Advanced Epitaxial Lift‐Off and Transfer Procedure for the Fabrication of High‐Quality Functional Oxide Membranes

Abstract

In the past 5 years, the transfer of epitaxial oxide thin films has drawn a renewed interest in the scientific community. The major challenge in this technology is to minimize the appearance of extended bulk defects such as plastic deformations, cracks, and delamination, which are induced by the transfer process to a new host substrate. In this work, a procedure for the transfer of epitaxial oxide films where a rigid bond to the final host holder is obtained via a metallic Au/Ag bonding layer is presented. Here, the transfer of SrRuO3 (SRO) and SrRuO3/SrTiO3 (STO) epitaxial films grown on a water‐soluble Sr3Al2O6 sacrificial layer is reported. These epitaxial films are grown on a STO substrate and transferred onto a Si host substrate. Roughness values lower than 1nm are observed for the transferred SRO membranes. Cross‐section analysis shows straight interfaces without plastic deformation of the membranes. X‐ray diffraction rocking‐curve analysis evidences that mechanical damage is minimized and the membranes remain close to their initial quality. This procedure represents an important step forward in the development of advanced technologies for membrane transfer of epitaxial oxides and superstructures.

Optimization of Bulk Heterojunction Organic Photovoltaics

“…the blend components, and thus the greater degree of crystallization, present when the film is annealed at the higher temperature [59]. Another advantage of thermal annealing is the decreasing of moisture within OPVs, ultimately preventing active layer oxidation, with higher temperatures increasing water evaporation from the polymer structure [60,61]. Generally, P3HT:PCBM device performance is improved by thermal annealing if this step is done either before or after the deposition of Al/Ca electrode [19].…”

On the Role of the Sr3−xCaxAl2O6 Sacrificial Layer Composition in Epitaxial La0.7Sr0.3MnO3 Membranes

“…[37] Nevertheless, there are other factors that could be investigated to further reduce the crack density of the released membranes, including the sacrificial layer and membrane thicknesses, [20] the use of additional capping layers [36,64] and modify the lift-off procedure. [35,66] Indeed, the exfoliation process is one of the most critical steps in the preparation of membranes. [67] Additional membrane analysis was performed on the LSMO obtained from SC 2 AO which showed the best compromise between crystallinity, electrical performance (T MI =310 K), moderate crack density, and can be released faster than from CAO.…”

“…[20] It is worth noting that the detachment of a faultless membrane, regardless of the nature of the sacrificial layer, remains a key challenge in the preparation of freestanding films. [35,36] A simple way to modify the properties of SAO is to engineer the metal-oxygen bond through cation substitution. The higher the M 2 + electronegativity (Ca 2 + > Sr 2 + > Ba 2 + ), the lower its bonding ionicity with the nonbridging oxygens of the structure, and thus it is more difficult to hydrolyze.…”

A review on recent advances in fabricating freestanding single-crystalline complex-oxide membranes and its applications

“…Water soluble layers are good candidates for sacrificial layers due to its sustainability, reliability, and nonaggressive etching (figure 2(a)). Sr 3 Al 2 O 6 (SAO) [21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36] is a complex-oxide that has been widely used as a watersoluble sacrificial layer for several reasons. First and foremost, it is readily dissolved in water.…”