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Barry P Rand - One of the best experts on this subject based on the ideXlab platform.
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Homoepitaxy of crystalline rubrene thin films
Nano Letters, 2017Co-Authors: Michael A Fusella, Frank Schreiber, Kevin Abbasi, Alejandro L Briseno, Barry P RandAbstract:The smooth surface of crystalline rubrene films formed through an abrupt heating process provides a valuable platform to study organic Homoepitaxy. By varying growth rate and substrate temperature, we are able to manipulate the onset of a transition from layer-by-layer to island growth modes, while the crystalline thin films maintain a remarkably smooth surface (less than 2.3 nm root-mean-square roughness) even with thick (80 nm) adlayers. We also uncover evidence of point and line defect formation in these films, indicating that Homoepitaxy under our conditions is not at equilibrium or strain-free. Point defects that are resolved as screw dislocations can be eliminated under closer-to-equilibrium conditions, whereas we are not able to eliminate the formation of line defects within our experimental constraints at adlayer thicknesses above ∼25 nm. We are, however, able to eliminate these line defects by growing on a bulk single crystal of rubrene, indicating that the line defects are a result of strain bui...
Lian Duan - One of the best experts on this subject based on the ideXlab platform.
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Homoepitaxy growth of well ordered rubrene thin films
Crystal Growth & Design, 2008Co-Authors: Xionghui Zeng, Liduo Wang, Lian DuanAbstract:Rubrene is a nonplanar molecule, it is recognized that only amorphous rubrene films can be obtained on such substrates as Au, SiO2, and Al2O3 by organic molecular beam deposition or ordinary vacuum evaporation. In this work, rubrene organic single crystals with very smooth surfaces were used as substrates. Well-ordered rubrene thin films were obtained by ordinary vacuum evaporation, and the substate temperature is room temperature. Two-dimensional nucleation-monolayer by monolayer growth and Homoepitaxy was demonstrated when the deposition rate was kept at 0.2 nm/min. Furthermore, when the deposition rate was increased to 0.6 nm/min, two-dimensional hexagons were observed in the growth process of rubrene thin films and are similar to the two-dimensional islands with regular shapes observed in Homoepitaxy growth of inorganic thin films.
Zhenyu Zhang - One of the best experts on this subject based on the ideXlab platform.
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nanocrystal formation and faceting instability in al 110 Homoepitaxy true upward adatom diffusion at step edges and island corners
Physical Review Letters, 2003Co-Authors: Francesco Buatier De Mongeot, C Boragno, Ugo Valbusa, Alessandro Molle, R Buzio, Enge Wang, Zhenyu ZhangAbstract:Using atomic force microscopy and spot-profile analyzing low energy electron diffraction, we have observed the existence of a striking faceting instability in Al(110) Homoepitaxy, characterized by the formation of nanocrystals with well-defined facets. These hut-shaped nanocrystals are over tenfold higher than the total film coverage, and coexist in a bimodal growth mode with much shallower and more populous surface mounds. We further use density functional theory calculations to elucidate the microscopic origin of the faceting instability, induced by surprisingly low activation barriers for adatom ascent at step edges and island corners.
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island shape selection in pt 111 submonolayer Homoepitaxy with or without co as an adsorbate
Physical Review Letters, 2002Co-Authors: Jing Wu, Zhenyu Zhang, Enge Wang, Kalman Varga, Sokrates T PantelidesAbstract:The microscopic selection mechanisms of single-layer island shapes in Pt(111) Homoepitaxy with or without minute amounts of CO adsorbate have been investigated theoretically. For clean growth, only triangular islands of a fixed orientation are obtained within a wide range of growth temperatures, with the orientation uniquely determined by a disparity in the rates of atom supply to an island corner site from the two island edges defining the corner. This novel picture is further corroborated by growth predictions in the presence of CO, whose preferential decoration of one type of the island edges reverses the intrinsic rate disparity for atom supply, thereby inverting the island orientation.
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Flux-dependent scaling behavior in Cu(100) submonolayer Homoepitaxy
Surface Science, 1997Co-Authors: Anna K. Swan, John F. Wendelken, Zhenyu ZhangAbstract:The average separation of two-dimensional islands in Cu(100) submonolayer Homoepitaxy as a function of the deposition flux at 213 K has been studied using spot profile analysis low-energy electron diffraction. As the flux decreases, a large change in the apparent critical island size, from one to a value between seven and 12 atoms, is obtained even though the temperature is held constant. This is shown to be consistent with a recently proposed dimer shearing mechanism which has a significant influence on the stability of islands with eight atoms or less.
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Effects of hydrogen in Ni(100) submonolayer Homoepitaxy
Physical Review B, 1997Co-Authors: Kenneth Haug, Zhenyu Zhang, David John, Curtis F. Walters, D. M. Zehner, Ward PlummerAbstract:The effects of hydrogen in Ni(100) submonolayer Homoepitaxy have been investigated by classical-potential total-energy calculations with semiclassical hydrogen zero-point-energy corrections. The fast diffusion of H on a flat Ni(100) surface is found to persist even when the surface is decorated with various intrinsic defects such as Ni adatoms, islands, and steps created during epitaxial growth. On the other hand, the presence of H significantly enhances the mobility of both Ni adatoms and Ni islands, resulting in a decrease in the Ni island density and a corresponding increase in the average island size. These results suggest that hydrogen will function as an antisurfactant in Ni(100) Homoepitaxy. Connections to available experiments are made. {copyright} {ital 1997} {ital The American Physical Society}
Hiroshi Tochihara - One of the best experts on this subject based on the ideXlab platform.
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microscopic mechanism of the Homoepitaxy on si 111 7 7
Physical Review B, 2016Co-Authors: Wataru Shimada, Tomoshige Sato, Hiroshi TochiharaAbstract:Very initial stages of the Homoepitaxy on the $\mathrm{Si}(111)7\ifmmode\times\else\texttimes\fi{}7$ surface are studied at 310, 356, and $366{\phantom{\rule{0.16em}{0ex}}}^{\ensuremath{\circ}}\mathrm{C}$ by in situ continuous observation using high-temperature scanning tunneling microscopy (HTSTM) at the atomic scale during Si deposition under a slow rate of 0.02 bilayer $(\mathrm{BL})\phantom{\rule{0.16em}{0ex}}{min}^{\ensuremath{-}1}$. The substrate surface is reconstructed to the well-established dimer-adatom-stacking fault (DAS) structure with the $7\ifmmode\times\else\texttimes\fi{}7$ unit cell consisting of two triangular half unit cells (HUCs): a stacking faulted (F)-HUC and a normally stacked one. It is expected that the complex, large unit cell compels the initial Homoepitaxy to proceed in a quite different manner from that on unreconstructed surfaces. Formation and growth of various adsorbed clusters are pursued by the continuous observation of the same narrow areas during the deposition, avoiding the tip-shadow effect. The most anomalous finding is a quasiliquid cluster (QLC) spreading to plural HUCs (spread QLC) on the $7\ifmmode\times\else\texttimes\fi{}7$ DAS substrate. This appears as a result of the difficulty of the F-HUC to be transformed into the normally stacked BL, being essential for the Homoepitaxy. After the transformation, the spread QLC undergoes the following structural changes with an increase of the Si deposition: crystallization to a small epitaxial BL \ensuremath{\rightarrow} surface reconstruction to the DAS structure. Validity and reasons of the transitional formation of the spread QLC are discussed. The spread QLC mediated Homoepitaxy mechanism is concluded and is a new mode in the crystal growth. Real in situ HTSTM observations of the same areas on the nanoscale during Si deposition are indispensable to explore for the dynamic atomistic mechanism of the homoepitaxial growth on the $\mathrm{Si}(111)7\ifmmode\times\else\texttimes\fi{}7$.
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Microscopic mechanism of the Homoepitaxy on Si (111 )7 ×7
Physical Review B, 2016Co-Authors: Wataru Shimada, Tomoshige Sato, Hiroshi TochiharaAbstract:Very initial stages of the Homoepitaxy on the $\mathrm{Si}(111)7\ifmmode\times\else\texttimes\fi{}7$ surface are studied at 310, 356, and $366{\phantom{\rule{0.16em}{0ex}}}^{\ensuremath{\circ}}\mathrm{C}$ by in situ continuous observation using high-temperature scanning tunneling microscopy (HTSTM) at the atomic scale during Si deposition under a slow rate of 0.02 bilayer $(\mathrm{BL})\phantom{\rule{0.16em}{0ex}}{min}^{\ensuremath{-}1}$. The substrate surface is reconstructed to the well-established dimer-adatom-stacking fault (DAS) structure with the $7\ifmmode\times\else\texttimes\fi{}7$ unit cell consisting of two triangular half unit cells (HUCs): a stacking faulted (F)-HUC and a normally stacked one. It is expected that the complex, large unit cell compels the initial Homoepitaxy to proceed in a quite different manner from that on unreconstructed surfaces. Formation and growth of various adsorbed clusters are pursued by the continuous observation of the same narrow areas during the deposition, avoiding the tip-shadow effect. The most anomalous finding is a quasiliquid cluster (QLC) spreading to plural HUCs (spread QLC) on the $7\ifmmode\times\else\texttimes\fi{}7$ DAS substrate. This appears as a result of the difficulty of the F-HUC to be transformed into the normally stacked BL, being essential for the Homoepitaxy. After the transformation, the spread QLC undergoes the following structural changes with an increase of the Si deposition: crystallization to a small epitaxial BL \ensuremath{\rightarrow} surface reconstruction to the DAS structure. Validity and reasons of the transitional formation of the spread QLC are discussed. The spread QLC mediated Homoepitaxy mechanism is concluded and is a new mode in the crystal growth. Real in situ HTSTM observations of the same areas on the nanoscale during Si deposition are indispensable to explore for the dynamic atomistic mechanism of the homoepitaxial growth on the $\mathrm{Si}(111)7\ifmmode\times\else\texttimes\fi{}7$.
Pierre Masri - One of the best experts on this subject based on the ideXlab platform.
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Silicon carbide and silicon carbide-based structures
Surface Science Reports, 2002Co-Authors: Pierre MasriAbstract:In this review, we discuss silicon carbide growth problems and the physics of epitaxy of this material in many aspects of Homoepitaxy and heteroepitaxy.