Atomistic simulation of hillock growth

Frolov, Timofey; Boettinger, William J.

doi:10.1016/j.actamat.2010.06.023

Cited by 20 publications

(13 citation statements)

References 20 publications

(25 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In the case of strained layers, the shape instability leads either to equilibrium-shaped hole or to equilibrium shaped hillock formation [22][23][24] depending on the competing relaxation mechanism. While the formation of hillocks as a consequence of stress relaxation is observed for various thin film materials 14,19,23,[25][26][27][28] , the formation of equilibrium shaped holes has been affirmed recently both experimentally and by kinetic Monte Carlo simulations 6 . However, the nature and transition between these two competing instability mechanisms is far from being fully understood.…”

Section: Introductionmentioning

confidence: 99%

“…Their stability has been subjected to research under several aspects: thermodynamics and kinetics [1][2][3] , mass transport via surface diffusion 1,4,5 , impact of surface energy anisotropies [6][7][8][9] , fingering instabilities 7,10,11 , Ostwald ripening of islands 12 , hole pattern 13 and hillock formation [14][15][16][17][18][19] .Most of the fundamental theoretical work has been carried out by Srolovitz and Safran who developed a complete stability theory for thin films covering kinetics 20 and energetics 21 . In the case of strained layers, the shape instability leads either to equilibrium-shaped hole or to equilibrium shaped hillock formation [22][23][24] depending on the competing relaxation mechanism.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Hillock formation of Pt thin films on single-crystal yttria-stabilized zirconia

et al. 2012

View full text Add to dashboard Cite

The stability of a metal thin films on a dielectric substrate is conditioned by the magnitude of the interactive forces at the interface. In the case of a non-reactive interface and weak adhesion, the minimization of free surface energy gives rise to an instability of the thin film. In order to study these effects, Pt thin films with a thickness of 50 nm were deposited via ion-beam sputtering on yttria stabilized zirconia single crystals. All Pt films were subjected to heat treatments up to 973 K for 2 h. The morphological evolution of Pt thin films has been investigated by means of scanning electron microscopy (SEM), atomic force microscopy (AFM) and standard image analysis techniques. Three main observations have been made: i) the deposition method has a direct impact on the morphological evolution of the film during annealing. Instead of hole formation, that is typically observed as response to a thermal treatment, anisotropic pyramidal shaped hillocks are formed on top of the film. ii) It is shown by comparing the hillocks' aspect ratio with finite element method (FEM) simulations that the hillock formation can be assigned to a stress relaxation process inside the thin film. iii) By measuring the equilibrium shapes and the shape fluctuations of the formed Pt hillocks the anisotropy of the step free energy and its stiffness have been derived in addition to the anisotropic kink energy of the hillock's edges.

show abstract

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Hillock formation of Pt thin films on single-crystal yttria-stabilized zirconia

et al. 2012

View full text Add to dashboard Cite

show abstract

“…Diusion of ad-atoms into GBs can lead to formation of compressive stress during deposition of metal lms, 12,15 while in turn stress may drive out-diusion via GBs 12 or cause GB migration. 13,16,17 In contrast to pure metal lms, in compound semiconductor lms, stress may form due to compositiondependent lattice parameters. In the case of Cupoor CIGSe, the lattice expands with increasing Cu concentration.…”

mentioning

confidence: 99%

“…Reduction of grain boundary (GB) energies or defect densities were proposed as possible driving forces for grain growth; 79 however, no attention has so far been paid to the potential role of stress energy for the microstructural changes. In other thin lm materials evolution of intrinsic stress and their interplay with grain growth has been studied intensely both experimentally 1214 and theoretically, 15,16 due to its importance for the mechanical stability of thin lms. Diusion of ad-atoms into GBs can lead to formation of compressive stress during deposition of metal lms, 12,15 while in turn stress may drive out-diusion via GBs 12 or cause GB migration.…”

mentioning

confidence: 99%

Sudden stress relaxation in compound semiconductor thin films triggered by secondary phase segregation

et al. 2015

View full text Add to dashboard Cite

In polycrystalline compound semiconductor thin lms, structural defects such as grain boundaries as well as lateral stress can form during lm growth, which may deteriorate their electronic performance and mechanical stability. In Cu-based chalcogenide semiconductors such as Cu(In, Ga)Se2 or Cu2ZnSn(S, Se)4, temporary Cu excess during lm growth leads to improved microstructure such as a reduced grain boundary density, a strategy that has been used for decades for high-eciency chalcopyrite thin lm solar cells. However, the mechanisms responsible for the benecial eect of Cu-excess are yet not fully claried. Here, we investigate the evolution of lateral stress, grain growth and Cu-Se segregation during Cu-Se deposition onto Cu-poor CuInSe2. Real-time x-ray diraction and uorescence analysis with a double-detector setup reveals that sudden stress relaxation occurs shortly prior to Cu-Se segregation at the surface and precisely coincides with domain growth and change of texture. Numerical reaction-diusion modeling provides an explanation for the observed delay of Cu-Se segregation. Our results show that partial recrystallization of the lm can be already reached without the necessity of an overall Cu-rich lm composition and thus suggest a new synthesis route for the fabrication of high-quality chalcopyrite absorber lms.Co-evaporation of Cu(In, Ga)Se 2 (CIGSe) lms -used as absorber layer in thin lm solar cells with world record energy conversion eciencies 1,2 -features a puzzling peculiarity: For the nal lm, a Cu-poor composi-is required to obtain highest eciencies; however, during deposition, the lm composition is changed from an initially Cu-poor composition to an intermediate Cu-rich composition and nally changed back to a Cu-poor composition. The composition modications during lm deposition are realized by varying the Cu and In+Ga evaporation uxes. Two crucial ndings point out the importance of the Cu-poor → Cu-rich transition: First, highest eciencies are only achieved if an intermediate Cu-rich lm composition was reached during lm deposition. 3 Second, a three-stage process with a Cu-poor → Cu-rich → Cu-poor sequence leads to higher eciencies than a two-stage process with only a Cu-rich → Cu-poor sequence. 46 Thus, it seems that the key challenge in understanding the success of the three-stage process over the two stage-process is -besides the adjustment of an ideal Ga gradient -the identication of the reactions and their driving forces acting during the Cu-poor → Cu-rich transition.While the eect of the Cu-poor → Cu-rich transition on structural and morphological changes in CIGSe lms such as grain growth 710 as well as on electronic properties of the material 3,11 has been thoroughly investigated in the past decade, the physical mechanisms and driving forces of these changes are not fully understood. Reduction of grain boundary (GB) energies or defect densities were proposed as possible driving forces for grain growth; 79 however, no attention has so far been paid to the potential role of stress energy for the mic...

show abstract

“…The formation of large facetted crystals during grain growth and dewetting of thin films during hydrogenation of Mg also suggests the importance of stress-induced coarsening to thin-film stability in the presence of a phase change. 106 Research on modeling and measuring stress generation and relaxation in thin films by competing processes during thin-film formation, 115 thermal cycling, 116 applied stresses, 107,117 or isothermal stress generation processes, such as intermetallic formation during room-temperature annealing of Sn films on Cu, [118][119][120][121] is revealing the role of microstructural heterogeneity and crystalline anisotropy on the response of different thin films to stress. Further progress will require a more detailed understanding of how grain boundaries and interfaces migrate and respond to applied stresses, the mechanisms and conditions for coupling stress and grain boundary motion, and the ability of grain boundaries and surfaces to act as vacancy sources and sinks for diffusional creep.…”

Section: Functionality and Control Of Materials Far From Equilibriummentioning

confidence: 99%

Emerging Science and Research Opportunities for Metals and Metallic Nanostructures

Handwerker

Pollock

2014

JOM

View full text Add to dashboard Cite

During the next decade, fundamental research on metals and metallic nanostructures (MMNs) has the potential to continue transforming metals science into innovative materials, devices, and systems. A workshop to identify emerging and potentially transformative research areas in MMNs was held June 13 and 14, 2012, at the University of California Santa Barbara. There were 47 attendees at the workshop (listed in the Acknowledgements section), representing a broad range of academic institutions, industry, and government laboratories. The metals and metallic nanostructures (MMNs) workshop aimed to identify significant research trends, scientific fundamentals, and recent breakthroughs that can enable new or enhanced MMN performance, either alone or in a more complex materials system, for a wide range of applications. Additionally, the role that MMN research can play in high-priority research and development (R&D) areas such as the U.S. Materials Genome Initiative, the National Nanotechnology Initiative, the Advanced Manufacturing Initiative, and other similar initiatives that exist internationally was assessed. The workshop also addressed critical issues related to materials research instrumentation and the cyberinfrastructure for materials science research and education, as well as science, technology, engineering, and mathematics (STEM) workforce development, with emphasis on the United States but with an appreciation that similar challenges and opportunities for the materials community exist internationally. A central theme of the workshop was that research in MMNs has provided and will continue to provide societal benefits through the integration of experiment, theory, and simulation to link atomistic, nanoscale, microscale, and mesoscale phenomena across time scales for an ever-widening range of applications. Within this overarching theme, the workshop participants identified emerging research opportunities that are categorized and described in more detail in the following sections in terms of the following: three-dimensional (3-D) and fourdimensional (4-D) materials science. Structure evolution and the challenge of heterogeneous and multicomponent systems. The science base for property prediction across the length scales. Nanoscale phenomena at surfaces-experiment, theory, and simulation. Prediction and control of the morphology, microstructure, and properties of ''bulk'' nanostructured metals. Functionality and control of materials far from equilibrium. Hybrid and multifunctional materials assemblies. Materials discovery and design: enhancing the theory-simulation-experiment loop. Following an introduction, these emerging research opportunities are discussed in detail, along with challenges and opportunities for the materials community in the areas of instrumentation, cyberinfrastructure, education, and workforce development.

show abstract

Atomistic simulation of hillock growth

Cited by 20 publications

References 20 publications

Hillock formation of Pt thin films on single-crystal yttria-stabilized zirconia

Hillock formation of Pt thin films on single-crystal yttria-stabilized zirconia

Sudden stress relaxation in compound semiconductor thin films triggered by secondary phase segregation

Emerging Science and Research Opportunities for Metals and Metallic Nanostructures

Contact Info

Product

Resources

About