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PhD position | 3D laser nano-printing

Despite the significant amount of applications, especially in optoelectronics and microelectronics, the fabrication of nano-objects with a digital and non-contact technology is still a dream. The main nanofabrication technologies, such as photolithography, E-beam lithography, focused ion beam or nano-imprint, are expensive, complex to operated, time consuming and for most of them not digital.

In this project, we propose to develop a digital printing technology to realize 3D structures by the deposition of pixels with elementary sizes ranging from 100nm to few micrometers. The approach is based on the double pulse Laser-Induced Forward Process (LIFT) and this study will be focused on metallic and semiconductor materials. The process consists in the irradiation by a first long duration laser pulse of a solid thin film deposited on a transparent donor substrate, to locally melt the film, followed by a second irradiation with a short pulse laser beam (fs, ps) to initiate the transfer of a liquid jet or a single droplet towards a receiver substrate, set in front of the donor one, and to form a solid pixel on the receiver. This double pulse LIFT technique has been patented in 2015 and the first studies have validated the concept and led to the printing of sub-micrometers pixels of copper [1, 2].

The development of laser printing at the nanometer scale represents a real challenge. The mechanisms leading to the formation of liquid jet in these conditions are not yet clearly determined, and the influence of the material properties (viscosity, surface tension, density …) in liquid phase on the formation, the dynamics and the stability of the jet have never been investigated at these spatial scales.

The main scientific objective of the thesis is to provide a better understanding of the physics of the double pulse LIFT process at the nanoscale. The dynamics of the ejection process will be experimentally investigated by means of time-resolved shadowgraphy and correlated with the morphologies of the printed pixels (SEM, AFM). Based on this knowledge, the experimental setup will be optimized (sub-micrometer laser spot size, control of the donor-receiver gap …) to allow a reproducible printing of nano-pixels of various materials. To reach this objective, both the thickness of the donor film and the beam diameter need to be downscaled. To do so, specific beam shaping will be implemented, as for instance the use of an axicon to transform the Gaussian beam into a Bessel beam. Then using this new architecture, printing experiments will be realized to transfer nano-droplets of metal (copper, gold, alloys) and semiconductors. A specific attention will be paid to the process repeatability (positioning, size …), which is quite challenging at the nanoscale but mandatory to build 3D structure.

To demonstrate the potential of this technology in terms of applications, 2D and 3D structures will be printed and their morphological, chemical and physical properties characterized. One of the objectives is the realization of photonic crystals and metamaterials with unique properties in the visible range. The design of these structures will be selected from the literature or defined thanks to a collaboration with Fresnel Institute. After printing, the optical properties of these structures will be characterized.

- [1] LI Q., ALLONCLE A.-P., GROJO D. DELAPORTE Ph., ‘Generating Liquid Nanojets from Copper by Dual Laser Irradiation for Ultra-High Resolution Printing’, Optics Express 25 (20), pp. 24164-24172 (2017)
- [2] LI Q., ALLONCLE A.-P., GROJO D. DELAPORTE Ph., ‘Laser-induced nano-jetting behaviors of liquid metals’, Applied Physics A 123, 718, (2017)

Keywords : Laser-matter interaction, laser printing, beam shaping, material characterization, nano-materials

Required skills : background in one or several of the following fields is required

  • Education : Optics & Photonics, material sciences
  • Practice : experimental, laser alignment, beam shaping, material characterization (SEM, AFM), imaging

Mode of application. To apply, please send an email to Philippe Delaporte, including a detailed CV, and contact details of at least two references (letters of recommendation are not required at this stage).

Starting date : From March 1st, 2018 for 3 years. Location : LP3 laboratory, Campus de Luminy, case 917, 13009 Marseille, France

PhD thesis supervisor : Philippe Delaporte (DR CNRS) ;

Funding : 1350 €/month

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