發(fā)布時間：2018-03-09 19:56

  本文選題：VO_x薄膜　切入點：碳納米管　出處：《電子科技大學(xué)》2017年博士論文　論文類型：學(xué)位論文

【摘要】：溶膠凝膠法(Sol-Gel)制備的氧化釩(VO_x)的結(jié)構(gòu)、光學(xué)和電學(xué)性能已經(jīng)被廣泛研究,然而,迅猛發(fā)展的實際應(yīng)用對材料性能不斷提出新的挑戰(zhàn)。為了提高該材料的綜合性能,基于VO_x的復(fù)合材料備受關(guān)注,其中,對氧化釩-碳納米管(VO_x-CNT)復(fù)合材料的研究最深入。目前,VO_x-CNT復(fù)合材料的研究及應(yīng)用主要集中在超級電容器和傳感器方面,該復(fù)合材料在紅外探測器中的研究尚未見報道。本文采用Sol-Gel制備了VO_x和VO_x-CNT復(fù)合薄膜(2≤x≤2.5),并通過多種材料表征方法對薄膜進(jìn)行了全面的研究。分析了氧化釩-單壁碳納米管(VO_x-SWCNT)復(fù)合薄膜作為紅外探測器熱敏材料的可行性。本文的研究內(nèi)容如下:采用Sol-Gel制備了VO_x薄膜并分析了其形貌、晶態(tài)和光電性能。結(jié)果表明,退火溫度太低、退火時間太短都會導(dǎo)致釩醇鹽不能充分分解,無法形成性能優(yōu)異的VO_x薄膜;而退火溫度太高會破壞VO_x的結(jié)構(gòu)、長時間退火會使薄膜被氧化為高價態(tài)V2O5,兩者都會降低薄膜綜合性能。與之相比,310℃退火1 h能夠得到綜合性能最優(yōu)的VO_x薄膜,其主要成分為V2O5,并含有少量低價態(tài)VO_x,其方阻較低,TCR達(dá)到-2.52%K-1、具有較高的吸收率,有望用作微測輻射熱計熱敏材料。基于Sol-Gel,采用三種不同的薄膜制備方法(混合旋涂、分層旋涂和分層噴涂)制備了VO_x-CNT復(fù)合薄膜。不同制備方法和碳納米管種類會影響VO_x的物理和化學(xué)性質(zhì)。在混合旋涂和分層旋涂制備的復(fù)合薄膜中,VO_x與CNT之間的相互作用比較弱,所以通過上述旋涂方式加入CNT對薄膜性能提升較小。對于分層噴涂法,MWCNT與VO_x之間的相互作用比較強烈,由此明顯地?fù)p壞了VO_x的結(jié)構(gòu)并降低薄膜方阻和TCR;然而,VO_x與SWCNT之間的相互作用適中,因而具有較好的均勻性、適當(dāng)?shù)姆阶韬洼^高的TCR,表現(xiàn)出更優(yōu)的綜合性能。在分層噴涂法制備VO_x-SWCNT的基礎(chǔ)上,深入探討了SWCNT濃度對薄膜性質(zhì)的影響。結(jié)果表明,在復(fù)合薄膜中,VO_x與SWCNT之間通過化學(xué)作用結(jié)合,該相互作用隨著碳納米管濃度的升高而增加,并在濃度約為6 wt%時達(dá)到飽和。與之對應(yīng),復(fù)合薄膜的V=O含量、光學(xué)透過率、光學(xué)帶隙、方阻和TCR均發(fā)生規(guī)律性變化,并在6 wt%時達(dá)到飽和。然而,值得注意的是,復(fù)合薄膜的綜合性能在碳納米管濃度約為4 wt%時達(dá)到最優(yōu),此濃度下的復(fù)合薄膜具有良好的微測輻射熱計應(yīng)用前景。進(jìn)一步使用橢圓偏振技術(shù)對Sol-Gel制備的VO_x-SWCNT復(fù)合薄膜進(jìn)行了深入研究。結(jié)果表明,5振子Tauc-Lorentz模型可以作為VO_x及VO_x-SWCNT的色散模型。研究發(fā)現(xiàn),使用橢偏儀對復(fù)合薄膜進(jìn)行表征測試得到的薄膜光學(xué)帶隙、定域態(tài)寬度等參數(shù)也隨著碳納米管濃度的增加而變化,并出現(xiàn)了與上一章內(nèi)容類似的飽和現(xiàn)象。此外,還對Tauc-Lorentz模型中不同的振子能量進(jìn)行了歸屬,這對于認(rèn)識VO_x薄膜及VO_x-SWCNT復(fù)合薄膜的能帶結(jié)構(gòu),拓展Tauc-Lorentz模型的應(yīng)用有重要的意義。重要的是,本文還對Sol-Gel制備的不同退火溫度下的VO_x薄膜和VO_x-SWCNT復(fù)合薄膜的電學(xué)性質(zhì)進(jìn)行了深入研究。不同退火溫度下的VO_x薄膜電導(dǎo)率的EMN為+16 meV,說明其電導(dǎo)率符合Meyer-Neldel Rule(MNR)。然而,當(dāng)SWCNT加入之后,低溫退火(≤310℃)的復(fù)合薄膜的EMN為+13 meV,仍然呈現(xiàn)MNR;令人驚奇的是,高溫退火(≥310℃)的復(fù)合薄膜EMN為-43 meV,出現(xiàn)反MNR現(xiàn)象。最后,對不同濃度VO_x-SWCNT復(fù)合薄膜的電學(xué)性能進(jìn)一步研究,結(jié)果表明不同碳納米管濃度的復(fù)合薄膜的電導(dǎo)率也出現(xiàn)MNR現(xiàn)象,EMN為+46 meV。本文還對三類薄膜電導(dǎo)率的MNR現(xiàn)象進(jìn)行了理論分析,這對于認(rèn)識VO_x和VO_x-SWCNT復(fù)合薄膜的電學(xué)性能以及深入了解MNR和反MNR現(xiàn)象有重要意義。
[Abstract]:Sol gel method (Sol-Gel) preparation of vanadium oxide (VO_x) structure, optical and electrical properties have been extensively studied, however, the practical application of rapid development and constantly put forward new challenges on the properties of the material. In order to improve the comprehensive performance of the material, composite materials based on VO_x have attracted much attention, which, on oxidation of vanadium carbon nanotubes (VO_x-CNT) composites most deeply. At present, the research and application of VO_x-CNT composite material mainly concentrated in the super capacitor and the sensor, the research of composite material in infrared detector is reported in this paper. The VO_x and VO_x-CNT composite thin films were prepared by Sol-Gel method (x = 2 ~ 2.5), and the films were characterized by various methods of comprehensive research materials. Analysis of vanadium oxide single walled carbon nanotubes (VO_x-SWCNT) composite film as the feasibility of infrared detector sensitive material. The research contents of this paper are as follows: Preparation of VO_x thin films and their morphology were analyzed by Sol-Gel, and the photoelectric properties of crystal. The results show that the annealing temperature is too low, the annealing time is too short will lead to vanadium alkoxide is not fully decomposed, unable to form a VO_x film of good performance; but too high annealing temperature will destroy the VO_x structure, long time annealing will make the film was oxidized to high valence V2O5, both of which reduce the comprehensive properties of the films. Compared with the VO_x thin films annealed at 310 C 1 h can obtain the optimal comprehensive performance, its main composition is V2O5, and contains a small amount of low valence VO_x, the resistance is low, TCR is up to -2.52%K-1, the absorption rate is high. Is expected to be used as micro bolometer thermistor materials. Based on Sol-Gel, using three different film preparation method (mixed spin coating, spin coating and layered layered spraying) VO_x-CNT composite films were prepared. Different preparation methods of carbon nanotubes and the kind of VO_x will affect the matter Physical and chemical properties. The composite film mixed spin coating and layered spin coating preparation, interaction between VO_x and CNT is relatively weak, so the way of adding CNT spin coating on the properties of the films increase smaller. For layered spraying method, interaction between MWCNT and VO_x is relatively strong, thus significantly damaged the structure of VO_x and reduce the sheet resistance and TCR; however, the interaction between VO_x and SWCNT is moderate, so it has good uniformity, proper resistance and higher TCR showed better performance. Based on the preparation of VO_x-SWCNT layered spraying method, discusses the effects of SWCNT concentration on the film nature. The results showed that in the composite films, between VO_x and SWCNT through the combination of chemical action, the interaction increases with the concentration of carbon nanotubes, and at a concentration of about 6 wt%. The corresponding saturated, thin composite The content of V=O film, optical transmittance, optical band gap, square resistance and TCR changes, and at 6 wt% reached saturation. However, it is worth noting that the overall performance of the composite film reached about 4 wt% for the optimal concentration of carbon nanotubes, the composite film has good concentration. The micro bolometer application. VO_x-SWCNT composite films further using ellipsometry on the preparation of Sol-Gel were studied. The results show that the Tauc-Lorentz model can be used as a 5 oscillator dispersion model of VO_x and VO_x-SWCNT. The study found that the composite films were characterized by optical band gap using ellipsometer localized width also changes along with the increase of the concentration of carbon nanotubes, and the emergence of a saturation phenomenon similar to the previous chapters. In addition, the oscillator of different Tauc-Lorentz model energy were assigned, this The band structure of VO_x film and VO_x-SWCNT composite film, has important significance to application of Tauc-Lorentz model. It is important that the electrical properties of VO_x thin films and VO_x-SWCNT composite films with different annealing temperature of the Sol-Gel prepared under studied. VO_x thin film conductivity under different annealing temperatures EMN +16 meV, the electrical conductivity in accordance with Meyer-Neldel Rule (MNR). However, when SWCNT was added after annealing at low temperature (less than or equal to 310 DEG C) composite film EMN +13 meV, is still MNR; surprisingly, high temperature annealing (less than 310 DEG C) composite film EMN -43 meV, anti MNR the phenomenon. Finally, further study on the electrical properties of different concentrations of VO_x-SWCNT composite films, the results show that the conductivity of composite films with different concentration of carbon nanotubes also appeared in MNR EMN +46 meV., the three kinds of films The theoretical analysis of the rate of MNR phenomenon has been carried out, which is of great significance for understanding the electrical properties of VO_x and VO_x-SWCNT composite films as well as in understanding MNR and anti MNR phenomena.

【學(xué)位授予單位】：電子科技大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2017
【分類號】：TB383.2

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本文編號：1590025