Equilibrium Domain Structures of Epitaxial Perovskite Ferroelectric Films

1997 ◽  
Vol 474 ◽  
Author(s):  
S. Pamir Alpay ◽  
Alexander L. Roytburd
Keyword(s):  
Misfit Dislocation ◽  
Growth Temperature ◽  
Ferroelectric Phase ◽  
Misfit Strain ◽  
Ferroelectric Films ◽  
Dislocation Generation ◽  
Elastic Interactions ◽  
Domain Structures ◽  
Domain Selection ◽  
Domain Stability

ABSTRACTPossible equilibrium domain structures due to elastic interactions between the film and the substrate as a result of a cubic-tetragonal transformation observed in epitaxial perovskite ferroelectric films are analyzed. The formation of both two- and three-domain states is taken into account. A stability map which shows domain stability regions as a function of temperature is developed in coordinates of misfit strain and tetragonality of the lattice of the ferroelectric phase. Misfit dislocation generation at the growth temperature is found to have a profound effect on domain selection. As an example a PbTiO3(001) film grown on a MgO(001) substrate is considered and theoretical findings are compared with experimental results in the literature.

scholarly journals Mobile and immobile boundaries in ferroelectric films

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
P. Yudin ◽  
K. Shapovalov ◽  
T. Sluka ◽  
J. Peräntie ◽  
H. Jantunen ◽  
...  
Keyword(s):  
Long Range ◽  
Domain Walls ◽  
Ferroelectric Properties ◽  
Practical Importance ◽  
Dynamic Responses ◽  
Ferroelectric Films ◽  
Domain Structures ◽  
Mobile Interfaces ◽  
Ferroelastic Domains ◽  
Viable Method

AbstractThe intrinsic mobile interfaces in ferroelectrics—the domain walls can drive and enhance diverse ferroelectric properties, essential for modern applications. Control over the motion of domain walls is of high practical importance. Here we analyse theoretically and show experimentally epitaxial ferroelectric films, where mobile domain walls coexist and interact with immobile growth-induced interfaces—columnar boundaries. Whereas these boundaries do not disturb the long-range crystal order, they affect the behaviour of domain walls in a peculiar selective manner. The columnar boundaries substantially modify the behaviour of non-ferroelastic domains walls, but have negligible impact on the ferroelastic ones. The results suggest that introduction of immobile boundaries into ferroelectric films is a viable method to modify domain structures and dynamic responses at nano-scale that may serve to functionalization of a broader range of ferroelectric films where columnar boundaries naturally appear as a result of the 3D growth.

Development of Cross-Hatch Morphology During Growth of Lattice Mismatched Layers

2001 ◽  
Vol 673 ◽  
Author(s):  
A. Maxwell Andrews ◽  
J.S. Speck ◽  
A.E. Romanov ◽  
M. Bobeth ◽  
W. Pompe
Keyword(s):  
Misfit Dislocation ◽  
Film Growth ◽  
Strain Relaxation ◽  
Dislocation Generation ◽  
Force Microscopy ◽  
Step Flow ◽  
Atomic Force ◽  
Subsequent Step ◽  
Step Flow Growth ◽  
Lateral Scale

ABSTRACTAn approach is developed for understanding the cross-hatch morphology in lattice mismatched heteroepitaxial film growth. It is demonstrated that both strain relaxation associated with misfit dislocation formation and subsequent step elimination (e.g. by step-flow growth) are responsible for the appearance of nanoscopic surface height undulations (0.1-10 nm) on a mesoscopic (∼100 nm) lateral scale. The results of Monte Carlo simulations for dislocation- assisted strain relaxation and subsequent film growth predict the development of cross-hatch patterns with a characteristic surface undulation magnitude ∼50 Å in an approximately 70% strain relaxed In0.25Ga0.75As layers. The model is supported by atomic force microscopy (AFM) observations of cross-hatch morphology in the same composition samples grown well beyond the critical thickness for misfit dislocation generation.

Heteroepitaxial Layer Morphology and Misfit Defect Formation

1995 ◽  
Vol 399 ◽  
Author(s):  
A.G. Cullis
Keyword(s):  
Free Energy ◽  
Misfit Dislocation ◽  
Defect Formation ◽  
Elastic Stress ◽  
Stress Relief ◽  
Misfit Strain ◽  
Theoretical Modelling ◽  
Initial Growth ◽  
Dislocation Source ◽  
Heteroepitaxial Layers

ABSTRACTThe manner in which misfit strain can influence the morphology of heteroepitaxial layers is reviewed. Following a brief consideration of theoretical modelling, examples of experimental observations for two important materials systems, SiGe/Si and InGaAs/GaAs, are given. It is demonstrated that the formation of undulations of specific types is driven by partial elastic stress-relief and a lowering of the system free energy. Under these conditions, islands of deposit can be formed during initial growth and ripples can be produced upon continuous layers. Furthermore, the presence of surface morphological distortions and the accompanying strain fluctuations also can have a significant impact upon misfit dislocation introduction. Relationships between these fluctuations and dislocation source behaviour are described.

Nanoscale Heterogeneity in Functional Materials

MRS Bulletin ◽  
2009 ◽  
Vol 34 (11) ◽  
pp. 822-831 ◽  
Author(s):  
Turab Lookman ◽  
Peter Littlewood
Keyword(s):  
Phase Transition ◽  
Shape Memory Alloys ◽  
Physical Properties ◽  
Shape Memory ◽  
Functional Materials ◽  
Single Domain ◽  
Elastic Interactions ◽  
Domain Structures ◽  
Parent State

AbstractThe physical properties that make “functional” materials worthy of their moniker frequently arise because of a phase transition that establishes a new kind of order as the material is cooled from a parent state. Such ordered states include ferroelectrics, ferromagnets, and structurally ordered martensites; because these states all break an orientational symmetry, and it is rare that one can produce the conditions for single domain crystallinity, the observed configuration is generally heterogeneous. However, the conditions under which domain structures form are highly constrained, especially by elastic interactions within a solid; consequently, the observed structures are far from fully random, even if disorder is present. Often the structure of the heterogeneity is important to the function, as in shape-memory alloys. Increasingly, we are surprised to discover new phases inside solids that are themselves a heterogeneous modulation of their parents.

Rapid Thermal Processing of Buried Sil−xGex Strained Layers; Photoluminescence Decay and Misfit Dislocation Generation.

1990 ◽  
Vol 198 ◽  
Author(s):  
D.C. Houghton ◽  
N.L. Rowell
Keyword(s):  
Quantum Wells ◽  
Misfit Dislocation ◽  
Thermal Processing ◽  
Internal Quantum Efficiency ◽  
Dislocation Nucleation ◽  
Multiple Quantum ◽  
Misfit Dislocations ◽  
Dislocation Generation ◽  
Strained Layers ◽  
Wide Range

ABSTRACTThe thermal constraints for device processing imposed by strain relaxation have been determined for a wide range of Si-Ge strained heterostructures. Misfit dislocation densities and glide velocities in uncapped Sil-xGex alloy layers, Sil-xGex single and multiple quantum wells have been measured using defect etching and TEM for a range of anneal temperatures (450°C-1000°C) and anneal times (5s-2000s). The decay of an intense photoluminescence peak (∼ 10% internal quantum efficiency ) from buried Si1-xGex strained layers has been correlated with the generation of misfit dislocations in adjacent Sil-xGex /Si interfaces. The misfit dislocation nucleation rate and glide velocity for all geometries and alloy compositions (0<x<0.25) were found to be thermally activated processes with activation energies of (2.5±0.2)eV and (2.3-0.65x)eV, respectively. The time-temperature regime available for thermal processing is mapped out as a function of dislocation density using a new kinetic model.

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