Surface studies of phase formation in Co–Ge system: Reactive deposition epitaxy versus solid-phase epitaxy

2001 ◽  
Vol 16 (3) ◽  
pp. 744-752 ◽  
Author(s):  
I. Goldfarb ◽  
G. A. D. Briggs
Keyword(s):  
Lattice Constant ◽  
Solid Phase ◽  
Morphological Evolution ◽  
Three Dimensional ◽  
High Energy ◽  
Scanning Tunneling ◽  
Solid Phase Epitaxy ◽  
Wetting Layer ◽  
Tunneling Microscopy ◽  
Reactive Deposition

Morphological evolution of cobalt germanide epilayers, CoxGey, was investigated in situ by scanning tunneling microscopy and spectroscopy and reflection high-energy electron diffraction, as a function of deposition method and, hence, the phase content of the epilayer. During reactive deposition epitaxy, in which Co atoms were evaporated onto a flat pseudomorphic Ge/Si(001) wetting layer at 773 K, the first phase formed was cobalt digermanide, CoGe2, in the form of elongated pyramidal islands. Each of these three-dimensional islands has locally exerted an additional strain on the Ge wetting layer already strained at the Ge/Si(001) interface, lifting the layer metastability and causing, in turn, the formation of three-dimensional Ge pyramids underneath every CoGe2 island. Solid-phase epitaxy of Co onto the same Ge/Si(001) epilayer resulted in the formation of more Co-rich germanide islands. Coupling of strain from these germanides to the epitaxial Ge/Si(001) strain has also facilitated a two-dimensional-to-three-dimensional transition of the Ge layer, however, with the germanide islands located at the Ge pyramid troughs, rather than crests. The difference in the relative location of germanide and germanium islands in these two cases is explained by accommodation of the large lattice-constant germanides at the more relaxed regions of the Ge pyramid crests and the smaller lattice-constant at the compressed Ge pyramid troughs.

Stm Observation of Solid Phase Epitaxy Processes of Ar-Sputtered Si(100) Surfaces

1992 ◽  
Vol 280 ◽  
Author(s):  
Katsuhiro Uesugi ◽  
Masamichi Yoshimura ◽  
Takafumi Yao ◽  
Tomoshige Sato ◽  
Takashi Sueyoshi ◽  
...  
Keyword(s):  
Surface Morphology ◽  
Scanning Tunneling Microscopy ◽  
Double Layer ◽  
Solid Phase ◽  
The Other ◽  
Scanning Tunneling ◽  
Nanometer Scale ◽  
Solid Phase Epitaxy ◽  
Tunneling Microscopy ◽  
Partially Observed

ABSTRACTScanning tunneling microscopy (STM) is used to investigate the surface morphology of Ar+-ion bombarded Si(100) surfaces and to elucidate the very beginning stages of solid phase epitaxy (SPE) processes of the Ar+-ion bombarded Si surfaces. The Ar+-ion bombarded Si surface consists of hillocks of 1–2 nm in diameter and 0.35–0.75 nm in height. The onset of SPE initiates at around 590°C, at which temperature a (2×2) structure surrounded by amorphous regions is partially observed on terraces of the surface. During annealing at 590–620°C, the areas of the c(2×2) and c(4×4) reconstruction surrounded by amorphous regions develops. New defect models for the (2×2) and c(4×4) structures are proposed w here alternating arrangements of the buckled dimers together with missing dimer defects are considered. On the other hand, after thermal annealing of the Ar+-ion bombarded Si at 830°C for 10 sec, terraces of (2×1) and (1×2) orientations arc observed on the surface, and pyramidal structures on a nanometer-scale which consists of double-layer step edges (dimer rows perpendicular to terrace edge) arc observed.

Slow Decay of Reflection High Energy Electron Diffraction Oscillations in Cal1-xMgxF2

1996 ◽  
Vol 441 ◽  
Author(s):  
Mitsuhiro Kushibe ◽  
Yuriy V. Shusterman ◽  
Nikolai L. Yakovlev ◽  
Leo J. Schowalter
Keyword(s):  
Phase Separation ◽  
Electron Diffraction ◽  
Lattice Constant ◽  
Room Temperature ◽  
High Energy ◽  
Energy Electron ◽  
Scanning Tunneling ◽  
High Energy Electron ◽  
Tunneling Microscopy ◽  
Slow Decay

AbstractMagnesium is incorporated into the growth of Ca1-xMgxF2 to reduce the lattice constant of fluorite (CaF2) which is 0.6% larger than that of Si at room temperature. When grown epitaxially on Si(111) substrates at 300°C, the lattice constant of the alloy became smaller than that of Si by 1.5% when the Mg concentration was around 20%. At higher Mg concentrations, the lattice constant did not decrease any further. This invariability of the lattice constant was caused by a phase separation of the Ca1-xMgxF2 layer into a Mg-rich region and a Mg-deficient region. When the growth temperature was increased, the critical Mg concentration for the phase separation became smaller. When Ca1-xMgxF2 was grown on vicinal Si(111) substrates, the reflection high energy electron diffraction (RHEED) intensity oscillations reflected no change in the composition, suggesting segregation of a Mg-rich phase along the steps. Nevertheless, the oscillations in the intensity of the specular spot for Ca1-xMgxF2 lasted longer than those observed for pure CaF2, suggesting a flatter surface for the alloy. Scanning tunneling microscopy (STM) observations support this model.

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.

MODIFICATION OF GROWTH MODE OF Ge ON Si BY PULSED LOW-ENERGY ION-BEAM IRRADIATION

2004 ◽  
Vol 03 (01n02) ◽  
pp. 19-27 ◽  
Author(s):  
A. V. DVURECHENSKII ◽  
J. V. SMAGINA ◽  
V. A. ZINOVYEV ◽  
S. A. TEYS ◽  
A. K. GUTAKOVSKII ◽  
...  
Keyword(s):  
Surface Defect ◽  
Kinetic Monte Carlo ◽  
Ion Beam ◽  
Three Dimensional ◽  
High Energy ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Growth Modes ◽  
Transmission Electron ◽  
Critical Film Thickness

Scanning tunneling microscopy (STM) and reflection high-energy electron diffraction (RHEED) experiments were performed to study growth modes induced by hyperthermal Ge + ion action during molecular beam epitaxy (MBE) of Ge on Si (100). The continuous and pulsed ion beams were used. These studies have shown that ion-beam bombardment during heteroepitaxy leads to decrease in critical film thickness for transition from two-dimensional (2D) to three-dimensional (3D) growth modes, enhancement of 3D island density and narrowing of island size distribution, as compared with conventional MBE experiments. The crystal perfection of Ge / Si structures with Ge islands embedded in Si was analyzed by Rutherford backscattering/channeling technique (RBS) and transmission electron microscopy (TEM). The results of Kinetic Monte Carlo (KMC) simulation have shown that two mechanisms of ion beam action can be responsible for stimulation of 2D–3D transition. They are: (1) surface defect generation by ion impacts and (2) enhancement of surface diffusion.

Evolution and Degeneration of Dimer-Adatom-Stacking-Fault Structure in Solid-Phase Epitaxy on Si(111) Surface Observed by Scanning Tunneling Microscopy

1998 ◽  
Vol 05 (01) ◽  
pp. 21-25
Author(s):  
Z. Zhang ◽  
M. A. Kulakov ◽  
B. Bullemer
Keyword(s):  
Scanning Tunneling Microscopy ◽  
Solid Phase ◽  
Stacking Fault ◽  
Structure Evolution ◽  
Scanning Tunneling ◽  
Solid Phase Epitaxy ◽  
Dangling Bonds ◽  
Tunneling Microscopy ◽  
Fault Structure ◽  
Unit Cells

Large unit cells of dimer-adatom-stacking-fault structure and related 2 × 2 and c(4 × 2) reconstructions have been prepared by low-temperature solid-phase epitaxy and observed by scanning tunneling microscopy. The size-different unit cells of the DAS structure are considered to be a structure evolution in which more electron charge transfers in a larger unit cell from the adatom dangling bonds to the rest-atom dangling bonds. In some cases the DAS structure can degenerate into triangular 2 × 2 domains and bundlinke c(4 × 2) domains. The rest atoms are always fully filled by electrons due to the charge transfer. The adatom dangling bonds are partially filled in a c(4 × 2) symmetry and essentially empty in a 2 × 2 symmetry. As a result, the rest atoms in 2 × 2 domains can be imaged without the adatom protrusions while in the c(4 × 2) domains the protrusions of the adatoms and the rest atoms appear in zigzag chains, when the sample is negatively biased.

Sign in / Sign up

Export Citation Format

Share Document