Very weak bonds to artificial atoms formed by quantum corrals

Abstract

We explored the bonding properties of the quantum corral (a circle of 48 iron atoms placed on a copper surface) reported by Crommie, Lutz and Eigler in 1993, along with variants, as an artificial atom using an atomic force microscope (AFM). The original corral geometry confines 102 electrons to 28 discrete energy states, and we find that these states can form a bond to the front atom of the AFM with an energy of about 5 millielectron volts. The measured forces are about 1/1000 of typical forces in atomically resolved AFM. The confined electrons showed covalent attraction to metal tips and Pauli repulsion to CO-terminated tips. The repulsion at close distance was evident from the response of corral states created by deliberately placing single iron atoms inside the corral. The forces scaled appropriately with a 24-atom corral.

Probing the Nature of Chemical Bonds by Atomic Force Microscopy

“…This corral holds electrons in 28 discrete energy levels with three quantum numbers, the number of radial nodes n , angular momentum l and magnetic quantum number [ 42 ], leading to wave functions . A total of 102 electrons are held in the corral, 10 of them are energetically close to the Fermi energy and thus visible to STM, 92 can only be observed by AFM [ 84 ].…”

“…( J ) Contrast, defined by the difference between the first maximum at nm and the average between the first and second minimum, evolution as a function of vertical distance z . See section 7 of [ 84 ] for details of data extraction. Adapted with permission by American Association for the Advancement of Science from Figure 2 in [ 84 ].…”

“…See section 7 of [ 84 ] for details of data extraction. Adapted with permission by American Association for the Advancement of Science from Figure 2 in [ 84 ].…”

Energy dissipation from confined states in nanoporous molecular networks

“…Since the first quantum corral built in 1993 in IBM Almaden, 1 atomic structures capable of confining Shockley surface states (SS) of noble metals into discrete energy levels (also referred to as artificial atom) are achieved by atom-by-atom manipulation with a scanning tunneling microscope (STM) 2,3 or by spontaneous assembly of molecules into nanoporous networks. 4 When a two-dimensional array of artificial atoms is formed, its geometry and symmetry as well as the interaction between the confined states -all depending on the precursor forming the network 5 -are key factors in determining the final topology of the band structure.…”

Hydration Dynamics and the Future of Small-Amplitude AFM Imaging in Air

“…Moreover, the user must cope with and understand the character of some dynamic variables, such as the sharpness of the tip [ 9 , 10 ], otherwise referred to as the tip radius, R, in high-resolution imaging applications. Perhaps counter-intuitively to the newcomer, the field has rapidly advanced in two extremes—in liquid [ 11 , 12 , 13 , 14 ] and UHV environments [ 15 ]—while several complex phenomena have hindered the imaging and quantification of phenomena in air [ 16 ] with similar resolutions, controls, or throughputs [ 3 ]. There has been research in air in terms of capillary interactions [ 17 ], spontaneous capillary condensation [ 16 ], and the way the air environment affects surfaces [ 18 ], molecules on it, and modes of imaging [ 3 , 19 , 20 , 21 ].…”