laboratoire pierre aigrain
électronique et photonique quantiques
laboratoire pierre aigrain

Seminar, 19th April 2017 (13h30)

Aurélie PIERRET "Materials" service of Laboratoire Pierre Aigrain
Growth, characterization and optical properties of semiconducting nanomaterials

In this talk I will give an overview of my previous research projects I worked on during my master, PhD and postdoc. They are focused on the growth or fabrication of semiconducting nanomaterials with the aim of having the suitable optical properties, thus characterizations were a key point.
First I will present the growth of arrays of GaP/InP nanowires by CVD. The patterning of the catalyst gold nanoparticules was successfully done by soft-nanoimprint lithography, but this method leaves residues on the substrate, which leads to unwanted nanowires. I will show how I managed to clean the substrate and obtain perfect samples, suitable to study their optical properties [1]. Indeed, an array of nanowires forms a photonic crystal, for which I show that we can obtain a preferential direction of the photoluminescence emission [2].
Second, I will present the growth of AlxGa1-xN nanowires by MBE. The composition (x) of this alloy is important to master as it allows tuning the emission in the deep UV range between 4 and 6eV. But, as a ternary alloy, AlxGa1-xN with a well-controlled composition is hard to obtain, due to the difference of behaviour of Ga and Al atoms on the surfaces during growth. This leads to huge inhomogeneity at different scales, that are also difficult to characterize. I will show the characterization scheme I used to understand their nanostructure and to propose in fine a growth mechanism of such nanowires [3].
Third, I will present the optical properties of hexagonal BN (h-BN) in different forms. h-BN is a wide band gap semiconductor ( 6eV) with lamellar structure. The properties of the excitonic emission is still under debate and I will present some results, that make me believed that h-BN has Frenkel exciton with a huge binding energy [4]. Then I will show you the first results obtained when thinning down this material, thus by looking at nanosheets down to 6ML [5]. I will finally shift to the nanotube form, for which I had to completely understand their crystallographic structure in order to propose an explanation of the broad-band optical emission [6].
Finally, I will present the exfoliation by dry transfer with PDMS of transition metal dichalcogenides (TMDs) and its influence on the optical properties of the monolayers. I will also show you my observations of excitonic luminescence up-conversion in a WS2 monolayer and the different spectroscopic methods I used to understand the involved mechanism [7].
To conclude, I will sum-up my different skills in growth and characterizations of nanomaterials and present the different projects in which I am involved for the teams of LPA.

[1] Pierret et al., Nanotechnology 21 065305 (2010)
[2] Diedenhofen et al., ACS Nano 5(7) 5830 (2011)
[3] Pierret et al., Nanotechnology, 24 115704 (2013) / Pierret et al. Nanotechnology, 24 305703 (2013)
[4] Museur et al., Physica status solidi (rrl) 5 214 (2011)
[5] Pierret et al., Physical Review B, 89 035414 (2014)
[6] Pierret et al., Journal of Applied Physics, 118, 234307 (2015)
[7] Pierret et al., to be published