高熵合金薄膜之太赫茲複數電學與光學常數之探討

Abstract

高熵合金的想法起源於1995年，有別於以一種主要金屬再另外添加微量金屬的傳統合金(如:鋼為大量的鐵加上少量的碳)，反而是利用多主元素的高熵效應來設計和金，來開發更多元的材料以符合新的科技發展需求。太赫茲光譜不僅對不同物質產生特定的圖譜，也是未來6G通訊的波段，開發太赫茲的相關元件勢在必行，為避免在檢測過程中對高熵合金樣品造成表面上的損傷，本研究採用太赫茲時域光譜系統來進行高熵合金在太赫茲頻譜下之光學常數與電導率的非接觸式量測。NbMoTaW這類的耐火高熵合金在2010年被美國空軍實驗室(AFRL)首次提出，目的是希望能找出在高溫能突破耐溫合金如超合金的溫度極限。本研究著重於Nb、Mo、Ta、W四個元素以三種不同組成比例(三種分別為Nb25Mo25Ta25W25、Nb15Mo15Ta35W35、Nb15Mo35Ta15W35)時，在奈米等級不同厚度下表現的光學特性與電導特性相互比較。研究結果顯示，在等比例的高熵合金Nb25Mo25Ta25W25薄膜與大多數的金屬薄膜一樣，除了折射率與吸收係數會隨著厚度的增加而上升之外，電導率亦隨著厚度的增加而上升。而三種不同元素比例的高熵合金Nb25Mo25Ta25W25、Nb15Mo15Ta35W35、Nb15Mo35Ta15W35在厚度相同時，其電導率會依照Mo、W兩者比例增加而上升，電導率的排序為Nb15Mo35Ta15W35> Nb25Mo25Ta25W25> Nb15Mo15Ta35W35 。

The idea of high-entropy alloys originated in 1995. It is different from traditional alloys that use one main metal and additional trace metals (for example, steel is a large amount of iron and a small amount of carbon). Instead, it uses the high-entropy effect of multiple main elements to design and gold to develop more. The materials to meet the needs of new technological development. Terahertz spectroscopy not only produces specific patterns for different substances, but is also the band of future 6G communications. It is imperative to develop terahertz-related components. In order to avoid surface damage to high-entropy alloy samples during the detection process, this study adopts The terahertz time-domain spectroscopy system is used for non-contact measurement of the optical constant and electrical conductivity of high-entropy alloys in the terahertz spectrum.Refractory high-entropy alloys were first proposed by the Air Force Research Laboratory (AFRL) in 2010. The purpose is to find out the temperature limit that can break through temperature-resistant alloys such as superalloys at high temperatures. This study focuses on the comparison of the optical properties and electrical conductivity properties of the four elements Nb, Mo, Ta, and W with three different composition ratios (Nb25Mo25Ta25W25、Nb15Mo15Ta35W35、Nb15Mo35Ta15W35) at different thicknesses in nanometer.The research results show that the same proportion of high-entropy alloy Nb25Mo25Ta25W25 film is the same as most metal films, except that the refractive index and absorption coefficient increase with the increase of thickness, the conductivity also increases with the increase of thickness. When the three high-entropy alloys with different element ratios, Nb25Mo25Ta25W25, Nb15Mo15Ta35W35, and Nb15Mo35Ta15W35 in the same thickness, their conductivity will increase according to the ratio of Mo and W. The order of conductivity is Nb15Mo35Ta15W35> Nb25Mo25Ta25W25> Nb15Mo15Ta35W35.