Switching the Charge State of Individual Surface Atoms at Si(111)-√3 × √3:B Surfaces

Abstract

We show that each surface atom of heavily boron-doped, (111)-oriented silicon with a √3 × √3 reconstruction has electrically switchable two charge states due to the strong electron-lattice coupling at this surface. The structural and electronic properties of the two charge states as well as their energetics are uncovered by employing scanning tunneling microscopy measurements and density functional theory calculations, which reveals that one of the two is a two-electron bound state or surface bipolaron. We also execute the single-atom bit operations on individual surface atoms by controlling their charge states while demonstrating implementation of the atomic scale memory at a silicon surface with an unprecedented recording density.

Ring charging of a single silicon dangling bond imaged by noncontact atomic force microscopy

“…An ultimate confined system is a surface adatom dangling bond (DB) consisting of a single electronic state in the bandgap of a semiconductor, whose charging can be controlled by a scanning-probe microscope [10,11]. DBs have been proposed for binary logic [12] and data storage [13,14] applications. They reveal a rich fundamental physics, such as polaronic transport [15,16] and carrier dynamics [17,18].…”

“…degenerately doped with boron (resistivity of ≈1 m • cm at 300 K), prepared by thermal annealing up to 1200 • C to obtain a Si(111)-( √ 3 × √ 3)R • 30 surface reconstruction (see Refs. [10,13,16,20]) for the surface preparation and defect identification). They have been investigated by scanning tunneling microscopy (STM) and nc-AFM, using length-extensional resonators with W tips (Kolibri sensors; SPECS, Berlin) of oscillation frequency f 0 ≈ 1 MHz and quality factor Q ≈ 10 5 [21,22].…”

Local geometry around B atoms in B/Si(1 1 1) from polarized x-ray absorption spectroscopy

“…As a whole, we conclude that the majority of B atoms occupies the L c 1 position but a sizable portion of them is sitting also somewhere else, possibly in the L a 1 position. Recently it was suggested that for the L c 1 geometry there may be also some larger B-Si distances present if two-electron bound states are formed in the system [18]. We checked that considering such geometry (with the atop Si higher above the B atom than what is shown in figure 3) has no significant effect on the calculated spectra.…”

“…Recently a combined experimental (STM) and theoretical study showed that there can be two charge states and consequently two local L c 1 configurations for the δ-doped Si(1 1 1) surface owing to electron-lattice coupling [18]. One state corresponds to the ground state of the ( √ 3 × √ 3)R30 • reconstruction while the second state is a two-electron bound state with an elevated Si adatom.…”

Photoinduced Persistent Electron Accumulation and Depletion in LaAlO3/SrTiO3 Quantum Wells

“…In many semiconductors, photoexcitation of DX centers leads to long-term changes of conductance, caused by the long decay of excited carriers to the ground state [1][2][3][4][5][6][7]. In most cases, photoexcitation drives carrier accumulation, while in other few cases, as reported for graphene [8], persistent photoconductance can be negative.…”