Single-atom fabrication with electron and ion beams: From surfaces and two-dimensional materials toward three-dimensiona
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troduction Ever since Democritus proposed the existence of atoms as the smallest indivisible unit of matter around 400 BC, this idea and its consequences have captured the attention of the scientific community. In the 19th century, broad adoption of atomistic theory led to remarkable progress in physics and chemistry, and eventually to the dawn of quantum physics in the early 20th century. The earliest direct observation of atoms originally dates to the first field-ion microscope in the early 1950s.1 The first lattice fringes were observed in the 1950s by Menter using an electron microscope, building on the developments of Ruska,2 von Ardenne,3,4 and others,5 with gradually improving resolution over the following decades. Direct observation of individual atoms in scanning transmission electron microscopy (STEM) was achieved by Crewe and co-workers in the 1960s,6 made possible by his development of the cold-fieldemission gun.7 Using an annular detector, direct imaging of atomic structures became possible,8–10 and in the last 30 years, the progress in STEM11 has rendered such observations routine. In comparison, scanning tunneling microscopy (STM)12–14 began
with direct demonstration of atomic resolution on Si surfaces, even though earlier examples of current- and force-based mesoscopic profilometry are available. Since the observation of atoms and the emergence of modern physics, a loftier dream has developed, as summarized by R. Feynman in his seminal talk “There is plenty of room at the bottom.”15 The modern field of nanotechnology, however, owes much to the experimental work of D. Eigler at IBM,16 and the visionary work of E. Drexler.17 The letters “I,” “B,” and “M” written in Xe atoms on a copper surface16 and the book “Engines of Creation”17 have provided the impetus by becoming firmly imprinted in societal perception of nanoscience as a pathway to control matter on the atomic scale, creating the machines and devices for ultimate medical devices and nanoassemblers. The evolution of social acceptance of nanotechnology is illustrated in Figure 1.
The first paradigm: Molecular machines The first paradigm of nanotechnology was popularized by Drexler, who proposed the controlled chemical synthesis of
Sergei V. Kalinin, Institute for Functional Imaging of Materials; and Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, USA; [email protected] Stephen J. Pennycook, Department of Materials Science and Engineering, National University of Singapore, Singapore; The University of Tennessee, USA; and Vanderbilt University, USA; [email protected]; or [email protected] doi:10.1557/mrs.2017.186
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Atomic Assembly by Electron Beams
molecular entities capable of autonom
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