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.

Using a Moderate Vacuum, Hot/Cryo-Stage Equipped AFM for In-Situ Observation of α-Phase Growth In 60SN40PB Hypoeutectic Solder

1998 ◽  
Vol 4 (S2) ◽  
pp. 316-317
Author(s):  
D. N. Leonard ◽  
P.E. Russell
Keyword(s):  
Surface Science ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Scanning Tunneling ◽  
In Situ Observation ◽  
Atmospheric Conditions ◽  
Tunneling Microscopy ◽  
Wide Range ◽  
Gas Environment

Atomic force microscopy (AFM) was introduced in 1984, and proved to be more versatile than scanning tunneling microscopy (STM) due to the AFM's capabilities to scan non-conductive samples under atmospheric conditions and achieve atomic resolution. Ultra high vacuum (UHV) AFM has been used in surface science applications when control of oxidation and corrosion of a sample's surface are required. Expensive equipment and time consuming sample exchanges are two drawbacks of the UHV AFM system that limit its use. Until recently, no hot/cryo-stage, moderate vacuum, controlled gas environment AFM was commonly available.We have demonstrated that phase transformations are easily observable in metal alloys and polymers with the use of a moderate vacuum AFM that has in-situ heating/cooling capabilities and quick (within minutes) sample exchange times. This talk will describe the results of experiments involving a wide range of samples designed to make use of the full capabilities of a hot/cryo-stage, controlled gas environment AFM.

Preferential Etching of Si(111) and Si(001) in Dilute NH4F Solutions: as Probed by In Situ STM

1995 ◽  
Vol 386 ◽  
Author(s):  
Kingo Itaya ◽  
Shueh-Lin Yau ◽  
Kazutoshi Kaji
Keyword(s):  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Cathodic Potential ◽  
Potential Control ◽  
In Situ Stm ◽  
Initial Stage ◽  
Defect Sites ◽  
The Difference ◽  
Stm Images

ABSTRACTIn situ scanning tunneling microscopy (STM) was used to examine the etching process of n-Si(11) and Si(001) electrodes in dilute NH4F under cathodic potential control. For Si(111), time-dependent STM images have revealed the pronounced effect of the microscopic structure of surface Si atoms on their dissolution rates. The multiple hydrogen bonded Si atoms at the kink sites and dihydride steps eroded faster than the monohydride terminated Si. Presumably, the higher polarity at these defect sites is responsible for the difference. Steric consideration further favors the higher activity at the more open kink sites. The monohydride terminated Si(111) surface represents the most stable surface structure, which guides the dissolution of the Si(001) surface to the formation of {111} facets. The initial stage {111} facet formation on a Si(001) surface was revealed by in situ STM.

Intrinsic Point Defects on a TiO2(110) Surface and Their Reaction with Oxygen: A Scanning Tunneling Microscopy Study

1997 ◽  
Vol 474 ◽  
Author(s):  
Markus Kuhn ◽  
J. F. Anderson ◽  
Jeremy Lehman ◽  
Talib Mahmoud ◽  
Ulrike Diebold
Keyword(s):  
Scanning Tunneling Microscopy ◽  
Molecular Oxygen ◽  
Point Defects ◽  
Healing Process ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Atomic Scale ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Defect Sites

ABSTRACTThe interaction of molecular oxygen, at room temperature, with a reduced TiO2(110) surface has been studied in situ by scanning tunneling microscopy (STM). Oxygen vacancies (point defects) were created on a clean TiO2(110) surface by annealing in ultra-high vacuum and successfully imaged on the atomic scale. These point defect sites were stable under ultrahigh vacuum conditions. During exposure to molecular oxygen, new point defects appear at different locations on the surface although their overall number is reduced. A mechanism for this dynamic healing process is proposed.

Structural Studies of Submonolayers of Carbon Atoms on Graphite

1992 ◽  
Vol 270 ◽  
Author(s):  
M. Ge ◽  
K. Sattler ◽  
J. Xhie ◽  
N. Venkateswaran
Keyword(s):  
Pyrolytic Graphite ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Carbon Particles ◽  
Linear Chains ◽  
High Vacuum Condition ◽  
Ultra High Vacuum Condition ◽  
Atomically Flat

ABSTRACTSubmonolayer coverages of carbon adsorbed on highly-oriented pyrolytic graphite were examined by scanning tunneling microscopy under ultra-high vacuum condition. Linear carbon wires were found on atomically flat graphite surfaces. The wires had different thicknesses, from single atomic width to about lnm. The long wires extended to over several hundred nanometers. Two directions, graphite β-β direction and 30° rotated, were preferred for the long wire orientation. Parallel wire alignment, with several nanometers of inter-wire spacings were observed. Carbon particles, from 0.7 to 2 nm in diameter were found to be attached to the carbon wires. Particles from different wires formed parallel linear chains about perpendicular to the wire direction.

Pulsed Laser Deposition and In Situ Scanning Tunneling Microscopy of Pd clusters supported on alumina

2011 ◽  
Vol 1351 ◽  
Author(s):  
C.S. Casari ◽  
S. Foglio ◽  
M. Corbetta ◽  
M. Passoni ◽  
C.E. Bottani ◽  
...  
Keyword(s):  
Scanning Tunneling Microscopy ◽  
Pulsed Laser Deposition ◽  
High Vacuum ◽  
Pulsed Laser ◽  
Ultra High Vacuum ◽  
Laser Deposition ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Pd Clusters

ABSTRACTWith the aim of addressing the material gap issue between model and real systems in heterogeneous catalysis, we exploited Pulsed Laser Deposition (PLD) to produce Pd clusters supported on ultrathin alumina films (Pd/Al2O3/NiAl(001) and Pd/Al2O3-x/HOPG). The structural properties have been investigated by in situ Scanning Tunneling Microscopy (STM) in ultra high vacuum (UHV). At first, Pd clusters were deposited by evaporation and by PLD on Al2O3 surfaces grown by thermal oxidation of NiAl(001). The system shows thermal stability up to 650 K. By PLD we deposited Pd clusters with a good size control obtained by varying the background gas pressure and the target-to-substrate distance. We then realized aPd/Al2O3-x/HOPG system where both Pd clusters and the alumina film are produced by PLD showing that, by exploiting the same deposition technique, it is possible to synthesize both a model system addressable by in situ STM and a thick film (∼100 μm) closer to realistic systems.

Nucleation and initial growth of Pd2Si crystals on Si(111)

1993 ◽  
Vol 51 ◽  
pp. 844-845
Author(s):  
Xianghong Tong ◽  
Oliver Pohland ◽  
J. Murray Gibson
Keyword(s):  
High Vacuum ◽  
Dark Field ◽  
Ultra High Vacuum ◽  
Initial Growth ◽  
Surface And Interface ◽  
Dark Field Imaging ◽  
Transmission Electron ◽  
Initial Stage ◽  
Effect Of Surface

The nucleation and initial stage of Pd2Si crystals on Si(111) surface is studied in situ using an Ultra-High Vacuum (UHV) Transmission Electron Microscope (TEM). A modified JEOL 200CX TEM is used for the study. The Si(111) sample is prepared by chemical thinning and is cleaned inside the UHV chamber with base pressure of 1x10−9 τ. A Pd film of 20 Å thick is deposited on to the Si(111) sample in situ using a built-in mini evaporator. This room temperature deposited Pd film is thermally annealed subsequently to form Pd2Si crystals. Surface sensitive dark field imaging is used for the study to reveal the effect of surface and interface steps.The initial growth of the Pd2Si has three stages: nucleation, growth of the nuclei and coalescence of the nuclei. Our experiments shows that the nucleation of the Pd2Si crystal occurs randomly and almost instantaneously on the terraces upon thermal annealing or electron irradiation.

scholarly journals Strain-Relief Patterns and Kagome Lattice in Self-Assembled C60 Thin Films Grown on Cd(0001)

2021 ◽  
Vol 22 (13) ◽  
pp. 6880
Author(s):  
Zilong Wang ◽  
Minlong Tao ◽  
Daxiao Yang ◽  
Zuo Li ◽  
Mingxia Shi ◽  
...  
Keyword(s):  
Thin Films ◽  
Self Assembly ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Scanning Tunneling ◽  
Kagome Lattice ◽  
Tunneling Microscopy ◽  
Kagomé Lattice ◽  
Temperature Scanning ◽  
C60 Films

We report an ultra-high vacuum low-temperature scanning tunneling microscopy (STM) study of the C60 monolayer grown on Cd(0001). Individual C60 molecules adsorbed on Cd(0001) may exhibit a bright or dim contrast in STM images. When deposited at low temperatures close to 100 K, C60 thin films present a curved structure to release strain due to dominant molecule–substrate interactions. Moreover, edge dislocation appears when two different wavy structures encounter each other, which has seldomly been observed in molecular self-assembly. When growth temperature rose, we found two forms of symmetric kagome lattice superstructures, 2 × 2 and 4 × 4, at room temperature (RT) and 310 K, respectively. The results provide new insight into the growth behavior of C60 films.

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