barrier thickness and find that TMRmax, defined by 〖TMR〗_max%=(R_(↑↑)-R_(↑↓))/R_(↑↑) ×100%, can be clearly observed . The maxium TMRmax of 73% is observed on sample with barrier thickness of 7nm. The maxium low field magnetoresistance (LFMR), defined by LFMR%=(R(H)-R(0))/(R(0))×100% , is obtain for 8.03% on the sample with barrier thickness 8nm. Using Julliere model, we calculate the spin polarization, defined by TMR=(2P_1 P_2)/(1-P_1 P_2 ) , and obtain 51.8% for the sample with 7-nm barrier thickness sample. The maxium magnetic sensitivity, defined by S=dMR/dH , the value is 0.061 MR%/Oe for thesample with 6-nm barrier thickness at 5 K. We further discussion the magnetic and electric properties of our devices.