A sequence of these regions will allow us to store useful data (e.g. - PowerPoint PPT Presentation

 Stored by digital magnetic storage  Concept: for a small region of ferromagnetic material to be in one of two well- defined magnetisation states, thus corresponding to a binary number  A sequence of these regions will allow us to store useful data (e.g. 1011011011001)  A magnetic field can be used to alter the magnetisation states of each region separately, thereby writing magnetic data

 Magnetic recording trilemma: Signal to Noise Ratio, writability and thermal stability which limits the grain size  Limits areal density to 1Tb in -2  To resolve: Bit Patterned Media (BPM) or Heat Assisted Magnetic Recording (HAMR)  In our study, we will be focusing on BPM, which allows a single grain to occupy a single magnetic island

By allowing one single magnetic grain to occupy each magnetic island, grain size can be optimised to increase the areal density

 Electron Beam Lithography (EBL)  Nanoimprint Lithography (NIL)  Self Assembly  Interference Lithography (IL)  In our study, we will be focusing on nanoimprint lithography

 Nanoimprint lithography – a low cost process to create nanostructures and patterns by the mechanical deformation of the resist  Resist is cured by UV radiation  Used to make magnetic nanostructures to store data

 Deposition of magnetic films atop substrate  Spin coating of resist on magnetic films  Pressing of template into resist  Curing of resist using UV light  Reactive Ion Etching (RIE)  Treatment of Piranha solution (mixture of sulfuric acid and hydrogen peroxide)

Resist is then cured by UV light.

- Removes exposed magnetic films and resist

- Mixture of sulfuric acid and hydrogen peroxide used to dissolve residual resist

 To lower the cost of production of making BPM using RNIL (reverse nanoimprint lithography)  Quality of nanostructures formed (uniformity, edge defects, etc.) must be the same as those produced using conventional NIL

 ‘ Reverse Nanoimprint Lithography (RNIL) for Fabrication of Nanostructures’ by A. Tavakkoli K. G., M. Ranjbar, S. N. Piramanayagam, S. K. Wong, W . C. Poh, R. Sbiaa and T.C. Chong  The only paper to research on RNIL  Shows us the potential for RNIL to be used in place of conventional NIL

 We are trying to find the method to fabricate nanostructures of the highest uniformity and least edge deformities  This is because it will allow magnetisation state of each individual magnetic nanostructure to be more stable and more writable, while also being less susceptible to superparamagnetism* *Superparamagnetism: situation where magnetic nanostructures affect magnetisation state of other adjacent magnetic nanostructures

 Hypothesis: RNIL can be used to fabricate NiFe (magnetic) nanostructures  Independent variable: method of fabricating nanostructures (NIL or RNIL)  Dependent variable: the presence of nano patterns  Results from NIL is used as a positive control

 Atomic Force Microscopy (AFM) is used to inspect the nanostructures formed using RNIL and NIL Images of nanostructures fabricated by NIL Images of nanostructures fabricated by RNIL

 Under the SAME imprinting conditions, NIL produced nanostructures of lesser edge deformities than RNIL  RNIL, however, still fabricated observable nanostructures which can still possibly be used for domain wall dynamics

 It is possible for us to make use of RNIL and NiFe to form nanostructures for domain wall dynamics  By referencing from the study ‘ Reverse Nanoimprint Lithography (RNIL) for Fabrication of Nanostructures’ , it is possible to optimise the nanostructures by reducing the pressure and temperature in the imprinting step and including a baking step after that  This could potentially lower the cost of fabricating nanostructures, especially when this experiment is conducted on a relatively cheap ferromagnetic material, NiFe, which is viable for commercial use

 We would like to optimise the RNIL process by changing the pressure and temperature during the imprinting step (130°C, 6 bars, 1 min) to produce nanostructures with less edge deformities and higher uniformity  From the same study previously, we might want to try and use a flexible mould so that the separation of the mould and the resist would be smoother, achieving nanostructures of higher uniformity

- ‘ Reverse Nanoimprint Lithography (RNIL) for Fabrication of Nanostructures’ by A. Tavakkoli K. G., M. Ranjbar, S. N. Piramanayagam, S. K. Wong, W . C. Poh, R. Sbiaa and T.C. Chong