Formation of Interfacial Dislocations in Hetero-Epitaxial Layers Grown in Two-Dimensional Mode

1995 ◽  
Vol 399 ◽  
Author(s):  
S. Oktyabrsky ◽  
J. Narayan
Keyword(s):  
Compressive Strain ◽  
Elastic Interaction ◽  
Misfit Strain ◽  
Layer Growth ◽  
Dislocation Network ◽  
Misfit Dislocations ◽  
Layer By Layer ◽  
Two Dimensional ◽  
Transmission Electron ◽  
Interfacial Dislocations

ABSTRACTHigh-resolution transmission electron microscopy has been used to study formation of interfacial defects related to misfit strain accommodation in Ge/Si heterostructures (mismatch 4%) grown in the two-dimensional mode. Special emphasis is placed on the conditions leading to a two-dimensional (layer-by-layer) growth mode. We discuss general features of a dislocation tangle resulted from glide-limited plastic relaxation, typical for highly mismatched (001)-diamond and zinc-blende heterostructures. The evolution of the dislocation network as a function of film thickness and thermal annealing is controlled by growth instabilities and dislocation interactions. The observed correlation in distribution of parallel misfit dislocations including pairing (at <2 nm) of misfit segments from intersecting glide planes and rearrangements in a nonequilibrium dislocation network driven by elastic interaction between 60° dislocation segments in the almost relaxed heterostructures are discussed in detail. Pairing of the 60° glide dislocations results either in their combination to form pure edge 90° dislocations or in the dissociation into partials. We propose and experimentally verify a model for the latter process involving the formation of extrinsic stacking faults in the heterolayers under compressive strain.

In situ TEM measurements of the electrical properties of interface dislocations

1992 ◽  
Vol 50 (2) ◽  
pp. 1338-1339
Author(s):  
F. M. Ross ◽  
R. Hull ◽  
D. Bahnck ◽  
J. C. Bean ◽  
L. J. Peticolas ◽  
...  
Keyword(s):  
Electrical Properties ◽  
Electronic Device ◽  
In Situ Tem ◽  
Device Performance ◽  
Misfit Dislocations ◽  
Electrical Characteristics ◽  
Strained Layer ◽  
Transmission Electron ◽  
Interfacial Dislocations

We describe an investigation of the electrical properties of interfacial dislocations in strained layer heterostructures. We have been measuring both the structural and electrical characteristics of strained layer p-n junction diodes simultaneously in a transmission electron microscope, enabling us to correlate changes in the electrical characteristics of a device with the formation of dislocations.The presence of dislocations within an electronic device is known to degrade the device performance. This degradation is of increasing significance in the design and processing of novel strained layer devices which may require layer thicknesses above the critical thickness (hc), where it is energetically favourable for the layers to relax by the formation of misfit dislocations at the strained interfaces. In order to quantify how device performance is affected when relaxation occurs we have therefore been investigating the electrical properties of dislocations at the p-n junction in Si/GeSi diodes.

Mechanisms of misfit strain relaxation in epitaxially grown BLT (Bi4-xLaxTi3O12, x = 0.75) thin films

2003 ◽  
Vol 779 ◽  
Author(s):  
Hyung Seok Kim ◽  
Sang Ho Oh ◽  
Ju Hyung Suh ◽  
Chan Gyung Park
Keyword(s):  
Electron Microscopy ◽  
Thin Films ◽  
Transmission Electron Microscopy ◽  
Strain Relaxation ◽  
Lattice Misfit ◽  
Misfit Strain ◽  
Misfit Dislocations ◽  
Transmission Electron ◽  
Means Of Transmission ◽  
20 Nm

AbstractMechanisms of misfit strain relaxation in epitaxially grown Bi4-xLaxTi3O12 (BLT) thin films deposited on SrTiO3 (STO) and LaAlO3 (LAO) substrates have been investigated by means of transmission electron microscopy (TEM). The misfit strain of 20 nm thick BLT films grown on STO substrate was relaxed by forming misfit dislocations at the interface. However, cracks were observed in 100 nm thick BLT films grown on the same STO. It was confirmed that cracks were formed because of high misfit strain accumulated with increasing the thickness of BLT, that was not sufficiently relaxed by misfit dislocations. In the case of the BLT film grown on LAO substrate, the magnitude of lattice misfit between BLT and LAO was very small (~1/10) in comparison with the case of the BLT grown on STO. The relatively small misfit strain formed in layered structure of the BLT films on LAO, therefore, was easily relaxed by distorting the film, rather than forming misfit dislocations or cracks, resulting in misorientation regions in the BLT film.

Metal-Organic chemical vapor deposition of BN on sapphire and its heterostructures with 2D and 3D materials

MRS Advances ◽  
2016 ◽  
Vol 1 (32) ◽  
pp. 2273-2283
Author(s):  
Qing Paduano ◽  
Michael Snure
Keyword(s):  
Electron Mobility ◽  
Substrate Surface ◽  
Chemical Vapor ◽  
High Electron Mobility Transistor ◽  
Layer Growth ◽  
Organic Chemical ◽  
Layer By Layer ◽  
High Electron ◽  
Two Dimensional ◽  
Direct Growth

ABSTRACTWe studied MOCVD processing for direct growth of BN on 2” sapphire substrates as a template for heterostructures with two dimensional (2D) and three dimensional (3D) materials. The combined experimental evidence points to three growth modes for BN: self-terminating, 3D random, and layer-by-layer, all of which are dependent on V/III ratio, temperature, pressure, and substrate surface modification via nitridation. At moderate temperature (950-1050°C), BN growth using high V/III ratio is self-terminating, resulting in c-oriented films aligned in-plane with respect to the orientation of the sapphire substrate. BN films grown under low V/III ratios are 3D, randomly oriented, and nano-crystalline. At higher temperature (1100°C), self-terminating growth transitions to a continuous layer-by-layer growth mode. When BN growth is self-terminating, films exhibit atomically smooth surface morphology and highly uniform thickness over a 2” sapphire wafer. Using these BN/sapphire templates we studied the growth of 2D and 2D/3D heterostructures. To study direct growth of 2D on 2D layered material we deposited graphene on BN in a continued process within the same MOCVD system. Furthermore, we explore the growth and nucleation of 3D materials (GaN and AlN) on BN. AlGaN/GaN based high electron mobility transistor (HEMT) structures grown on BN/sapphire exhibited two-dimensional electron gas characteristics at the AlGaN/GaN heterointerface, with room-temperature electron mobility and sheet electron density about 1900cm2/Vs and 1x1013cm-2, respectively.

Rheed Intensity Oscillation During Layer-by-Layer Growth of Bi-Sr-Ca-Cu-O Thin Films

1992 ◽  
Vol 275 ◽  
Author(s):  
K. Yoshikawa ◽  
N. Sasaki
Keyword(s):  
Thin Films ◽  
Buffer Layer ◽  
High Energy ◽  
Layer Growth ◽  
Layer By Layer ◽  
Two Dimensional ◽  
Growth Interruption ◽  
Layer Deposition ◽  
Unit Cells ◽  
Layered Growth

ABSTRACTUsing in-situ reflection high-energy electron diffraction (RHEED), we studied the growth of Bi-Sr-Ca-Cu-O (BSCCO) thin films prepared by reactive evaporation using layer-by-layer deposition. Bi2Sr2CaCu2Ox(2212) tends to be grown three-dimensionally if it is grown directly on (100) SrTiO3, in contrast to Bi2Sr2CuOx(2201) which is easily grown two-dimensionally on SrTiO3. Two-dimensional 2212 growth can be realized, if a buffer layer of 2201 is deposited on (100) SrTiO3 and growth interruption is utilized after SrO layer deposition. A buffer layer of only two 2201 unit cells improved the surface crystallinity of the substrate for the epitaxial growth of 2212. Growth interruption for two minutes after the 2nd SrO layer in the half unit cell is necessary to keep two-dimensional layered growth. The resulting Tc (zero) is 76 K and Jc (at 4.2 K) is 1.5 × 106 (A/cm2) with these epitaxial films.

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.

Defect Generation And Evolution In The Hydrothermal Growth Of Epitaxial BaTiO3 Thin Films

1997 ◽  
Vol 474 ◽  
Author(s):  
L. Zhao ◽  
A. T. Chien ◽  
F. F. Lange ◽  
J. S. Speck
Keyword(s):  
Thin Films ◽  
Cross Section ◽  
Interfacial Layer ◽  
Dislocation Network ◽  
Misfit Dislocations ◽  
Plan View ◽  
Transmission Electron ◽  
Defects Analysis ◽  
Film Substrate ◽  
Growth Evolution

ABSTRACTThe structure of epitaxial BaTiO3 thin films prepared by hydrothermal synthesis on (001) SrTiO3 substrates was studied by transmission electron microscopy (TEM). The growth evolution was followed from initial island formation, through island impingement and fusion. Plan view and cross-section imaging demonstrated that the films grew by an unusual islanding mechanism. Electron diffraction showed the islands and the fully formed film are single crystal with mosaic character and in all cases strain relaxed. Cross-section TEM of the early growth films showed a several monolayer thick interfacial layer and the film/substrate region had no misfit dislocations. In the fully formed films, this interfacial layer was not observed, however a clear misfit dislocation network was observed. Defects analysis shows that the misfit dislocations have pure edge character with <100> Une directions, and <010> Burgers vectors (parallel to the film/substrate interface).

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.

Relationship Between Crystal Defects, Ge Outdiffusion and V/III Ratio in MOVPE Grown (001) GaAs/Ge

1993 ◽  
Vol 319 ◽  
Author(s):  
C. Frigeri ◽  
G. Atrolini ◽  
C. Pelosi ◽  
F. Longo
Keyword(s):  
Stacking Faults ◽  
Layer Growth ◽  
Crystal Defects ◽  
Misfit Dislocations ◽  
Layer By Layer ◽  
Island Growth ◽  
Planar Defects ◽  
Fault Density ◽  
Unintentional Doping ◽  
Enhanced Mobility

AbstractTwo regimes of defect generation have been found in MOVPE GaAs/Ge layers upon changing the V/III ratio between 1.3 and 11.8. For low V/III ratio the layers contained misfit dislocations along with stacking faults that had been generated by dissociation of the misfit dislocations. The stacking fault density increased with decreasing V/III ratio. This might be explained by an enhanced mobility of the dissociated partials due the reduced unintentional doping of the layer caused by reduced Ge outdiffusion from the substrate when V/III is small. The secon regime corresponds to high V/III ratios and is characterized by the absence of misfit dislocations and the presence of a high density of planar defects. This means that breakdown of the 2D layer-by-layer growth occurred and 3D island growth prevailed.

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