Growth of Co Nanoclusters on SiC Honeycomb Templates

2004 ◽  
Vol 818 ◽  
Author(s):  
Wei Chen ◽  
Kian Ping Loh ◽  
Hai Xu ◽  
A.T.S. Wee
Keyword(s):  
Substrate Temperature ◽  
Room Temperature ◽  
Scanning Tunneling ◽  
Nucleation Process ◽  
Desorption Rate ◽  
Tunneling Microscopy ◽  
Scale Range ◽  
Reconstructed Surface ◽  
Substrate Temperatures

AbstractA honeycomb-like SiC reconstructed surface with regular, periodic porosity in the nano-scale range has been used as an effective template for the formation of monodispersed Co nanoclusters. In-situ scanning tunneling microscopy (STM) was used to study the nucleation process of the Co nanoclusters on this template. The deposition of Co at different substrate temperature was investigated by STM. It is found that the failure in the deposition of Co nanoclusters on the SiC honeycomb template with substrate temperatures higher than room temperature (RT) might be due to the high desorption rate of the adsorbed Co atoms.

Epitaxy of Germanium on SI(001) Grating Templates

1993 ◽  
Vol 317 ◽  
Author(s):  
C.C. Umbach ◽  
J.M. Blakely
Keyword(s):  
Room Temperature ◽  
Elevated Temperatures ◽  
Scanning Tunneling ◽  
Growth Morphology ◽  
Tunneling Microscopy ◽  
Step Flow ◽  
Growth Modes ◽  
Step Density ◽  
Temperature Scanning ◽  
Substrate Temperatures

ABSTRACTEpitaxial Ge films (< 3 ML) have been grown at elevated temperatures on Si (001) grating substrates (repeat spacing of 2.0 μm) and imaged using room temperature scanning tunneling Microscopy (STM). The Ge films exhibit the 2×n reconstruction associated with missing dimer rows. The value of n and the growth morphology are influenced by the deposition rate and by annealing. At substrate temperatures of 600° C and deposition rates >0.5 ML/Min., islands elongated along the the dimer row direction nucleate at steps and on terraces. With sufficient annealing at 800° C, the islands coarsen and are eventually eliminated. The roughness of the A-type step becomes greater than that of the B-type step, which is the reverse of the situation with pure Si (001). The separation between missing dimer rows and hence the value of n are increased by annealing. Differences in substrate terrace widths due to the periodically varying step density of thegratings affect the growth Modes: two-dimensional islands occur near the extrema of the gratings whereas step flow occurs when steps are separated by ∼150 Å or less.

IN SITU STM INVESTIGATION OF Ge NANOSTRUCTURES WITH AND WITHOUT Sb ON GRAPHITE

2006 ◽  
Vol 13 (02n03) ◽  
pp. 241-249
Author(s):  
SUNIL SINGH KUSHVAHA ◽  
ZHIJUN YAN ◽  
MAO-JIE XU ◽  
WENDE XIAO ◽  
XUE-SEN WANG
Keyword(s):  
Room Temperature ◽  
Pyrolytic Graphite ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Initial Stage ◽  
Defect Sites ◽  
Substrate Defects

Germanium was deposited onto highly oriented pyrolytic graphite (HOPG) with and without antimony in ultra-high vacuum. The surface morphology was analyzed using in situ scanning tunneling microscopy (STM) at room temperature (RT). The film grows exclusively in 3D island mode and was affected significantly by substrate defects. At initial stage, nucleation of cluster occurred at step edges and defect sites. Later, we found various types of Ge nanostructures on HOPG in different deposition conditions and stages, including cluster chains, cluster islands, nanowires, and double layer ramified islands at RT. Compact Ge islands were observed when depositing at a substrate temperature of 450 K or after an annealing at 600 K following RT deposition. In addition, the pre-deposited Sb on graphite enhances the sticking probability and suppresses the surface diffusion of Ge atoms, resulting in a significant increase in Ge cluster island density on HOPG terraces.

DIFFERENT GROWTH BEHAVIOR OF Ge, Al AND Sb ON GRAPHITE

2006 ◽  
Vol 13 (02n03) ◽  
pp. 287-296 ◽  
Author(s):  
WENDE XIAO ◽  
ZHIJUN YAN ◽  
SUNIL SINGH KUSHVAHA ◽  
MAOJIE XU ◽  
XUE-SEN WANG
Keyword(s):  
Double Layer ◽  
Room Temperature ◽  
Pyrolytic Graphite ◽  
Three Dimensional ◽  
Growth Behavior ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Defect Sites ◽  
Unique Nature

Growth of Ge , Al and Sb on highly oriented pyrolytic graphite (HOPG) was systematically investigated using in situ scanning tunneling microscopy (STM). At room temperature (RT), three dimensional (3D) clusters of all three elements nucleate and grow at the step edges and defect sites of HOPG. The clusters of Al and Ge form chains, while Sb islands are mostly isolated. With further deposition at RT, Al clusters grow and coarsen into faceted islands with craters on the top (111) facets, whereas ramified single- and double-layer cluster islands are observed for Ge . When deposited or annealed at T ≥ 175° C , Ge forms crystallites but with randomly oriented facets. As spherical Sb islands grow beyond certain size, (111) facets appear on the top. Additionally, crystalline 2D films and 1D nanorods are observed for Sb deposited at RT. At T ≈ 100° C and higher flux, only the 2D and 1D Sb islands are formed. These different growth behaviors reflect the unique nature in which the atoms (molecules), clusters and crystallites of each element interact with HOPG surface and with each other.

Adsorption of Pyrrole on the Si(111)-7×7 Surface: Effect of Substrate Temperature

2015 ◽  
Vol 1117 ◽  
pp. 35-38
Author(s):  
Masaru Shimomura ◽  
Keisuke Ota
Keyword(s):  
Substrate Temperature ◽  
Scanning Tunneling Microscopy ◽  
Self Assembly ◽  
Room Temperature ◽  
Surface Effect ◽  
Bond Cleavage ◽  
The Self ◽  
Scanning Tunneling ◽  
Tunneling Microscopy

Adsorption of pyrrole on the Si(111)-7×7 surface was investigated using scanning tunneling microscopy (STM). Template-induced molecular corral structure was observed at room temperature though the N-H bond cleavage. At the substrate temperature of 130 °C, the pyrrolyl adsorbates were observed by STM with reserving the 7×7 substrate. However, the self-assembly of the molecular corral structure was disarranged at 130 °C. Then, pyrrolyl group was decomposed or desorbed from the surface at the substrate temperature of 200 °C. The defect-induced attachment of pyrrole was also observed.

scholarly journals Au(100) as a Template for Pentacene Monolayer

Molecules ◽  
2021 ◽  
Vol 26 (8) ◽  
pp. 2393
Author(s):  
Artur Trembułowicz ◽  
Agata Sabik ◽  
Miłosz Grodzicki
Keyword(s):  
Self Assembly ◽  
Molecular Layer ◽  
High Vacuum ◽  
Gold Surface ◽  
Ultra High Vacuum ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Height Difference ◽  
Characteristic Features ◽  
Reconstructed Surface

The surface of quasi-hexagonal reconstructed Au(100) is used as the template for monolayer pentacene (PEN) self-assembly. The system is characterized by means of scanning tunneling microscopy at room temperature and under an ultra-high vacuum. A new modulated pattern of molecules with long molecular axes (MA) arranged along hex stripes is found. The characteristic features of the hex reconstruction are preserved herein. The assembly with MA across the hex rows leads to an unmodulated structure, where the molecular layer does not recreate the buckled hex phase. The presence of the molecules partly lifts the reconstruction—i.e., the gold hex phase is transformed into a (1×1) phase. The arrangement of PEN on the gold (1×1) structure is the same as that of the surrounding molecular domain on the reconstructed surface. The apparent height difference between phases allows for the distinction of the state of the underlying gold surface.

Ge-Quantum Dots on SI(001) Tailored by Carbon Predeposition

1998 ◽  
Vol 533 ◽  
Author(s):  
O. Leifeld ◽  
D. Grützmacher ◽  
B. Müller ◽  
K. Kern
Keyword(s):  
Surface Roughness ◽  
Critical Thickness ◽  
Carbon Deposition ◽  
Compressive Strain ◽  
Second Step ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Island Nucleation ◽  
Facet Formation

AbstractThe morphology of Si(001) after carbon deposition of 0.05 to 0.11 monolayers (ML) was investigated in situ by ultrahigh vacuum scanning tunneling microscopy (UHV-STM). The carbon induces a c(4×4)-reconstruction of the surface. In addition, carbon increases the surface roughness compared to clean Si(001) (2×1). In a second step, the influence of the carbon induced restructuring on Ge-island nucleation was investigated. The 3D-growth sets in at considerably lower Ge coverage compared to the clean Si(001) (2×1) surface. This leads to a high density of small though irregularly shaped dots, consisting of stepped terraces, already at 2.5 ML Ge. Increasing the Ge-coverage beyond the critical thickness for facet formation, the dots show { 105 }- facets well known from Ge-clusters on bare Si(001) (2×1). However, they are flat on top with a (001)-facet showing the typical buckled Ge rows and missing dimers. This indicates that the compressive strain is not fully relaxed in these hut clusters.

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