Dynamics of copper atoms on Si(111)-7×7 surfaces

Energetics and kinetics of Cu atoms and clusters on the Si(111)-7 × 7 surface: first-principles calculations

“…2(c)), which is in excellent agreement with the experimentally estimated value of 0.88 AE 0.01 eV. 16 In path (III), the high energy barrier is due to the breaking of the strong Cu-Si adatom (rest atom) bonds, indicating that the outward diffusion from the potential wells is strongly confined by the boundaries between the HUCs in a low temperature regime. Now we estimate the hopping rates R of the Cu atom along different paths at room temperature by assuming a thermally activated motion formulated by R = R 0 exp(ÀE b /k B T), where R 0 is the characteristic frequency, E b is the energy barrier, k B is the Boltzmann constant, and T is the temperature, respectively.…”

“…Therefore, the present findings convincingly support previous experimental deduction that the apparent triangular bright spots are resulted from a single Cu ad-atom frequently hopping among adjacent adsorption sites. 5,16 Furthermore, in a low coverage regime of around 0.15 ML, we find that the previously claimed hexagonal ring-like magic Cu 6 species is considerably unstable and the most stable Cu 6 /Si(111) complex also possesses a distinct simulated STM image with an experimental pattern. Instead, an energetically preferred solid-centered Cu 7 /Si(111)-(7 Â 7) structure exhibits a reasonable agreement between the simulated STM patterns and the experimental images, convincingly kicking out the tentative six-atom model in explaining the STM patterns.…”

“…When the coverage of the deposited noble metal elements such as Cu is slightly increased, the formation of ordered magic cluster arrays can be probed by STM at room and elevated temperatures. [13][14][15][16] Note that these Cu cluster arrays on Si(111)-(7 Â 7) provide an invaluable bridge for elucidating the mechanism of formation of the Cu/Si(111)-(7 Â 7) interface and nanodevices grown from the deposited single Cu atom. To rationalize their observed STM patterns, Zhang et al 13 and Ho et al 16 proposed a six-atom model to explain the Cu magic cluster, which form a ring-like aggregation with three sitting on the top of the Si center adatoms and three binding to the Si rest atoms.…”

“…[13][14][15][16] Note that these Cu cluster arrays on Si(111)-(7 Â 7) provide an invaluable bridge for elucidating the mechanism of formation of the Cu/Si(111)-(7 Â 7) interface and nanodevices grown from the deposited single Cu atom. To rationalize their observed STM patterns, Zhang et al 13 and Ho et al 16 proposed a six-atom model to explain the Cu magic cluster, which form a ring-like aggregation with three sitting on the top of the Si center adatoms and three binding to the Si rest atoms. Later, Saranin et al 15 provided a draft hint that the Cu cluster array may consist of around 20 Cu atoms.…”

“…Instead, an energetically preferred solid-centered Cu 7 /Si(111)-(7 Â 7) structure exhibits a reasonable agreement between the simulated STM patterns and the experimental images, convincingly kicking out the tentative six-atom model in explaining the STM patterns. 13,16 2. Computational methods Our first-principles calculations are performed based on the density functional theory (DFT) using the projector augmented wave (PAW) method, 18 which is implemented in the VASP code.…”