錳摻雜ZnxSn1-xO3薄膜在室溫下鐵磁特性

Abstract

本論文研究以脈衝雷射蒸鍍的方式，在Al2O3 (0001)基板上成長錳摻雜ZnxSn1-xO3之稀磁性的半導體薄膜，並期望藉由改變薄膜的載子濃度探討其磁性的發生機制。我們發現在溫度為700℃氧壓在10-3torr的情況下，雖然形成的薄膜並非純相的ZnSnO3，但卻具有室溫鐵磁性磁滯曲線的薄膜。利用四環繞射以及X rayψ方向的掃描發現鐵磁性僅出現在同時具有錳摻雜以及ZnSnO3相存在的薄膜，顯示ZnSnO3確實可能成為極佳的稀磁性半導體材料。進一步的利用溫度300 oC的熱處理方式改變載子濃度，發現飽和磁化量的大小的確隨載子濃度變大而跟著變大，顯示其鐵磁性之形成機制應與載子媒介雙重交換機制有關。另薄膜在可見光區範圍內，其透光率在80%以上，且吸收光譜圖顯示能隙值會因為Mn的摻雜而變大。

In this thesis, the fabrication of Mn-doped ZnxSn1-xO3 thin film on Al2O3 (0001) substrate by pulse laser deposition would be studied and were carried out to understand the origin of the ferromagnetism and the role played by changing the carrier concentration. Although in the present study the obtained a films appeared to contain two different phases, the existence of ferromagnetic property at 300K is reproducibly obtained for films deposited only at 700℃ with 10-3 torr of oxygen partial pressure. X-ray four-circle diffraction scan and ψ scan suggested that the existence of Mn containing ZnSnO3 phase might have resulted in the observed room-temperature ferromagnetism. With annealing treatment carried out at 300℃,the overall carrier concentration of the film can be changed. The results also showed that the effect magnetic moment in the ferromagnetic state indeed increased with increasing carrier concentration. Finally, we note that the average transmittance in the visible region is above 80％. The absorption spectrum shows that the optical bandgap is enhanced notably by Mn-doping. The increment of optical band gap value suggests a uniform substitution of Mn ions for Zn ions.