Modeling of Metal(100) Homoepitaxial Film Growth at Very Low Temperatures

2000 ◽  
Vol 619 ◽  
Author(s):  
K.J. Caspersen ◽  
C.R. Stoldt ◽  
P.A. Thiel ◽  
J.W. Evans
Keyword(s):  
Low Temperatures ◽  
Film Growth ◽  
Diffusion Processes ◽  
Variable Temperature ◽  
Scanning Tunneling ◽  
Film Morphology ◽  
Tunneling Microscopy ◽  
Adsorption Sites ◽  
Temperature Scanning ◽  
Homoepitaxial Film

ABSTRACTWe model the growth of Ag films deposited on Ag(100) below 140K. Our recent Variable-Temperature Scanning Tunneling Microscopy (VTSTM) studies reveal “smooth growth” from 120-140K, consistent with earlier diffraction studies. However, we also find rougher growth for lower temperatures. This unexpected behavior is modeled by describing the deposition dynamics using a “restricted downward funneling” model, wherein deposited atoms get caught on the sides of steep nanoprotrusions (which are prevalent below 120K), rather than always funneling down to lower four-fold hollow adsorption sites. At OK, where no thermal diffusion processes are operative, this leads to the formation of overhangs and internal defects (or voids). Above 40K, low barrier interlayer diffusion processes become operative, producing the observed smooth growth by 120K. We also discuss how the apparent film morphology mapped out by the STM tip “smears” features of the actual film morphology (which are small at low temperature), and also can lead to underestimation of the roughness.

scholarly journals Kinetic Roughening of Multilayer Ag/Ag(100) Films: Complex Temperature-Dependence in a Simple System

2000 ◽  
Vol 619 ◽  
Author(s):  
C.R. Stoldt ◽  
K.J. Caspersen ◽  
M.C. Bartelt ◽  
C.J. Jenks ◽  
J.W. Evans ◽  
...  
Keyword(s):  
Lattice Gas ◽  
Film Growth ◽  
Kinetic Monte Carlo ◽  
Variable Temperature ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Adsorption Sites ◽  
Lattice Gas Models ◽  
Temperature Scanning ◽  
Complex Temperature

ABSTRACTMetal(100) homoepitaxial systems constitute perhaps the simplest class of systems in which to study thin film growth. Yet, our Variable-Temperature Scanning Tunneling Microscopy (VTSTM) analysis of Ag/Ag(100) homoepitaxy reveals that the variation of roughness with temperature is extraordinarily complex. As the deposition temperature is reduced from 300K to 50K, the roughness of 25 monolayer films first increases, then decreases, and then increases again. Furthermore, a transition from mound formation to self-affine (semi-fractal) growth occurs at around 135K. We postulate that the following the atomistic mechanisms underly this behavior: the existence of a small step-edge barrier inhibiting diffusive downward transport; “downward funneling” of atoms deposited at step edges and microprotrusions towards lower four-fold hollow adsorption sites; and statistically significant deviations from “complete” downward funneling at lower temperatures, where deposited atoms instead become trapped on the sides of (the more prevalent) small steep microprotrusions. To support these postulates, we employ kinetic Monte Carlo simulations to show that atomistic (lattice-gas) models for epitaxial growth, which incorporate these mechanisms, reproduce the experimental data quantitatively.

Geometric and Electronic Structure of Fullerene Film Growth as a Function of Coverage

1994 ◽  
Vol 359 ◽  
Author(s):  
B. Reihl
Keyword(s):  
Electronic Structure ◽  
Low Temperatures ◽  
Film Growth ◽  
Theoretical Calculations ◽  
Scanning Tunneling ◽  
Island Growth ◽  
Tunneling Microscopy ◽  
Adsorption Sites ◽  
Adsorbed Monolayer ◽  
Inverse Photoemission

ABSTRACTWe have employed scanning tunneling microscopy at room and low temperature, i.e. 300, 50, and 5 K, to study the epitaxy and growth of fullerene films on the noble-metal surfaces Ag(110) and Au(110). Initial island growth occurs on terrace sites away from substrate step edges. Particularly at low temperatures where the rotational and vibrational movements of the fullerene molecules are frozen in, different intra-molecular topographic patterns become visible in ordered films, which are characteristic of particular adsorption sites. Complementary tunneling spectroscopy and direct and inverse photoemission measurements reveal distinct differences between the first adsorbed monolayer and additional fullerene layers indicating differences in bonding and charge transfer. Our results are compared to theoretical calculations.

Density fluctuations as door-opener for diffusion on crowded surfaces

Science ◽  
2019 ◽  
Vol 363 (6428) ◽  
pp. 715-718 ◽  
Author(s):  
Ann-Kathrin Henß ◽  
Sung Sakong ◽  
Philipp K. Messer ◽  
Joachim Wiechers ◽  
Rolf Schuster ◽  
...  
Keyword(s):  
High Speed ◽  
Density Functional ◽  
Local Density ◽  
Variable Temperature ◽  
Industrial Process ◽  
Density Fluctuations ◽  
Scanning Tunneling ◽  
Fast Diffusion ◽  
Tunneling Microscopy ◽  
Adsorption Sites

How particles can move on a catalyst surface that, under the conditions of an industrial process, is highly covered by adsorbates and where most adsorption sites are occupied has remained an open question. We have studied the diffusion of O atoms on a fully CO-covered Ru(0001) surface by means of high-speed/variable-temperature scanning tunneling microscopy combined with density functional theory calculations. Atomically resolved trajectories show a surprisingly fast diffusion of the O atoms, almost as fast as on the clean surface. This finding can be explained by a “door-opening” mechanism in which local density fluctuations in the CO layer intermittently create diffusion pathways on which the O atoms can move with low activation energy.

In Situ Variable-Temperature Scanning Tunneling Microscopy Studies of Graphene Growth Using Benzene on Pd(111)

ACS Nano ◽  
2019 ◽  
Vol 14 (1) ◽  
pp. 1141-1147 ◽  
Author(s):  
Pedro Arias ◽  
Jan Tesař ◽  
Abby Kavner ◽  
Tomáš Šikola ◽  
Suneel Kodambaka
Keyword(s):  
Scanning Tunneling Microscopy ◽  
Variable Temperature ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Graphene Growth ◽  
Temperature Scanning

Mapping of local electronic properties in nanostructured CMR thin films by Scanning Tunneling Microscopy (STM) and Local Conductance Map (LCMAP)

2004 ◽  
Vol 838 ◽  
Author(s):  
Sohini Kar ◽  
Barnali Ghosh ◽  
L. K. Brar ◽  
M A. Paranjape ◽  
A. K. Raychaudhuri
Keyword(s):  
Magnetic Field ◽  
Thin Films ◽  
Grain Boundaries ◽  
Electronic Properties ◽  
Variable Temperature ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Colossal Magnetoresistive ◽  
Spatially Resolved ◽  
Temperature Scanning

ABSTRACTWe have investigated the local electronic properties and the spatially resolved magnetoresistance of a nanostructured film of a colossal magnetoresistive (CMR) material by local conductance mapping (LCMAP) using a variable temperature Scanning Tunneling Microscope (STM) operating in a magnetic field. The nanostructured thin films (thickness ≈500nm) of the CMR material La0.67Sr0.33MnO3(LSMO) on quartz substrates were prepared using chemical solution deposition (CSD) process. The CSD grown films were imaged by both STM and atomic force microscopy (AFM). Due to the presence of a large number of grain boundaries (GB's), these films show low field magnetoresistance (LFMR) which increases at lower temperatures.The measurement of spatially resolved electronic properties reveal the extent of variation of the density of states (DOS) at and close to the Fermi level (EF) across the grain boundaries and its role in the electrical resistance of the GB. Measurement of the local conductance maps (LCMAP) as a function of magnetic field as well as temperature reveals that the LFMR occurs at the GB. While it was known that LFMR in CMR films originates from the GB, this is the first investigation that maps the local electronic properties at a GB in a magnetic field and traces the origin of LFMR at the GB.

Island decay on the anisotropic Ag(110) surface

2000 ◽  
Vol 648 ◽  
Author(s):  
Karina Morgenstern ◽  
Erik Lægsgaard ◽  
Flemming Besenbacher
Keyword(s):  
Decay Mode ◽  
Ostwald Ripening ◽  
Variable Temperature ◽  
Scanning Tunneling ◽  
Two Dimensional ◽  
Tunneling Microscopy ◽  
Sharp Transition ◽  
One Dimensional ◽  
Temperature Scanning ◽  
Rate Limiting

AbstractWe have investigated the decay of two-dimensional islands on the anisotropic Ag(110) surface using variable-temperature scanning tunneling microscopy. Contrary to predictions from traditional Ostwald ripening theory, a quasi-one-dimensional decay mode is observed at low temperatures (175-220 K). A surprisingly sharp transition to the quasi-two-dimensional decay mode is observed around 220 K. This transition is accompanied by a fast equilibration of the island shape. These findings have tentatively been rationalized within a simple model to identify the underlying rate limiting atomistic processes.

scholarly journals Temperature-Dependent Accommodation of Two Lattices of Largely Different Size during Growth

Nanomaterials ◽  
2019 ◽  
Vol 9 (5) ◽  
pp. 710
Author(s):  
Carsten Sprodowski ◽  
Karina Morgenstern
Keyword(s):  
Low Temperature ◽  
Variable Temperature ◽  
Lattice Misfit ◽  
Scanning Tunneling ◽  
Temperature Structure ◽  
Misfit Dislocations ◽  
Tunneling Microscopy ◽  
Large Lattice ◽  
Higher Temperature ◽  
Temperature Scanning

If a material grows on another material with a largely different lattice constant, which of the two adapts for an energetically favorable growth? To tackle this question, we investigate the growth of Ag on Cu(111) by variable temperature scanning tunneling microscopy. The structures grown between 120 and 170 K are remarkably different from those grown between 200 and 340 K. The low-temperature structure is rectangular-like and consists of stacked rods, 7 to 8 Ag atoms long, which form a superstructure without long-range order. This structure covers the whole surface prior to nucleation of further layers. The high-temperature structure is hexagonal and consists of misfit dislocations forming 8 × 8 to 10 × 10 superstructures. For this structure, second layer nucleation sets in far before the closure of the first monolayer. While both structures are driven by the large lattice misfit between the two materials, the growing Ag layer adapts to the Cu surface at low temperature, while the Cu surface adapts to the growing Ag layer at higher temperature.

Influence of Cu adatoms on the molecular assembly of 4,4′-bipyridine on Cu(111)

2018 ◽  
Vol 20 (22) ◽  
pp. 15350-15357 ◽  
Author(s):  
M.-A. Dubois ◽  
O. Guillermet ◽  
S. Gauthier ◽  
G. Zhan ◽  
Y. Makoudi ◽  
...  
Keyword(s):  
Low Temperature ◽  
Scanning Tunneling Microscopy ◽  
First Principles ◽  
Variable Temperature ◽  
Molecular Assembly ◽  
Scanning Tunneling ◽  
First Principles Calculations ◽  
Tunneling Microscopy ◽  
Temperature Scanning

The formation of highly organized structures based on two ligands with pyridyl functionalities, 4,4′-bipyridine (BPY) and 1,4-di(4,4′′-pyridyl) benzene (BPYB), and Cu adatoms on the Cu(111) surface has been studied with low temperature and variable temperature scanning tunneling microscopy (STM) and first-principles calculations.

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