Laser transfer of sol–gel ferroelectric thin films using an ITO release layer

Abstract

A new laser transfer process is reported which allows damage-free transfer of ferroelectric thin films from a growth substrate directly to a target substrate. The thin film ferroelectric material is deposited on a fused silica growth substrate with a sacrificial release layer of ITO (indium tin oxide). Regions of the film that are to be transferred are then selectively metallised, and bonded to the target substrate. Separation from the growth substrate is achieved by laser ablation of the ITO release layer by a single pulse from a KrF excimer laser, with the laser light being incident through the growth substrate. The residual ITO on the transferred ferroelectric layer is electrically conducting, and may be suitable for incorporation into the final device, depending on the application. The new process has been demonstrated for 500 nm-thick layers of sol-gel PZT which were thermosonically bonded to a silicon target substrate prior to laser release. The transferred films show ferroelectric behaviour and have a slightly reduced permittivity compared to the as-deposited material.

Laser induced extraplanar propulsion for three-dimensional microfabrication

“…1, proceeds as follows: after photolithographic definition of metallic rectangular structures, the substrate is inverted relative to the incident laser and positioned such that the rectangular laser beam is incident upon the substrate/ITO interface illuminating a portion of the feature. Bansal et al 9 recently demonstrated using ITO as a means for release, enabling a laser based bonding process. 1͒.…”

Innovative method to produce large-area freestanding functional ceramic foils

“…And since growing functional ceramics generally requires a minimal temperature around 500°C, it is preferable to integrate freestanding microscale foils on low-thermal stability printed circuits or polymers for flexible electronics, rather than growing them directly in-situ. Solutions such as thinning bulk functional ceramics [9], removing the growth substrate [10] or transferring the functional ceramic foil to a new carrier substrate [11,12] using respectively grinding, etching or a laser process, have been suggested. However, thinning functional bulk materials to less than 30 μm is long, tedious and very challenging as they are generally friable ceramics and the process results in subsurface damage [9].…”

“…Besides, there is the technical challenge to focus the beam of a very expensive-to-operate laser at the functional ceramic layer/glass growth substrate interface to transfer the functional layer to a new carrier without creating cracks in the ceramic film. Indeed, the high energy density produced by the laser and the difference between the αCTE of the functional film and the growth substrate, are likely to generate stresses and cause cracks [11,12].…”

Piezoelectric characterization of Pb(Zr,Ti)O3thin films deposited on metal foil substrates by dip coating

“…20,21) On the other hand, further applications in piezoelectric MEMS, for example, wearable devices for monitoring human motions and artificial muscles for robots, are limited owing to the high brittleness of Si. 22) To expand the application of piezoelectric devices, flexible piezoelectric materials and their fabrication methods, such as the piezoelectric polymer 23,24) and transfer methods of piezoelectric thin films, [25][26][27][28][29] have been investigated. Poly(vinylidene difluoride) (PVDF), which is a typical piezoelectric polymer, has been used as energy harvesters.…”