Understanding Defects Generated by the Low Temperature Aqueous Synthesis of ZnO

了解低温水相合成 ZnO 产生的缺陷

• 批准号: 0905254
• 负责人: Steven DenBaars
• 金额: $ 33万
• 依托单位: University of California-Santa Barbara
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-08-15 至 2012-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0905254&HistoricalAwards=false
• 关键词: Understanding; Defects; Generated; Low; Temperature

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.

非技术描述：氧化锌 (ZnO) 单晶薄膜和周期性结构具有潜在的应用，包括节能发光二极管 (LED)、基于 GaN 合金的当今数十亿 LED 行业的透明电极以及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 周期性结构的能力，ZnO 已成为限制和引导光通信用光的光子晶体应用的重要候选者。 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。事实上，ZnO 的大部分特性与 GaN 相似或优于 GaN，而 GaN 目前是用于 LED 的材料，已经并将以显着降低能耗的方式照亮我们的世界。作为一种宽带隙半导体，在 20 世纪 90 年代初 Shuji Nakamura 进行创新之前，ZnO 面临着与 GaN 相同的技术障碍。由于性能、原材料可用性和成本方面的优势，一旦克服了这一技术障碍，ZnO 预计将在价值数十亿美元的固态照明行业中取代 GaN。这项研究将涉及本科生实习生和研究生。重点将放在选择代表性不足的学生上。技术细节：将在稳态、平衡条件下，在低温（约 90°C）连续水反应器中合成 ZnO 外延膜，该反应器是根据热力学计算和 ZnO 的逆行溶解度构建的。 （JJ Richardson 和 FF Lange，《控制 ZnO 的低温水相合成第一部分和第二部分》，《晶体生长与设计》，9 [6], 2570-81 (2009)）。连续水反应器还被用于合成周期性 2D 和 3D 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。该研究强调合成参数的优化，即pH、温度、氨浓度和速率控制生长剂的添加。主要目标是使用连续反应器来了解产生无意的 n 型导电性的点缺陷、外延核聚结引起的小角度晶界处的位错，以及在 200 ℃ 热处理期间观察到的空洞形成。 250°C。这种理解反过来将用于优化水相合成 ZnO 的光电特性，以便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。