New Stored by digital magnetic storage · 2019. 4. 25. · Stored by digital magnetic storage...
Transcript of New Stored by digital magnetic storage · 2019. 4. 25. · Stored by digital magnetic storage...
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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
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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
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By allowing one
single magnetic grain
to occupy each
magnetic island,
grain size can be
optimised to increase
the areal density
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Electron Beam Lithography (EBL)
Nanoimprint Lithography (NIL)
Self Assembly
Interference Lithography (IL)
In our study, we will be focusing on nanoimprint lithography
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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
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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)
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Resist is then cured by UV light.
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- Removes exposed magnetic
films and resist
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- Mixture of sulfuric acid and
hydrogen peroxide used to
dissolve residual resist
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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
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‘ 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
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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
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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
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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
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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
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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
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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
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- ‘ 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