【摘要】：熱電材料是一種可以實(shí)現(xiàn)熱能和電能直接相互轉(zhuǎn)換的功能材料,在溫差發(fā)電和熱電制冷等領(lǐng)域有廣泛的應(yīng)用前景。碲化鉍(Bi_2Te_3)基化合物作為室溫附近性能最好的熱電材料,近年來(lái)備受關(guān)注。但是經(jīng)過(guò)幾十年的研究,室溫下塊體Bi_2Te_3材料的熱電優(yōu)值仍然在1左右,導(dǎo)致能量轉(zhuǎn)換效率較低,無(wú)法與傳統(tǒng)發(fā)電和制冷系統(tǒng)相媲美。隨著納米科技在熱電材料中的應(yīng)用,熱電材料低維化可通過(guò)量子禁閉效應(yīng)提高材料的功率因子,通過(guò)界面的聲子散射效應(yīng)降低材料的熱導(dǎo)率,從而提高熱電優(yōu)值;因此,低維材料具有更大的空間提高熱電性能。本文通過(guò)磁控濺射方法在不同條件下制備Bi_2Te_3薄膜,系統(tǒng)研究了薄膜的結(jié)構(gòu)、形貌及熱電性能。首先在石英玻璃襯底上制備Bi_2Te_3薄膜,并探索了沉積溫度、薄膜成分及Ar流量對(duì)薄膜結(jié)構(gòu)和熱電性能的影響。研究表明,隨沉積溫度升高,薄膜表面形貌和晶粒取向發(fā)生變化,Seebeck系數(shù)不斷增大,當(dāng)沉積溫度為400℃時(shí),薄膜的Seebeck系數(shù)取得最大值83.96μV/K,此時(shí)電導(dǎo)率為11.89×10~4 S/m,同時(shí)功率因子具有最佳值6.79μW/cmK~2。當(dāng)通過(guò)Te靶與Bi_2Te_3合金靶共濺射制備Bi_2Te_3薄膜時(shí),發(fā)現(xiàn)薄膜中的過(guò)量的Te有利于提高Seebeck系數(shù)和功率因子;在相同的沉積溫度下通過(guò)共濺射制備的薄膜的Seebeck系數(shù)比單靶濺射制備的薄膜的Seebeck系數(shù)高,400℃時(shí),Seebeck系數(shù)最大值為92.42μV/K。為了確定最佳的Ar流量,通入不同流量的Ar,同時(shí)通過(guò)限流閥控制工作氣壓恒定,制備Bi_2Te_3薄膜;結(jié)果發(fā)現(xiàn),工作氣壓一定時(shí),Ar流量對(duì)薄膜的結(jié)構(gòu)和形貌的影響并不明顯;但是過(guò)高或過(guò)低的Ar流量會(huì)影響鍍膜效率。其次本文探討了擇優(yōu)取向結(jié)構(gòu)及Te靶功率對(duì)Bi_2Te_3薄膜結(jié)構(gòu)和性能的影響,以單晶MgO作為襯底,在400℃下通過(guò)Te靶與Bi_2Te_3合金靶共濺射制備了具有高度(00l)取向的Bi_2Te_3薄膜,此時(shí)薄膜的Seebeck系數(shù)最大值為103.6μV/K,比相同條件下在石英玻璃襯底上制備的薄膜的Seebeck系數(shù)高。由于薄膜中的Te含量對(duì)熱電性能有很大的影響,因此確定最佳的Te含量至關(guān)重要。本文中通過(guò)調(diào)控Te靶的濺射功率,制備了具有不同Te含量的Bi_2Te_3薄膜,并分析了薄膜中的Te含量對(duì)Bi_2Te_3薄膜結(jié)構(gòu)及熱電性能的影響。結(jié)果表明,隨著Te靶功率的增加,薄膜的Seebeck系數(shù)和電導(dǎo)率先增加后減少,當(dāng)Te靶濺射功率為8 W時(shí),薄膜具有最高的Seebeck系數(shù)和電導(dǎo)率,分別為157.7μV/K及9.68×10~4 S/m,此時(shí)功率因子為24.6μW/cmK~2;而Te靶濺射功率為5 W及12 W時(shí),功率因子僅有3.95μW/cmK~2及5.24μW/cmK~2。最后,在優(yōu)化的工藝參數(shù)的基礎(chǔ)上,制備了具有高度擇優(yōu)取向及高功率因子的Bi_2Te_3薄膜,其Seebeck為145.6μV/K,電導(dǎo)率為9.68×104 S/m,功率因子高達(dá)39.1μW/cm K~2。
[Abstract]:Thermoelectric material is a kind of functional material which can realize the direct conversion between heat energy and electric energy. It has a wide application prospect in thermoelectric power generation and thermoelectric refrigeration. Bismuth telluride (Bi_2Te_3)-based compounds, as the best thermoelectric materials near room temperature, have attracted much attention in recent years. However, after decades of research, the thermoelectric excellence of bulk Bi_2Te_3 at room temperature is still about 1, which leads to low energy conversion efficiency and can not be compared with the traditional generation and refrigeration systems. With the application of nanotechnology in thermoelectric materials, the low-dimensional thermoelectric materials can increase the power factor of the materials by quantum confinement, and reduce the thermal conductivity of the materials by phonon scattering effect at the interface, thus improving the thermoelectric excellence. Low dimensional materials have more space to improve thermoelectric properties. In this paper, Bi_2Te_3 thin films were prepared by magnetron sputtering under different conditions. The structure, morphology and thermoelectric properties of the films were systematically studied. Firstly, Bi_2Te_3 thin films were prepared on quartz glass substrates. The effects of deposition temperature, composition and ar flow rate on the structure and thermoelectric properties of the films were investigated. The results show that the surface morphology and grain orientation of the films increase with the increase of deposition temperature, and the Seebeck coefficient increases continuously when the deposition temperature is 400 鈩，

本文編號(hào)：2140006