Projects proposed by the NAM

During their curriculum, EPFL students must conduct several research projects (Semester projects) as well as a main research project (Master thesis) at the end of their study. The Nanophotonics & Nanophotonics Laboratory (NAM) proposes a variety of projects to the students belonging to most EPFL sections.

The following list gives our current offer, but we always welcome suggestions from the students. So if you have a great idea in the field of photonics or modelling that you would like to tackle, please come talk with us!

Bien que nous donnions cette liste en anglais, le Laboratoire de Nanophotonique & Métrologie (NAM) parle évidemment aussi le français et nous sommes heureux d'accueillir des étudiants francophones!


Realization of plasmonic aluminium nanodiscs embedded photoelectrode using
hole-mask colloidal lithography

hole-mask colloidal lithography (HCL) Fabrication of plasmonic aluminium nanodiscs (AlNds) embedded semiconductor photoelectrode is fascinating in plasmonic heterogeneous photocatalysis. Plasmonic properties such as near filed effect and hot electron generation from Al are proved to enhance the efficiency of semiconductor (SC) to harvest solar energy to drive chemical reactions. Patterning embedded AlNds on SC is challenging. Though electron beam lithography (EBL) is common to produce such nanostructures on the scale of tens to hundreds of microns, the time and cost required to fabricate over larger areas using EBL is prohibitive. Recently, hole-mask colloidal lithography (HCL) is being used to fabricate embedded structures over few cm2 substrates. In this project, HCL technique will be used to realize the 2 cm2 large AlNds embedded TiO2 photoelectrode. Briefly, thin film of sacrificial PMMA layer will be spin coated on TiO2 substrate followed by oxygen plasma etching to make it hydrophilic. Then, positively charged polyelectrolyte will be pipetted onto the PMMA surface forming a thin adhesive layer. This is followed by deposition of negatively charged colloidal PS beads forming a short-range-ordered PS nanoparticle array. A thin film of chromium will be deposited and then PS beads tape-stripped away, leaving nanoholes in the plasma-resistant film (“hole-mask”). CF4 plasma etching will be used to etch PMMA layer and also few nanometres of TiO2 forms embedded AlNds after Al evaporation. Optical and electrochemical properties of the electrode will be studied using UV-Vis. spectrometer and electrochemical potentiostat.

An ideal candidate has preferentially a solid background in material chemistry or physics.

What you will learn in this project:
  • Nanofabrication of Al and semiconductor photoelectrode
  • Optical and electrochemical characterization

Contact: Dr. Madasamy Thangamuthu

Second harmonic generation in Al, Ag, and Au thin film (Master project)

Second harmonic generation in Al, Ag, and Au thin film Since the first observation of plasmonic-enhanced second harmonic generation (SHG) at the surface of a 57-nm silver film, different noble metals have been employed to enhance the second harmonic emission by exploring the plasmonic effects which can lead to a strong near-field enhancement. The optical properties of noble metals at both the excitation and second harmonic frequencies, together with the second-order nonlinear susceptibility, play a central role in this second-order nonlinear optical process. Nevertheless, SHG in thin films made of various noble metals have not been compared yet, which is essential for selecting the best noble metal for efficient SHG in a plasmonic system. The main advantage of studying the thin film systems compared with the plasmonic nanostructures is associated with the wavevector-selective excitation of propagating surface plasmons on the thin films. For example, the propagating surface plasmons on a 40-nm silver film can only be excited at around 42° incidence by the Otto-Kretschmann configuration for the 800-nm excitation wavelength. In this case, one can compare the on- and off-resonance properties of SHG by simply tuning the incident angle of excitation light. In this project, we aim to investigate the SHG in thin films composed of the most interested plasmonic materials: aluminum (Al), silver (Ag), and gold (Au).

What you will learn in this project:
  • Design the dispersion of propagating surface plasmons
  • Thin film evaporation techniques
  • Nonlinear Fourier-plane imaging system

Contact: Kuang-Yu Yang

Automation of the sHRIM(spectral High Resolution Interference Microscope)
(semester project)

spectral High Resolution Interference Microscope The sHRIM is a custom-made interference microscope, which is operational across a wide range of the visible spectrum. It is capable of recording information about both the intensity and phase, giving a complete picture of the interaction between light and the samples under study. Since the phase domain is not constrained by the Abbe resolution limit, it can be utilised for achieving the so-called super-resolution, making the sHRIM a prominent instrument for characterising structures from a variety of fields (e.g. optics, plasmonics, metamaterials), as well as for fundamental research about phase-singularities. Additionally, all the information is recorded in a 3D volume, enabling the reconstruction of the complete field (tomography). In order to achieve all these, different components from different providers have to work together and seamlessly be integrated into the setup. This is the exact aim of this semester project. The student will have to develop a functional LabVIEW code for controlling the instrument, implementing all of its features and providing a user-friendly interface. The code should be modular, to allow the replacement of individual components, without the need of writing the code from scratch. The project can be expanded to include the data post-processing, as well as the recording and evaluation of measurements.

During this project, the student will:
  • Improve LabVIEW skills
  • Gain laboratory soft-skills
  • Develop critical thinking through the application of his/her own ideas

Prerequisites:
  • LabVIEW programming knowledge
  • Basic understanding of optics
  • Engineering background would help, as the majority of the problems will be technical

Contact: Michail Symeonidis

Electrodeposition of plasmonic nanomaterials (semester or master project)

Electrodeposition of plasmonic nanomaterials Plasmonic nanostructures (PNs) have been proved to enhance the efficiency of conventional semiconductor (SC) to harvest solar energy to generate electric current or drive chemical reactions. PNs concentrate light near SC surface and enhance hot carrier generation through antenna effect and surface plasmon resonance (SPR). Patterning PNs on SC is crucial, receiving high attention to fabricate facile and inexpensive photocatalysts. Though electron beam lithography (EBL) is common to generate such nanostructures on the scale of tens to hundreds of microns, the time and cost required to fabricate arrays over larger areas using EBL is prohibitive. Alternatively, nanochannel glass replica membranes (mask technology), colloidal lithography, and evaporative self-assembly have been used to fabricate patterned nanostructures. In this project, electrochemical deposition technique will be used to deposit noble metal nanoparticles over large surface of SC. PNs such as Au and Ag will be electrodeposited through direct deposition or template assisted deposition, later will give more uniform structures. Plasmonic properties of the electrodeposited photoelectrode will be characterized using UV-Vis. spectrometer and electrochemical potentiostat. This project will show the potential of electrodeposition technique to be a better alternative to fabricate plasmonic nanomaterials modified substrates.

An ideal candidate has preferentially a solid background in chemistry or physics.

What you will learn in this project:
  • Electrodeposition of Au and Ag nanoparticles
  • Optical and electrochemical characterization

Contact: Dr. Madasamy Thangamuthu

Electrochemical investigation of hot electron dynamics(semester or master project)

Electrochemical investigation of hot electron The outstanding light-trapping and electromagnetic-field-concentrating properties of surface plasmons open up a wide range of applications in the field of plasmonics. Recent investigations have shown that plasmonic nanostructures can also directly convert the collected light into electrical energy by generating hot electrons. Investigation of these hot electrons dynamics is highly useful for solar energy conversion to realize photovoltaic and photocatalytic devices. In this project, hot electrons dynamics will be investigated electrochemically to understand the mechanism and life time of this process. The metal–semiconductor Schottky junction will be configured by putting the plasmonic nanostructures in contact with semiconductor and then hot electrons generated photocurrent will be observed using photoelectrochemical cell. In addition transfer of these hot electrons into nearby electron acceptor molecules will also be investigated by employing cyclic voltammetry or amperometry techniques. Further, to correlate the visible-light activity of the photoanode to the optical properties of the Au NPs, the open-circuit voltage (Voc) will be monitored as a function of incident photon energy.

An ideal candidate has preferentially a solid background in chemistry or physics.

What you will learn in this project:
  • Fabrication of plasmonic photoelectrode
  • Optical and electrochemical characterization
  • Hot electron dynamics

Contact: Dr. Madasamy Thangamuthu

Fabrication of periodic plasmonic structures at large scale using colloidal lithography (semester or master project)

colloidal lithography The peculiar properties of nanostructured surfaces are of high interest for many applications in optics, plasmonic, photocatalysis, photovoltaics, biology or tribology. Colloidal lithography appears to be a cheap and suitable solution for the fabrication of periodical arrays of surface nanostructures. In contrast to sequential techniques such as focused ion beam (FIB) and electron beam lithography (EBL), colloidal lithography enables simple and fast patterning of large surface areas. The colloidal arrangement can be directly used for its inherent properties or as a mask for pattern transfer onto the underlying substrate by reactive ion etching or deposition of an appropriate material of interest.

The present project aims the patterning of large areas using dip-coating and Langmuir-Blodgett technique. The first step consists of optimising the process parameters to obtain a uniform colloidal arrangement containing large domains. In a following step the colloidal arrangement will be further optimised combining dip-coating with Langmuir-Blodgett thin films. Using lift-off technique the colloidal pattern will be transferred onto a glass substrate in order to achieve large area periodical nanostructures. The outcoming nanostructures will be experimentally characterised using scanning electron (SEM) and optical microscopy and spectroscopy. At the end, the results will be compared with modelled data. During the course of this project the student will be confronted with basics of nanofabrication, physics and chemistry of surfaces, plasmonics, optical spectroscopy and modelling. In addition, the project will be partly carried out using the cleanroom facilities of CMI. An ideal candidate has preferentially a solid background either in near-field optics, physics, chemistry, chemical physics or material science.

During the course of the project, the student will:
  • Develop processes for colloidal lithography using state-of-the-art machines
  • Practice nanotechnology at the CMI
  • Gain some knowledge of optical nanostructures

Prerequisites:

Nonlinear plasmonics (semester or master project)

SHG in a plasmonic nanostructure During the last decades, nanophotonics and, in particular, plasmonics have emerged as vivid fields of research, triggered by the promises of new applications and supported by recent technologic developments. Indeed, plasmonic nanostructures have the unique ability to localize electromagnetic fields in nanoscale volumes, far-beyond the limit established by the diffraction, permitting to control the properties of light at dimension much smaller than its wavelength. The optical properties of plasmonic nanostructures are explained by a physical phenomenon called localized surface plasmon resonances (LSPR), which corresponds to the collective oscillations of the conduction electrons over a static ionic background. The combination of the strong near-field intensity close to plasmonic systems with the intrinsic nonlinearities of metals results in different nonlinear optical processes giving rise to a new research field called nonlinear plasmonics.


What you will learn in this project:

The candidate will work in close interaction with PhD students and post-docs and will be involved in our recent developments in nonlinear plasmonics. The project can be tailored following the wishes of the student, with emphasis either on nanofabrication, numerical simulation or optical measurements based on femtosecond lasers. Come discuss with us, so we can find the topic that interest you most.


Contact: Dr. Jeremy Butet

Fabrication and optical characterisation of metallic nanocubes
(semester or master project)

Fabrication and optical characterisation of metallic nanocubes Precious metal nanoparticles exhibit unique optical properties which pave the way for many applications in material science, physics, chemistry, and biology. Due to there beneficial properties gold and silver are the most prominent metals for the fabrication of metallic nanoparticles. Such nanoparticles are, for instance, used as active substrates for Surface-Enhanced Raman Spectroscopy (SERS), enhanced near-field optical probes, and biological imaging. Size and shape of the particles are of crucial importance for those types of applications. Control of those parameters, however, remains a challenging task.
The present project aims (1) the fabrication of monodisperse silver nanocubes of specific size. (2) hydrophilic or hydrophobic surface functionalisation using self assembled monolayers (SAMs) (3) modelling of optical properties, and (4) experimental verification of the model.
An ideal candidate has preferentially a solid background either in near-field optics, physics, chemistry, or chemical physics.

Contact: Dr. Christian Santschi (photo: Y. Sun et al., Science 298, 2176, 2002)