scholarly journals Effect of CO Molecule Orientation on the Reduction of Cu-Based Nanoparticles

Nanomaterials ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 279
Author(s):  
Sergey Y. Sarvadii ◽  
Andrey K. Gatin ◽  
Vasiliy A. Kharitonov ◽  
Nadezhda V. Dokhlikova ◽  
Sergey A. Ozerin ◽  
...  
Keyword(s):  
Electric Field ◽  
External Electric Field ◽  
Adsorption Process ◽  
Co Adsorption ◽  
Reduction Rate ◽  
Sample Surface ◽  
Potential Difference ◽  
Precipitation Method ◽  
Scanning Tunneling ◽  
Tunneling Microscopy

The adsorption of CO on the surface of Cu-based nanoparticles was studied in the presence of an external electric field by means of scanning tunneling microscopy (STM) and spectroscopy (STS). Nanoparticles were synthesized on the surface of a graphite support by the impregnation–precipitation method. The chemical composition of the surface of the nanoparticles was determined as a mixture of Cu2O, Cu4O3 and CuO oxides. CO was adsorbed from the gas phase onto the surface of the nanoparticles. During the adsorption process, the potential differences ΔV = +1 or −1 V were applied to the vacuum gap between the sample and the grounded tip. Thus, the system of the STM tip and sample surface formed an asymmetric capacitor, inside which an inhomogeneous electric field existed. The CO adsorption process is accompanied by the partial reduction of nanoparticles. Due to the orientation of the CO molecule in the electric field, the reduction was weak in the case of a positive potential difference, while in the case of a negative potential difference, the reduction rate increased significantly. The ability to control the adsorption process of CO by means of an external electric field was demonstrated. The size of the nanoparticle was shown to be the key factor affecting the adsorption process, and particularly, the strength of the local electric field close to the nanoparticle surface.

Scanning tunneling microscopy of polymers: A status report

1989 ◽  
Vol 47 ◽  
pp. 330-331
Author(s):  
P.E. Russell ◽  
I.H. Musselman
Keyword(s):  
High Resolution ◽  
Scanning Tunneling Microscopy ◽  
Sample Surface ◽  
Atomic Scale ◽  
Constant Current ◽  
Scanning Tunneling ◽  
Status Report ◽  
Tunneling Microscopy ◽  
Research Issues ◽  
Wide Range

Scanning tunneling microscopy (STM) has evolved rapidly in the past few years. Major developments have occurred in instrumentation, theory, and in a wide range of applications. In this paper, an overview of the application of STM and related techniques to polymers will be given, followed by a discussion of current research issues and prospects for future developments. The application of STM to polymers can be conveniently divided into the following subject areas: atomic scale imaging of uncoated polymer structures; topographic imaging and metrology of man-made polymer structures; and modification of polymer structures. Since many polymers are poor electrical conductors and hence unsuitable for use as a tunneling electrode, the related atomic force microscopy (AFM) technique which is capable of imaging both conductors and insulators has also been applied to polymers.The STM is well known for its high resolution capabilities in the x, y and z axes (Å in x andy and sub-Å in z). In addition to high resolution capabilities, the STM technique provides true three dimensional information in the constant current mode. In this mode, the STM tip is held at a fixed tunneling current (and a fixed bias voltage) and hence a fixed height above the sample surface while scanning across the sample surface.

scholarly journals Electronic structures and unusually robust bandgap in an ultrahigh-mobility layered oxide semiconductor, Bi2O2Se

2018 ◽  
Vol 4 (9) ◽  
pp. eaat8355 ◽  
Author(s):  
Cheng Chen ◽  
Meixiao Wang ◽  
Jinxiong Wu ◽  
Huixia Fu ◽  
Haifeng Yang ◽  
...  
Keyword(s):  
Electronic Structures ◽  
High Mobility ◽  
Sample Surface ◽  
Substrate Material ◽  
Oxide Semiconductor ◽  
Scanning Tunneling ◽  
Modern World ◽  
Fermi Velocity ◽  
Tunneling Microscopy ◽  
Spatial Uniformity

Semiconductors are essential materials that affect our everyday life in the modern world. Two-dimensional semiconductors with high mobility and moderate bandgap are particularly attractive today because of their potential application in fast, low-power, and ultrasmall/thin electronic devices. We investigate the electronic structures of a new layered air-stable oxide semiconductor, Bi2O2Se, with ultrahigh mobility (~2.8 × 105cm2/V⋅s at 2.0 K) and moderate bandgap (~0.8 eV). Combining angle-resolved photoemission spectroscopy and scanning tunneling microscopy, we mapped out the complete band structures of Bi2O2Se with key parameters (for example, effective mass, Fermi velocity, and bandgap). The unusual spatial uniformity of the bandgap without undesired in-gap states on the sample surface with up to ~50% defects makes Bi2O2Se an ideal semiconductor for future electronic applications. In addition, the structural compatibility between Bi2O2Se and interesting perovskite oxides (for example, cuprate high–transition temperature superconductors and commonly used substrate material SrTiO3) further makes heterostructures between Bi2O2Se and these oxides possible platforms for realizing novel physical phenomena, such as topological superconductivity, Josephson junction field-effect transistor, new superconducting optoelectronics, and novel lasers.

Physical and chemical model of ion stability and movement within the dynamic and voltage-gated STM tip–surface tunneling junction

2017 ◽  
Vol 204 ◽  
pp. 159-172 ◽  
Author(s):  
Brandon E. Hirsch ◽  
Kevin P. McDonald ◽  
Steven L. Tait ◽  
Amar H. Flood
Keyword(s):  
Electric Field ◽  
Experimental Evidence ◽  
Electrostatic Interactions ◽  
Scanning Tunneling ◽  
Chemical Transformations ◽  
Tunneling Microscopy ◽  
Mobility Of Ions ◽  
Negative Surface ◽  
Ion Stability ◽  
And Migration

The interaction and mobility of ions in complex systems are fundamental to processes throughout chemistry, biology, and physics. However, nanoscale characterization of ion stability and migration remains poorly understood. Here, we examine ion movements to and from physisorbed molecular receptors at solution–graphite interfaces by developing a theoretical model alongside experimental scanning tunneling microscopy (STM) results. The model includes van der Waals forces and electrostatic interactions originating from the surface, tip, and physisorbed receptors, as well as a tip–surface electric field arising from the STM bias voltage (Vb). Our model reveals how both the electric field and tip–surface distance, dtip, can influence anion stability at the receptor binding sites on the surface or at the STM tip, as well as the size of the barrier for anion transitions between those locations. These predictions agree well with prior and new STM results from the interactions of anions with aryl-triazole receptors that order into functional monolayers on graphite. Scanning produces clear resolution at large magnitude negative surface biases (−0.8 V) while resolution degrades at small negative surface biases (−0.4 V). The loss in resolution arises from frequent tip retractions assigned to anion migration within the tip–surface tunneling region. This experimental evidence in combination with support from the model demonstrates a local voltage gating of anions with the STM tip inside physisorbed receptors. This generalized model and experimental evidence may help to provide a basis to understand the nanoscale details of related chemical transformations and their underlying thermodynamic and kinetic preferences.

ELECTRIC-FIELD DEPENDENCE OF MOLECULAR CONFORMATIONS OBSERVED BY USING SCANNING TUNNELING MICROSCOPY

NANO ◽  
2008 ◽  
Vol 03 (02) ◽  
pp. 83-94
Author(s):  
XIAO JING MA ◽  
RUI ZHANG ◽  
YONG TAO SHEN ◽  
XIAO HUI QIU ◽  
YAN LIAN YANG ◽  
...  
Keyword(s):  
Electric Field ◽  
Scanning Tunneling Microscopy ◽  
Functional Groups ◽  
Field Dependence ◽  
Conformational Changes ◽  
Supramolecular Structures ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Molecular Conformations ◽  
Electric Field Dependence

We review the progress in observation of electrically induced conformational changes of a range of single molecules and molecular assemblies using scanning tunneling microscopy (STM). Recent results using species with optical active functional groups and supramolecular structures confirmed the previously observed effects that the cholesterol molecules with soft linkers have the conformational bistability when switching the bias polarity, while no discernable changes were observed for the mesogen molecules, containing rigid linking units. In addition, it was also observed that the linker units could have appreciable impacts on the assembling characteristics.

Industrial Applications of Scanning Probe Microscopy

1998 ◽  
Vol 4 (S2) ◽  
pp. 522-523
Author(s):  
S. Magonov
Keyword(s):  
Scanning Probe Microscopy ◽  
High Vacuum ◽  
Sample Surface ◽  
Industrial Applications ◽  
Ultra High Vacuum ◽  
Scanning Probe ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Probe Microscopy ◽  
Force Microscopy

The evolution of scanning tunneling microscopy (STM) into atomic force microscopy (AFM) have led to a family of scanning probe techniques which are widely applied in fundamental research and in industry. Visualization of the atomic- and molecular-scale structures and the possibility of modifying these structures using a sharp probe were demonstrated with the techniques on many materials. These unique capabilities initiated the further development of AFM and related methods generalized as scanning probe microscopy (SPM). The first STM experiments were performed in the clean conditions of ultra-high vacuum and on well-defined conducting or semi-conducting surfaces. These conditions restrict SPM applications to the real world that requires ambient-condition operation on the samples, many of which are insulators. AFM, which is based on the detection of forces between a tiny cantilever carrying a sharp tip and a sample surface, was introduced to satisfy these requirements. High lateral resolution and unique vertical resolution (angstrom scale) are essential AFM features.

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