Defect-Mediated Growth of YBa2Cu3O7-δ Films

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.

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Surface Evolution During Mbe Growth of Eute Studied by Uhv-Stm and Rheed Investigations

MRS Proceedings ◽

10.1557/proc-317-173 ◽

1993 ◽

Vol 317 ◽

Cited By ~ 2

Author(s):

N. Frank ◽

G. Springholz ◽

G. Bauer

Keyword(s):

Layer Thickness ◽

Growth Conditions ◽

High Energy ◽

Layer Growth ◽

Scanning Tunneling ◽

Root Mean Square Roughness ◽

Layer By Layer ◽

Tunneling Microscopy ◽

Surface Evolution ◽

Mbe Growth

ABSTRACTMBE growth of 2% lattice-Mismatched EuTe on PbTe (111) is studied combining in-situ reflection high-energy electron diffraction (RHEED) with UHV scanning tunneling Microscopy (STM) to investigate the evolution of the EuTe surface Morphology. Using RHEED we have found that 2D nucleation and layer-by-layer growth occurs only in a very narrow range of growth conditions as a result of a strain induced coherent islanding of the surface[l], which leads to a roughening transition at the critical layer thickness hc of 45 Monolayers (ML). Starting with a very smooth initial (111) PbTe surface with terrace widths of 50 to 200 nm, islands of monolayer height are formed due to 2D nucleation of EuTe. For EuTe layer thicknesses below hc, the root mean square roughness (RMS) is essentially constant and equal to about one ML. Beyond hc, the surface roughness increases strongly and islands of about 20 ML height are observed for an EuTe layer thickness of 66 ML.

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Scanning tunneling microscopy of polymers: A status report

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100153622 ◽

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.

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

Science Advances ◽

10.1126/sciadv.aat8355 ◽

2018 ◽

Vol 4 (9) ◽

pp. eaat8355 ◽

Cited By ~ 61

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.

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

Microscopy and Microanalysis ◽

10.1017/s143192760002170x ◽

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.

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Sb-terminated InAs(001)-(2×4) and (2×8) studied using scanning tunneling microscopy and ab initio density functional theory

MRS Proceedings ◽

10.1557/proc-692-h8.4.1 ◽

2001 ◽

Vol 692 ◽

Cited By ~ 1

Author(s):

William Barvosa-Carter ◽

Frank Grosse ◽

James H. G. Owen ◽

Jennifer J. Zinck

Keyword(s):

Density Functional Theory ◽

Scanning Tunneling Microscopy ◽

Ab Initio ◽

Density Functional ◽

Scanning Tunneling ◽

Tunneling Microscopy ◽

Functional Theory ◽

Subsequent Formation ◽

Wide Range ◽

Symmetry Surface

AbstractWe have studied the structure of MBE-grown InAs(001)-(2×4) surfaces exposed to low Sb2 fluxes by scanning tunneling microscopy (STM) and ab initio density functional theory (DFT). Experimentally, we observe an Sb-terminated α2(2×4) phase over a wide range of temperatures (400–510 °C) for low Sb2 flux (<0.1 ML/s), whereas temperature and As2 flux must be carefully controlled to achieve the same As-terminated surface structure. At lower temperatures, we observe indications of an Sb-terminated (2×8) symmetry surface phase, and we report briefly on its proposed structure and stability, as well as its possible role in subsequent formation of the Sb-terminated (1×3) phase found at typical Sb2 fluxes used during heterostructure growth.

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The Morphology of Cu Clusters on SrTiO3(001) at Initial Stages of Metal Film Growth

MRS Proceedings ◽

10.1557/proc-357-3 ◽

1994 ◽

Vol 357 ◽

Cited By ~ 1

Author(s):

Y. Liang ◽

D. L. Carroll ◽

D. A. Bonnell

Keyword(s):

Vapor Deposition ◽

Metal Film ◽

Elevated Temperatures ◽

Film Growth ◽

Three Dimensional ◽

Scanning Tunneling ◽

Low Density ◽

Tunneling Microscopy ◽

Defect Sites ◽

Island Density

AbstractCopper overlayers deposited on nearly stoichiometric SrTiO3(001) have been investigated with scanning tunneling microscopy (STM). Vapor deposition of Cu on a SrTiO3(001) surface at ambient temperature leads to the formation of three dimensional islands (clusters). The distribution of Cu islands appears to be inhomogeneous with two characteristic morphologies. In regions with a low density of Cu islands the Cu was always associated with step edges or defect sites. In regions with a high density of Cu islands the islands exhibit a random but nearly close packed morphology. The variation of Cu island density is indicative of diffusion of Cu clusters on the SrTiO3(001) surface. Diffusion was further confirmed by annealing the Cu/SrTiO3 at elevated temperatures yielding agglomeration of Cu clusters.

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Scanning Tunneling Microscopy and Spectroscopy Studies of Single Wall Carbon Nanotubes

Journal of Materials Research ◽

10.1557/jmr.1998.0331 ◽

1998 ◽

Vol 13 (9) ◽

pp. 2380-2388 ◽

Cited By ~ 36

Author(s):

Teri Wang Odom ◽

Jin-Lin Huang ◽

Philip Kim ◽

Min Ouyang ◽

Charles M. Lieber

Keyword(s):

Carbon Nanotubes ◽

Scanning Tunneling Microscopy ◽

Single Wall Carbon Nanotubes ◽

Scanning Tunneling ◽

Tunneling Microscopy ◽

Metallic Behavior ◽

Single Wall Carbon ◽

Wide Range ◽

Theoretical Predictions ◽

Spectroscopy Studies

Scanning tunneling microscopy and spectroscopy have been used to characterize the atomic structure and tunneling density of states of individual single wall carbon nanotubes (SWNT's) and ropes containing many SWNT's. Analysis of atomically resolved SWNT images shows that the nanotubes consist of a wide range of diameters and helicities with no one structure clearly dominant. Tunneling spectroscopy measurements made simultaneously on atomically resolved SWNT's exhibit semiconducting and metallic behavior that depend predictably on helicity and diameter. In addition the band gaps of the semiconducting tubes were also found to depend inversely on diameter. These results are compared to theoretical predictions, and the implications of these studies as well as important future directions are discussed.

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Step bunching during Si(001) homoepitaxy caused by the surface diffusion anisotropy

MRS Proceedings ◽

10.1557/proc-749-w1.8 ◽

2002 ◽

Vol 749 ◽

Cited By ~ 1

Author(s):

J. Mysliveček ◽

C. Schelling ◽

F. Schäffler ◽

G. Springholz ◽

P. Šmilauer ◽

...

Keyword(s):

Kinetic Monte Carlo ◽

Monte Carlo Model ◽

Growth Conditions ◽

Scanning Tunneling ◽

Diffusion Anisotropy ◽

Island Growth ◽

Tunneling Microscopy ◽

Step Bunching ◽

Step Flow ◽

Step Flow Growth

ABSTRACTScanning tunneling microscopy experiments show that the unstable growth morphology observed during molecular beam homoepitaxy on slightly vicinal Si(001) surfaces consists of straight step bunches. The instability occurs under step-flow growth conditions and vanishes both during low-temperature island growth and at high temperatures. An instability with the same characteristics is observed in a 2D Kinetic Monte Carlo model of growth with incorporated Si(001)-like diffusion anisotropy. This provides strong evidence that the diffusion anisotropy destabilizes growth on Si(001) and similar surfaces towards step bunching. This new instability mechanism is operational without any additional step edge barriers.

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