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Biosensing Applications of Digital Photocorrosion in GaAs/AlGaAs Nano-Heterostructures

Date : Wednesday, June 14th, 2017 4:00 pm 〜 Place : Seminar Room 5 (A615), 6th Floor, ISSP Lecturer : Prof. Jan J. Dubowski Affiliation : Interdisciplinary Institute for Technological Innovation (3IT), Université de Sherbrooke Committee Chair : Shojiro Takeyama (ext: 65316)
e-mail: takeyama@issp.u-tokyo.ac.jp

Etching of semiconducting materials at rates approaching atomic level resolution is of high interest to the advancement of technologies addressing fabrication of low-dimensional devices, tunability of their optoelectronic properties and precise control of device surface structure. The so-called digital etching that takes advantage of a self-limiting reaction has the potential to address some of these challenges. However, conventional applications of this approach proposed almost 30 years ago, require specialized and expensive equipment, which contributed to a relatively slow progress in penetration of digital etching to micro/nanofabrication processing schemes. We have observed that for photoluminescence (PL) emitting materials with negligible dark corrosion, it is possible to carry out PLmonitored photocorrosion in cycles analogous to those employed in digital etching. The advantage of this approach is that photocorrosion of materials, such as GaAs/AlGaAs heterostructures, could be carried in a water environment. This digital photocorrosion (DIP) process could be carried out in cycles, each approaching sub-monolayer precision. I will discuss fundamentals of DIP and, in particular, mechanisms responsible for achieving high-resolution etch rates of semiconducting materials. For instance, we have demonstrated a successful dissolution of a 1-nm thick layer of GaAs embedded between Al0.35Ga0.65As barriers in a 28% NH4OH:H2O, and we claimed that under optimized conditions a further enhanced resolution is feasible. The nm-scale depth resolution achieved with DIP and lowcost of the instrumentation required by this process is of a potential interest to specialized diagnostics, structural analysis of multilayer nanostructures and, e.g., revealing in situ selected interfaces required for the fabrication of advanced nano-architectures.  We have explored the sensitivity of DIP to perturbations induced by electrically charged molecules, such as bacteria, immobilized on semiconductor surfaces. Here, I will highlight our recent studies on detection of Escherichia coli and Legionella pneumophila bacteria immobilized on antibody functionalized GaAs/AlGaAs biochips. I will also discuss the application of this approach for studying antibiotic reactions of bacteria growing on biofunctionalized surfaces of GaAs/AlGaAs biochips.


(Published on: Wednesday May 31st, 2017)