Nanotechnology – Flashcards

1. Lithography

2. Cutting, Etching, Grinding

A method of producing raw materials, such as molecules and particles, which can then be used either directly in products of more advanced ordered materials.

1. Chemical Synthesis

2. Self-Assembly

3. Positional Assembly

1. Top-Down

2. Bottom-up

– Type of bottom-up synthesis

– requires the attachment of a single molecular organic layer (self-assembled monolayer) to the colloidal particles (organic or inorganic) and subsequent self-assembly of these components into a complex structure.

1. First Generation

2. Second Generation

3. Third Generation

4. Fourth Generation

Exploits the tendency of mono-dispersed nano- or submicro colloidal spheres to organize into a face-centered cubic (FCC) lattice.

Driving force <-> thermodynamically stable state (minimum free energy)

Example: Cool a saturated solution of sugar or salt and the molecules self assemble into crystals.

A bottom-up technique in which atoms or molecules arrange themselves into ordered nanoscale structures by physical or chemical interactions between the units.

Passive nanostructures

Examples: Coatings, Nanoparticles, Nanowires, etc

Heterogeneous Molecular Nanosystems

Examples: Where each molecule in the nanosystem has a specific structure and plays a different role, molecular machines.

Active Nanostructures

Examples: Transistors, amplifiers, targeted drugs and chemicals, sensors, actuators, and adaptive structures

Three Dimensional Nanosystems

Examples: Using various synthesis and assembling techniques such as bioassembling, nanoscale robotics, networking at a nanoscale and multiscale architecture.

1. Order: The self-assembled structures must have a higher order than isolated components.

2. Interaction: The key role of weak interactions (e.g., van der waals forces, hydrogen bonds, etc).

3. Building Blocks: The building blocks are not only atoms and molecules, but span a wide range of nano and mesoscopic structures, with different chemical compositions, shapes and functionalities.

A type of self assembly bottom-up technique. Atoms, molecules or clusters are deliberately manipulated and positioned one-by-one.

The sol-gel process, also known as chemical solution deposition, is a wet-chemical technique widely used in the fields of materials science and ceramic engineering. Such methods are used primarily for the fabrication of materials (typically a metal oxide) starting from a chemical solution (or sol) that acts as the precursor for an integrated network (or gel) of either discrete particles or network polymers. Typical precursors are metal alkoxides and metal chlorides, which undergo various forms of hydrolysis and polycondensation reactions.

Sol Gel Process

An evaporative source is used to generate the powder particles, which are convectively transported to and collected on a cold substrate. The nanoparticles develop in a thermalizing zone just above the evaporative source, due to interactions between the hot vapor species and the much colder inert gas atoms (typically 1-20 mbar pressure) in the chamber.

A ball mill is a type of grinder used to grind materials into extremely fine powder for use in mineral dressing processes, paints, pyrotechnics, and ceramics.

Photolithography (or “optical lithography”) is a process used in microfabrication to selectively remove parts of a thin film or the bulk of a substrate. It uses light to transfer a geometric pattern from a photo mask to a light-sensitive chemical photo resist, or simply “resist,” on the substrate. A series of chemical treatments then engraves the exposure pattern into the material underneath the photo resist. In complex integrated circuits, for example a modern CMOS, a wafer will go through the photolithographic cycle up to 50 times.

1. Implementation is complex + expensive.

2. UV light has a wavelength of 250 nm (weak resolution).

3. Masks need to be perfectly aligned with the pattern of the wafer.

In technology, soft lithography refers to a family of techniques for fabricating or replicating structures using “elastomeric stamps, molds, and conformable photomasks” (in the words of Rogers and Nuzzo, p. 50, as cited in “References”). It is called “soft” because it uses elastomeric materials, most notably PDMS. Soft lithography is generally used to construct features measured on the micrometer to nanometer scale. According to Rogers and Nuzzo (2005), development of soft lithography expanded rapidly during the period 1995 to 2005.

1. Once the master template has been made, no special equipment is required

2. Methods are capable of producing nanostructures in a wide range of materials and can print or mold on curves as well as planar surfaces

Focused ion beam, also known as FIB, is a technique used particularly in the semiconductor and materials science fields for site-specific analysis, deposition, and ablation of materials. An FIB setup is a scientific instrument that resembles a scanning electron microscope (SEM). However, while the SEM uses a focused beam of electrons to image the sample in the chamber, an FIB setup instead uses a focused beam of ions. FIB can also be incorporated in a system with both electron and ion beam columns, allowing the same feature to be investigated using either of the beams. FIB should not be confused with using a beam of focused ions for direct write lithography (such as in proton beam writing), where the material is modified by different mechanisms.

1. TEM

2. SEM

3. STM

1. FT-IR

2. NMR

Atomic Force Microscopy

TEM

1. Scanning Electron Microscopy (SEM)

2. Transmission Electron Microscopy (TEM)

3. Scanning Transmission Electron Microscopy (STEM)

Uses a beam of electrons to illuminate the specimen and create a magnified image of it.

Electron can interact with the atomic nucleus or the electrons in the inner or outer shells. If it hits the nucleus it will bounce back.

Electrons may also impart it’s energy to one of the atom’s electrons and knock it off.

A microscopy technique whereby a beam of electrons is transmitted through an ultra thin specimen, interacting with the specimen as it passes through it.

Offers the capability of 3D visualization and both qualitative and quantitative information on many physical properties including size, morphology, surface area, surface texture and roughness.

AFM consists of a cantilever with a sharp force-sensing tip (probe with a diameter as small as 20 nm) at its end that is used to scan the specimen surface

Measures the atomic force between the atoms at the surface of the sample and the tip of a needle at the end of a cantilever.

Only technique capable of measuring particles in a solution or dispersion in a fast process with little or no sample preparation.

Cylindrical molecules with a diameter ranging from 1 nm to a few nanometres and length up to a few micrometers.

Their structure consists of a graphene sheet wrapped into a cylinder.

Can be either single walled or multiwalled.

Discovered multi walled carbon nanotubes in 1991.

The real breakthrough came in 1993, with the discovery of single-wall carbon nanotubes by Iijima and his group at NEC laboratory…

MWNTs more popular than Carbon Nanofibers which are more popular than SWNTs.

1. Zigzag

2. Chiral

3. Armchair

The easiest MWNT to imagine is the concentric type (c-MWNT) in which the sheets of a graphite are arranged in concentric cylinders, single-walled nanotubes within a larger single-walled nanotube.

A single sheet of graphite is rolled in around itself, resembling a scroll of parchment or a rolled up newspaper.

A family of flat polycyclic aromatic hydrocarbons.

A one-atom-thick-planar sheet sheet of SP2 bonded carbon atoms that are densely packed in a honeycomb crystal lattice.

1. High electron mobility at room temp

2. Current carrying capacity by a minimum of two orders of magnitude higher than copper

3. 2D property

4. An unexpectedly high opacity for an atomic monolayer

5. very high thermal conductivity

6. One of the strongest materials ever made

The three dimensional form of carbon is diamond.

It is SP3 bonded forming 4 covalent bonds with the neighbouring carbon atoms into a face-centered cubic atomic structure.

Produced by stacking of graphenes into sheets that allow van der Waals forces to develop.

Bonding: 3 SP2 and 1 PI

1. Powder preparation

2. Shape forming

3. Baking

4. Graphitization

5. Pyrolytic Graphite

Any molecule composed entirely of carbon, in the form of a hollow sphere, ellipsoid, or tube.

Discovered in 1985 by R. E. Smalley (shared the Nobel prize in 1996)

Molecule named after Richard Buckminster Fuller

Involves the condensation of carbon atoms generated from evaporation of solid carbon sources.

inside the pores

in the interstitial triangular channels between the tubes

on the outer surface of the bundle

in a groove formed at the contact between adjacent tubes on the outside of the bundl

High electrical conductivity

Very high tensile strength

Highly flexible – can be bent considerably without damage

High thermal conductivity

Low thermal expansion coefficient

Good electron field emitters

High aspect ratio (length = approx 1000 x diameter)