STM Study of Self-assembly of Quantum Dot Formed by Selective Laser Heating

2013 ◽  
Vol 1527 ◽  
Author(s):  
Haeyeon Yang ◽  
Casey M. Clegg
Keyword(s):  
Self Assembly ◽  
High Vacuum ◽  
Laser Pulses ◽  
Ultra High Vacuum ◽  
Scanning Tunneling ◽  
Mbe Growth ◽  
Optical Wavelength ◽  
Growth Method ◽  
Dot Density ◽  
Average Size

ABSTRACTScanning Tunneling Microscope (STM) was used to examine the morphologies of selfassembled InGaAs quantum dots (QDs). In order to induce the self-assembly, unlike the conventional Stranski-Krastanov (S-K) growth method, spatial thermal modulations in nanoscale were created in-situ on strained-but-flat InGaAs surfaces in a Molecular Beam Epitaxy (MBE) growth reactor by applying interferential irradiations of laser pulses (IILP). As-irradiated surfaces were examined using an attached ultra-high vacuum (UHV) STM. STM images indicate that the irradiation of 7 nano second laser pulse induces self-assembly of QDs. The average size of laser-induced QDs is smaller while their density is larger than that of QDs formed by annealing strained but flat epilayers conventionally. Furthermore, the dot density is modulated sinusoidally with a periodicity commensurate with that of the interference, which suggests that the placement of QDs can be controlled on the scale of the optical wavelength used. QD volume analysis suggests that dots grow faster laterally than vertically so that dots become flattened as they get larger.

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.

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.

Self-Assembly of Nickel Icosahedrons and Truncated Octahedral Nanocrystals on a SrTiO3 (111) Support

Microscopy ◽  
2020 ◽  
Author(s):  
Atif Rasheed
Keyword(s):  
Self Assembly ◽  
Scanning Tunneling Microscope ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Work Of Adhesion ◽  
Scanning Tunneling ◽  
Equilibrium Crystal Shapes ◽  
Crystal Properties ◽  
Energy Ratios ◽  
Octahedral Nanocrystals

Abstract Nickel nanocrystals have received much attention for their ferromagnetic properties. The crystal properties are strongly dependent on their facets and therefore detailed study of their morphology, facets and orientation is critical for magnetic applications. In this work, equilibrium crystal shapes of self-assembled nickel nanocrystals on the (111) termination of strontium titanate (SrTiO3) at room temperature and under ultra-high vacuum (UHV) conditions have been investigated using scanning tunneling microscope (STM). SrTiO3 (111) substrate was sputtered (0.5 keV, 2.5 µA, 10 min) and annealed (900 °C, 1 h) under UHV conditions. Three different periodicities were observed: (2.21 ± 0.01) nm corresponding to (4 × 4) reconstruction, (3.31 ± 0.02) nm corresponding to (6 × 6) reconstruction, and (2.85 ± 0.05) nm, rotated at 30° with respect to (4 × 4) reconstruction, corresponding to (3√3 × 3√3)R30° reconstruction. Nickel (~1 ML) was deposited using an e-beam evaporator on the substrate preheated to 320 °C and the sample was post-annealed multiple times. Nickel took platonic shapes of supported icosahedron comprising of (111) facets and truncated octahedron comprising of (001) and (111) facets. Based on surface energy ratios of truncated octahedrons at equilibrium the work of adhesion was calculated to be (3.889 ± 0.167) J/m2.

Shape-Controlled Growth of Indium and Aluminum Nanostructures on MoS2(0001)

2008 ◽  
Vol 8 (5) ◽  
pp. 2707-2712 ◽  
Author(s):  
S. S. Kushvaha ◽  
H. Xu ◽  
H. L. Zhang ◽  
A. T. S. Wee ◽  
X.-S. Wang
Keyword(s):  
Self Assembly ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Scanning Tunneling ◽  
Deposition Flux ◽  
Average Height ◽  
High Flux ◽  
Molybdenum Disulphide ◽  
Tunneling Microscopy ◽  
Al Nanoparticles

The growth of indium and aluminum nanostructures on molybdenum disulphide (MoS2)(0001) substrate has been studied using scanning tunneling microscopy in ultra-high vacuum. At low coverage and room temperature (RT), mostly ultra-thin (∼1.2–2 nm) triangular In islands were observed on MoS2. With increasing coverage or high flux, large coalesced irregular islands along with triangular and round-shaped ones of increased average height were found. Triangular and round-shaped islands were obtained after annealing the RT-deposited In on MoS2 sample at 450 K. At ∼375 K, exclusively triangular In islands were observed. Al nanoparticles with diameter in 4–16 nm range were obtained after a low-flux deposited whereas ramified islands were observed in a high flux at RT. Ultra-thin (∼1.20–2 nm) Al islands and films were obtained on MoS2 after deposition at 500 K. These results demonstrate that the shape of In and Al nanostructures grown on MoS2 can be controlled in self-assembly by adjusting substrate temperature, deposition flux and amount.

scholarly journals A modular ultra-high vacuum millikelvin scanning tunneling microscope

2020 ◽  
Vol 91 (2) ◽  
pp. 023703 ◽  
Author(s):  
Dillon Wong ◽  
Sangjun Jeon ◽  
Kevin P. Nuckolls ◽  
Myungchul Oh ◽  
Simon C. J. Kingsley ◽  
...  
Keyword(s):  
Scanning Tunneling Microscope ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Scanning Tunneling ◽  
Tunneling Microscope

A reliable compact ultra-high vacuum scanning tunneling microscope

Vacuum ◽  
1995 ◽  
Vol 46 (3) ◽  
pp. 219-222 ◽  
Author(s):  
IV Lyubinetsky ◽  
PV Mel'nik ◽  
NG Nakhodkin ◽  
AE Anisimov
Keyword(s):  
Scanning Tunneling Microscope ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Scanning Tunneling ◽  
Tunneling Microscope

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.

Low-temperature ultra-high-vacuum scanning tunneling microscope

1992 ◽  
Vol 42-44 ◽  
pp. 1621-1626 ◽  
Author(s):  
R. Gaisch ◽  
J.K. Gimzewski ◽  
B. Reihl ◽  
R.R. Schlittler ◽  
M. Tschudy ◽  
...  
Keyword(s):  
Low Temperature ◽  
Scanning Tunneling Microscope ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Scanning Tunneling ◽  
Tunneling Microscope
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