Part 1: ELECTRON AND SCANNING PROBE MICROSCOPIES

The course aims at providing a picture of the electronic probe microscopy techniques as general as possible, starting from the basics of the major techniques and examples of prototypical applications up to state of the art scientific cases. The main goal is to provide the student with the ability of assessing the feasibility and effectiveness of microscopic measurements to tackle a given problem. The couse will focus on the information that can be obtained (morphology, chemical contrast, short-and long-range structure, spectroscopy) and on the choice of the microscopic techniques that can be effectively employed to investigate a system in a given environment.

Part 2: MICRO AND NANOSTRUCTURE FABRICATION

The objective of the course is to introduce the student to the theory and technology of micro- and nano-fabrication, providing her/him with the essential knowledge on the basic and advanced processing techniques. In the first part different deposition techniques for the realization of films and heterostructures are presented, whereas the second part is focused on the realization of devices by conventional and advanced lithography. Applicative examples from different fields (electronics, spintronics, optics) are reported and discussed. The main goal is to provide the student with the ability to design a conventional process flow for the fabrication of simple electrical and magneto-electrical devices.

Part 1: ELECTRON AND SCANNING PROBE MICROSCOPIES

DdD1 - Knowledge and understanding

Upon passing the exam, the student knows the fundamentals of electron and scanning probe microscopies microscopy: she/he is able to draw the layout of a microscope and to comment its main assembly in terms of fundamental Physics (main phenomena and their order of magnitude).

DdD2 - Applying knowledge and understanding

Upon passing the exam, the student is able to select the most appropriate microscopical approach, within the range of techniques discussed, to address a standard problem in material microscopy and to discuss its advantages and disadvantages with respect to the other techniques.

DdD3 - Making judgements, Communication, Lifelong learning skills

Upon passing the exam, the student is able to read critically the scientific literature on microscopy: she/he is able to explain and discuss the techniques adopted by researchers and the evidences supporting their conclusions, eventually proposing a different approach to attain the same or and improved result.

Part 2: MICRO AND NANOSTRUCTURE FABRICATION

DdD1 - Knowledge and understanding

Upon passing the exam, the student:
- knows the principles of vacuum technologies
- knows the foundations of surface thermodynamics and epitaxy
- knows the basic physical vapor deposition (PVD) and chemical vapor deposition (CVD) techniques
- knows the basic lithography and etching techniques
- understands the difference between the main deposition techniques
- understands the difference between the main lithography techniques

DdD2 - Applying knowledge and understanding

Upon passing the exam, the student:
- is able to design a simple vacuum system
- is able to predict the growth dynamics of a film and an heterostructure
- is able to choose between different deposition techniques depending on the application
- is able to choose between different lithography techniques depending on the application

DdD3 - Making judgements, Communication, Lifelong learning skills

Upon passing the exam, the student:
- is able to design a conventional process flow for the fabrication of simple electrical and magneto-electrical devices

Part 1: ELECTRON AND SCANNING PROBE MICROSCOPIES

Topics

- Probes with high spatial resolution and state of the art in research and applications.

- Interaction of free electrons and bound electrons with matter.

- Information obtained by using electronic probes.

a) Far field electron microscopy

- Introduction to electron microscopy

- Diffraction limit and ray optics

- The scanning electron microscope (SEM)

  - Interaction between electron and matter

  - Secondary electron contrast

  - Depth of field

  - Charging and other imaging artifacts

  - Back-scattered electron contrast

  - Auger and X-ray Micro-spectroscopy probes in SEM

- The transmission electron microscope (TEM)

  - Sample preparation

  - Bright and dark field imaging

  - The mass-thickness contrast

  - Direct and reciprocal space imaging

  - The diffraction contrast

  - The phase contrast

- The scanning transmission electron microscope (STEM)

  - Electron energy loss spectroscopy in STEM

- The time resolution in Electron Microscopy

  - Real time acquisition

  - Ultrafast pump-probe acquisition

b) Scanning probe microscopies

- Introduction to scanning probe microscopy

- Elements of a scanning-probe microscope

- Tip-sample forces

- Static AFM operation: constant height and constant force- Shift in the natural frequency of a harmonic oscillator under a force gradient

- Amplitude-modulation dynamic AFM operation

- Dynamic AFM operation: sensitivity in amplitude modulation, frequency-modulation techniques

- Noise and resolution in AFM

- Image analysis in AFM

- Magnetic force microscopy

- Other magnetic microscopy techniques

- Imaging artifacts in scanning probe microscopy

- Scanning near-field optical microscopy

- Super-resolution fluorescence microscopy

- Introduction to scanning tunneling microscopy

- Bardeen approach (time-dependent perturbation theory) to the tunneling current

- WKB approximation for the evaluation of the tunneling probability

- Atomic resolution with STM

- Scanning tunneling spectroscopy

Laboratory visit
Image analysis and practical use of research instrumentation.

Schedule
The couse will be held in the first half of the first term, from mid September to the beginning of November.

Notes
The range and detail of the course will be adapted to the level of the class during the course and may change significantly.

Part 2: MICRO AND NANOSTRUCTURE FABRICATION

I - Deposition

- Introduction to micro and nanofabrication: objectives, examples.
- Vacuum technology: kinetic theory of gases, gas transport and pumping, vacuum pumps, vacuum systems
- Surface thermodynamics: surface properties, homogeneous and heterogeneous nucleation, film growth modes, nucleation
- Epitaxy: mechanisms, lattice orientation, strain
- Physical Vapor Deposition: introduction, difference between techniques
- Thermal Evaporation: rate and uniformity, electrically heated and e-beam sources, MBE, PLD
- Sputtering: sputtering mechanisms, introduction to plasma physics, DC, RF, reactive and magnetron sputtering
- Chemical Vapor Deposition: introduction, types of reactions, thermodynamic and gas flow, classification of thermally- and plasma-activated CVD techniques
- Characterization techniques: optical methods (ellipsometry), mechanical methods (profilometry, quartz microbalance), XRD, microscopies, electron spectroscopies (AES, XPS), electron diffraction (RHEED, LEED)

II - Lithography

- Introduction to lithography: device scaling, Moore’s law
- Optical lithography: process flow and technology
- Physics of optical exposure: diffraction, numerical aperture, types of illumination
- Resolution enhancement technologies: illuminations, masks, lenses, resists
- Advanced photolithographic techniques: maskless optical lithography, extreme ultraviolet lithography, X-ray lithography
- Electron beam lithography: physical principles, process flow and technology
- Other advanced lithographic techniques: soft and nanoimprint lithography, focused ion beam, scanning probe lithography
- Pattern transfer: dry and wet etching
- CMOS process flow and other examples

Laboratory activities
The main deposition and lithography techniques will be shown to students in the clean-room at the PoliFab laboratory.

Schedule
The course will be held in the second half of the first semester, from November to December.

Part 1: ELECTRON AND SCANNING PROBE MICROSCOPIES

The course makes use of the formalism learned in the fundamental courses of Mathematics and of Physics at the Bachelor in Ingeneering Physics, although any other engineering course may satisfy the following minimal pre-requisites:

- Mechanics and Thermodynamics

- Electromagnetism

- Fundamentals of Quantum Mechanics

- Fundamental of electronics

The following topics are particularly relevant:

- Oscillations (forced, damped and multiple degrees of freedom)

- Ray optics (properties and defects of single lenses and multiple lenses)

- Interference and diffraction

Part 2: MICRO AND NANOSTRUCTURE FABRICATION

The program is designed for students of Engineering Physics course. Students from Electronic Engineering, Biomedical Engineering, Material Engineering and Nanotechnology may also benefit from this course. A good knowledge of solid state physic is required.

Part 1: ELECTRON AND SCANNING PROBE MICROSCOPIES

The exam consists of an oral test in two parts of about half an hour each, one about Electron Microscopy and the other about Scanning Probe microscopy.

In each part:

- The student asked to present selected topics of the course, starting from the fundamentals through increasing level of detail and difficulty.

- The student will be asked to select its microscopic technique of choice to address a scientific case and to comment about the limits of application, advantages, and disadvantages.

- The student will be required to briefly present a scientific paper, chosen in agreement with the teacher, where electron or SPM microscopies is the main investigation techniques. The presentation will be focused on the information attained by the use of microscopy and the technical approach adopted to obtain it.

Part 2: MICRO AND NANOSTRUCTURE FABRICATION

The examination is oral, on the topics of the course(section I - Deposition and section II - Lithography).

textbook for the TEM and SEM section

Introductory reading on TEM, in French.

Advanced text on Electron Microscopy

Introduction to Scanning Probe Microscopy by a well-known manufacturer

Examples of applications

textbook for Section I- Deposition

textbook for Section II- Lithography