Harnessing the Ion Bombardment process to create novel nanostructures

Cover picture courtesy: Ms. Nandini Bhosale, IDC

The rapidly evolving field of micro- and nano-fabrication is the meeting ground of physics, chemistry, biology, medicine, and engineering.

Conventional lithography techniques are widely used to fabricate microstructures commercially. However, such techniques have limitations at the nano level. Research in areas related to nanofabrication is therefore crucial in order to develop and improve novel manufacturing techniques.

This is where Vivek Garg, a research scholar with the IITB-Monash Research Academy, is hoping to make a significant contribution.

“My research is based on Focused Ion Beam (FIB) process for nanofabrication and its application in creating novel nanostructures,” explains Vivek. “The aim is to model ion-material interactions followed by rapid computation ion beam-based material removal (milling or etching), in order to create 2D/3D structures at both micro- and nano-scale for diverse applications like anti-reflection, colour filters, and sensors, to name a few.”

The Academy is a collaboration between India and Australia that endeavours to strengthen scientific relationships between the two countries. Graduate research scholars like Vivek study for a dually-badged PhD from both IIT Bombay and Monash University, spending time at both institutions to enrich their research experience.

Says Vivek, “FIB is a promising technique due to its capability range and diverse applications”.

For instance, it can be used for:

  • milling, thus making it suitable for micro- / nano-machining,
  • deposition, allowing for additive nanomanufacturing applications, and
  • imaging, which makes it even more powerful for microscopy analysis and materials applications.

Vivek plans to develop a reliable modelling methodology to predict optimized FIB process parameters for milling, which is expected to lead to robust and accurate 2D/3D structures at the micro- / nano-scale. He is currently working on ion induced, in-situ controlled manipulation of nanostructures and investigation through molecular dynamics simulations, in order to arrive at a feasible methodology. This work will be critical for 3D nanofabrication with promising nanoscale-controlled manipulation, strain engineering of nanostructures, opening new avenues in the diverse field of ion beams and applications beyond material science for realization of future nanoscale devices.

Optimization of Focused Ion Beam (FIB) milling process: Simulation results for a spherical profile obtained from optimization algorithm at a beam current of 20 pA and pixel size of 3 nm (a) Designed spherical profile, (b) Simulated spherical profile, (c) Error between the designed and simulated profile [1]

Rapid prototyping of subwavelength silicon nanostructures for light trapping and antireflection Properties (a) Scanning electron microscopic (SEM) image of fabricated designed Si Gaussian pillar nanostructures, (b) Antireflection properties exhibited through fabricated pillars and comparison with simulation results, (c) Optical absorption per unit volume exhibiting light trapping [2]

Structural colour printing with FIB: (a) Direct fabrication of subwavelength nanostructures for multicolour generation, (b) A wide colour palette shown with optical microscopic images of fabricated colour filters, (c) Nanoscale structural color printing: few examples, such as butterfly, Kangaroo, letters, shown via SEM image and including corresponding optical microscopic image showing generation of unique structural colours [3], [4]

Microscopic Gardening: Tiny Blossoms of Silicon
The image shows scanning electron micrograph of silicon nanoflowers realized with focused ion beam in conjunction with wet chemical etching methods. The bulk structuration of Si substrate, based on the ion implantation design and area, allows fabrication of exotic functional and 3D micro/nanostructures on Si substrate exhibiting unique optical properties for applications in nanophotonics and physical sciences (Image scale bar 400 nm)

Prof Murali Sastry, CEO of the IITB-Monash Research Academy and a leading nanomaterial scientist says, “Nanofabrication is an art. Future applications require materials with improved electronic, magnetic, optical, and mechanical properties. Many of these properties are defined by the structure and composition in the size range below 100 nm. It is most important to maintain the material integrity and composition as we move towards the nano-scale, which is what makes Vivek’s project so challenging.”

Oftentimes, it pays to think small when we need to think big!

Research scholar: Vivek Garg, IITB-Monash Research Academy
Project title: Focused Ion Beam (FIB) Fabrication of Novel 2D/3D Nanoscale Structures: Process Modeling and Applications
Supervisors: Prof. Rakesh G. Mote, Prof. Jing Fu
Contact details: vivekgarg@iitb.ac.in, vivek.garg@monash.edu

[1] V. Garg, R. G. Mote, and J. Fu, “Focused Ion Beam Fabrication: Process Development and Optimization Strategy for Optical Applications,” in Precision Product-Process Design and Optimization, Springer, Singapore, 2018, pp. 189–209.
[2] V. Garg, R. G. Mote, and J. Fu, “FIB fabrication of highly ordered vertical Gaussian pillar nanostructures on silicon,” in 2017 IEEE 17th International Conference on Nanotechnology (IEEE-NANO), 2017, pp. 707–712.
[3] V. Garg, R. G. Mote, and J. Fu, “Coloring with Focused Ion Beam Fabricated Nanostructures,” Microscopy and Microanalysis, vol. 24, no. S1, pp. 856–857, Aug. 2018.
[4] V. Garg, R. G. Mote, and J. Fu, “Focused Ion Beam Direct Fabrication of Subwavelength Nanostructures on Silicon for Multicolor Generation,” Advanced Materials Technologies, vol. 3, no. 8, p. 1800100, Aug. 2018.

The above story was written by Mr Krishna Warrier based on inputs from the research student, his supervisors, and IITB-Monash Research Academy. Copyright IITB-Monash Research Academy.