TY - JOUR

T1 - 2D Si island nucleation on the Si(111) surface at initial and late growth stages: On the role of step permeability in pyramidlike growth

AU - Rogilo, D. I.

AU - Fedina, L. I.

AU - Kosolobov, S. S.

AU - Ranguelov, B. S.

AU - Latyshev, A. V.

N1 - Publisher Copyright: © 2016 Elsevier B.V.

PY - 2017/1/1

Y1 - 2017/1/1

N2 - Initial and late stages of 2D Si island nucleation and growth (2DNG) on extra-large (~100 μm) and medium size (1–10 μm) atomically flat Si(111)-(7×7) terraces bordered by step bunches have been studied by in situ REM at T=600–750 °С. At first, the layer-by-layer 2DNG takes place on whole terraces and 2D island concentration dependence on deposition rate R corresponds to critical nucleus size i=1. Continuous 2DNG triggers morphological instabilities: elongated pyramidlike waves and separate pyramids emerge on all terraces at T≤720 °С and T=750 °С, respectively. Both instabilities arise due to the imbalance of uphill/downhill adatom currents related with large Ehrlich-Schwöbel (ES) barriers and permeability of straight [11¯2]-type step edges. However, the first one is initiated by dominant downhill adatom current to distant sinks: bunches, wave's step edges, and “vacancy” islands emerging on terraces due to 2D island coalescence. As a result, top layer size decreases to the critical terrace width λ where 2DNG takes place. From the analysis of λ∝R−χ/2 scaling at T=650 °C, we have found that i increases from i=2 on a three-layer wave to i=6–8 on a six-layer wave. This authenticates the significance of downhill adatom sink to distant steps related to the step permeability. The second instability type at T>720 °C is related to the raising of uphill adatom current due to slightly larger ES barrier for step-up attachment comparing to the step-down one (EES −~0.9 eV [Phys. Rev. Lett. 111 (2013) 036105]). This leads to “second layer” 2D nucleation on top layers, which triggers the growth of separate pyramids. Because of small difference between ES barriers, net uphill/downhill adatom currents are nearly equivalent, and therefore layer coverage distributions of both instabilities display similar linear slopes.

AB - Initial and late stages of 2D Si island nucleation and growth (2DNG) on extra-large (~100 μm) and medium size (1–10 μm) atomically flat Si(111)-(7×7) terraces bordered by step bunches have been studied by in situ REM at T=600–750 °С. At first, the layer-by-layer 2DNG takes place on whole terraces and 2D island concentration dependence on deposition rate R corresponds to critical nucleus size i=1. Continuous 2DNG triggers morphological instabilities: elongated pyramidlike waves and separate pyramids emerge on all terraces at T≤720 °С and T=750 °С, respectively. Both instabilities arise due to the imbalance of uphill/downhill adatom currents related with large Ehrlich-Schwöbel (ES) barriers and permeability of straight [11¯2]-type step edges. However, the first one is initiated by dominant downhill adatom current to distant sinks: bunches, wave's step edges, and “vacancy” islands emerging on terraces due to 2D island coalescence. As a result, top layer size decreases to the critical terrace width λ where 2DNG takes place. From the analysis of λ∝R−χ/2 scaling at T=650 °C, we have found that i increases from i=2 on a three-layer wave to i=6–8 on a six-layer wave. This authenticates the significance of downhill adatom sink to distant steps related to the step permeability. The second instability type at T>720 °C is related to the raising of uphill adatom current due to slightly larger ES barrier for step-up attachment comparing to the step-down one (EES −~0.9 eV [Phys. Rev. Lett. 111 (2013) 036105]). This leads to “second layer” 2D nucleation on top layers, which triggers the growth of separate pyramids. Because of small difference between ES barriers, net uphill/downhill adatom currents are nearly equivalent, and therefore layer coverage distributions of both instabilities display similar linear slopes.

KW - A1. Morphological stability

KW - A1. Nucleation

KW - A1. Surface processes

KW - A3. Molecular beam epitaxy

KW - B2. Semiconducting silicon

KW - MOLECULAR-BEAM

KW - ATOMIC PROCESSES

KW - Nucleation

KW - MAGIC ISLANDS

KW - Morphological stability

KW - HOMOEPITAXY

KW - SUBMONOLAYER EPITAXY

KW - 2-DIMENSIONAL NUCLEATION

KW - TEMPERATURES

KW - KINETICS

KW - Molecular beam epitaxy

KW - Semiconducting silicon

KW - SCANNING-TUNNELING-MICROSCOPY

KW - THIN-FILM GROWTH

KW - Surface processes

UR - http://www.scopus.com/inward/record.url?scp=84996644279&partnerID=8YFLogxK

U2 - 10.1016/j.jcrysgro.2016.06.028

DO - 10.1016/j.jcrysgro.2016.06.028

M3 - Article

AN - SCOPUS:84996644279

VL - 457

SP - 188

EP - 195

JO - Journal of Crystal Growth

JF - Journal of Crystal Growth

SN - 0022-0248

ER -