Nirupam Banerjee

Ph.D. thesis

Thesis title:

Epitaxial perovskite oxide devices fabricated by lift-off technology

[thesis in pdf format]




Prof. dr. ing. A.J.H.M. Rijnders

Date defense:



Perovskite oxides are a fascinating class of materials owing to their ability to display diverse functional properties while retaining similar crystal structures. In the past decades intense research efforts was focused on achieving novel/enhanced functionalities in perovskite films and interfaces, requiring also the development of new patterning technologies for structuring high quality hetero-interfaces and epitaxial multilayers. This thesis demonstrates the development of a novel lithographic technology, termed as "epitaxial lift-off patterning strategy", for in situ patterning of high temperature grown epitaxial complex perovskite oxide multilayers and detailed investigations of various lift-off fabricated functional devices.

Employing the epitaxial lift-off strategy, precise patterns of the conducting heterointerface between LaAlO3 and SrTiO3 (001) were successfully fabricated without using any physical ion etching step and preserving the high quality interfacial transport properties. It was also demonstrated that the lift-off pathway can precisely pattern even more complex interface systems such as SrCuO2-LAO-STO(001), containing high mobility carriers. In addition, the patterning process was modified and integrated with e-beam lithographic process, enabling fabrication of nano-scale devices to enable the future studies of low-dimensional confinement on high mobility interface conductivity as well as interfacial magnetism.

To demonstrate the versatility of the method, the thesis includes detailed discussion on the fabrication of all-oxide freestanding piezo-MEMS devices which are capable of functioning as very high sensitivity mass sensors. The fabrication is enabled by the lift-off pathway, facilitating a single step lift-off patterning of heteroepitaxial oxide multilayers. These freestanding epitaxial devices were studied in detail to characterize different intrinsic (material mediated) and extrinsic (from the operational medium) mechanisms causing vibrational damping, which were optimized to achieve a high quality factor of the electromechanical resonance leading to enhanced mass sensitivity. These results establish that the developed lift-off patterning strategy is a potential pathway to accomplish high performance micro and nano-devices incorporating delicate perovskite heterointerfaces and/or functional epitaxial perovskite multilayers.