利用脈衝雷射沉積法成長ZnO以及ZnO:Ga的奈米結構之研究

Growth and Characterization of ZnO and ZnO:Ga Nanostructures by Pulsed Laser Deposition

謝政達(cheng ta hsieh)

指導教授 ： 洪魏寬

國立臺北科技大學/電資學院/光電工程系研究所/碩士(2007年)

摘要

本文使用脈衝雷射蒸鍍法在c面的sapphire基板上以無催化劑輔助的方式成長出氧化鋅奈米柱以及摻雜Ga2O3的氧化鋅奈米柱。我們以不同的靶材，在1Torr的氧氣壓力成長出奈米柱。靶材分成不同的純度和晶粒，我們可以發現較高的純度，可以成長出直徑較短的奈米柱，並且隨著的純度的增加，PL光譜綠光區的峰值會大幅的降低。
再來摻雜Ga2O3於4N的ZnO粉末中，壓製成靶，成長出氧化鋅奈米柱，再與未摻雜的ZnO作比較。我們發現摻雜Ga到一定的比例 (靶材的ZnO粉末與Ga2O3粉末莫耳數比100:1)，可使奈米柱直徑變的較細(由90nm變成50nm)。也可發現摻雜Ga2O3之後可以使因缺陷所產生的PL光譜綠光區的峰值大幅降低。我們由一些改變沉積時間的樣品推測摻雜Ga的氧化鋅奈米柱成長的方式是Srtranski-Krastanov growth mode。我們改變摻雜Ga2O3的濃度，發現外觀以及光學性質和Ga所摻雜的比例有很大的關係。我們觀察到當摻雜Ga2O3的莫耳比例由0.1% ~ 0.5%(靶的莫耳數比)，PL光譜的峰值位置會有紅移的現象，而由1% ~ 2%摻雜比例會產生藍移的現象，推測紅移與band gap renormalization effect有關而藍移與Burstein-Moss effect有關。

關鍵字

脈衝雷射蒸鍍 ； 氧化鋅 ； 摻雜鎵 ； 奈米柱

並列摘要

In this study, we employed pulsed laser deposition to synthesize ZnO and ZnO:Ga nanostructures on c-plane sapphire substrates without any catalyst. Various kinds of sintered targets were ablated under relatively high oxygen pressure (1 Torr) to form nanorods on the substrates. For the growth of ZnO nanorods, ZnO targets of different purity and grain size were used. We found that using the target of higher purity leads to a reduced mean diameter of the nanorods and reduced defect-related visible emissions in the photoluminescence (PL) spectra. For the growth of ZnO:Ga nanorods, mixed powders of ZnO and Ga2O3 with various ratios were pressed and sintered into targets. Compared with the nanorods grown using pure ZnO targets, the nanorods grown using the target with suitable Ga content (ZnO:Ga2O3 = 100:1 in molecular ratio) had smaller diameters and smoother surfaces. Also, the visible emissions in the PL spectrum were suppressed due to the Ga incorporation. By studying a series of samples with increasing growth time, we suggested that Srtranski-Krastanov growth mode may be responsible for the formation of ZnO:Ga nanorods, and longer growth time leads to thicker rods. Furthermore, the morphologies and optical properties of the produced ZnO:Ga nanostructures strongly depend on the Ga content of the target. We found that the UV peak in the PL spectrum redshifs then blueshifts with increasing Ga content. Such a phenomenon might be attributed to the bandgap renormalization and Burstein-Moss effects.

並列關鍵字

Pulsed Laser Deposition ； ZnO ； Ga-doped ； nanorod

參考文獻

[3] J. E. Jaffe and A. C. Hess： Phys. Rev. B48（1993） 7903.

[7] S. Pizzini, N. Butta, D. Narducci and M. Palladino： J. Electrochem. Soc.136（1989） 1945.

[9] Numerical Data and Functional Relationships in Science and Technology, 22, Subvolume a. Intrinsic Properties of Group IVElements and III-V, II-IV and I-VII Compound, Berlin: Springer-Verlag (1987).

[10] A. B. Djurisic: Appl. Phys. Lett. 88, 103107 (2006).

[22] B. D. Cullity, S. R. Stock: Element of X-RayDiffraction, third edition, 2001