Atomic level studies of step dynamics in the homogeneous growth of metal crystals

摘要：晶体材料的生长是制造许多电子器件的第一步，包括用于计算机的微处理器、用于人体健康的化学传感器和用于应对恐怖主义威胁的生物探测器。今天，单个原子正在被操纵，试图在原子尺度上制造这样的处理器和传感器。我们需要提高对原子尺度表面过程的理解，例如原子输运及其在晶体材料生长中的作用，以便可以常规地使用单个原子来提高现有设备的性能，以及开发新设备。这个项目独特地结合了使用显微镜观察单个原子运动的能力和使用质谱仪识别运动中的原子种类的能力。因此，它允许对元素晶体材料的生长进行详细的原子水平研究。本研究为一名研究生的博士论文项目，并聘请一名理科生协助实验。该项目固有的跨学科性质是在广泛的技术领域训练学生，从而帮助他们为开始物理科学的职业生涯做好充分的准备。未被充分代表的群体有很好的机会来填补这项研究工作的学生职位，因为新墨西哥大学在将高评价的研究项目结合起来方面非常出色，并且被指定为少数族裔和西班牙裔服务机构。技术摘要：晶体表面台阶动力学是控制原子输运和晶体生长的重要过程之一。在这个项目中，在原子尺度上的阶跃动力学在原型情况下，元素晶体，是第一次被研究。为了能够研究这样的均匀系统，我们采用了一种新的方法-使用一个合原子，它是元素底物的稳定同位素。这保留了均相系统的化学性质，但由于已知的质量和同位素丰度，同位素合原子是可区分的。场离子显微镜正被用于原子分辨率表面成像。原子传输过程中可能发生的同位素adatom-substrate原子交换过程通过去除单个原子作为离子通过场蒸发和随后的基于战斗时间的原子探针微分析来确定它们的质量来检测。该项目正在研究各种过渡金属表面上的步骤动力学，通过研究：第一年-同位素吸附原子在台阶上的下降和同位素吸附原子沿着台阶边缘的扩散，第二年-由激光脉冲发起的纳秒时间尺度扩散，以捕获任何“非平衡”同位素吸附原子-衬底构型，以及第三年-步骤彼此接近对同位素吸附原子-步骤动力学的影响。

NON-TECHNICAL ABASTRACT:The growth of crystalline materials is the first step in the manufacture of numerous electronic devices including microprocessors for computers, chemical sensors for human health, and biological detectors to counter terrorism threats. Today, individual atoms are being manipulated in attempts to create such processors and sensors at the atomic scale. Improvement in our understanding of atomic scale surface processes, such as atom transport and its role in the growth of crystalline materials, is required so that the manipulation of individual atoms can be routinely employed to enhance the performance of existing devices, as well as develop new devices. This project uniquely combines the ability to view the motion of individual atoms using a microscope with the capability of identifying the atomic species in motion using a mass spectrometer. It thereby allows for a detailed atomic level study of the growth of an elemental crystalline material. This research is serving as the Ph.D. thesis project for one graduate student and employing an undergraduate science major to assist with the experiments. The inherent interdisciplinary nature of the project is training the students in a wide variety of technical areas and thereby helping to thoroughly prepare them to begin a career in the physical sciences. Underrepresented groups have a good opportunity to fill the student positions on this research effort because the University of New Mexico is exceptional in combining a highly rated research program and designated as both a Minority-serving institution and a Hispanic-serving institution. TECHNICAL ABSTRACT: The dynamics of steps on crystal surfaces is one of the most important processes governing atom transport and the resulting crystal growth. In this project, step dynamics at the atomic scale in the prototypic case, elemental crystals, is being investigated for the first time. To enable the study of such homogeneous systems we are employing a novel approach - the use of an adatom that is a stable isotope of the elemental substrate. This preserves the chemical nature of the homogeneous system, yet the isotope adatom is distinguishable due to its known mass and isotopic abundance. The field ion microscope is being used for atomic resolution surface imaging. Possible isotope adatom-substrate atom exchange processes that occur during atom transport are detected by the removal of individual atoms as ions with field evaporation and subsequent time-of-fight-based atom-probe microanalysis to determine their mass. The project is investigating step dynamics on various transition metal surfaces by studies of: Year 1 - The descent of isotope adatoms over steps and the diffusion of isotope adatoms along step edges, Year 2 - Nanosecond-time-scale diffusion initiated by laser pulses to capture any 'non-equilibrium' isotope adatom-substrate configurations, and Year 3 - The impact of the proximity of steps to one another on isotope adatom-step dynamics.