使用電漿輔助式分子束磊晶法成長硒化銅薄膜和奈米結構與光學特性分析

Growth and Optical Properties of CuSe Epilayers and Nanostructure by Plasma-Assisted Molecular Beam Epitaxy

郄勝喬(Sheng-Chiau Chieh)

指導教授 ： 楊祝壽

大同大學/電機資訊學院/光電工程研究所/碩士(2011年)

摘要

以分子束磊晶法在砷化鎵基板上成長硒化銅(CuSe)薄膜和奈米線。並利用X-ray繞射儀(XRD)觀察結晶相及電子式顯微鏡(SEM)觀察表面形貌。在固定基板溫度及改變不同的銅/硒成份比例下，則表面形貌將經由微粒結構轉變成薄膜型態。其相轉變過程細分如下:當銅/硒比例在1.54時會出現二硒化三銅(Cu3Se2)結晶相的微粒結構。當銅/硒的比例在1.44到0.92之間，則會出現二硒化三銅和硒化銅(CuSe)的多晶結構。而單一結晶相的硒化銅則在比例0.72呈現。更進一步，我們將銅硒的通量比(flux ratio) 固定，改變成長溫度從250 ℃到500 ℃。當成長溫度在250 ℃出現四硒化七銅(Cu7Se4)的結構，當成長溫度上升到300 ℃至400 ℃之間出現，則會出現硒化銅和(Cu2-xSe)的硒化的多晶結構。在500 ℃時，則Cu2-xSe相則被抑制。而當成長溫度持續上升至550 ℃，發現有奈米線的生成。利用穿透式電子顯微鏡(TEM)發現在成長溫度550 ℃時，基板和薄膜之間存在一個非結晶結構。從X射線繞射儀與能量散佈光譜儀可知其為銅鎵合金相。成長溫度550 oC下，改變銅/硒的比例，其奈米線的密度可由3.7×10-5 cm-2 到2.8×10-6 cm-2。利用聚焦離子束(FIB)技術將奈米線製作元件，並利用I-V來觀察奈米線本質特性，得知電阻率為0.08169 Ω-cm，在變溫I-V曲線中擬合出奈米線的活化能為約18 meV。

關鍵字

分子束磊晶 ； 奈米線 ； 硒化銅

並列摘要

Nanowire and thin films of CuSe were grown on the GaAs substrates by PA-MBE. Surface morphologies of CuSe were varied from particle to thin films on the different Cu/Se ratio and fixed substrate temperature. The Surface morphologies were estimated by scanning electron microscopy (SEM), and due to the phase separation by X-ray Diffraction (XRD). Surface morphologies of Cu3Se2 were construed by particles when the Cu/Se ratio is between 1.44 and 0.92. Single crystal of Cu3Se2 is produced that the Cu/Se ratio is at 0.72. Furthermore, substrate temperature were varied from 250 to 500 ℃ and fixed the Cu/Se ratio to grow Cu7Se4. The CuSe structure were produced when the growth temperature is at 250 ℃. Poly type Cu2-xSe were formed that the growth temperature is between 300 and 400 ℃. The structure of Cu2-xSe is suppressed when the temperature is at 500 ℃. When the growth temperature is increased to 550 ℃, the nanowires of CuSe are produced. An amorphous structure was observed in the interface between substrate and films in cross-sectional transmittance electron microscopy images. The amorphous structure is that eutectic of CuGa by XRD and EDS instrument. It is observed that the density of Cu2Se nanowire was varied with the growth temperature and the Cu/Se ratio. When the growth temperature is 550 ℃, The density of Cu2Se nanowire was varied from 3.7×105 cm-2 to 2.8×106 cm-2. Nanowire devices of Cu2Se were synthesized by focus ion beam technique and characterized electrical properties by I-V curve. The activation energy of Cu2Se nanowire is determined about 18 meV by temperature dependent of I-V curve measurement.

並列關鍵字

MBE ； nanowire ； CuSe

參考文獻

[5] M. Altosaar and E. Mellikov, Jpn Journal of Physics and Chemistry of Solids 66, 1915 (2005).

[9] B. Pejova, I. Grozdanov, Journal of Solid State Chemistry 158, 49

[10] S. Xu, H. Wang, J. J. Zhu, H. Y. Chen. Journal of Crystal Growth

234 263, (2002).

[11] Materials Research Bulletin 27, 2509 (2002).