Ag/PbO奈米複合材料的電子傳輸與異常磁阻探討; The discovery of electron transport and abnormal magnetoresistivity in Ag/PbO nanocomposites

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题名:	Ag/PbO奈米複合材料的電子傳輸與異常磁阻探討;The discovery of electron transport and abnormal magnetoresistivity in Ag/PbO nanocomposites
作者:	林品全;Pin-Chuan Lin
贡献者:	物理研究所
关键词:	奈米複合材料;氧化鉛;銀;nanocomposites;PbO;Ag
日期:	2004-06-05
上传时间:	2009-09-22 10:55:43 (UTC+8)
出版者:	國立中央大學圖書館
摘要:	本實驗室利用了蒸鍍法製作了銀微粒，並且與氧化鉛微粒以一定質量比均勻混合，其樣品為(Ag)x(PbO)100-x(x=30、50、70)，因氧化鉛不導電所以用以增加銀微粒之間的距離，並且施以外加壓力造成樣品密度不同，探討其電子傳輸效應，我們利用電子定域跳躍模型解釋此現象，發現只有在銀較多且密度較小的樣品其電子傳輸才能用此模型解釋，在密度較大樣品中電阻率會在溫度為25~300K間上升，這可能來自於銀的金屬性。此外有三組樣品分別為(Ag)30(PbO)70、(Ag)20(PbO)80 、(Ag)10(PbO)90，密度分別為2.2mg/mm3、2.25mg/mm3、2.6mg/mm3，其樣品空隙較多所以電子傳輸以穿隧電導為主，而穿隧的能量大部分來自於外加電場，另外這三組樣品會具有正負磁阻的變化，我們推論此現象來自於穿隧性磁阻，由磁化強度的實驗當中可以觀察到銀微粒的磁化強度在小磁場下會顯現出順磁性當磁場超過2T時則會顯現出抗磁性，因此由穿隧磁阻的定義可以得知會有正負磁阻發生，這與磁阻實驗結果吻合。 We make Silver nanoparticle by evaporation,and mix with PbO nanoparticle by different mass ratio.The mass ratio we choise is(Ag)x(PbO)100-x(X=70、50、30).Because PbO nanoparticle is insulator,so that we can make different distance between Silver nanoparticle by mixing PbO nanoparticle.On the other hand, density in sample is a important factor,we can control the factor by variety’s pressure.Then we discuss the electron transport behavior, we try to explain the phenomenon by VRH model.The result is the model cant suit experiment data.In biggest density’s sample,the resistivity increase between 25~300K,we think the phenomenon come from properties of Silver bulk. Furthermore,we make three sample without pressure,the mass ratio of these sample are (Ag)30(PbO)70、(Ag)20(PbO)80、(Ag)10(PbO)90.The electron transport behavior is caused by tunneling,we think the gap between Silver nanoparticle is enough to tunnel by electron.Accorging to fitting parameters,we found the tunneling energy come from applied electric field. In magnetoresistivity experiment,we observe the change of positive to negative magnetoresistivity. We think the electron tunneling effect make this phenomenon. In experiment of magnetization,we observe the paramagnetism in small field,and appearance of diamagnetism when applied magnetic field over 2 tesla.According to the definition of tunneling magnetoresistivity,the magnetization can explain magnetoresistivity.
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