O'Donoghue Richard, Rechmann Julian, Aghaee Morteza, Rogalla Detlef, Becker Hans-Werner, Creatore Mariadriana, Wieck Andreas Dirk, Devi Anjana
Inorganic Materials Chemistry, Faculty of Chemistry and Biochemistry, Ruhr-University Bochum, 44801 Bochum, Germany.
Max-Planck-Institut für Eisenforschung GmbH, 40237 Düsseldorf, Germany.
Dalton Trans. 2017 Dec 21;46(47):16551-16561. doi: 10.1039/c7dt03427j. Epub 2017 Nov 21.
Herein we describe an efficient low temperature (60-160 °C) plasma enhanced atomic layer deposition (PEALD) process for gallium oxide (GaO) thin films using hexakis(dimethylamido)digallium [Ga(NMe)] with oxygen (O) plasma on Si(100). The use of O plasma was found to have a significant improvement on the growth rate and deposition temperature when compared to former GaO processes. The process yielded the second highest growth rates (1.5 Å per cycle) in terms of GaO ALD and the lowest temperature to date for the ALD growth of GaO and typical ALD characteristics were determined. From in situ quartz crystal microbalance (QCM) studies and ex situ ellipsometry measurements, it was deduced that the process is initially substrate-inhibited. Complementary analytical techniques were employed to investigate the crystallinity (grazing-incidence X-ray diffraction), composition (Rutherford backscattering analysis/nuclear reaction analysis/X-ray photoelectron spectroscopy), morphology (X-ray reflectivity/atomic force microscopy) which revealed the formation of amorphous, homogeneous and nearly stoichiometric GaO thin films of high purity (carbon and nitrogen <2 at.%) under optimised process conditions. Tauc plots obtained via UV-Vis spectroscopy yielded a band gap of 4.9 eV and the transmittance values were more than 80%. Upon annealing at 1000 °C, the transformation to oxygen rich polycrystalline β-gallium oxide took place, which also resulted in the densification and roughening of the layer, accompanied by a slight reduction in the band gap. This work outlines a fast and efficient method for the low temperature ALD growth of GaO thin films and provides the means to deposit GaO upon thermally sensitive polymers like polyethylene terephthalate.
在此，我们描述了一种高效的低温（60 - 160°C）等离子体增强原子层沉积（PEALD）工艺，用于在硅（100）上使用六（二甲基氨基）二镓[Ga(NMe)]和氧（O）等离子体生长氧化镓（GaO）薄膜。与以前的GaO工艺相比，发现使用O等离子体对生长速率和沉积温度有显著提高。就GaO原子层沉积而言，该工艺产生了第二高的生长速率（每循环1.5 Å），并且是迄今为止GaO原子层沉积生长的最低温度，并确定了典型的原子层沉积特性。通过原位石英晶体微天平（QCM）研究和非原位椭偏测量，推断该工艺最初受衬底抑制。采用了互补的分析技术来研究结晶度（掠入射X射线衍射）、成分（卢瑟福背散射分析/核反应分析/X射线光电子能谱）、形态（X射线反射率/原子力显微镜），结果表明在优化的工艺条件下形成了高纯度（碳和氮<2原子%）的非晶、均匀且接近化学计量比的GaO薄膜。通过紫外 - 可见光谱获得的Tauc图给出了4.9 eV的带隙，并且透过率值超过80%。在1000°C退火后，发生了向富氧多晶β - 氧化镓的转变，这也导致了层的致密化和粗糙化，同时带隙略有减小。这项工作概述了一种用于低温原子层沉积生长GaO薄膜的快速有效方法，并提供了在聚对苯二甲酸乙二酯等热敏感聚合物上沉积GaO的手段。
