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

2002 ◽  
Vol 749 ◽  
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.

Characterization of Etching Processes on CU Surfaces

1996 ◽  
Vol 451 ◽  
Author(s):  
C. Y. Nakakura ◽  
V. M. Phanse ◽  
G. Zheng ◽  
E. I. Altman
Keyword(s):  
Step Edge ◽  
Scanning Tunneling ◽  
Desorption Peak ◽  
Tunneling Microscopy ◽  
Step Flow ◽  
Low Energy Electron ◽  
Temperature Programmed ◽  
Step Flow Growth ◽  
Adsorbate Structure

ABSTRACTThe etching of single crystal and polycrystalline Cu surfaces by halogens was studied using temperature programmed desorption (TPD), low energy electron diffraction (LEED), and scanning tunneling microscopy (STM). For Br2 and Cl2 on Cu(100) and polycrystalline Cu, the etching mechanism could be characterized as a two step process: 1) formation of a bulk Cu(I) halide, and 2) removal of the halide by sublimation. In all cases the first step was found to be adsorption rate limited. Halide formation was observed to consume Cu atoms from the step edge and thus etching can be considered the reverse of step flow growth. While STM showed that Cl2 reacts isotropically with steps on Cu(100), the rate of CuBr formation was observed to be sensitive to the local adsorbate structure at the step edge. For Cl2, it was found that halide removal could be characterized as a simple bulk sublimation process independent of the structure of the underlying Cu. In contrast, a CuBr desorption peak at temperatures lower than anticipated from bulk vapor pressure data was observed. The presence of narrowly spaced steps on the Cu surface was observed to stabilize this low-temperature desorption peak.

Controlling the morphology transition between step-flow growth and step-bunching growth

2017 ◽  
Vol 478 ◽  
pp. 187-192 ◽  
Author(s):  
Konrad Bellmann ◽  
Udo W. Pohl ◽  
Christian Kuhn ◽  
Tim Wernicke ◽  
Michael Kneissl
Keyword(s):  
Step Bunching ◽  
Morphology Transition ◽  
Step Flow ◽  
Step Flow Growth

Scanning tunneling microscopy of step bunching on vicinal GaAs(100) annealed at high temperatures

1994 ◽  
Vol 65 (6) ◽  
pp. 722-724 ◽  
Author(s):  
S. L. Skala ◽  
S. T. Chou ◽  
K.‐Y. Cheng ◽  
J. R. Tucker ◽  
J. W. Lyding
Keyword(s):  
Scanning Tunneling Microscopy ◽  
High Temperatures ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Step Bunching

The Dynamical Transition to Step-Flow Growth During Homoepitaxy of GaAs (001)

1993 ◽  
Vol 312 ◽  
Author(s):  
B. G. Orr ◽  
J. Sudijono ◽  
M. D. Johnson
Keyword(s):  
Scanning Tunneling Microscope ◽  
Molecular Beam ◽  
Scanning Tunneling ◽  
Oscillatory Regime ◽  
Step Flow ◽  
Microscope Images ◽  
Step Density ◽  
Step Flow Growth ◽  
Direct Correspondence ◽  
Density Results

AbstractThe evolution of surface morphology of molecular-beam-epitaxy-grown GaAs (001) has been studied by scanning tunneling microscope. Images show that in the early stages of deposition the morphology oscillates between one -with twodimensional nucleation and coalescing islands, i.e. flat terraces. After the initial oscillatory regime, the system evolves to a dynamical steady state. This state is characterized by a constant step density. As such, the growth mode can be called a generalized step flow. Comparison with RHEED shows that there is a direct correspondence between the surface step density and the RHEED specular intensity. An increase in step density results in a decrease in specular intensity. Additionally, further deposition beyond 120 monolayers (up to 1450 monolayers) display a slowly increasing surface roughness.

Relating Surface Structure and Growth Mode of γ′Fe4N

2003 ◽  
Vol 10 (02n03) ◽  
pp. 405-411 ◽  
Author(s):  
D. O. Boerma ◽  
S. Y. Grachev ◽  
D. M. Borsa ◽  
R. Miranda ◽  
J. M. Gallego
Keyword(s):  
Growth Mechanism ◽  
Plasma Source ◽  
Thin Layers ◽  
Scanning Tunneling ◽  
Rf Plasma ◽  
Nitride Phase ◽  
Tunneling Microscopy ◽  
Metallic Conductor ◽  
Device Applications ◽  
Step Flow Growth

We have grown thin layers of γ′Fe4N on Cu(100) substrates by molecular beam epitaxy in a flow of atomic nitrogen, delivered by a radio-frequency (RF) plasma source. This nitride phase is a ferromagnetic metallic conductor and has interesting properties for device applications. In addition it has an intriguing growth mechanism. In earlier work we found that pure crystalline layers can be grown at substrate temperatures higher than 250°C, with excess nitrogen and in the presence of hydrogen.1 To gain insight into the growth mechanism, we studied the structure and composition with scanning tunneling microscopy (STM), Auger electron spectroscopy (AES), low-energy electron diffraction (LEED) and X-ray diffraction (XRD). This was done for a coverage range of Fe4N on Cu(100) between 0.5 and 30 monolayers (ML) equivalent of Fe, deposited at 400°C, or at 300°C in one case. Here a preliminary account of this study is presented. We found that at sub-ML coverage, first "depressed" (with respect to the Cu surface) islands of Fe–N are formed. Then, on top of these islands a second layer is growing. Subsequently the space between the islands is filled up by a Fe–N layer growing directly on Cu. This gives rise to a smooth surface with patches differing in height by only 0.5 Å. The following layers grow by step-flow growth. The smooth terraces still show patches with a 0.5 Å height difference. The phase is γ′Fe4N with a distorted (p4g-like) structure as observed with LEED and STM, where a p(2 × 2) symmetry is seen. The c(2 × 2) symmetry expected for γ′Fe4N is observed after growing 30 ML or more. A model for the growth mechanism based on our observations is proposed.

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.

Dynamics of Ga Clusters on GaAs(001) Surface

2000 ◽  
Vol 648 ◽  
Author(s):  
Shiro Tsukamoto ◽  
Nobuyuki Koguchi
Keyword(s):  
Substrate Temperature ◽  
Surface Reconstruction ◽  
High Energy ◽  
Gaas Layer ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Additional Layer ◽  
Surface Reconstructions ◽  
Migration Enhanced Epitaxy ◽  
Step Flow Growth

AbstractDynamics of Ga clusters and GaAs epitaxial growth on a GaAs (001) surface were successfully observed by a system in which scanning tunneling microscopy (STM) and molecular beam epitaxy (MBE) were incorporated into one unit rather than in separate chambers. With the substrate temperature of 528°C, reflection high-energy diffraction (RHEED) patterns showed a (4×6) Ga-stabilized surface reconstruction and dynamics of steps and islands were clearly observed. The detaching and attaching of small Ga clusters might cause the change of steps and islands. It seems that the small Ga clusters migrated with the diameter of about 0.8 to 1.2 nm and around the steps and islands. These clusters could be observed only when they were detached from or attached to the steps and islands. Moreover, even under the substrate temperature of 440 oC and the As4 partial pressure of 2×10−6 torr, STM images were clearly observed. After 0.1 ML Ga was additionally supplied to the sample by migration enhanced epitaxy mode, step flow growth occurred, resulting in an additional GaAs layer grown on the B-step side. Moreover, the c(4×4) As-stabilized surface reconstruction was moderate. It seems that there is an equilibrium additional layer of As amorphous adatoms on the c(4x4) surface reconstructions.

Growth of Laser Ablated YBa2Cu3O7−δ Films as Examined by Rheed and Scanning Tunneling Microscopy

1992 ◽  
Vol 285 ◽  
Author(s):  
Stephen E. Russek ◽  
Alexana Roshko ◽  
Steven C. Sanders ◽  
David A. Rudman ◽  
J. W. Ekin ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Scanning Tunneling Microscopy ◽  
Three Dimensional ◽  
High Energy ◽  
Spiral Growth ◽  
Scanning Tunneling ◽  
Initial Growth ◽  
Rheed Pattern ◽  
Island Growth ◽  
Tunneling Microscopy

ABSTRACTUsing scanning tunneling microscopy (STM) and reflection high energy electron diffraction (RHEED) we have examined the growth morphology, surface structure, and surface degradation of laser ablated YBa2Cu3O7−δ thin films. Films from 5 nm to ltm thick were studied. The films were deposited on MgO and LaAlO3 substrates using two different excimer laser ablation systems. Both island nucleated and spiral growth morphologies were observed depending on the substrate material and deposition rate used. The initial growth mechanism observed for a 5–10 nm thick film is replicated through different growth layers up to thicknesses of 200 run. Beyond 200 rnm, the films show some a-axis grains and other outgrowths. The thinnest films (5–10 nm) show considerable surface roughness on the order of 3–4 nm. For both growth mechanisms the ledge width remains approximately constant (∼ 30 nm) and the surface roughness increases as the film thickness increases. The films with spiral growth have streaked RHEED patterns despite having considerable surface roughness, while the films with island growth have more of a three dimensional diffraction pattern. RHEED patterns were obtained after the film surfaces were degraded by exposure to air, KOH developer, a Br-methanol etch, and a shallow ion mill. Exposure to air and KOH developer caused only moderate degradation of the RHEED pattern whereas a shallow (I nm deep) 300 V ion mill completely destroyed the RHEED pattern.

Epitaxy of Germanium on SI(001) Grating Templates

1993 ◽  
Vol 317 ◽  
Author(s):  
C.C. Umbach ◽  
J.M. Blakely
Keyword(s):  
Room Temperature ◽  
Elevated Temperatures ◽  
Scanning Tunneling ◽  
Growth Morphology ◽  
Tunneling Microscopy ◽  
Step Flow ◽  
Growth Modes ◽  
Step Density ◽  
Temperature Scanning ◽  
Substrate Temperatures

ABSTRACTEpitaxial Ge films (< 3 ML) have been grown at elevated temperatures on Si (001) grating substrates (repeat spacing of 2.0 μm) and imaged using room temperature scanning tunneling Microscopy (STM). The Ge films exhibit the 2×n reconstruction associated with missing dimer rows. The value of n and the growth morphology are influenced by the deposition rate and by annealing. At substrate temperatures of 600° C and deposition rates >0.5 ML/Min., islands elongated along the the dimer row direction nucleate at steps and on terraces. With sufficient annealing at 800° C, the islands coarsen and are eventually eliminated. The roughness of the A-type step becomes greater than that of the B-type step, which is the reverse of the situation with pure Si (001). The separation between missing dimer rows and hence the value of n are increased by annealing. Differences in substrate terrace widths due to the periodically varying step density of thegratings affect the growth Modes: two-dimensional islands occur near the extrema of the gratings whereas step flow occurs when steps are separated by ∼150 Å or less.

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