Effect of growth temperature on the microstructure of the nucleation layers of GaN grown by MOCVD on (1120) sapphire

2002 ◽  
Vol 743 ◽  
Author(s):  
T. Wojtowicz ◽  
P. Ruterana ◽  
M. E. Twigg ◽  
R. L. Henry ◽  
D. D. Koleske ◽  
...  
Keyword(s):  
High Temperature ◽  
Structural Analysis ◽  
Growth Temperature ◽  
Structural Parameters ◽  
Three Dimensional ◽  
Nucleation Mechanism ◽  
Structural Defects ◽  
Orientation Relationships ◽  
Island Growth ◽  
Work Done

AbstractMost of the work done on GaN has taken into account layers grown on the (0001) sapphire plane. However one would expect the growth on the (1120) plane to lead to different structural defects. As has been shown, in one direction, the mismatch is rather small. In this work, we have carried out structural analysis of nucleation layers grown at temperatures ranging from 600°C to 1100°C. It is shown that for many of the structural parameters, such as the orientation relationships, the layer morphology and the nucleation mechanism critically depend on the growth temperature. At the lowest temperatures, the growth is completely three dimensional with a mixture of the two traditional orientation relationships, but the coalescence thickness is small. In a next step, the A orientation relationship predominates and the layer roughness tends to slightly decrease. This orientation is never perfect, and there is always 1.5° misorientation to the same direction in sapphire, whereas the B orientation is always perfect. At an intermediate temperature, island growth is predominant, whereas towards the high temperature end the B orientation becomes predominant. For the highest growth temperatures, the nucleated layers are completely flat and with the B orientation, although they contain a quite large number of defects such as inversion domains.

Microstructure of GaN Grown on (1120) Sapphire

2000 ◽  
Vol 639 ◽  
Author(s):  
P. Ruterana ◽  
A. E. Wickenden ◽  
M. E. Twigg ◽  
D.D. Koleske ◽  
R. L. Henry ◽  
...  
Keyword(s):  
Grain Size ◽  
Structural Analysis ◽  
Misfit Dislocation ◽  
Large Distance ◽  
Random Distribution ◽  
Interface Structure ◽  
Atomic Scale ◽  
Structural Defects ◽  
Work Done ◽  
Dislocation Spacing

ABSTRACTMost of the work done on GaN has taken into account layers grown on the (0001) sapphire. However one would expect the growth on (1120) to lead to different structural defects. As has been shown, in one direction, the mismatch is rather small. In this work, we have carried out structural analysis of layers and interfacial relationship. Inside the layers, the density of defects is comparable to that found conventionally in layers grown on top of (0001) sapphire. The growth mode is also mosaic with a grain size of a few microns. One interesting result is the interface structure, which differs from conventional growth where a flat or stepped interface is formed with a large distance between steps. In this case, the interface is found to be rough at the atomic scale so that this roughness has a random distribution. Moreover, the misfit dislocation spacing is 1nm which is only half the dislocation spacing found in GaN growth on (0001) sapphire.

High temperature epitaxial growth and structure of Nb films on α–Al2O3(0001)

1998 ◽  
Vol 13 (3) ◽  
pp. 693-702 ◽  
Author(s):  
Thomas Wagner
Keyword(s):  
Electron Microscopy ◽  
Growth Temperature ◽  
Basal Plane ◽  
Three Dimensional ◽  
High Energy ◽  
Total Density ◽  
X Ray Diffraction ◽  
Island Growth ◽  
Transmission Electron ◽  
Α Al2o3

Epitaxial Nb thin films were grown via molecular beam epitaxy (MBE) at different substrate temperatures on α–Al2O3(0001) substrates. For temperatures of 900 °C to 1100 °C, it was found that Nb grows in the Volmer–Weber growth mode (formation of three-dimensional crystallites). Depending on the growth temperature, different epitaxial orientations of Nb films can be found. At a growth temperature of 900 °C, the Nb{111} planes are parallel to the sapphire basal plane whereas at 1100 °C the Nb grows with the {110} planes on the basal plane of sapphire. These orientations are present even in the initial stages of growth at both temperatures. The formation of two different epitaxial orientations of thick Nb films can be conclusively explained only by considering both the change in the total density of Nb islands with temperature and the influence of island size on the total energy of the islands. The Nb island growth process has been investigated in situ using reflection high energy electron diffraction (RHEED) and Auger electron spectroscopy (AES). Scanning electron microscopy (SEM), x-ray diffraction (XRD), and transmission electron microscopy (TEM) were employed to determine the morphology and structure of Nb islands, Nb films, and Nb/α–Al2O3 interfaces.

Thickness Dependence of Epitaxial TiSi2 on Si(111).

1990 ◽  
Vol 202 ◽  
Author(s):  
Hyeongtag Jeon ◽  
J. W. Honeycutt ◽  
C. A. Sukow ◽  
G. A. Rozgonyi ◽  
R. J. Nemanich
Keyword(s):  
Three Dimensional ◽  
Titanium Silicide ◽  
Orientation Relationships ◽  
Island Growth ◽  
Si Substrates ◽  
Different Types ◽  
Disordered Layer ◽  
Temperature Deposition ◽  
Higher Temperature

ABSTRACTThe epitaxy and morphology of TiSi2 on Si(l 11) are studied as a function of Ti thickness. Titanium thicknesses of 1–2 monolayers and Ti films with thicknesses of 50Å; were examined. The titanium silicide films were formed on atomically clean Si substrates by ultrahigh vacuum (UHV) deposition of Ti followed by in situ annealing. In situ LEED and AES measurements characterized the reaction process. For room temperature deposition of less than two monolayers of Ti the LEED pattern associated with the reconstructed substrate disappeared, and the 1×1 bulk pattern also disappeared completely. Annealing at 200°C resulted in a decrease in the Ti AES signal indicating interdiffusion. For annealing up to 500°C, a series of changes in the LEED patterns were observed, which indicated that the disordered layer transformed to an ordered surface layer. Annealing to higher temperature resulted in the reappearance of the diffraction pattern associated with the 7×7 reconstructed Si(111) surface. This indicated three dimensional island growth. For the TiSi2 formed by in situ annealing of 50Å of Ti on Si(111), three different types of island morphologies were observed and identified as the C49 phase of TiSi2. The C49 TiSi2 was proven to be an epitaxial titanium silicideby HRTEM and SAD. Two different orientation relationships of the TiSi2 islands are found: 1) [3 1 1] C49 TiSi2 // [112]Si and (130) C49 TiSi2 //(11 1) Si, and 2) [1 1 2] C49 TiSi2 // [110] Si and (021) C49 TiSi2 //(1 11) Si. The C49 nucleation and island morphologies are discussed in terms of the character of the epitaxial interface.

scholarly journals Computer aided geological design: AutoCAD® applications in structural geology

2017 ◽  
Vol 13 (2) ◽  
pp. 113
Author(s):  
Sebastián González Chiozza
Keyword(s):  
Structural Geology ◽  
Structural Analysis ◽  
3D Modeling ◽  
Dimensional Space ◽  
Structural Parameters ◽  
Three Dimensional ◽  
Geological Structures ◽  
Computer Aided ◽  
Fault Displacement ◽  
Three Dimensional Space

The three-dimensional (3D) modeling environment of AutoCAD is used to represent and solve problems of structural geology. As an alternative to bi-dimensional (2D) techniques of classical structural analysis, the 3D capabilities of the software are used for modeling, positioning and measuring geological structures. To introduce the proposed method, two practical examples are presented as exercises with detailed instructions. The technique consists in precisely representing the geometrical entities that comprise the geological problem within three-dimensional space to enable the direct measurement of structural parameters. Accurate results, such as fault displacement and the attitude of several structures, are obtained with the dimension tools of the program, so no calculations are required. Diverse 3D viewing perspectives can be adopted to enhance the comprehension of the analyzed situation.

Segregation and Interdiffusion of in Atoms in GaAs/InAs/GaAs Heterostructures

1993 ◽  
Vol 312 ◽  
Author(s):  
T. Kawai ◽  
H. Yonezu ◽  
Y. Ogasawara ◽  
D. Saito ◽  
K. Pak
Keyword(s):  
Growth Temperature ◽  
Three Dimensional ◽  
Film Surface ◽  
Growth Direction ◽  
Layer Growth ◽  
Growth Mode ◽  
Layer By Layer ◽  
Island Growth ◽  
Alas Layer ◽  
Secondary Ion

AbstractThe segregation and interdiffusion of In atoms in the GaAs/InAs/GaAs heterostructures were investigated by secondary ion mass spectroscopy. When the 1 ML thick InAs layer was grown in a layer-by-layer growth mode with no dislocations, the segregation of In atoms became marked with the increase of the growth temperature. However, the segregation was observed even at relatively low growth temperature of 400°C in molecular beam epitaxy. It was found that the segregation was markedly enhanced by dislocations near the heterointerface when the thick InAs layers were grown in a three-dimensional island growth mode. The interdiffusion of In atoms toward the growth direction occurred after thermal annealing, which could be assisted by vacancies propagating from the film surface into epilayer. It became apparent that the interdiffusion was effectively suppressed by a thin AlAs layer inserted in the GaAs cap layer.

Silicon layers grown over SiO2 by liquid phase epitaxy: Electron Microscopical study

1990 ◽  
Vol 48 (4) ◽  
pp. 566-567
Author(s):  
F. Banhart ◽  
F.O. Phillipp ◽  
R. Bergmann ◽  
E. Czech ◽  
M. Konuma ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Liquid Phase ◽  
Plasma Etching ◽  
Liquid Phase Epitaxy ◽  
Three Dimensional ◽  
Microscopical Study ◽  
Sample Temperature ◽  
Structural Defects ◽  
Si Substrates ◽  
Etched Surface

Defect-free silicon layers grown on insulators (SOI) are an essential component for future three-dimensional integration of semiconductor devices. Liquid phase epitaxy (LPE) has proved to be a powerful technique to grow high quality SOI structures for devices and for basic physical research. Electron microscopy is indispensable for the development of the growth technique and reveals many interesting structural properties of these materials. Transmission and scanning electron microscopy can be applied to study growth mechanisms, structural defects, and the morphology of Si and SOI layers grown from metallic solutions of various compositions.The treatment of the Si substrates prior to the epitaxial growth described here is wet chemical etching and plasma etching with NF3 ions. At a sample temperature of 20°C the ion etched surface appeared rough (Fig. 1). Plasma etching at a sample temperature of −125°C, however, yields smooth and clean Si surfaces, and, in addition, high anisotropy (small side etching) and selectivity (low etch rate of SiO2) as shown in Fig. 2.

High temperature compressive behavior of three-dimensional five-directional braided composites

2018 ◽  
Vol 60 (7-8) ◽  
pp. 772-776 ◽  
Author(s):  
Jiayi Liu ◽  
Junmeng Zhou ◽  
Yu Wang ◽  
Jie Mei ◽  
Jialin Liu
Keyword(s):  
High Temperature ◽  
Three Dimensional ◽  
Compressive Behavior ◽  
Braided Composites

3D Structural Analysis of Selected High-Temperature Materials

2018 ◽  
Vol 55 (7) ◽  
pp. 424-446
Author(s):  
U. Jäntsch ◽  
M. Klimenkov ◽  
A. Möslang ◽  
F. Reinauer ◽  
J. Reiser ◽  
...  
Keyword(s):  
High Temperature ◽  
Structural Analysis ◽  
High Temperature Materials

Cardiovascular Imaging for Guiding Interventional Therapy in Structural Heart Diseases

2020 ◽  
Vol 16 (2) ◽  
pp. 111-122
Author(s):  
Nora Rat ◽  
Iolanda Muntean ◽  
Diana Opincariu ◽  
Liliana Gozar ◽  
Rodica Togănel ◽  
...  
Keyword(s):  
Heart Diseases ◽  
Interventional Procedure ◽  
Imaging Techniques ◽  
Ductus Arteriosus ◽  
Three Dimensional ◽  
High Specificity ◽  
Interventional Therapy ◽  
Structural Defects ◽  
Imaging Method ◽  
Three Dimensional Echocardiography

Development of interventional methods has revolutionized the treatment of structural cardiac diseases. Given the complexity of structural interventions and the anatomical variability of various structural defects, novel imaging techniques have been implemented in the current clinical practice for guiding the interventional procedure and for selection of the device to be used. Three– dimensional echocardiography is the most used imaging method that has improved the threedimensional assessment of cardiac structures, and it has considerably reduced the cost of complications derived from malalignment of interventional devices. Assessment of cardiac structures with the use of angiography holds the advantage of providing images in real time, but it does not allow an anatomical description. Transesophageal Echocardiography (TEE) and intracardiac ultrasonography play major roles in guiding Atrial Septal Defect (ASD) or Patent Foramen Ovale (PFO) closure and device follow-up, while TEE is the procedure of choice to assess the flow in the Left Atrial Appendage (LAA) and the embolic risk associated with a decreased flow. On the other hand, contrast CT and MRI have high specificity for providing a detailed description of structure, but cannot assess the flow through the shunt or the valvular mobility. This review aims to present the role of modern imaging techniques in pre-procedural assessment and intraprocedural guiding of structural percutaneous interventions performed to close an ASD, a PFO, an LAA or a patent ductus arteriosus.

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