Focused Ion Beam Liquid-Phase Deposition (FILD)
Introduction
Focused ion beam liquid-phase deposition (FILD) is a novel process of atomic-level surface modification and device fabrications, able to spatially control the crystalline orientation of thin films. It has been shown to be a very effective tool for modern nanotechnology fabrication in an automated, high-precision and cost-effective manner.
FILD is an additive manufacturing process which selectively deposits liquids onto a substrate by a focused beam of vapourising atoms. It works in a similar manner to the photolithographic processes used in microfabrication but with much greater precision. The process starts with a focused ion beam, usually of some kind of noble gas such as argon, which is directed onto the sample and atoms of the vaporised material are deposited as a thin film.
FILD also provides a way of making vertically aligned nanostructures such as nano-beams, nano-tubes and nano-ribbons which can be used in the fabrication of micro-electro-mechanical systems (MEMS) and integrated circuits. Atomic control of the crystalline orientation of a monolayer is made possible by the atomic-scale interaction of FILD with the substrate surface.
The Process
FILD achieves resolution down to nanometer length scales by combining a very small (1–10 nm) focused ion beam spot size and gas pressure for depositing the liquid into the substrate. The focused ion beam is typically focused by an electrostatic or magnetic lens to a small spot size, 1–10 nm in diameter.
At this spot, the focused ion beam is used to deposit a small quantity of liquid at the surface of the substrate. This liquid will then start to evaporate due to the heat generated by the ion beam, thus forming a liquid-vapour deposition front. This liquid front then self-propels up the substrate and due to the vertical motion of the liquid, it forms a vertical direction, thus allowing for the crystalline alignment of the resulting thin film.
FILD is also able to form vertically aligned nanostructures such as nano-beams, nano-tubes and nano-ribbons. Abstract nanostructures can be designed and fabricated with the help of computer-aided design software and then constructed using the FILD process.
Benefits of FILD
FILD has many benefits to offer when compared to other techniques such as chemical vapor deposition (CVD) for fabricating nano-scale devices.
FILD is able to deposit small amounts of material, as low as 1–2nm, with a highly localized accuracy leading to a high degree of flexibility and control over the process. As such, FILD is a highly promising and cost-effective fabrication process for atomic-level devices.
Moreover, FILD can be used to deposit a wider range of materials than CVD, including both organic and inorganic compounds, making it suitable for a variety of applications.
In addition, FILD is an automated process that does not generate any chemical waste. This makes it an environmentally friendly technology that can be used in “green” microfabrication and manufacturing processes.
Conclusion
Focused ion beam liquid-phase deposition (FILD) is an innovative technique of atomic-level material modification and device fabrication. It offers a way to spatially control the crystalline orientation of thin films with a high degree of precision, as well as the ability to fabricate vertically aligned nanostructures.
FILD is an automated, cost-effective and environmentally friendly process that can deposit a wide range of materials with a localized accuracy. Due to these advantages, FILD is an increasingly popular technique for modern nanotechnology fabrication.
