Structural Defects and Their Relationship to Nucleation of Gan Thin Films

1996 ◽  
Vol 423 ◽  
Author(s):  
Weida Gian ◽  
Marek Skowronski ◽  
Greg S. Rohrer
Keyword(s):  
Film Growth ◽  
Three Dimensional ◽  
Scanning Force Microscopy ◽  
Columnar Structure ◽  
Layer Growth ◽  
Buffer Layers ◽  
Structural Defects ◽  
Layer By Layer ◽  
Extended Defects ◽  
Edge Dislocations

AbstractMicrostructure and extended defects in α-GaN films grown by organometallic vapor phase epitaxy on sapphire substrates using low temperature AIN (or GaN) buffer layers have been studied using transmission electron microscopy. The types and distribution of extended defects were correlated with the film growth mode and the layer nucleation mechanism which was characterized by scanning force microscopy. The nature of the extended defects was directly related to the initial three-dimensional growth. It was found that inhomogeneous nucleation leads to a grain-like structure in the buffer; the GaN films then have a columnar structure with a high density of straight edge dislocations at grain boundaries which are less likely to be suppressed by common annihilation mechanisms. Layer-by-layer growth proceeds in many individual islands which is evidenced by the observation of hexagonal growth hillocks. Each growth hillock has an open-core screw dislocation at its center which emits monolayer-height spiral steps.

Pb Induced Layer-by-Layer Growth and the Dependence on an Amount of Surfactant in the Growth of Ni on Ni(100) Surface

1996 ◽  
Vol 441 ◽  
Author(s):  
M. Iwanami ◽  
M. Kamiko ◽  
T. Matsumoto ◽  
R. Yamamoto
Keyword(s):  
Film Growth ◽  
Three Dimensional ◽  
High Energy ◽  
Layer Growth ◽  
Embedded Atom Method ◽  
Layer By Layer ◽  
Homoepitaxial Growth ◽  
Embedded Atom ◽  
Series Of Experiments ◽  
Modified Embedded Atom Method

AbstractSurfactant epitaxy has been expected to be a powerful method to improve thin film growth from three dimensional island mode to layer-by-layer growth one. Supposing that Pb is the surfactant and Ni is the substrate and deposition metal, we have investigated how the surfactant atoms segregate on surface by computer simulations using the modified embedded atom method. To verify the effect of Pb on the homoepitaxial growth of Ni, we have performed a series of experiments on the growth of Ni on Ni(100) surface with and without Pb using reflection high energy electron diffraction (RHEED). It was clearly found that Pb induced layer-by-layer growth of Ni metal film. The result of the dependence of the growth behavior on the thickness of Pb layer suggests that there is the most suitable thickness of a surfactant layer which is not always the monolayer.

Germanium Nanostructures on Silicon Observed by Scanning Probe Microscopy

MRS Bulletin ◽  
2004 ◽  
Vol 29 (7) ◽  
pp. 484-487 ◽  
Author(s):  
Masahiko Tomitori ◽  
Toyoko Arai
Keyword(s):  
Scanning Probe Microscopy ◽  
Film Growth ◽  
Three Dimensional ◽  
Layer Growth ◽  
Scanning Probe ◽  
Scanning Tunneling ◽  
Layer By Layer ◽  
Tunneling Microscopy ◽  
Probe Microscopy ◽  
History Of

AbstractScanning tunneling microscopy and noncontact atomic force microscopy have been used to observe germanium growth on Si(001) and Si(111). The atomically resolved images provide invaluable information on heteroepitaxial film growth from the viewpoints of both industrial application and basic science. We briefly review the history of characterizing heteroepitaxial elemental semiconductor systems by means of scanning probe microscopy (SPM), where the Stranski–Krastanov growth mode can be observed on the atomic scale:the detailed phase transition from layer-by-layer growth to three-dimensional cluster growth was elucidated by the use of SPM. In addition, we comment on the potential of SPM for examining the spectroscopic aspects of heteroepitaxial film growth, through the use of SPM tips with well-defined facets.

scholarly journals Modeling the Layer-by-Layer Growth of HKUST-1 Metal-Organic Framework Thin Films

Nanomaterials ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 1631
Author(s):  
Qiang Zhang ◽  
Yohanes Pramudya ◽  
Wolfgang Wenzel ◽  
Christof Wöll
Keyword(s):  
Thin Films ◽  
Surface Roughness ◽  
Deposition Rate ◽  
Layer Growth ◽  
Coarse Grained ◽  
Structural Defects ◽  
Effect Of Temperature ◽  
Layer By Layer ◽  
Reactant Concentration ◽  
Metal Organic

Metal organic frameworks have emerged as an important new class of materials with many applications, such as sensing, gas separation, drug delivery. In many cases, their performance is limited by structural defects, including vacancies and domain boundaries. In the case of MOF thin films, surface roughness can also have a pronounced influence on MOF-based device properties. Presently, there is little systematic knowledge about optimal growth conditions with regard to optimal morphologies for specific applications. In this work, we simulate the layer-by-layer (LbL) growth of the HKUST-1 MOF as a function of temperature and reactant concentration using a coarse-grained model that permits detailed insights into the growth mechanism. This model helps to understand the morphological features of HKUST-1 grown under different conditions and can be used to predict and optimize the temperature for the purpose of controlling the crystal quality and yield. It was found that reactant concentration affects the mass deposition rate, while its effect on the crystallinity of the generated HKUST-1 film is less pronounced. In addition, the effect of temperature on the surface roughness of the film can be divided into three regimes. Temperatures in the range from 10 to 129 °C allow better control of surface roughness and film thickness, while film growth in the range of 129 to 182 °C is characterized by a lower mass deposition rate per cycle and rougher surfaces. Finally, for T larger than 182 °C, the film grows slower, but in a smooth fashion. Furthermore, the potential effect of temperature on the crystallinity of LbL-grown HKUST-1 was quantified. To obtain high crystallinity, the operating temperature should preferably not exceed 57 °C, with an optimum around 28 °C, which agrees with experimental observations.

Modeling of Titanium Oxide Layer Growth Produced by Fiber Laser Beam

2013 ◽  
Vol 336 ◽  
pp. 11-18 ◽  
Author(s):  
Farida Hamadi ◽  
El Hachemi Amara ◽  
Djamila Bennaceur-Doumaz ◽  
R. Boutaka ◽  
H. Kellou ◽  
...  
Keyword(s):  
Temperature Field ◽  
Laser Beam ◽  
Film Growth ◽  
Three Dimensional ◽  
Layer Growth ◽  
Heat Diffusion ◽  
Metallic Surface ◽  
Heat Diffusion Equation ◽  
Computational Procedures ◽  
Volume Method

In this paper, we study the oxidation process during the heating of a titanium metallic surface by a Nd-YAG fiber pulsed laser beam under air environment. For this, we adopted an approach that considers a three-dimensional heat diffusion model coupled with an oxidation parabolic law (oxidation kinetics). The heat diffusion equation solved numerically, gives the temperature field. The oxide film growth is simulated by implementing a dynamic mesh technique. We developed computational procedures UDFs (User Defined Function) running interactively with the Fluent fluid dynamics software [ that implements the finite volume method. These UDFs are developed to insert the oxidation law, the temperature field, the specific boundary conditions and the mesh deformation into the calculation.

Effects of Stress on Step Energies and Surface Roughness

MRS Bulletin ◽  
1996 ◽  
Vol 21 (4) ◽  
pp. 27-30 ◽  
Author(s):  
Christopher Roland
Keyword(s):  
Thin Films ◽  
Strain Relaxation ◽  
Three Dimensional ◽  
Layer Growth ◽  
Growth Mode ◽  
Misfit Dislocations ◽  
Layer By Layer ◽  
Strained Layers ◽  
The Subject ◽  
Growth Changes

Strain relaxation in lattice-mismatched, heteroepitaxial systems is one of the classic problems in materials physics, which has gained new urgency with the increased applications of strained layers in microelectronic systems. In general both the structure and the integrity of the thin films are strongly influenced by strain. For instance it has long been known that under strain, the growth changes from an initial layer-by-layer growth mode to one with three-dimensional islanding. In the seminal works of van der Merwe, and Matthews and Blakeslee, this change in growth mode is explained in terms of the introduction of strain-relieving misfit dislocations, which appear when the film has reached some critical thickness. Recently it has become clear that this change in growth mode can take place even without the introduction of misfit dislocations. Such dislocation-free coherent islanding, or “roughening,” has been observed experimentally both in Ge/Si and in InGaAs/GaAs systems. Furthermore recent experiments show that in Ge/Si(100) systems, the thin films display a curious asymmetry with respect to the sign of the strain: Films under compression roughen by forming coherent islands while those under tension remain relatively smooth. A possible mechanism behind this strain-induced type of roughening is the subject of this article.

Energetics of AlN Epitaxial Wetting Layers on SiC (0001)

1996 ◽  
Vol 449 ◽  
Author(s):  
R. Di Felice ◽  
J. E. Northrup ◽  
J. Neugebauer
Keyword(s):  
First Principles ◽  
Three Dimensional ◽  
Layer Growth ◽  
Layer By Layer ◽  
Two Dimensional ◽  
Charge Accumulation ◽  
Wetting Layer ◽  
Interface Charge ◽  
Wetting Layers

ABSTRACTWe present a first-principles characterization of the initial stages of formation of AlN films on c-plane SiC substrates. Studying the competition between two-dimensional films and three-dimensional islands as a function of Al and N abundances, we find that a two-dimensional film can wet the surface in N-rich conditions. Ordered layer-by-layer growth can proceed to some extent on this wetting layer, and is improved by the formation of an atomically mixed interface which eliminates interface charge accumulation. Our results indicate that the stable AlN films grow in the (0001) orientation on the Si-terminated SiC(0001) substrate.

An Investigation of PT/PT (111) Homoepitaxy with Molecular Dynamics Simulation and Static-Energy Calculation.

1993 ◽  
Vol 317 ◽  
Author(s):  
Ruoping wang ◽  
Bryan S. Kalp ◽  
Kristen A. Fichthorn
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulation ◽  
Film Growth ◽  
Effective Medium Theory ◽  
Layer Growth ◽  
Dynamics Simulation ◽  
Energy Calculation ◽  
Layer By Layer ◽  
Static Energy ◽  
Step Edges

ABSTRACTWe present the results of a study of Pt/Pt (111) epitaxial thin-film growth with Molecular-dynamics simulation and static-energy calculation. Interatomic forces are modeled with Corrected-Effective-Medium theory. Atomic details of deposition, such as dissipation of the kinetic energy of an impinging gas atom, adatom motion on and approaching descending step edges, effects of the geometry of a step edge on the interlayer transport of adatoms, etc., have been intensively investigated. We have observed a novel mechanism for adatom incorporation into descending-step edges which involves a concerted motion of the adatom and edge atoms. Our study supports the “island size and shape” model which has been proposed to explain the reentrant layer-by-layer growth mode seen experimentally in Pt/Pt (111) homoepitaxy.

scholarly journals Multilayer Self-Assemblies as Electronic and Optical Materials

1997 ◽  
Vol 488 ◽  
Author(s):  
DeQuan Li ◽  
M. Lütt ◽  
Xiaobo Shi ◽  
M. R. Fitzsimmons
Keyword(s):  
Thin Film ◽  
Self Assembly ◽  
Film Growth ◽  
Building Blocks ◽  
Layer Growth ◽  
The Self ◽  
Growth Surface ◽  
Layer By Layer ◽  
Self Assembled ◽  
Average Electron

AbstractThe layer-by-layer growth of film structures consisting of sequential depositions of oppositely charged polymers and macrocycles (ring-shaped molecules) have been constructed using molecular self-assembly techniques. These self-assembled thin films were characterized with X-ray reflectometry, which yielded (1) the average electron density, (2) the average thicknesses, and (3) the roughness of the growth surface of the self-assembled multilayer of macrocycles and polymers. These observations suggest that inorganic-organic interactions play an important role during the initial stages of thin-film growth, but less so as the thin film becomes thicker. Optical absorption techniques were also used to characterize the self-assembled multilayers. Phorphyrin and phthalocyanine derivatives were chosen as the building blocks of the self-assembled multilayers because of their interesting optical properties.

Oxygen Pressure Dependence of Morphology of Morphology of La2-xSrxCuO4 Ultra-Thin Films

1997 ◽  
Vol 11 (21n22) ◽  
pp. 981-987
Author(s):  
H. Q. Yin ◽  
T. Arakawa ◽  
Y. Kaneda ◽  
T. Yoshikawa ◽  
N. Haneji ◽  
...  
Keyword(s):  
Thin Films ◽  
Pressure Dependence ◽  
Film Growth ◽  
Ambient Pressure ◽  
High Energy ◽  
Layer Growth ◽  
Growth Mode ◽  
Layer By Layer ◽  
Island Growth ◽  
Experimental Conditions

La 2-x Sr x CuO 4 ultra-thin films with thickness 200 Å were fabricated by pulsed laser deposition method in oxygen ( O 2) atmosphere. The morphology of deposited films was investigated by reflection high energy electron diffraction (RHEED), atomic force microscopy (AFM) and scanning electronic microscopy (SEM). The strong oxygen ambient pressure dependence of film morphology was observed. In high oxygen ambient pressure, the film growth is dominated by island growth mode. The results imply that the experimental conditions of oxygen ambient pressure and substrate temperature are critical for the layer-by-layer growth mode.

Atomic Layer Growth of SiO2 on Si(100) Using the Sequential Deposition of SiCl4 and H2O

1993 ◽  
Vol 334 ◽  
Author(s):  
Ofer Sneh ◽  
Michael L. Wise ◽  
Lynne A. Okada ◽  
Andrew W. Ott ◽  
Steven M. George
Keyword(s):  
High Pressure ◽  
Film Growth ◽  
Atomic Layer ◽  
Reaction Scheme ◽  
Layer Growth ◽  
Film Deposition ◽  
Layer By Layer ◽  
High Pressure Cell ◽  
Experimental Apparatus ◽  
Binary Reaction

AbstractThis study explored the surface chemistry and the promise of the binary reaction scheme:(A) Si-OH+SiCl4 → Si-Cl + HCl(B) Si-Cl + H2O → Si-OH + HClfor controlled SiO2 film deposition. In this binary ABAB… sequence, each surface reaction may be self-terminating and ABAB… repetitive cycles may produce layer-by-layer controlled deposition. Using this approach, the growth of SiO2 thin films on Si(100) with atomic layer control was achieved at 600 K with pressures in the 1 to 50 Torr range. The experiments were performed in a small high pressure cell situated in a UHV chamber. This design couples CVD conditions for film growth with a UHV environment for surface analysis using laser-induced thermal desorption (LITD), temperature-programmed desorption (TPD) and Auger electron spectroscopy (AES). The controlled layer-by-layer deposition of SiO2 on Si(100) was demonstrated and optimized using these techniques. A stoichiometric and chlorine-free SiO2 film was also produced as revealed by TPD and AES analysis. SiO2 growth rates of approximately 1 ML of oxygen per AB cycle were obtained at 600 K. These studies demonstrate the methodology of using the combined UHV/high pressure experimental apparatus for optimizing a binary reaction CVD process.

Sign in / Sign up

Export Citation Format

Share Document