臺灣博碩士論文加值系統

電洞掺雜(p-type)之化合物La0.7Ca0.3MnO3，因其在外加磁場下具有龐大磁阻之特性引起廣泛的注意，此類材料稱為龐磁阻(colossal magnetoresistance，CMR)。而近來CMR家族另一成員，電子掺雜(n-type)之La0.7Ce0.3MnO3，因其不同於先前電洞掺雜之特性，亦引起相當程度的關注。
因此本實驗利用脈衝式雷射鍍膜系統於SrTiO3(100)基板上成長La0.7Ce0.3MnO3-La0.7Ca0.3MnO3雙層薄膜，及各個單層薄膜，期望於雙層薄膜之p-n介面形成電中性之反鐵磁層，並研究所其物理特性。
根據本實驗之結果分析，發現中間層之電阻極大，外加電流僅能在上層有限厚度中傳導，表示介面確實因電荷中和形成空乏區，阻止電流往下層傳導。由於空乏層的形成，其電及磁的特性極可能類似其原始之反鐵磁(anti-ferromagnetic，AFM)絕緣體化合物LaMnO3。該層分離上下p，n層，僅餘微弱之磁耦合，同時該層之AFM特性能將上層磁矩釘扎於垂直於基板的方向上，產生極為不同之磁阻特性。

Hole-doped manganite La0.7Ca0.3MnO3 (LCMO) was extensively studied because of its colossal magnetoresistance (CMR) characteristic in a magnetic field. Recently, a new member of CMR family La0.7Ce0.3MnO3 (LCeMO), an electron-doped manganite, raises a new wave of attention for possible application in p-n junction.
In this present study, LCMO and LCeMO single layer and bi-layer were grown on SrTiO3 (100) substrate by a pulse laser ablation technique. Due to the neutralization at the p-n junction a possible insulating layer with the anti-ferromagnetic (AFM) property is expected. There is no systematically study of this matter up to date, thus, it is worth to systematically investigate the physical properties of this junction.
The result indicates the possible neutralization layer exhibits huge resistance comparison with two lateral layers, the bias current is constrained on the limited thickness of the top layer, which implies the neutralization layer forms a depletion layer that block the current to flow through to the bottom layer. Its electric and magnetic properties may similar to the parent compound LaMnO3 with insulating and anti-ferromagnetic characteristics. Separated by this possible layer, the magnetic coupling between lateral layers is weak. However, the possible AFM layer does pin the magnetic moment of the top layer along the direction perpendicular to the substrate that make a distinct magnetoresistance at low magnetic field.

第一章 簡介··············································01
第二章 理論基礎··········································03
2-1 物質之磁性··········································03
2-2 磁阻簡介·············································11
2-3 Double-Exchange Model································16
2-4 Jahn-Teller distortion·······························19
2-5 LaMnO3···············································21
2-6 La1-xCaxMnO3·········································22
2-7 La1-xCexMnO3·········································24
2-8 Exchange Bias········································26
2-9 CMR p-n junction·····································27
第三章 實驗方法··········································29
3-1 樣品製備·············································29
3-1-1 薄膜成長···········································29
3-1-2 黃光製程···········································29
3-2 電性及磁阻量測系統簡介·······························30
3-3 電性及磁阻量測·······································32
3-4 磁性量測·············································33
3-5 成份分析·············································34
3-5-1 歐傑電子能譜分析···································34
3-5-2 XRD pattern········································36
第四章 結果與討論·····················38
4-1 薄膜品質·············································38
4-1-1 La0.7Ca0.3MnO3(113) ·······························38
4-1-2 La0.7Ce0.3MnO3(113) ·······························40
4-1-3 La0.7Ce0.3MnO3/La0.7Ca0.3MnO3 雙層薄膜·············43
4-1-4 成份分析···········································45
4-2 薄膜電性·············································46
4-2-1 La0.7Ca0.3MnO3·····································46
4-2-2 La0.7Ce0.3MnO3·····································48
4-2-3 La0.7Ce0.3MnO3/La0.7Ca0.3MnO3······················50
4-2-4 電性分析···········································52
4-3 薄膜磁阻·············································54
4-3-1 垂直磁場···········································54
4-3-2 平行磁場···········································56
4-4 薄膜磁性·············································57
4-4-1垂直磁場············································58
4-4-2平行磁場············································59
第五章 結論························62
參考資料··························63
附錄·····························65

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