Occurrence | Teaching cycle |
---|---|

A | Autumn Term 2019-20 to Spring Term 2019-20 |

**On Introduction to Nanophysics:**

To introduce the fundamental physics important at the nanoscale such as tunnelling, surface proximity effect, quantum size effect, and Coulomb blockade; as well as important nanomaterials and nanosystems of current interests such as atomic clusters, quantum dots, nanowires, quantum wells as well as single electron devices.

To give an overview of the nanotechnology of fabrication and characterisation, with specialized module on electron microscopy (See below for more details).

To give a flavour of the state-of- art developments as well as the challenges in fundamental science and applications of nanophysics, a rapidly developing area of science in the new century, with special section on magnetic nanomaterials (See below for more details).

**On electron microscopy:**

The properties of nanomaterials and microfabrications depend critically on the structure- property relationships. Electron microscopy techniques, including diffraction, atomic resolution imaging, and spectroscopy offer the most powerful tool for investigating matter down to the scale of a single atom. The module introduces the general concepts and physics background of electron microscopy, develops system components and surveys selected applications in the physical sciences. It is intended as a stand-alone course and as an introduction to the use of state of the art tools for characterising the nanoworld. A number of applications from real world (including graphene based devices) will be demonstrated in the York-Nanocentre that host premium suite of electron microscope. Finally through tutorials the taught material will be reinforced.

**On magnetic nanomaterials:**

To develop an understanding of the key properties of magnetic materials , especially the behaviour of magnetic materials on a reduced length scale (1nm or below). To understand the different magnetic interactions present in magnetic materials. To understand the requirements for applications of such materials in information storage and biomedical applications.

**Nano Physics :At the end of this module successful students will be able to:**

- Discuss the importance of length and energy scales governing the transitions from bulk to nanoscale physics
- Calculate the De Broglie wavelength important for size quantization effect and the corresponding device operation temperature.
- Explain the concept of coherence length in quantum conductance and interference
- Discuss the concept of surface-to- volume ratio
- Describe the statistical fluctuation in finite particle systems and their physical consequence.
- Describe the general approaches in nanofabrication and specific examples of construction for quantum corral, quantum dots and nanowires
- Explain the basic physics behind the characterization techniques of electron microscopy, scanning probe microscopy
- Discuss the features of carbon nanostructures and their physical origin and Euler’s geometric description
- Discuss the knowledge of the common non-crystallographic structures in atomic clusters and the magic atomic number effect and its geometrical origin
- Describe what is meant by low dimensional systems; give examples of quantum wires, dots and wells.
- Derive expressions for the energy levels and density-of- states of quantum dots and quantum wires and quantum wells and the operation of solid-state lasers based on quantum structures.
- Use the shell model to understand the electronic magic number effect in metallic atomic clusters.
- Outline what is meant by exciton and be able to calculate the condition for the localization of excitons in quantum-size confined structure
- Qualitatively describe the difference in electron conduction in bulk materials and mesoscopic structure.
- Use quantum tunnelling theory to explain the physical principle of scanning tunnelling microscope
- Outline the physical origin of quantum conductance in 1D
- Outline what is meant by Coulomb blockade and be able to estimate the temperature and size range within which this is important.
- Describe the operations of single electron devices.

**Magnetism at the end of this module students will be able to:**

- Describe in detail the various types of exchange interaction both direct and indirect.
- Demonstrate in depth knowledge of the role of exchange and dipolar interactions on the hysteretic properties of magnetic materials.
- Explain the underlying physics of magnetics technology and information storage, in particular STT- MRAM.
- Understand the physics behind MRI and MRI contrast enhancement.
- Be aware of other biomedical applications of magnetic materials such us magnetic hyperthermia.

**Syllabus for Introduction to Nanophysics**

__Overview and review (2)__

Scale and scaling laws in nanoscale:

- Characteristic lengths: de Broglie wavelength, Coherence
- Characteristic energy: thermal, electrostatic, quantum
- Finite particle systems, surface-to- volume ratio
- Scaling in Physics

Fabrication and Structural Characterization:

- Top-down: lithography, Microelectronics
- Bottom-up: Directed and Self-organized structures
- Diffraction and Microscopy (to be expanded in terms of EM module)

__Structure and Stability of Nanosystems (3)__

Review of bonding and stability of bulk materials:

- Metallic, inert gas, covalent, ionic

Structure of fullerene and carbon nanotubes

Structure of atomic clusters

- Non-crystalline structure, magic number effect

__Electrons in quantum confinement (4)__

Review of electrons in solids:

- Free Fermi gas,
- Nearly-free electrons and excitons in periodic potential

Electronic shell model for metallic clusters:

- Electronic magic number effect

Quantum dots and quantum wells:

- Density of states of low dimensional systems
- Excitons in confinement

__Nanoelectronics (4)__

Review of semiclassical conduction

Mesoscopic (quantum) effects:

- Tunnelling and mapping of wavefunctions of artificially created quantum states
- Quantum conductance
- Coulomb blockade and single electron devices

**Syllabus for electron microscopy**

__I Introduction__

- Basic introduction to Transmission Electron Microscopy (TEM), Scanning Electron
- Microscopy (SEM) and Scanning Transmission Electron Microscopy (STEM)
- Vacuum environment
- Beam specimen interaction basics for signals, preservation and nanofabrication
- Electron optics
- Main types of electron sources
- Electron gun principles – thermionic and field emission, brightness, coherence
- Magnetic lenses, properties, attributes, apertures and major aberrations (spherical, chromatic, astigmatism)

__Microscopy Modes__

- Transmission Electron Microscopy (TEM)
- Electron scattering
- Diffraction and basic image formation in transmission
- Scanning Electron Microscopy (SEM)
- High resolution TEM imaging (HRTEM/HREM) basics
- Scanning Transmission Electron Microscopy (STEM)
- Major signals in TEM, STEM and SEM
- Z-contrast STEM, atom column by atom column analysis
- Signal types, characteristics, information content and application examples

__Performance (resolution, intensity, sensitivity)__

- Performance measure definitions – resolution, probe intensity, analysis sensitivity
- Phase contrast and the Contrast Transfer Function (CTF)
- Practical requirements

__Selected Application Topics__

- Atomic resolution imaging – TEM
- Dislocation and other defect analysis
- Atomic resolution imaging and analysis – STEM
- Electron Diffraction as major analytical tool and in support of imaging
- Energy Dispersive X-ray Spectroscopy (EDX/EDS) elemental microanalysis
- Basic corrections for data quantification
- Electron Energy Loss Spectroscopy (EELS) and Energy Filtered TEM (EFTEM)

**Syllabus for magnetism**

__1. Basics__

- Heisenberg exchange (1)
- Ferromagnetism (1)
- Indirect RKKY interaction (1)

__2. Phenomena__

- Hysteresis (Zhu + Bertran) (1)
- Dipolar interactions (1)
- Exchange bias (1)

__3. Applications__

- Magnetoresistance (AMR + Mott) (1)
- GMR (1)
- Tunnelling TMR (1)
- Heads + STT-MRAM (1)

__4. Novel applications__

- MRI imaging (1)
- MRI contrast enhancement (1)
- Magnetic hyperthermia (1)

Task | Length | % of module mark |
---|---|---|

Essay/courseworkWritten report |
N/A | 33 |

University - closed examinationNanomaterials: from Graphene to Spintronics |
2.5 hours | 67 |

None

Task | Length | % of module mark |
---|---|---|

Essay/courseworkWritten report |
N/A | 33 |

University - closed examinationNanomaterials: from Graphene to Spintronics |
2.5 hours | 67 |

Marks for the individual exams from the supervisor. Detailed model answers will be provided on the intranet. Feedback within assignment.

**Nano Physics:**

C. Kittel:* Introduction to Solid State Physics* (8 th edition, Wiley and Sons)

N.W. Ashcroft and N.D. Mermin: *Solid State Physics* (Saunders College Publishing)

**Electron Microscopy**

Williams and Carter, *Transmission Electron Microscopy*, Springer, 2009

Egerton, *Electron energy Loss Spectroscopy in the Electron Microscope*, Plenum, 1996

Goodhew, P.J. and Humphreys, F.J.,* Electron Microscopy and Analysis*, 2nd Edition, Taylor & Francis, 1988

Goldstein et al, *Scanning Electron Microscopy and X-ray Microanalysis*, Springer, 2003

http://www.matter.org.uk/tem/

http://www.matter.org.uk/diffraction/Default.htm

**Magnetism**

Jiles D: Introduction to Magnetism and Magnetic Materials 2nd Ed (Chapman & Hall)

Cullity B D and C Graham. An Introduction to Magnetic Materials. IEEE Press.