摻雜鑭系元素(鏑,釓)氧化鋅與單層二(硫,硒)化鎢薄膜的光譜性質研究

Abstract

我們量測摻雜（鏑,釓）氧化鋅薄膜的拉曼散射光譜、穿透光譜及橢圓偏振光譜，進而研究不同摻雜量對氧化鋅薄膜光譜性質的影響。此外，我們量測單層過渡金屬二硫屬化物薄膜（二硫化鎢和二硒化鎢）的拉曼散射光譜及橢圓偏振光譜，進而探討單層二硫化鎢和二硒化鎢薄膜的光譜性質。氧化鋅薄膜是用脈衝雷射沉積法製成在藍寶石基板上，摻雜鏑離子和釓離子的濃度範圍分別為1% ~ 10%及3% ~ 30%。單層二硫化鎢和二硒化鎢薄膜是用化學氣相沉積法製成在藍寶石基板上。這篇論文的目的是探討上述所有材料的晶格結構和電子結構。 我們發現純氧化鋅薄膜的拉曼散射光譜，顯示2個拉曼峰，其頻率位置為98.7 cm-1和437.1 cm-1,分別為E2(low)和E2(high)對稱性。隨著鏑離子和釓離子摻雜濃度增加，拉曼峰E2(low)和E2(high)的峰值強度會逐漸下降。在穿透光譜中發現，隨著鏑離子和釓離子摻雜濃度增加，（鏑,釓）氧化鋅薄膜在紫外光區的光穿透率會提高。在吸收能譜中發現，隨著鏑離子和釓離子摻雜濃度增加，氧化鋅薄膜的直接能隙值會受到鏑離子和釓離子的影響，產生偏移，其現象可被能帶隙變窄理論和伯斯坦-莫斯位移理論解釋。 我們發現單層二硫化鎢和二硒化鎢薄膜在532奈米雷射光激發下的拉曼散射光譜具有多種類的拉曼峰。在室溫的吸收能譜中發現，單層二硫化鎢和二硒化鎢薄膜具有明顯的激子A和B吸收峰。此外，我們分析了單層二硫化鎢和二硒化鎢薄膜的室溫直接能隙值和激子束縛能值。其室溫直接能隙值，分別為2.1電子伏特和1.72電子伏特；其室溫激子束縛能值，分別為0.32電子伏特和0.24電子伏特。在變溫的吸收能譜中發現，單層二硫化鎢和二硒化鎢薄膜的直接能隙值會產生紅移現象，此現象是由單層二硫化鎢和二硒化鎢薄膜的晶格受到熱膨脹和電子及聲子間的交互作用所造成。We report the dysprosium (Dy) and gadolinium (Gd) doping effects on optical properties of ZnO thin films and the results of Raman scattering and spectroscopic ellipsometric measurements of monolayer transition metal dichalcogenides thin film (WS2 and WSe2). The Dy doped ZnO thin films with doping concentration of 1%, 3%, 5%, and 10% were fabricated on (0001) sapphire substrates by means of the pulsed laser deposition (PLD). The ZnO thin films with doping Gd concentration ranging from 3% to 30% were deposited on (0001) sapphire substrates by PLD. Monolayer WS2 and WSe2 thin films were deposited onto sapphire substrates by chemical vapor deposition (CVD). Our purpose is to investigate the changes of lattice dynamics and electronics structures of these materials. Raman scattering spectrum of pure ZnO thin film shows both E2(low) and E2(high) phonon modes at approximately 99 and 438 cm-1. With an increase in Dy and Gd doping, the intensity of both E2(low) and E2(high) phonon modes is decreased. Optical transmission spectra show increase in both transmittance in ultraviolet region with increasing Dy and Gd doping. The Dy and Gd doping effects on optical band gap of ZnO thin films can be explained by both energy band gap narrowing and Burstein-Moss shifted. Raman scattering spectra of monolayer WS2 and WSe2 thin films excited by 532-nm laser line show full phonon modes. The room-temperature absorption spectra of monolayer WS2 and WSe2 thin films exhibit emerging A and B excitons. Additionally, monolayer WS2 and WSe2 thin films show room temperature direct band gap at approximately 2.1 and 1.72 eV. The exciton binding energy of monolayer WS2 and WSe2 thin films is found to be approximately 0.32 and 0.24 eV at 300 K. With increasing temperature, the direct band gap of monolayer WS2 and WSe2 thin films shows a redshift, which can be elucidated by thermal expansion and electron-phonon interaction.