鑭鈣錳氧穿隧磁阻元件與碲化鉍/鑭鈣錳氧異質接面特性之研 究

Abstract

本論文研究穿隧磁阻元件 (TMR) / 超導混合的感測元件，主要結構為在雙晶(bi-crystal) 基板上成長釔鋇銅氧 ( YBCO ) / 鈦酸鍶 (STO) / 鑭鈣錳氧 (LCMO)，我們利用磁控濺鍍先在雙晶基板上沉積鑭鈣錳氧，製作成穿隧元件後再利用雷射脈衝蒸鍍 ( PLD ) 成長鈦酸鍶當作絕緣層去隔絕上下的超導層跟絕緣層，再接著也是利用雷射脈衝蒸鍍鍍上釔鋇銅氧。我們牛軛設計在有超導相變溫度以下，有超導環的磁阻會較大，從22%提升到27.5%。我們設計兩種不同的磁阻元件，一個是以鑭鈣錳氧薄膜，以及利用新的Washer-type的圖形設計。製作出來的鑭鈣錳氧薄膜像變溫度為240K以及已被銅氧超導相變溫度為86 K皆有良好的相變溫度，並量測元件特性。我們比較有有無超導環以及有無雙晶的樣品，因為雙晶上的缺陷導致在重複實驗上沒有看到良好的超導性質。 另一部份是探討鍗化鉍/鑭鈣錳氧雙層膜異質結構，我們先利用磁控濺鍍系統，先在下層鍍上鑭鈣錳氧，再用真空蒸鍍系統鍍上鍗化鉍薄膜，探討異質結構中的特性，鍗化鉍薄膜藉由Hikami-Larkin-Nagaoka(HLN)公式∆σ_xx=(αe^2)/(2π^2 ℏ)[Ψ(1/2+ℏ/(4el_φ^2 B))-ln(ℏ/(4el_φ^2 B))]做擬合得到α=1為自旋軌道交互作用力以及磁性散射皆很弱，異質結構的能隙為0.5eV左右，主要來自於鑭鈣錳氧的貢獻，計算出在Sample 1 之位能障高度 V_bi=5.48 eV，而位能障寬度 t=2.07 nm ；在Sample 2 之位能障高度 V_bi=5.52 eV，而位能障寬度 t=2.08 nm。異質接面最大的磁阻為4.5%

This thesis studies the tunneling magnetoresistance / superconducting hybrid sensing components. The main structure is the growth of yttrium copper oxide (YBa2Cu3O7-δ) / barium titanate (SrTiO3) / barium calcium manganese oxide (La0.67Ca0.33MnO3) on a bi-crystal substrate. We use RF magnetron sputtering to deposit LCMO on the bi-crystal substrate, and then make the tunneling component and then use the laser pulse evaporation (PLD) to grow STO as the insulating layer to isolate the upper and lower superconducting layer and the insulating layer, and then YBCO is also plated by laser pulse evaporation. We use the yoke design below the superconducting phase transition temperature, and the reluctance ring has a larger reluctance, from 22% to 27.5%. We designed two different magnetoresistive elements, a YBCO film, and a new Washer-type graphic design. The LCMO film has a phase transition temperature of 240 K and a YBCO superconducting phase transition temperature of 86 K. It has a good phase transition temperature. We compare the presence or absence of superconducting rings and samples with or without twins because the defects on the twins did not show good tunneling reluctance properties in repeated experiments. The other part is to explore the characteristics of Bi2Te3 / LCMO bilayer membrane heterostructure. We first use the RF magnetron sputtering system to first coat the lower layer with LCMO film and then vacuum-evaporate the Bi2Te3 film to explore the characteristics of the heterostructure. Bi2Te3 film by Hikami-Larkin-Nagaoka (HLN) formula ∆σ_xx=(αe^2)/(2π^2 ℏ)[Ψ(1/2+ℏ/(4el_φ^2 B))-ln(ℏ/(4el_φ^2 B))] do the fitting to get α=1. It shows that the spin-orbit interaction force and magnetic scattering are very weak, and the energy gap of the heterostructure is about 0.50 eV, mainly from the contribution of LCMO. Calculate the energy barrier height at sample 1 V_bi=5.48 eV, and the potential barrier width t=2.07 nm. The energy barrier height at sample 2 is V_bi=5.52 eV, and the potential barrier width is t = 2.08 nm. The maximum reluctance of the heterojunction is 4.5%.