Understanding Defects Generated by the Low Temperature Aqueous Synthesis of ZnO

非技术描述：氧化锌（ZnO）单晶薄膜和周期结构具有潜在的应用，包括节能发光二极管（led），透明电极。美国数十亿美元的LED产业基于氮化镓合金和染料敏化太阳能电池。由于其相对较高的折射率（n = 2.05, lambda= 500 nm），以及产生2D和3D周期结构的能力，ZnO已成为光子晶体应用的重要候选材料，用于限制和指导用于光通信的光。作为一种光电材料，它具有宽带隙（~3.4 eV）、激子结合能是GaN的两倍、高饱和速度、高辐射硬度和高光学透明度等优点。事实上，氧化锌的大多数特性与氮化镓相似或优于氮化镓，而氮化镓是目前用于led的材料，它已经并将显著降低我们的世界的能耗。作为一种宽带隙半导体，在20世纪90年代初由中村修二（Shuji Nakamura）发明之前，ZnO面临着与GaN相同的技术障碍。由于ZnO在性能、原材料可用性和成本方面的优势，一旦克服这一技术障碍，ZnO有望取代GaN，在价值数十亿美元的固态照明产业中占有一席之地。这项研究将涉及本科生实习生和一名研究生。重点将放在挑选代表性不足的学生上。技术细节：ZnO外延薄膜将在稳态平衡条件下，在低温（≤ 90°C）连续水反应器中合成，该反应器是基于热力学计算和ZnO的逆行溶解度构建的。（JJ Richardson和FF Lange） ？控制ZnO的低温水合成（一、二）晶体生长与设计，9 bbb, 2570-81（2009）。连续水反应器也被用于合成周期二维和三维纳米结构，其尺寸相当于蓝光到红光的波长，具有作为光子晶体的潜在应用。研究重点是对合成参数的优化，即pH、温度、氨浓度和控速生长剂的添加量。主要目标是使用连续反应器来了解产生无意的n型电导率的点缺陷，外延核聚并引起的低角度晶界位错，以及在热处理&amp；#8805时观察到的空洞形成；250°C。反过来，这种理解将用于优化水性合成ZnO的光电性能，从而可以在带隙工程和有意的n型和p型掺杂方面迈出重要的一步。

NON-TECHNICAL DESCRIPTION: Zinc oxide (ZnO) single crystal films and periodic structures have potential applications that include energy saving light emitting diodes (LEDs), transparent electrodes for today?s multi-billion LED industry based on GaN alloys, and dye-sensitized solar cells. Due to its relatively high index of refraction (n = 2.05, lambda= 500 nm), and the ability to produce 2D and 3D periodic structures, ZnO has become an important candidate for photonic crystal applications that confine and direct the light used for optical communication. As an optical-electronic material, it has a wide band gap (~3.4 eV), an excitonic binding energy twice that of GaN, a high saturation velocity, a high radiation hardness, and a high optical transparency. In fact, most of these properties of ZnO are either similar or superior to those of GaN, which today is the material used for LEDs that has and will light our world at significant energy reduction. As a wide band gap semiconductor, ZnO faces the same technical hurdle as GaN prior to the innovations made by Shuji Nakamura in the early 1990?s. Due to advantages in properties, raw material availability and cost, ZnO is expected to displace GaN in the multi-billion dollar solid-state lighting industry once this technical hurdle is overcome The research will involve undergraduate interns and a graduate student. Emphasis will be placed on selecting underrepresented students.TECHNICAL DETAILS: ZnO epitaxial films will be synthesized, under steady-state, equilibrium conditions, in a low temperature (≤ 90°C) continuous, aqueous reactor that has been constructed based on thermodynamic calculations and the retrograde solubility of ZnO. (JJ Richardson and FF Lange, ?Controlling Low Temperature Aqueous Synthesis of ZnO Part I and II,? Crystal Growth & Design, 9 [6], 2570-81 (2009)). The continuous aqueous reactor has also been used to synthesize periodic 2D and 3D nanostructures, with dimensions equivalent to the wavelength of blue to red light, with potential applications as photonic crystals. The research emphasizes the optimization of synthesis parameters, namely, pH, temperature, ammonia concentration, and additions of rate controlling growth agents. The primary goal is to use the continuous reactor to understand the point defects that produce unintentional n-type conductivity, the dislocations at low angle grain boundaries introduced by the coalescence of epitaxial nuclei, and void formation observed during heat treatments at ≥ 250°C. This understanding will, in turn, be used to optimize the optoelectronic properties of aqueous synthesized ZnO so that significant steps can be taken towards band gap engineering and intentional n- and p-type doping.