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.

The Nature of Oxide Surfaces: Topographic and Electronic Structure

1993 ◽  
Vol 51 ◽  
pp. 966-967
Author(s):  
Dawn A. Bonnell ◽  
Yong Liang
Keyword(s):  
Transition Metal Oxides ◽  
Electronic Structures ◽  
Recent Progress ◽  
Spatial Localization ◽  
Level Of Detail ◽  
Scanning Tunneling ◽  
Oxide Surfaces ◽  
Tunneling Microscopy ◽  
Considerable Effort ◽  
Complete Understanding

Recent progress in the application of scanning tunneling microscopy (STM) and tunneling spectroscopy (STS) to oxide surfaces has allowed issues of image formation mechanism and spatial resolution limitations to be addressed. As the STM analyses of oxide surfaces continues, it is becoming clear that the geometric and electronic structures of these surfaces are intrinsically complex. Since STM requires conductivity, the oxides in question are transition metal oxides that accommodate aliovalent dopants or nonstoichiometry to produce mobile carriers. To date, considerable effort has been directed toward probing the structures and reactivities of ZnO polar and nonpolar surfaces, TiO2 (110) and (001) surfaces and the SrTiO3 (001) surface, with a view towards integrating these results with the vast amount of previous surface analysis (LEED and photoemission) to build a more complete understanding of these surfaces. However, the spatial localization of the STM/STS provides a level of detail that leads to conclusions somewhat different from those made earlier.

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 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.

scholarly journals Self-assembly of N-heterocyclic carbenes on Au(111)

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Alex Inayeh ◽  
Ryan R. K. Groome ◽  
Ishwar Singh ◽  
Alex J. Veinot ◽  
Felipe Crasto de Lima ◽  
...  
Keyword(s):  
Self Assembly ◽  
Density Functional ◽  
Surface Coverage ◽  
High Mobility ◽  
Heterocyclic Carbenes ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Surface Geometry ◽  
Functional Theory ◽  
Interesting Alternative

AbstractAlthough the self-assembly of organic ligands on gold has been dominated by sulfur-based ligands for decades, a new ligand class, N-heterocyclic carbenes (NHCs), has appeared as an interesting alternative. However, fundamental questions surrounding self-assembly of this new ligand remain unanswered. Herein, we describe the effect of NHC structure, surface coverage, and substrate temperature on mobility, thermal stability, NHC surface geometry, and self-assembly. Analysis of NHC adsorption and self-assembly by scanning tunneling microscopy and density functional theory have revealed the importance of NHC-surface interactions and attractive NHC-NHC interactions on NHC monolayer structures. A remarkable way these interactions manifest is the need for a threshold NHC surface coverage to produce upright, adatom-mediated adsorption motifs with low surface diffusion. NHC wingtip structure is also critical, with primary substituents leading to the formation of flat-lying NHC2Au complexes, which have high mobility when isolated, but self-assemble into stable ordered lattices at higher surface concentrations. These and other studies of NHC surface chemistry will be crucial for the success of these next-generation monolayers.

How to realize ultimate spatial and temporal resolutions by laser-combined scanning tunneling microscopy?

2005 ◽  
Vol 901 ◽  
Author(s):  
Hidemi Shigekawa ◽  
Osamu Takeuchi ◽  
Masahiro Aoyama ◽  
Yasuhiko Terada ◽  
Hiroyuki Kondo ◽  
...  
Keyword(s):  
Scanning Tunneling Microscopy ◽  
Pulse Laser ◽  
Electronic Structures ◽  
Femtosecond Pulse ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Optical Pump ◽  
Pump Probe ◽  
Probe Technique ◽  
Femtosecond Pulse Laser

AbstractBy combining scanning tunneling microscopy (STM) and the optical pump-probe technique using a femtosecond pulse laser, we have developed a new microscopy, shaken pulse-pair-excited STM (SPPX-STM), that enables us to observe the dynamics of electronic structures with the ultimate spatial and temporal resolutions.

Defect-Mediated Growth of YBa2Cu3O7-δ Films

1992 ◽  
Vol 280 ◽  
Author(s):  
D. G. Schlom ◽  
D. Anselmetti ◽  
J. G. Bednorz ◽  
Ch. Gerber ◽  
J. Mannhar
Keyword(s):  
Growth Conditions ◽  
Substrate Material ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Surface Evolution ◽  
Screw Dislocations ◽  
Surface Steps ◽  
Defect Sites ◽  
Wide Range ◽  
Intrinsic Feature

ABSTRACTThe evolution of the surface microstructure of sputtered c-axis oriented epitaxial YBa2Cu3O7-δ films has been monitored by scanning tunneling microscopy (STM). The results indicate that growth is dominated by the incorporation of depositing species at defect sites. These defect sites, which provide energetically favorable positions for accommodating the arriving species, are at ledges—either along growth spirals emanating from screw dislocations, or due to the closely spaced surface steps arising from the macroscopic tilt of the substrate. If the substrate is misoriented sufficiently, the depositing species may diffuse to and be accommodated by these surface steps, without the supersaturation on the terraces attaining a high enough level for two-dimensional nucleation to occur. Under these conditions, growth occurs by step propagation. Otherwise, a high density of screw dislocations (≈109 cm-2) is nucleated during the initial stages of growth, which provides a continual supply of ledge incorporation sites in the vicinity of the depositing species. The surface evolution reported appears to be an intrinsic feature of c-axis oriented YBa2Cu3O7-δ films for a wide range of growth conditions, irrespective of the substrate material or vapor phase deposition method.

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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