紅熒烯多晶薄膜之成長與特性探討

本實驗利用物理汽相沉積法 (Physical vapor deposition, PVD)，藉由固定粉末端溫度 (Tsou = 300℃)，調控基板端溫度 (Tsub = 103 ~ 221℃) 成長一系列多晶薄膜。使用 SEM（Scanning electron microscope, SEM）觀察 Tsub 與表面形貌和晶粒大小關係，當 Tsub 越大，表面結晶尺寸越大，超過 214℃ 會有明顯熱蝕刻現象。由 X-ray 繞射 (X-ray diffraction, XRD) 確認紅熒烯晶粒結構為正交晶系 (Orthorhombic)，並且計算出 Tsub = 189℃ ~ 221℃ 的同調長度 (Coherent length, 〈LC〉) 與晶格微應變 (Lattice microstrain, 〈e〉)。Tsub = 189℃ 之薄膜樣品的同調長度較大，221℃ 之薄膜樣品的晶格微應變較大。藉由 Arrhenius 分析成長速率，得到活化能 EA = 0.69 ± 0.01 eV，並且與其他小分子薄膜比較，發現因紅熒烯結構較平坦所以所需跨越之活化能較大。再由分析光穿透頻譜與光致發光頻譜得到能隙 (Optical energy bandgap, Eop) ，發現 Tsub 越大溫度 Eop 越小。本實驗觀察到基板溫度對於紅熒烯的多晶薄膜的表面形貌、生長速率與光學性質都有影響。

關鍵字

紅熒烯多晶薄膜

並列摘要

In this study, rubrene polycrystalline films growth from a physical vapor deposition system (with a fixed source temperature of 300℃) were characterized with respect to various substrate temperatures (Tsub = 103 ~ 221℃). The growth behavior of these as-deposited polycrystalline films is confirmed to follow an activated surface-adsorption process with an activation energy EA = 0.69 ± 0.01 eV. Then, the surface morphology and the temporal evolution of the grain size in these polycrystalline films with respect to Tsub are described and discussed. Furthermore, by X-ray diffraction, these rubrene crystalline grains are confirmed to have an orthorhombic structure, and the average coherent length and lattice microstrain of the crystallites deposited at high Tsub (189 ~ 221℃) are estimated and compared. From optical transmission and photoluminescence spectra, the optical properities of these rubrene polycrystalline films are discussed by using the energy terms diagram, and the temperature dependence of Eop is analysed. This experimental work reveals that Tsub has a strong influence on the growth rate, the surface morphology, and the structural properties of the as-deposited rubrene polycrystalline films.

並列關鍵字

Rubrene polycrystalline films

參考文獻

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[4] J. Kim, L. R. Faulkner, “Environmental control of product states in the chemiluminescent electron transfer between rubrene radical ions,” J. Am. Chem., Vol. 110, pp. 112–119, 1988

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紅熒烯多晶薄膜之成長與特性探討

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