Nanomechanical characterization of cavity growth and rupture in hydrogen-implanted single-crystal BaTiO3

Abstract

A thermodynamic model of cavity nucleation and growth in ion-implanted single-crystal BaTiO 3 layer is proposed, and cavity formation is related to the measured mechanical properties to better understand hydrogen implantation-induced layer transfer processes for ferroelectric thin films. The critical radius for cavity nucleation was determined experimentally from blistering experiments performed under isochronal anneal conditions and was calculated using continuum mechanical models for deformation and fracture, together with thermodynamic models. Based on thermodynamic modeling, we suggest that cavities grow toward the cracking criteria at a critical blister size whereupon gas is emitted from ruptured cavities. The main driving force for layer splitting is the reduction of the overall elastic energy stored in the implanted region during the cavity nucleation and growth as the gaseous H 2 entrapped within the cavities is released. Nanoindentation measurements reveal locally the mechanical property changes within the vicinity of a single cavity. Using the measured mechanical properties at the single-cavity level, we developed three-dimensional strain and stress profiles using finite element method.

Coarsening model of cavity nucleation and thin film delamination from single-crystalBaTiO3with proton implantation

“…2 and from AFM/nanoindentation characterization, the thickness ͑h͒ of the delaminating layer is 0.50 m, and the interdistance ͑D͒ of bubbles is found to be 16 m. The initial diameter ͑b͒ of blisters is 4.0 m. The material properties are assumed to be linear elastic, with Young's modulus for the layers taken to be 120.0 GPa, and Poisson's ratio ͑͒ is assumed to be 0.3. 17 Three-dimensional 8-node brick elements are adopted for the both top and bottom layers for FEM simulation. All the nodes at the bottom layer representing the donor wafer are held at fixed positions.…”

“…At the bottom of the BaTiO 3 donor substrate layer, pressure increasing linearly in time is imposed up to a maximum of 200 MPa, as calculated using bubble geometry. 17 As the internal pressure of a cavity increases, both cavity growth and debonding at the interface occur. As shown in Fig.…”

“…We additionally found a critical cavity size based on thermodynamic considerations and studied cavity growth and exfoliation by atomic force microscopy and nanoindentation techniques. 17 In this paper, we have simulated the cavity growth and layer splitting phenomena using a finite element method ͑FEM͒ in conjunction with a unique force equilibrium criterion model. Samples were prepared for this study by H + ion implantation into a bulk single crystal BaTiO 3 donor substrate ͑double side polished, ͑001͒-orientation 10 mmϫ 10 mm ϫ 1 mm͒.…”

“…Nanomechanical characterization of annealed BaTiO 3 samples was performed using a nanoindentation system in conjunction with an AFM. 17 Finite element method ͑FEM͒ simulation was performed with a commercially available code ͑LS-dyna͒.…”

Single crystalline BaTiO3 thin films synthesized using ion implantation induced layer transfer

“…In previous work, the authors showed that the layer splitting mechanism induced a change in the hardness and Young's modulus of the implanted BaTiO 3 donor wafer. 28 This can be explained by an increase in strain near the bubble region during the layer exfoliation process. After postbond annealing, the micro-Raman curve is almost identical to the unprocessed, single crystal BaTiO 3 .…”