Activities during UK-Japan Young Scientist Workshop

Dr Riz Khan

Room 31DJ02, x6062, e-mail: r.khan@surrey.ac.uk

Advanced Technology Institute

University of Surrey

Learning Outcomes

• What do we want you to learn?

• Which techniques will you be using?

• What will you take away?

Literature searching

• We have set up a number of computers in the CAD room for you to use

• We want you to search for information on the internet related to nanotechnology

• Also search for the experiments that you will be doing

• Research is the key to scientific success!

Computer aided design

• We will ask you to design structures to be written on a nano-scale

• This will be done in the CAD laboratory (04DJ01)

• The images should be of different sizes so that you can see what the resolution of the equipment is

• How would you do this??

• Good examples are e.g. your names in English and Japanese, scanned-in pictures etc

Focussed Ion Beams

• Focussed ion beams (FIBs) are used to write structures on the nanoscale

• Creates a beam of ions (5-30 keV) that bombard and erode the sample

• Milling commonly done in high vacuum

• Resolutions approaching 10 nm

• What is the resolution of ours?

Focussed ion beams

• 10 superconducting junctions, University of Cambridge Materials dept

• Our machine!

• (and out PhD students and scientific staff)

Imaging / microscopy techniques

Limit Resolution

Eye Retina 70 000 nm

Optical microscope Diffraction of light

300 nm

Scanning electron microscope

Diffraction of electrons

3 nm

Transmission electron microscope

Diffraction of electrons

0.1 nm

Scanning probe microscope

Aperture 0.01 nm

Light versus electrons…

Scanning electron microscopy

• Use a beam of highly energetic electrons to examine objects on a very fine scale:

• Topography• Morphology• Composition (if appropriate detector equipped)

• Samples normally conductive or coated with thin conductive layer

Electron beam (0.1-50 keV)

10 nm { } 1 micron

Backscattered electrons (high E)

Secondary electrons (low E)

X-raysLight (cathodoluminescence)

Scanning electron microscopy

• Electron beam source - filament (W or LaB6) or field emission• Focused to 1-5 nm spot size, scanned over sample• Incident electrons either:

• Scatter back• Knock other electrons out (secondary electrons)• Secondary electrons - greater in number

Backscattered electrons - Z sensitiveSecondary electrons - Z-insensitive

compositional information

• Analysis of x-ray emission (energy dispersive x-ray spectroscopy, EDX) gives elemental analysis

Scanning electron microscopy• Typical image…

Already well used in microelectronics, biology, materials science, etc

Atomic Force Microscopy

• Tip mounted on flexible cantilever• Atomic (Van der Waals) forces result in deflection of tip• Measured using deflection of a laser beam incident on the

cantilever

laser

detector

cantilevertip

Atomic Force Microscopy

• Contact mode • constant force between tip and surface

(constant deflection)

• Non-contact mode• Cantilever is oscillated• Oscillation frequency changed by atomic force• Compared to reference frequency• More sensitive

Contact mode is simpler to perform• but has poorer resolution / contrast and can damage

the film surface

Timetable

• Monday 2-4:30• Talks - JA, RK• Tour of facilities - Steve Lyth, Yoji• Introduction of CAD and internet facilities

• Tuesday 10-12 • design structures to be FIB'd. • Place - CAD room (Yoji)

• Tuesday 2-4:30 • Nanostructures written by FIB (David Cox) - three groups!• Place - FIB / microscopy room• Waiting students perform internet research in CAD room

Timetable

• Thursday 10-4:30 • AFM and SEM on the structures. (Yann Tison, Steve Lyth) -

same groups as before• Place - FIB / microscopy room• We have a number of other secret structures to look at!• Other students perform internet research in CAD room

• Friday morning • Preparation for presentation• Place - CAD room• Assistance - Yoji

• Friday afternoon - presentations!

• Any questions?