二氧化錫薄膜之負電阻特性研究;Study of negative differential resistance characteristic in tin oxide thin film

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Title:	二氧化錫薄膜之負電阻特性研究;Study of negative differential resistance characteristic in tin oxide thin film
Authors:	謝之翊;Hsieh,Chih-Yi
Contributors:	化學工程與材料工程學系
Keywords:	負電阻;二氧化錫;薄膜;穿隧二極體;Negative differential resistance;NDR;SnO2;thin film;tunnel diode
Date:	2016-07-19
Issue Date:	2016-10-13 12:40:32 (UTC+8)
Publisher:	國立中央大學
Abstract:	此篇論文研究之目的為探討二氧化錫薄膜中兩種不同的負電阻機制以及特性。第一部份為典型的穿隧二極體，著重在p-n介面形成之機制。以二氧化錫薄膜摻雜氮化鋁，氮離子取代氧離子貢獻電洞產生p+區域，鋁的氧化反應產生氧空缺貢獻電子並產生n+區域，藉由光電子能譜儀XPS分析可得知，氮離子與鋁離子在二氧化錫中的擴散速率存在差異，透過擴散速率差異可形成p+-AlN:SnO2/n+-Al:SnO¬2之穿隧介面，進而得到具有顯著負電阻特性之穿隧二極體。第二部分則是提出新穎的負電阻機制，透過操作二氧化錫薄膜對氧氣的高敏感度性質，在單一結構且組成均勻的二氧化錫薄膜中，可以量測到具有顯著負電阻特性的電壓電流曲線，經過文獻蒐集後發現，實驗結果無法以任何現有的負電阻機制解釋。由實驗結果可得知，由於二氧化錫薄膜在高濃度的氧氣環境下會形成大量存在間隙位置的氧原子，並生成可侷限電子的陷阱。在施加外加電場的情況下，流經陷阱的電子會被侷限，並在薄膜內部形成與外加電場方向相反的內建電場，降低電流進而產生負電阻特性，因此，電流密度與陷阱密度會是決定負電阻特性的關鍵性質，而透過電荷累積與電場及電位的計算，可得到與實驗數據相符的內建電場變化及電壓-電流曲線，經過交叉驗證後提出一個創新且完整的負電阻機制。;In this study, two type of negative differential resistance in SnO2 thin film are discussed. Chapter 1 introduces the mechanism of negative differential resistance. In Chapter 2, we focus on the common negative differential resistance device, a simple structure of p+-AlN:SnO2/n+Al:SnO2 tunnel diode was fabricated. The characteristic of negative differential resistance and the formation mechanism of the p+ and the n+ region are discussed. This tunnel diode shows a remarkable negative differential resistance current-voltage characteristic. The N3--O-2 substitution creates hole carriers and forms the p+-type region. The oxidation of Al atoms induces the oxygen vacancies and further creates the electrons, which is the n+-type region. The difference of diffusion rate can be observed in the X-ray photoelectron spectroscopy, and it is the key to form the p+/n+ tunnel junction. A new mechanism of negative differential resistance is proposed in Chapter 3 . The oxygen sensitive property of SnO2 was manipulated to form the negative differential resistance device, which had one single structure and the uniform component. The remarkable negative differential resistance characteristics can also be observed in this SnO2 thin film. But, there is no available mechanism can be used to explain the phenomenon of this negative differential resistance device. According to the experimental results, the high oxygen partial pressure during sputtering process induces the interstitial oxygen, and the interstitial oxygen will be the trap centers for electrons. As a voltage was applied to this device, the electrons will be trapped at the trap centers and form an accumulation region. The accumulation region further forms a built-in potential, which is against the applied voltage and reduces the current. The built-in potential under various applied voltages is the key to form the negative differential resistance characteristic. The quantity of trapped electrons shows positive correlation to the current density and the density of trap center. By these concepts, a mathematical model can be established. The mathematical model matches the tendency of the experimental results.
Appears in Collections:	[National Central University Department of Chemical & Materials Engineering] Electronic Thesis & Dissertation

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