Quantum dots with single-atom precision

2014 ◽  
Vol 9 (7) ◽  
pp. 505-508 ◽  
Author(s):  
Stefan Fölsch ◽  
Jesús Martínez-Blanco ◽  
Jianshu Yang ◽  
Kiyoshi Kanisawa ◽  
Steven C. Erwin
Keyword(s):  
Quantum Dots ◽  
Single Atom

QUANTUM-CONFINED IMPURITIES AS SINGLE-ATOM QUANTUM DOTS: APPLICATION TO TERAHERTZ EMITTERS

2003 ◽  
Author(s):  
P. HARRISON ◽  
M. P. HALSALL ◽  
W.-M. ZHENG ◽  
J.-P. R. WELLS ◽  
I. V. BRADLEY ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Single Atom ◽  
Terahertz Emitters ◽  
Quantum Confined

scholarly journals Single atom laser in normal-superconductor quantum dots

2019 ◽  
Vol 100 (8) ◽  
Author(s):  
Gianluca Rastelli ◽  
Michele Governale
Keyword(s):  
Quantum Dots ◽  
Single Atom ◽  
Atom Laser

scholarly journals Electron dynamics of tip-tunable oxygen species on TiO2 surface

2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Yuuki Adachi ◽  
Ján Brndiar ◽  
Huan Fei Wen ◽  
Quanzhen Zhang ◽  
Masato Miyazaki ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Atomic Force Microscopy ◽  
Low Temperatures ◽  
Electron Tunneling ◽  
Single Atom ◽  
Oxygen Species ◽  
Redox States ◽  
Force Microscopy ◽  
Atomic Force ◽  
Highly Sensitive

AbstractThe redox states of oxygen species on the surface of TiO2 can be altered by electron tunneling by varying the applied bias voltage of an atomic force microscope tip. However, tunneling is stochastic in nature and typically requires ultra-low temperatures to obtain statistically significant data. Here, we use a highly sensitive fast atomic force microscopy setup to study redox transitions of oxygen atoms on a TiO2 surface, in the form of reactive oxygen species and single-atom quantum dots, at 78 K. The fast and highly sensitive nature of our experimental setup enables a statistically necessary amount of data to be collected without having to resort to ultra-low temperatures. This enabled us to study multiple dots and provide insight into the electronic structure and correlation between the oxygen species, which are inaccessible by standard atomic force microscopy. We show that single-atom quantum dots exist in two charge states with drastically different conductance, with one being conducting and the other non-conducting.

scholarly journals Atomically dispersed Ni in cadmium-zinc sulfide quantum dots for high-performance visible-light photocatalytic hydrogen production

2020 ◽  
Vol 6 (33) ◽  
pp. eaaz8447 ◽  
Author(s):  
D. W. Su ◽  
J. Ran ◽  
Z. W. Zhuang ◽  
C. Chen ◽  
S. Z. Qiao ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Zinc Sulfide ◽  
Active Sites ◽  
Heterogeneous Catalysts ◽  
Surface Engineering ◽  
High Efficiency ◽  
Single Atom ◽  
Intrinsic Activity ◽  
Cadmium Zinc Sulfide ◽  
Cadmium Zinc

Catalysts with a single atom site allow highly tuning of the activity, stability, and reactivity of heterogeneous catalysts. Therefore, atomistic understanding of the pertinent mechanism is essential to simultaneously boost the intrinsic activity, site density, electron transport, and stability. Here, we report that atomically dispersed nickel (Ni) in zincblende cadmium–zinc sulfide quantum dots (ZCS QDs) delivers an efficient and durable photocatalytic performance for water splitting under sunlight. The finely tuned Ni atoms dispersed in ZCS QDs exhibit an ultrahigh photocatalytic H2 production activity of 18.87 mmol hour−1 g−1. It could be ascribed to the favorable surface engineering to achieve highly active sites of monovalent Ni(I) and the surface heterojunctions to reinforce the carrier separation owing to the suitable energy band structures, built-in electric field, and optimized surface H2 adsorption thermodynamics. This work demonstrates a synergistic regulation of the physicochemical properties of QDs for high-efficiency photocatalytic H2 production.

General synthesis of single-atom catalysts with high metal loading using graphene quantum dots

2021 ◽  
Author(s):  
Chuan Xia ◽  
Yunrui Qiu ◽  
Yang Xia ◽  
Peng Zhu ◽  
Graham King ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Graphene Quantum Dots ◽  
Single Atom ◽  
Metal Loading ◽  
High Metal ◽  
General Synthesis

Single Atom Image Contrast in Fixed Beam Dark Field Electron Microscopy

1974 ◽  
Vol 32 ◽  
pp. 366-367
Author(s):  
Wah Chi
Keyword(s):  
Scattering Amplitude ◽  
Present Report ◽  
Dark Field ◽  
Image Contrast ◽  
Single Atom ◽  
Optical Theorem ◽  
Hartree Fock ◽  
Heavy Atoms ◽  
Beam Stop ◽  
Fixed Beam

Resolution and contrast are the important factors to determine the feasibility of imaging single heavy atoms on a thin substrate in an electron microscope. The present report compares the atom image characteristics in different modes of fixed beam dark field microscopy including the ideal beam stop (IBS), a wire beam stop (WBS), tilted illumination (Tl) and a displaced aperture (DA). Image contrast between one Hg and a column of linearly aligned carbon atoms (representing the substrate), are also discussed. The assumptions in the present calculations are perfectly coherent illumination, atom object is represented by spherically symmetric potential derived from Relativistic Hartree Fock Slater wave functions, phase grating approximation is used to evaluate the complex scattering amplitude, inelastic scattering is ignored, phase distortion is solely due to defocus and spherical abberation, and total elastic scattering cross section is evaluated by the Optical Theorem. The atom image intensities are presented in a Z-modulation display, and the details of calculation are described elsewhere.

Atomic Spectroscopy in the FIM

1986 ◽  
Vol 44 ◽  
pp. 758-761
Author(s):  
J. J. Hren ◽  
S. D. Walck
Keyword(s):  
Electron Microscope ◽  
Electric Fields ◽  
Atom Probe ◽  
Atomic Spectroscopy ◽  
Single Atom ◽  
Statistical Sampling ◽  
Commercial Instrument ◽  
Available Technology ◽  
High Electric Fields ◽  
Field Ion Microscope

The field ion microscope (FIM) has had the ability to routinely image the surface atoms of metals since Mueller perfected it in 1956. Since 1967, the TOF Atom Probe has had single atom sensitivity in conjunction with the FIM. “Why then hasn't the FIM enjoyed the success of the electron microscope?” The answer is closely related to the evolution of FIM/Atom Probe techniques and the available technology. This paper will review this evolution from Mueller's early discoveries, to the development of a viable commercial instrument. It will touch upon some important contributions of individuals and groups, but will not attempt to be all inclusive. Variations in instrumentation that define the class of problems for which the FIM/AP is uniquely suited and those for which it is not will be described. The influence of high electric fields inherent to the technique on the specimens studied will also be discussed. The specimen geometry as it relates to preparation, statistical sampling and compatibility with the TEM will be examined.

Field ion microscope investigations of atomic processes at surfaces

1989 ◽  
Vol 47 ◽  
pp. 228-229
Author(s):  
G. L. Kellogg ◽  
P. R. Schwoebel
Keyword(s):  
Single Crystal ◽  
Crystal Surface ◽  
Linear Chain ◽  
Atom Probe ◽  
Nucleation And Growth ◽  
Single Atom ◽  
Initial Structure ◽  
Atomic Processes ◽  
Single Crystal Surfaces ◽  
Field Ion Microscope

Although no longer unique in its ability to resolve individual single atoms on surfaces, the field ion microscope remains a powerful tool for the quantitative characterization of atomic processes on single-crystal surfaces. Investigations of single-atom surface diffusion, adatom-adatom interactions, surface reconstructions, cluster nucleation and growth, and a variety of surface chemical reactions have provided new insights to the atomic nature of surfaces. Moreover, the ability to determine the chemical identity of selected atoms seen in the field ion microscope image by atom-probe mass spectroscopy has increased or even changed our understanding of solid-state-reaction processes such as ordering, clustering, precipitation and segregation in alloys. This presentation focuses on the operational principles of the field-ion microscope and atom-probe mass spectrometer and some very recent applications of the field ion microscope to the nucleation and growth of metal clusters on metal surfaces.The structure assumed by clusters of atoms on a single-crystal surface yields fundamental information on the adatom-adatom interactions important in crystal growth. It was discovered in previous investigations with the field ion microscope that, contrary to intuition, the initial structure of clusters of Pt, Pd, Ir and Ni atoms on W(110) is a linear chain oriented in the <111> direction of the substrate.

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