Aim of the course
Politecnico di Milano - P.zza L. da Vinci, 32 - 20133 Milano - Tel. +39.02.2399.1

Aim of the course


Since the mid-80', when Binning and Roher made possible to "see" the atoms piece by piece, it has become more and more common, often necessary, to study and to develop structures with nanometric dimensions. In disciplines like electronics, material science, functional chemistry, molecular biology and optoelectronics the approach "atom-by-atom" or "molecule-by-molecule" has made devices with nanometric dimensions affordable, with original functionalities and often with stunning performance. Accessing the physical/chemical properties of these devices has therefore become essential and various techniques and methods (electrical, optical, chemical, mechanical etc.) have been developed to accomplish this task.

This course focuses on the method and the instrumentation to perform the electrical characterisation of the matter . The investigation of the electrical properties of nanoscopic samples (carrier mobility, conductance, dielectric costant, charge density, impedance, charge trapping times, etc.) is not only essential when the samples are going to be used directly as a pure electronic device. Their knowledge is often beneficial also as a complementary information in conjunction with other techniques (spectroscopic, morphological, etc.) to address the primary chemical/physical properties of the matter at the nanoscale.

On a more practical basis, monitoring the electrical properties of nanobiosamples and tracking their variations upon interaction with external forces is a powerfull way to build electronic nanobiosensors . The counting of cells by detecting conductance variations, the tracking of neuronal cell differentiation by cathecolamine exocitosys monitoring through amperometric measurements or the "transparent" detection of light in silicon waveguides all demonstrate how electrical measurements, in all possible domains of science, have reached a high degree of sophistication. Not to mention how compact, flexible and cheap an electronic system can be when compared with other kind of measurement techniques.

The course aims to cover various aspects of electronic measurements, from the measurement techniques used to access the electrical properties of the nanoscopic systems to the specific circuits necessary to sense the tiny electric signals with the best possible resolution.

The course is thus intended for :
- nanobioscience scientists who desire to have a deeper insight into the realm of electrical measurements on nanosamples and of the ultimate performance that can be achieved with dedicated instumentation;
- electronic designers of circuits who desire to approach or to focus their realisations towards the vast and growing field of the instrumentation for the nano-bioscience;
- Ph-D students attracted by both fields who have not yet made up their minds, for them to continue to balance on both !

The program is structured to be a University-style course and not a collection of seminars. Topics are taken from the "basics" and developed untill examples of state-of-art realisations. A documentation will be provided at the beginning of each lesson. Time for discussions will be available at the end of each lesson.

In particular the course will focus on :

- How to use and possibly to design dedicated instrumentation for the measurement of currents, voltages, impedance and noise with the state-of-the-art sensitivity. The course will introduce the best commercial instrumentation and the best circuit architectures, the design considerations for maximum resolution and their achievable performance together with the specific aspects to be taken into account when integrating the full instrument on a single chip.

- How to perform impedance spectroscopy measurements with sub-attofarad resolution and nanoscale position resolution .
The course will introduce capacitance measurements tecniques and impedance spectroscopy applications, eventually coupled with Atomic Force Microscopes to complement the electrical information with a position information of nanometric precision.

- How to perform electrical measurements on biomolecules in-vitro in the presence of physiological saline solution. In particular how to make ohmic contacts (DC electrical access) to the liquid, how to use the electrolite as conformal conductive electrode and how to prevent DC conduction through metal-liquid interfaces (AC electrical access). .
The course will discuss how to manage the electrical signals extracted from neutral molecules via electrochemical measurements with 3 electrodes, the electronic circuits to interface electrodes whose size can be as small as few tens of nanometer square and various applications in the biological domain from olfactory receptors, to cathecolamine exocitosis, to cell counting, etc.

- How to use electronic noise as a signal to access the physical properties of matter at the nanoscale .
The course will recall the most advanced methods to measure very low noise levels, even lower than the input noise of standard instrumentation. It will then highlight, through examples, the tecniques of noise characterisation to extract physical quantities: from telegraph noise to electron spin, from shot noise to dielectric relaxation times, showing the importance of adeguate instrumentation like the correlation spectum analyzer.

At the end of the course, an attendance certificate will be provided.
PhD students may undergo, if desired, an examination to certify the acquisition of the fundamental aspects of the course and to collect the corresponding 5 credits.
Examination will consist of 20 questions on the subjects of the course, to be answered in two hours in a web-based platform. Examination date will be decided during the Course.

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