Nanotechnology
I) Describe what Nanotechnology means:
-One-Millionth of a millimeter/Specific surface area: SSA= surface area A [m2]/mass[g]. /At nanoscale, the physical, chemical, biological, optical, electrical, and
almost all material properties are different/Graphene can be described as a one-atom-thick layer of carbon - Graphene it is strongest and thinnest materials
known to exist.
Provide some examples of Nanotechnology around us:
Nanotechnology Socks contain nanoparticles of silver. These particles help kill the bacteria that makes our feet smell. / Material that change in color when they
interact with light using gold nanoparticles. / Hydrophobic materials. / Decreasing costs and improving quality of life by: -Early corrective reaction to initial
“dangerous” patterns -Very early-stage detection of diseases -Continuous monitoring -Personalised solutions -Localised treatment./ Nanotech breath testing
sensors to detect chronic diseases. / nanocomposites exhibit excellent mechanical properties, but also display outstanding combination of optical, electrical,
thermal, magnetic and other physico-chemical properties.
Determine basic safety measures for using nanoparticles:
Nanoparticles can pass the blood and skin barriers. / MSDS lists information relating to occupational safety and health for the use of a product. /PPE: (Personal
Protection for nanomaterials Exposure) Protective gloves - Eye protection -Protective clothing. /Safety Engineering Controls are enclosed boxes with ventilation
to maintain maximum protection and reduce human error. / The disposal of all waste material should comply with all applicable local Government Regulations.
Distinguish between bottom-up and top-down nanofabrication approaches:
Top-Down: Continued reduction in size of bulk materials and requires expertise in the Engineering and Physics. / Bottom-up: Design molecules with specific
functions and connecting molecules to the microscopic world and requires expertise in Chemistry.
II) Describe Top-down Nano-fabrication steps:
Lithography: There are 4 steps, Spinning: resist is put onto a wafer that is spinning at high speed.causes the resist to spread out thinly and evenly./ Expose: The
wafer with its film of resist is now placed in a tool that will expose it to a specific wavelength light source through a mask or electron beam./ Develop: The
patterned resist is placed in a developer chemical which washes away the exposed OR unexposed resist(Positive Resist: After
exposure the cross-links in the exposed part of the resist breakdown and become softened (photo solubilization) and get
dissolved off by the developer./ Negative Resist: the exposed parts of the resist become cross-linked and polymerized due to
the photochemical reaction. This causes it to harden and remain on the wafer after the develop process.)/ Transfer FOR
electron-beam evaporation: An ingot of material is heated in a crucible within a high vacuum until it evaporates/The
material is deposited everywhere, including on the substrate/A vibrating quartz crystal is used to control of thickness /Directional
Deposition/ The best for Lift-off/ better for material with high melting point/Transfer FOR Sputtering of thin films: Low pressure inert
gas (such as Argon) enters a vacuum chamber/The material to be deposited is placed in a “target”, which is excited by a strong electric
field/The electric field ionises the gas, and the atoms are attracted to the target/The atoms hit the target with high energy, causing
material to be ejected which hits the substrate/Can deposit a wide range of materials/Sputtering is non-directional/ not suited to lift-
off techniques./Lif-off: With some chemistry we the dissolve (remove) the resist selectively
Wet etching relies on chemical dissolution, while dry etching uses plasma for precision and control, Wet etching is cost-effective.
Distinguish between Laser interference lithography, Nanosphere lithography, Nano-imprint lithography, and Micro-lens array
lithography:
Direct Laser Writing (DLW) is a technique that uses a tightly focused laser beam to create three-dimensional micro structures
directly within a material. The laser induces photochemical or thermal reactions in a photosensitive material, such as photoresist or
polymers, enabling controlled removal or modification of the material(is only limited to micrometer scale).
Focused ion milling, or focused ion beam (FIB) milling, uses a concentrated beam of ions, usually gallium, to precisely remove material from a surface at the
nanoscale, Resolution down to 10nm and is mostly used for fabricating holes.
Provide some examples of photon-based characterisation techniques, and explain their principle of working:
Ellipsometry: Technique that determines the change in polarisation state of light reflected from a sample. Typically used to characterise the refractive index or
thickness of a thin film./ Ellipsometry is a non-destructive technique./ Ellipsometers are extremely sensitive devices, able to measure layers as thin as one atom.
They are widely used in semiconductor manufacturing./Fourier-Transform Infra-Red (FTIR): It is primarily a non-destructive structural characterization tool,
particularly useful for carbon-based organic compounds./ 2.5-20μm wavelength range/→Use a Michelson interferometer with variable delay between the two
arms, broadband source and detector → The intensity is measured as a function of delay to obtain interferogram → Interferogram is Fourier transformed to
obtain spectrum./Scanning near-field optical microscopy (SNOM): is a technique that works by bringing a sharp, nanosized optical probe, typically a tapered fiber
or metal-coated tip, very close to the sample surface (within a few nanometers). This allows the collection or delivery of light in the near-field region, enabling
high-resolution imaging of optical properties like fluorescence, refractive index, and absorption.
III) Describe the principle of electron-based characterisation techniques
Molecules in the air can deflect the electrons → We need a vacuum → We need a chamber (1 Torr = 133.3224 Pascal)
Distinguish between XPS, SEM, and EDS
X-ray Photoelectron Spectroscopy (XPS):[PHOTON IN ELECTRON OUT ] A beam of X-ray is directed onto the sample, providing energy to the atoms, the xray
photons transfer energy to the core electrons, causing them to eject from the material surface then the kinetic energy of the emitted electrons is measured.
/detects all elements except for H and He [ bcs they only have one layer k-L-m-n ]./ Non-destructive analysis (except depth profiling)./ Eb = hv – Ek-W(Where hv is
the photon energy, EK is the kinetic energy of the electron, and W is the spectrometer work function, Eb is Binding energy the energy that must be expended in
removing an electron./ What happens to the atom, after it loses an electron?: Once a photoelectron has been emitted, the ionised atom can relax either by Auger
process or X-ray emission./ The loss in energy from the electron is emitted as a photon Ef-Eo=Hv, Ef= final energy of the electron after scattering, E0 = initial
energy of the electron before scattering/h = Planck constant,ν= frequency of electromagnetic radiation./ XPS: mostly from top 3 nm of surface. But we have more
to happen/X-ray Fluorescence (XRF): high precision analysis method for analysing (usually) non-organic materials i.e. iron & steel,ceramics/XRF is more a “bulk”
technique rather than a surface./Scanning Electron Microscopy (SEM):[electron in electron out] SEM uses an electron gun to produce a focused beam of
electrons towards the sample, when it hits the sample it interacts with the atoms of the surface, producing various signals that are converted into images./ if the
number of absorbed electrons is much higher than ejected electrons, the electrons get accumulated in one spot. It is called charging. Thus, the surface become
super bright and one cannot see anything./ To avoid charging, it is crucial to make the surface conductive, so that the electrons can move/Secondary electrons:
Show surface features and Look 3D→ Surface topology/ Backscattered electrons: Fewer surface features ( very flat) and Contrast is due to the difference average
atomic numbers → Chemical Composition.
I) Describe what Nanotechnology means:
-One-Millionth of a millimeter/Specific surface area: SSA= surface area A [m2]/mass[g]. /At nanoscale, the physical, chemical, biological, optical, electrical, and
almost all material properties are different/Graphene can be described as a one-atom-thick layer of carbon - Graphene it is strongest and thinnest materials
known to exist.
Provide some examples of Nanotechnology around us:
Nanotechnology Socks contain nanoparticles of silver. These particles help kill the bacteria that makes our feet smell. / Material that change in color when they
interact with light using gold nanoparticles. / Hydrophobic materials. / Decreasing costs and improving quality of life by: -Early corrective reaction to initial
“dangerous” patterns -Very early-stage detection of diseases -Continuous monitoring -Personalised solutions -Localised treatment./ Nanotech breath testing
sensors to detect chronic diseases. / nanocomposites exhibit excellent mechanical properties, but also display outstanding combination of optical, electrical,
thermal, magnetic and other physico-chemical properties.
Determine basic safety measures for using nanoparticles:
Nanoparticles can pass the blood and skin barriers. / MSDS lists information relating to occupational safety and health for the use of a product. /PPE: (Personal
Protection for nanomaterials Exposure) Protective gloves - Eye protection -Protective clothing. /Safety Engineering Controls are enclosed boxes with ventilation
to maintain maximum protection and reduce human error. / The disposal of all waste material should comply with all applicable local Government Regulations.
Distinguish between bottom-up and top-down nanofabrication approaches:
Top-Down: Continued reduction in size of bulk materials and requires expertise in the Engineering and Physics. / Bottom-up: Design molecules with specific
functions and connecting molecules to the microscopic world and requires expertise in Chemistry.
II) Describe Top-down Nano-fabrication steps:
Lithography: There are 4 steps, Spinning: resist is put onto a wafer that is spinning at high speed.causes the resist to spread out thinly and evenly./ Expose: The
wafer with its film of resist is now placed in a tool that will expose it to a specific wavelength light source through a mask or electron beam./ Develop: The
patterned resist is placed in a developer chemical which washes away the exposed OR unexposed resist(Positive Resist: After
exposure the cross-links in the exposed part of the resist breakdown and become softened (photo solubilization) and get
dissolved off by the developer./ Negative Resist: the exposed parts of the resist become cross-linked and polymerized due to
the photochemical reaction. This causes it to harden and remain on the wafer after the develop process.)/ Transfer FOR
electron-beam evaporation: An ingot of material is heated in a crucible within a high vacuum until it evaporates/The
material is deposited everywhere, including on the substrate/A vibrating quartz crystal is used to control of thickness /Directional
Deposition/ The best for Lift-off/ better for material with high melting point/Transfer FOR Sputtering of thin films: Low pressure inert
gas (such as Argon) enters a vacuum chamber/The material to be deposited is placed in a “target”, which is excited by a strong electric
field/The electric field ionises the gas, and the atoms are attracted to the target/The atoms hit the target with high energy, causing
material to be ejected which hits the substrate/Can deposit a wide range of materials/Sputtering is non-directional/ not suited to lift-
off techniques./Lif-off: With some chemistry we the dissolve (remove) the resist selectively
Wet etching relies on chemical dissolution, while dry etching uses plasma for precision and control, Wet etching is cost-effective.
Distinguish between Laser interference lithography, Nanosphere lithography, Nano-imprint lithography, and Micro-lens array
lithography:
Direct Laser Writing (DLW) is a technique that uses a tightly focused laser beam to create three-dimensional micro structures
directly within a material. The laser induces photochemical or thermal reactions in a photosensitive material, such as photoresist or
polymers, enabling controlled removal or modification of the material(is only limited to micrometer scale).
Focused ion milling, or focused ion beam (FIB) milling, uses a concentrated beam of ions, usually gallium, to precisely remove material from a surface at the
nanoscale, Resolution down to 10nm and is mostly used for fabricating holes.
Provide some examples of photon-based characterisation techniques, and explain their principle of working:
Ellipsometry: Technique that determines the change in polarisation state of light reflected from a sample. Typically used to characterise the refractive index or
thickness of a thin film./ Ellipsometry is a non-destructive technique./ Ellipsometers are extremely sensitive devices, able to measure layers as thin as one atom.
They are widely used in semiconductor manufacturing./Fourier-Transform Infra-Red (FTIR): It is primarily a non-destructive structural characterization tool,
particularly useful for carbon-based organic compounds./ 2.5-20μm wavelength range/→Use a Michelson interferometer with variable delay between the two
arms, broadband source and detector → The intensity is measured as a function of delay to obtain interferogram → Interferogram is Fourier transformed to
obtain spectrum./Scanning near-field optical microscopy (SNOM): is a technique that works by bringing a sharp, nanosized optical probe, typically a tapered fiber
or metal-coated tip, very close to the sample surface (within a few nanometers). This allows the collection or delivery of light in the near-field region, enabling
high-resolution imaging of optical properties like fluorescence, refractive index, and absorption.
III) Describe the principle of electron-based characterisation techniques
Molecules in the air can deflect the electrons → We need a vacuum → We need a chamber (1 Torr = 133.3224 Pascal)
Distinguish between XPS, SEM, and EDS
X-ray Photoelectron Spectroscopy (XPS):[PHOTON IN ELECTRON OUT ] A beam of X-ray is directed onto the sample, providing energy to the atoms, the xray
photons transfer energy to the core electrons, causing them to eject from the material surface then the kinetic energy of the emitted electrons is measured.
/detects all elements except for H and He [ bcs they only have one layer k-L-m-n ]./ Non-destructive analysis (except depth profiling)./ Eb = hv – Ek-W(Where hv is
the photon energy, EK is the kinetic energy of the electron, and W is the spectrometer work function, Eb is Binding energy the energy that must be expended in
removing an electron./ What happens to the atom, after it loses an electron?: Once a photoelectron has been emitted, the ionised atom can relax either by Auger
process or X-ray emission./ The loss in energy from the electron is emitted as a photon Ef-Eo=Hv, Ef= final energy of the electron after scattering, E0 = initial
energy of the electron before scattering/h = Planck constant,ν= frequency of electromagnetic radiation./ XPS: mostly from top 3 nm of surface. But we have more
to happen/X-ray Fluorescence (XRF): high precision analysis method for analysing (usually) non-organic materials i.e. iron & steel,ceramics/XRF is more a “bulk”
technique rather than a surface./Scanning Electron Microscopy (SEM):[electron in electron out] SEM uses an electron gun to produce a focused beam of
electrons towards the sample, when it hits the sample it interacts with the atoms of the surface, producing various signals that are converted into images./ if the
number of absorbed electrons is much higher than ejected electrons, the electrons get accumulated in one spot. It is called charging. Thus, the surface become
super bright and one cannot see anything./ To avoid charging, it is crucial to make the surface conductive, so that the electrons can move/Secondary electrons:
Show surface features and Look 3D→ Surface topology/ Backscattered electrons: Fewer surface features ( very flat) and Contrast is due to the difference average
atomic numbers → Chemical Composition.
