二氧化釩薄膜之動態電阻特性研究;Dynamic resistance characteristic of Vanadium oxide thin film

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Title:	二氧化釩薄膜之動態電阻特性研究;Dynamic resistance characteristic of Vanadium oxide thin film
Authors:	林佳樺;Lin, Chia-Hua
Contributors:	化學工程與材料工程學系
Keywords:	二氧化釩;動態電阻;透明導電薄膜;Vanadium oxide;Dynamic resistance;n-type;transparent conductive film
Date:	2019-08-07
Issue Date:	2019-09-03 12:32:20 (UTC+8)
Publisher:	國立中央大學
Abstract:	中文摘要本論文研究之目的為探討二氧化釩薄膜中動態電阻機制及特性。第一部份討論在室溫下的二氧化釩薄膜之導電機制，將二氧化釩薄膜在不同溫度進行熱處理，透過XPS分析可知，二氧化釩薄膜經過500 oC熱處理溫度，有最高的V5+離子濃度，透過控制不同熱處理溫度可以改變V5+離子濃度。在熱處理過程中，會發生V4+離子被V5+離子所取代，在本研究稱之為取代反應。此V5+離子取代V4+離子反應會產生自由電子而有n-type特性，進而提高二氧化釩薄膜的載子濃度，使得二氧化釩薄膜具有透明導電薄膜之特性。第二部分則是提出新穎的動態電阻機制，利用二氧化釩薄膜對溫度的高敏感度性質，在二氧化釩薄膜施加溫度過程，可以量測到具有顯著動態電阻特性，由文獻回顧可知此現象眾說紛紜無法完整解釋此現象。實驗結果發現，在施加溫度的情況下，二氧化釩薄膜在67 oC時，電阻變化兩個數量級且此變化為可逆的現象，即為動態電阻轉變的現象。經由熱處理500 oC的二氧化釩薄膜甚至可以在50 oC會有明顯的動態電阻轉變，由於在氧氣環境中所濺鍍製備的二氧化釩薄膜會生成不同價態的釩離子，利用XPS測得V5+離子佔二氧化釩薄膜的離子中比例與電阻轉變的臨界溫度變化量成正比，當V5+離子取代V4+離子時，因V5+的離子鍵比V4+離子鍵短而改變位於晶格中心的V與旁邊6個O配位體之間在能帶上的間距，造成能隙縮減，進而有降低電阻轉變臨界溫度的變化。因此，價數比例與鍵長會是決定動態電阻特性的關鍵性質，經過交叉驗證後提出一個創新且完整的動態電阻機制。 ;Abstract In this study, dynamic resistance mechanism and characteristics of vanadium oxide thin films are discussed. At first, discusses the conduction mechanism of vanadium oxide thin film at room temperatures. According to X-ray photoelectron spectroscopy analysis, the vanadium oxide thin film has the highest V5+ ion concentration after annealing temperature at 500 oC. The V5+ ion for the V4+ ion produces free electrons and has n-type characteristic, thereby increasing the carrier concentration of the vanadium oxide film. So the vanadium oxide thin film has the characteristics of a transparent conductive film. Secondly, propose a novel dynamic resistance mechanism. The temperature sensitive property of vanadium oxide thin film was manipulated to form. The remarkable dynamic resistance characteristics can also observe in this vanadium oxide thin film. But there is no current mechanism can be used to explain the phenomenon. The experimental results show that the vanadium oxide thin film changes at two orders of magnitude at 67 °C, which is the phenomenon of dynamic resistance transition. Annealing temperature at 500 °C of vanadium oxide thin film can even have a significant dynamic resistance transition at 50 °C. Since the vanadium oxide thin film prepared by sputtering in an oxygen environment generates vanadium ions of different valence states, V5+ is measured by X-ray photoelectron spectroscopy analysis. The proportion of ions in the vanadium oxide thin film is proportional to the critical temperature change of the resistance transition. When theV5+-V4+ substitution, the V5+ ion bond is shorter than the V4+ ion bond and changes to the V at the center of the lattice. The spacing between the oxygen ligands on the energy band causes the energy gap to decrease, which in turn reduces the change in the critical temperature of the resistance transition. Therefore, the valence ratio and bond length are the key properties that determine the dynamic resistance characteristics.
Appears in Collections:	[National Central University Department of Chemical & Materials Engineering] Electronic Thesis & Dissertation

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