Structural Evolution During the Initial Epitaxial Growth of Moon on Sapphire

1999 ◽  
Vol 584 ◽  
Author(s):  
P. A. Ryan ◽  
F. Tsui
Keyword(s):  
Epitaxial Growth ◽  
Structural Evolution ◽  
Lattice Relaxation ◽  
High Energy ◽  
Layer Growth ◽  
Scanning Tunneling ◽  
Layer By Layer ◽  
Initial Growth ◽  
Tunneling Microscopy ◽  
Length Scales

AbstractStructural evolution during initial epitaxial growth of Mo (111) and (110) on Al2O3 substrates has been studied using real-time reflection high energy electron diffraction and in-situ scanning tunneling microscopy. The Mo (111) growth on sapphire (0001) is initiated by the formation of small mound-like 3-dimensional (3D) islands that are correlated with unique length scales. The observed surface length scales depend on growth temperature and rate, and they coarsen as the thickness increases. The initial growth of Mo (110) on sapphire (1120) begins with layer-by-layer growth for the first monolayer, and subsequently the growth is 3D with mound-like features that are larger than those corresponding (111) counterparts. In both orientations lattice relaxation occurs within the first 2 – 3 monolayers.

Influence of Surface Structure on Epitaxial Growth of Si on Si(111)-(7 × 7) Substrate

1998 ◽  
Vol 05 (03n04) ◽  
pp. 865-872 ◽  
Author(s):  
Yukichi Shigeta
Keyword(s):  
Surface Structure ◽  
Epitaxial Growth ◽  
High Energy ◽  
Layer Growth ◽  
Scanning Tunneling ◽  
Layer By Layer ◽  
Initial Growth ◽  
Lateral Growth ◽  
Tunneling Microscopy ◽  
Starting Point

To make clear the influence of surface structure on epitaxial growth, we have studied the growth of Si on a Si(111)-(7 × 7) superlattice surface by using scanning tunneling microscopy and reflection high energy electron diffraction. In the initial growth stage on the 7 × 7 superlattice, multilayer islands are formed because lateral growth of the first layer is prevented by the stable 7 × 7 structure and some migrating atoms climb up the first layer and nucleate on it. However, lateral growth of the second layer on the first one is not prevented and the layer-by-layer growth starts, because the structure of the first layer is composed of small domains with some metastable surface structures, which is rather easier to rearrange than the 7 × 7 structure. The starting point of the layer-by-layer growth depends on the substrate temperature, because the surface structure formed on a growing layer is influenced by the temperature. We obtained the result that the nucleation of a two-dimensional island on the 7 × 7 superlattice is also influenced by the surface structure. The island, whose size is less than the half-unit of the 7 × 7 structure, is unstable. The result suggests that, for the nucleation on the stable surface structure, the activation energy of rearrangement of the surfue structure should be taken into the consideration of the formation energy of the nucleus.

Initial Growth and morphology of Ultrathin Magnetic Films Studied Using Scanning Tunneling Microscopy.

1993 ◽  
Vol 313 ◽  
Author(s):  
David D. Chambliss ◽  
K.E. Johnson ◽  
K. Kalki ◽  
S. Chiang ◽  
R.J. Wilson
Keyword(s):  
Magnetic Films ◽  
Layer Growth ◽  
Scanning Tunneling ◽  
Layer By Layer ◽  
Initial Growth ◽  
Island Growth ◽  
Tunneling Microscopy ◽  
High Coverage ◽  
Local Structures ◽  
Low Coverage

ABSTRACTThe room-temperature growth of Fe on Cu(100) has been studied using the scanning tunneling Microscope (STM) to determine low-coverage growth mode and local structures related to the FCC-BCC structural transformation. Results for submonolayer deposition demonstrate an initial interchange of deposited Fe atoms with substrate Cu. This leads to a highly rough Fe-Cu interface and growth characteristics that for different experimental techniques can resemble 3-D island growth or layer-by-layer growth. For a thickness ∼14 Monolayers, the FCC-BCC transition is observed to occur via the formation of fairly large martensitic grains, rather than by a change in atomic aggregation. The implications of the instability of FCC-Fe, as evident in both low- and high-coverage data, are considered.

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

1993 ◽  
Vol 317 ◽  
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.

Direct Observations of the Strain-Limited Island Growth of Sn-Doped GaAs(100)

1998 ◽  
Vol 05 (03n04) ◽  
pp. 783-795 ◽  
Author(s):  
A. M. Dabiran ◽  
S. M. Seutter ◽  
P. I. Cohen
Keyword(s):  
Native Species ◽  
Surface Segregation ◽  
High Surface ◽  
Three Dimensional ◽  
High Energy ◽  
Layer Growth ◽  
Scanning Tunneling ◽  
Layer By Layer ◽  
Island Growth ◽  
Tunneling Microscopy

We have used scanning tunneling microscopy (STM) in ultrahigh vacuum and atomic force microscopy (AFM) in air to investigate the microscopic mechanisms of Sn surface segregation during the molecular beam epitaxial growth of GaAs and AlAs(100). Submonolayer amounts of Sn segregate to the surface during growth and strongly modify the growth kinetics. This is indicated by both extra-ordinary reflection high energy electron diffraction (RHEED) measurements, and the STM and AFM images of rapidly quenched growth fronts. At the high surface coverages of 0.1–0.6 monolayers of Sn, studied in this work, neither step bunching nor three-dimensional (3D) growth of GaAs(100), was observed. Instead, STM and RHEED measurements indicated a significantly enhanced layer-by-layer growth of GaAs with increasing surface coverage of Sn. STM snapshots of the initial stages of GaAs growth revealed 2D islands which contained a higher-than-equilibrium bulk concentration of Sn, in Ga-substitutional sites, of up to 50%. Other directly observed Sn effects which are presented in this work include the removal of GaAs(100) island growth anisotropy and the formation of 2D islands with a relatively narrow distribution of size and separation. The completion of the top layers is shown to proceed by the coalescence of these islands before any significant nucleation of the next layer islands. This effect is used to explain the Sn enhancement of the layer-by-layer growth which was indicated in our RHEED and scanning probe observations. A model is presented for Sn segregation which explains these results based on an island-size-dependent, strain-driven, oscillatory Sn occupation of Ga-substitutional sites and surface interstitial sites on top GaAs(100) layers during growth. This model, which introduces a strain-limiting mechanism for the size and shape of the 2D islands, can also explain the observed enhancement of postgrowth surface recovery, as well as a delayed onset in increasing adatom surface diffusion length with increasing Sn coverage. The main conclusion is that, if impurity incorporation results in significant strain, then in addition to step climbing by surface impurities, the exchange of incorporated impurities with native species in top layers can be an important path for impurity segregation during expitaxial growth.

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.

scholarly journals Epitaxial growth of (001) and (111) Ni films on MgO substrates

2000 ◽  
Vol 648 ◽  
Author(s):  
Rosa Alejandra Lukaszew ◽  
Vladimir Stoica ◽  
Ctirad Uher ◽  
Roy Clarke
Keyword(s):  
Epitaxial Growth ◽  
Supported Catalysts ◽  
High Energy ◽  
Scanning Tunneling ◽  
Magnetic Storage ◽  
Tunneling Microscopy ◽  
Ceramic Substrates ◽  
Storage Media ◽  
Annealing Conditions ◽  
Magnetic Storage Media

AbstractMetal-ceramic interfaces are important in applications as diverse as magnetic storage media and supported catalysts. It is very important to understand how the crystallography and microstructure of metallic films deposited onto ceramic substrates depend on growth and/or annealing conditions so that their physical properties (e.g. magnetic, electronic, etc.) can be tailored for specific applications. To this end, we have studied the epitaxial growth and annealing of (001) and (111) Ni films MBE grown on MgO substrates, where we have observed the evolution of the surface using correlated in- situ RHEED (reflection high-energy-electron diffraction) and STM (scanning tunneling microscopy) measurements.

Investigation of growth rates and morphology for diamond growth by chemical vapor deposition

1992 ◽  
Vol 7 (6) ◽  
pp. 1438-1444 ◽  
Author(s):  
M.P. Everson ◽  
M.A. Tamor
Keyword(s):  
Chemical Vapor Deposition ◽  
Vapor Deposition ◽  
Chemical Vapor ◽  
Layer Growth ◽  
Diamond Growth ◽  
Scanning Tunneling ◽  
Layer By Layer ◽  
Tunneling Microscopy ◽  
Limited Growth ◽  
Diffusion Limited

We describe two complementary studies of diamond growth by chemical vapor deposition. In the first, the early stages of growth of randomly distributed nuclei on silicon are studied by scanning tunneling microscopy. For growth times from 1 to 30 min nearly all crystallites are three dimensional, and increase in volume as t1.5. Although this result could be interpreted in terms of diffusion limited growth, the conditions for diamond CVD are more consistent with rate limited growth where the crystals are expected to gain volume as t3. This anomaly can be explained in terms of a two-species growth mechanism in which the rate constant for carbon addition is proportional to the diffusion limited flux of atomic hydrogen. Other mechanisms giving rise to the observed t1.5 dependence are also considered. The second study uses both scanning electron and tunneling microscopies to examine the morphology of a boron-doped film homoepitaxial to the {100} surface of natural type 2a diamond. In regions distant from gross defects, this film is very smooth. However, gross defects appear to initiate growth of new epitaxial layers at a rate much higher than in defect-free regions. This observation suggests that diamond growth is promoted by “enabling defects” and that without such defects nucleation of new layers is a slow process and permits layer-by-layer growth at a much lower rate.

Substrate-Surface Effect on Initial Growth Process of Microcrystalline Silicon Films

1996 ◽  
Vol 452 ◽  
Author(s):  
K. Ikuta ◽  
J. W. Park ◽  
L. H. Kuo ◽  
T. Yasuda ◽  
S. Yamasaki ◽  
...  
Keyword(s):  
Surface Effect ◽  
Substrate Surface ◽  
Chemical Vapor ◽  
High Energy ◽  
Scanning Tunneling ◽  
Initial Growth ◽  
Microcrystalline Silicon ◽  
Tunneling Microscopy ◽  
Growth Processes ◽  
Wet Processing

AbstractInitial growth processes of hydrogenated microcrystalline silicon (μc-Si:H) films have been investigated by scanning tunneling microscopy (STM), high-resolution transmission electron microscopy (HRTEM), and reflection high energy electron diffraction (RHEED). The μc-Si:H films were prepared by plasma enhanced chemical vapor deposition (PECVD) on H-terminated Si(111) and plasma-oxidized SiO2/Si(111) surfaces that were made atomically-flat by a careful wet processing. On H-terminated Si(111) the initial growth was epitaxial as evidenced by HRTEM and RHEED, while on SiO2/Si(111) the initial process was nucleation of amorphous Si followed by formation of randomly oriented μc-Si:H structure. STM observation revealed that, on both H-terminated and SiO2-terminated surfaces, initial growth processes proceed through the nucleation-and-coalescence mechanism.

NANOWIRES ON STEPPED METAL SURFACES

1997 ◽  
Vol 04 (02) ◽  
pp. 371-380 ◽  
Author(s):  
F. J. HIMPSEL ◽  
T. JUNG ◽  
J. E. ORTEGA
Keyword(s):  
Metal Surfaces ◽  
Electronic States ◽  
Surface States ◽  
Energy Shift ◽  
Layer Growth ◽  
Scanning Tunneling ◽  
Layer By Layer ◽  
Tunneling Microscopy ◽  
One Dimensional ◽  
Inverse Photoemission

The electronic properties of solids can be tailored by structuring them on the nanometer scale. Such a program is becoming reality as surface analysis techniques and sophisticated growth methods are merging. Here, we present results of a venture into one-dimensional nanostructures, grown by decoration of steps at metal surfaces. The growth modes and electronic states are studied using scanning tunneling microscopy (STM) and inverse photoemission. Two-dimensional analogs of Stranski–Krastanov and layer-by-layer growth are found for Cu on stepped Mo(110) and W(110), respectively. Contrast between different metals is achieved in STM pictures by resonant tunneling via surface states and image states, with the latter providing a map of the work function. The limit of single atomic rows decorating step edges is studied by inverse photoemission, and an energy shift of 0.4 eV is found for electronic states of step atoms. Stripe structures are attractive for the study of two- versus one-dimensional magnetism, for magnetoresistive sensors, and in the design of anisotropic materials.

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