Hexagonal Boron Nitride Crystal Growth from Solution: A Study of Fundamentals

用于手机、计算机和发光二极管(LED)的二极管和晶体管等固态电子设备需要最完美的材料。它们必须近乎无懈可击，并且杂质浓度较低，才能使设备正常工作。根据该奖项，将开发一种新的电子材料--六方氮化硼的单晶生产方法，该方法具有很高的完美性。目前，这种材料只能作为粉末使用，但许多应用都需要更大的晶体。在这个研究项目中，六方氮化硼晶体将从高温冷却的熔融金属溶液中生产出来。将确定溶液的最高温度和冷却速度等参数对晶体大小和完整性的影响。高质量的六方氮化硼单晶有望使新型电子器件成为可能，如用于净水和消毒医疗设备的紫外线发光二极管，用于阻挡材料制造核武器的柔性电子器件和辐射传感器。影响从熔融镍铬溶剂中析出的六方氮化硼单晶尺寸和质量的工艺参数将通过统计响应面法进行考察。选择溶液生长是因为它对温度(1600℃)和压力(1个大气压)的要求相对较低。硼和氮的浓度、溶液的最高温度和溶液的冷却速度有望成为重要的参数。溶液中的硼和氮(成对或孤立元素)的浓度和分布将作为温度的函数进行测量。温度和过饱和度对晶体生长速度、面积、厚度、习性、表面形态以及位错类型和密度的影响将通过光学和电子显微镜、X射线衍射和成分分析相结合来确定。还将考察杂质(特别是氧和碳)对生长速度、各向异性和结晶习性的影响。这项研究将建立基本的热力学和动力学参数，这些参数对于控制六方氮化硼单晶的尺寸和质量是最重要的，以便优化工艺。它将支持博士生的教育，并将为其他研究人员提供高质量的材料，以研究六方氮化硼的光学、电学和机械性能及其应用。

Solid state electronic devices such as diodes and transistors used in cell phones, computers, and light emitting diodes (LEDs) require materials of the highest perfection. They must be close to flawless and have low impurity concentrations in order for the device to function properly. Under this award, a method of producing single crystals of a new electronic material, hexagonal boron nitride, with high perfection will be developed. Currently, this material is only available as a powder, but much larger crystals are necessary for many applications. In this research program, hexagonal boron nitride crystals will be produced from a molten metal solution as it is cooled from a high temperature. The effect of parameters such as the solution's maximum temperature and cooling rate on the size and perfection of the crystals will be determined. High quality hexagonal boron nitride single crystals are expected to enable new types of electronic devices, such as ultraviolet light emitting diodes for water purification and sterilizing medical equipment, flexible electronics, and radiation sensors for interdicting materials to make nuclear weapons.The processing parameters that affect the size and quality of hexagonal boron nitride single crystals precipitated from a molten nickel-chromium solvent will be examined by the statistical response surface methodology. Solution growth was selected due to its relatively low temperature (1600 C) and pressure ( 1 atmosphere) requirements. The boron and nitrogen concentrations, the maximum temperature of the solution, and the solution cooling rate are expected to be important parameters. The concentrations and distributions of boron and nitrogen (as pairs or isolated elements) in the solution will be measured as a function of temperature. The impact of temperature and supersaturation on the crystal's growth rate, area, thickness, habit, surface morphology, and dislocation types and densities will be determined by a combination of optical and electron microscopy, x-ray diffraction, and compositional analysis. The influence of impurities (specifically oxygen and carbon) on the growth rate anisotropy and crystal habit will also be examined. This investigation will establish the fundamental thermodynamic and kinetic parameters that are most important for controlling the size and quality of hexagonal boron nitride single crystals so the process can be optimized. It will support the education of a PhD student and will provide high quality materials to other researchers to investigate hexagonal boron nitride's optical, electrical, and mechanical properties and applications.