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

非技术摘要：晶体材料的生长是制造众多电子设备的第一步，包括用于计算机的微处理器、用于人类健康的化学传感器以及用于反恐威胁的生物探测器。如今，人们正在操纵单个原子，试图在原子尺度上制造此类处理器和传感器。需要提高我们对原子尺度表面过程（例如原子输运及其在晶体材料生长中的作用）的理解，以便可以常规地利用单个原子的操纵来增强现有器件的性能以及开发新器件。该项目独特地将使用显微镜观察单个原子运动的能力与使用质谱仪识别运动中的原子种类的能力结合起来。因此，它可以对元素晶体材料的生长进行详细的原子水平研究。这项研究正在作为博士学位。一名研究生的论文项目，并聘请一名科学专业的本科生来协助实验。该项目固有的跨学科性质正在对学生进行各种技术领域的培训，从而帮助他们为开始物理科学职业生涯做好充分准备。代表性不足的群体有很好的机会填补这项研究工作的学生职位，因为新墨西哥大学在结合高评价的研究项目方面表现出色，并被指定为少数族裔服务机构和西班牙裔服务机构。 技术摘要：晶体表面台阶的动力学是控制原子传输和由此产生的晶体生长的最重要过程之一。在该项目中，首次研究了原型案例（元素晶体）中原子尺度的阶跃动力学。为了能够研究这种均质系统，我们采用了一种新方法 - 使用作为元素底物的稳定同位素的吸附原子。这保留了均质系统的化学性质，但同位素吸附原子由于其已知的质量和同位素丰度而可区分。场离子显微镜用于原子分辨率表面成像。通过场蒸发去除单个原子作为离子，并随后进行基于战斗时间的原子探针微分析以确定其质量，从而检测原子传输过程中可能发生的同位素吸附原子-基底原子交换过程。该项目正在通过以下研究来研究各种过渡金属表面的阶跃动力学：第一年 - 同位素吸附原子在台阶上的下降以及同位素吸附原子沿台阶边缘的扩散，第二年 - 由激光脉冲引发的纳秒时间尺度扩散，以捕获任何“非平衡”同位素吸附原子基底构型，以及第三年 - 台阶彼此接近对同位素吸附原子台阶动力学的影响。

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.