Emmanuel Lhuillier - Academia.edu (original) (raw)

Papers by Emmanuel Lhuillier

HAL (Le Centre pour la Communication Scientifique Directe), 2015

Proceedings of the nanoGe Spring Meeting 2022, 2022

ACS Photonics, 2022

Intraband absorption in doped nanocrystals offers an interesting alternative to narrow band gap m... more Intraband absorption in doped nanocrystals offers an interesting alternative to narrow band gap materials to explore mid infrared optoelectronic device designs. However, the performance of such device clearly lags behind the ones relying on intrinsic materials. Livache et al. have proposed a dye sensitized approach to overcome the limitations observed from intraband materials (high dark current, slow response, low activation energy), where the intraband absorber is coupled to an undoped material which takes care of the charge conduction. Here, we unveil the coupling between both materials using mid-infrared transient reflectivity (TR) measurement. We show that hybrid material displays a unique feature in the TR signal that we attribute to a charge transfer and for which the dynamic matches the hopping time. We then developed a strategy to enhance the photodetection performances of the hybrid material by coupling for the first time intraband absorption to a light resonator. The latter is used to enhance the absorption by a factor 4 and enables an increase of the operating temperature by 80 K compared to the reference device. The obtained device matches the performance of best devices relying on intraband absorption.

Applied Physics Letters, 2021

van der Waals materials offer a large variety of electronic properties depending on chemical comp... more van der Waals materials offer a large variety of electronic properties depending on chemical composition, number of layers, and stacking order. Among them, As2Te3 has attracted attention due to the promise of outstanding electronic properties, and high photo-response. Precise experimental determinations of the electronic properties of As2Te3 are yet sorely needed for better understanding of potential properties and device applications. Here, we study the structural and electronic properties of α-As2Te3. Scanning transmission electron microscopy coupled to energy X-ray dispersion (STEM-EDX), and micro-Raman spectroscopy all confirm that our specimens correspond to α-As2Te3. Scanning tunneling spectroscopy (STS) at 4.2K demonstrates that α-As2Te3 exhibits an electronic band gap of about 0.4 eV. The material can be exfoliated, revealing the (100) anisotropic surface. Transport measurements on a thick exfoliated sample (bulk-like) confirm the STS results. These findings allows for a dee...

HgTe colloidal nanocrystals (NCs) have become a promising building block for infrared optoelectro... more HgTe colloidal nanocrystals (NCs) have become a promising building block for infrared optoelectronics. Despite their cubic zinc blende lattice, HgTe NCs tend to grow in a multipodic fashion, leading to poor shape and size control. Strategies to obtain HgTe NCs with well-controlled sizes and shapes remain limited and sometimes challenging to handle, increasing the need for a new growth process. Here, we explore a synthetic route via seeded growth. In this approach, the small HgTe seeds are nucleated in the first step, and they show narrow and bright photoluminescence with 75% quantum yield in the near infrared region. Once integrated into Light emitting diodes (LEDs), these seeds lead to devices with high radiance up to 20 WSr-1 m-2 and a long lifetime. Heating HgTe seeds formed at the early stage leads to the formation of sphere-shaped HgTe with tunable band edges from 2 to 4 µm. Last, the electronic transport tests conducted on sphere-shaped HgTe NC arrays reveals enhanced mobility and stronger temperature dependence than the multipodic shaped particles.

Journal of Physics: Conference Series, 2020

Photons have been identified early on as a very good candidate for quantum technologies applicati... more Photons have been identified early on as a very good candidate for quantum technologies applications, as carriers of quantum information, either by polarization encoding, time encoding or spatial encoding. Quantum cryptography, quantum communications, quantum networks and quantum computing are some of the applications targeted by the so called quantum photonics. Nevertheless, it was also clear at an early stage that bulk optics for handling quantum states of light would not be the best option for these technologies. More recently, single photons, entangled photons and quantum light in general have been coupled to integrated approaches coming from classical optics in order to meet the requirements of scalability, reliability and efficiency for quantum technologies. In this article, we describe our recent advances using elongated optical nano-fibers. We also present our latest results on nanocrystals made of perovskites and discuss some of their quantum properties. Finally, we will di...

Proceedings of the nanoGe Fall Meeting 2018, 2018

Advanced Optical Materials

Two-dimensional II-VI semiconductor nanoplatelets (NPLs) present exceptionally narrow optical fea... more Two-dimensional II-VI semiconductor nanoplatelets (NPLs) present exceptionally narrow optical features due to their thickness defined at the atomic scale. Since thickness drives the bandedge energy, its control is of paramount importance. Here, we demonstrate that native carboxylate ligands can be replaced by halides that partially dissolve cadmium chalcogenide NPLs at the edges. The released monomers then recrystallize on the wide top and bottom facets, leading to an increase in NPL thickness. This dissolution/recrystallization method is used to increase NPL thickness to 9 MLs while using 3 ML NPLs as the starting material. We also demonstrate that this method is not limited to CdSe and can be extended to CdS and CdTe to grow thick NPLs. When the metal halide precursor is introduced with a chalcogenide precursor on the NPLs, CdSe/CdSe, CdTe/CdTe, CdSe/CdTe core/shell homo-and heterostructures are achieved. Finally, when an incomplete layer is grown, NPLs with steps are synthesized. These stress-free homostructures are comparable to type I heterostructures, leading to recombination of the exciton in the thicker area of the NPLs. Following the growth of core/crown and core/shell NPLs, it affords a new degree of freedom for the growth of structured NPLs with designed band engineering, which has so far been only achievable for heteromaterial nanostructures.

Physical Review B, 2012

, file = rsa-modlock-29dec11.tex, printing time = 6 : 58) The coherent spin dynamics of resident ... more , file = rsa-modlock-29dec11.tex, printing time = 6 : 58) The coherent spin dynamics of resident carriers, electrons and holes, in semiconductor quantum structures is studied by periodical optical excitation using short laser pulses and in an external magnetic field. The generation and dephasing of spin polarization in an ensemble of carrier spins, for which the relaxation time of individual spins exceeds the repetition period of the laser pulses, are analyzed theoretically. Spin polarization accumulation is manifested either as resonant spin amplification or as mode-locking of carrier spin coherences. It is shown that both regimes have the same origin, while their appearance is determined by the optical pump power and the spread of spin precession frequencies in the ensemble.

Arxiv preprint arXiv:1011.1412, 2010

L'imagerie infrarouge bas flux requiert des détecteurs grandes longueurs d'onde de hautes perform... more L'imagerie infrarouge bas flux requiert des détecteurs grandes longueurs d'onde de hautes performances. Les détecteurs à puits quantiques (QWIP), de par la maturité de GaAs, la facilité à ajuster la longueur d'onde détectée sur une très large gamme et la possibilité de réaliser de larges matrices uniformes constituent d'excellents candidats pour ces applications. Afin de confirmer leur intérêt nous avons procédé à la caractérisation électro-optique fine d'un composant QWIP détectant à 15µm. Les performances mesurées ont été utilisées pour simuler celles d'une caméra basée sur ce détecteur et dédiée à un scénario faible flux et ont permis de valider la capacité de la filière QWIP à répondre à de telles missions infrarouges. Ces simulations ont aussi mis en évidence le rôle extrêmement préjudiciable joué par le courant d'obscurité. Nous avons alors mis au point une simulation basée sur un code de diffusion entre états localisés qui nous a permis de mieux appréhender le transport dans ces structures. Un important travail de développement de l'outil de simulation a été nécessaire. Ce code a révélé le rôle déterminant du profil de dopage sur le niveau de courant d'obscurité. Nous avons ainsi pu réaliser de nouvelles structures aux profils de dopage optimisés et dont le niveau de courant d'obscurité est abaissé de 50%. Nous avons par ailleurs pu apporter une interprétation quantique à la forme des courbes I(V) observée. Mais notre code de simulation s'avère plus généralement un outil puissant de simulation du transport dans les hétérostructures. L'influence des défauts de croissance (défauts d'interface et désordre) a pu être quantifiée et nous avons pu apporter les premières prédictions de performances de QCD THz. Enfin l'influence des effets non locaux sur le transport a été étudiée. L'observation de dents de scie sur les courbes I(V) de QWIP a pu être modélisée et son influence sur la détectivité évaluée.

Lead sulfide (PbS) colloidal quantum dots-based photodiodes are remarkable structures obtained vi... more Lead sulfide (PbS) colloidal quantum dots-based photodiodes are remarkable structures obtained via colloidal engineering because of their outstanding optoelectronic performances. They combine surface ligand engineering to design a p-n junction with all solution processability. Here we investigate the PbS diode electronic structure combining static and dynamic photoemissions with transport measurements. We show that the n-type nature of the Icapped PbS CQDs shifts the valence band away from the Fermi level compared to the thiol capped nanocrystals. This change in majority carriers can be probed using time resolved X-ray photoemission spectroscopy (TRXPS). We also prove that the photo-induced binding energy shift depends on the nanoparticle surface chemistry. Finally, we demonstrate the ability of TRXPS to selectively probe the electronic structure of each side of an interface. We explore the PbS/MoO3 interface used as hole extractor in the PbS solar cell, using this method. We demonstrate that the PbS layer photosensitizes the MoO3 layer and that the two layers have a quasi-rigid electrostatic coupling. We identify the band bending occurring on the PbS(EDT)/MoO3 to be a limiting factor for the device performance and suggest strategies to overcome this limitation.

Mercury telluride (HgTe) nanocrystals are among of the most versatile infrared (IR) materials wit... more Mercury telluride (HgTe) nanocrystals are among of the most versatile infrared (IR) materials with the absorption of first optical absorption which can be tuned from visible to the THz range. Therefore, they have been extensively considered as near IR emitters and as absorbers for low-cost IR detectors. However, the electroluminescence of HgTe remains poorly investigated in spite of its ability to go toward longer wavelengths compared to traditional lead sulfide (PbS). Here, we demonstrate a light emitting diode (LED) based on an indium tin oxide (ITO)/zinc oxide (ZnO)/ZnO-HgTe/PbS/gold stacked structure, where the emitting layer consists of a ZnO/HgTe bulk heterojunction which drives the charge balance in the system. This LED has low turn-on voltage, long lifetime, and high brightness. Finally, we conduct short wavelength infrared (SWIR) active imaging, where illumination is obtained from a HgTe NC-based LED, and demonstrate moisture detection.

ACS Applied Nano Materials, 2019

Nanocrystals are often described as interesting materials for the design of low-cost optoelectron... more Nanocrystals are often described as interesting materials for the design of low-cost optoelectronic devices especially in the infrared range. However the driving materials reaching infrared absorption are generally heavy metalcontaining (Pb and Hg) with a high toxicity. An alternative strategy to achieve infrared transition is the use of doped semiconductors presenting intraband or plasmonic transition in the short, mid and long-wave infrared. This strategy may offer more flexibility regarding the range of possible candidate materials. In particular, significant progress have been achieved for the synthesis of doped oxides and for the control of their doping magnitude. Among them, tin doped indium oxide (ITO) is the one providing the broadest spectral tunability. Here we test the potential of such ITO nanoparticles for photoconduction in the infrared. We demonstrate that In2O3 nanoparticles present an intraband absorption in the mid infrared range which is transformed into a plasmonic feature as doping is introduced. We have determined the cross section associated with the plasmonic transition to be in the 1-3x10-13 cm 2 range. We have observed that the nanocrystals can be made conductive and photoconductive due to a ligand exchange using a short carboxylic acid, leading to a dark conduction with n-type character. We bring evidence that the observed photoresponse in the infrared is the result of a bolometric effect.

IEEE Journal of Quantum Electronics, 2012

Sawtooth patterns in the I(V) curves of superlattices result from the bistability induced by the ... more Sawtooth patterns in the I(V) curves of superlattices result from the bistability induced by the negative differential resistance of the local J(F) curve. This behavior has been extensively studied in weakly coupled superlattices from a transport point of view. In this paper, we show that the sawtooth pattern not only affects the dark current but also the noise and responsivity properties of a quantum well infrared photodetector. The impact on the imaging properties of the detector is also quantified.

HAL (Le Centre pour la Communication Scientifique Directe), 2015

Proceedings of the nanoGe Spring Meeting 2022, 2022

ACS Photonics, 2022

Intraband absorption in doped nanocrystals offers an interesting alternative to narrow band gap m... more Intraband absorption in doped nanocrystals offers an interesting alternative to narrow band gap materials to explore mid infrared optoelectronic device designs. However, the performance of such device clearly lags behind the ones relying on intrinsic materials. Livache et al. have proposed a dye sensitized approach to overcome the limitations observed from intraband materials (high dark current, slow response, low activation energy), where the intraband absorber is coupled to an undoped material which takes care of the charge conduction. Here, we unveil the coupling between both materials using mid-infrared transient reflectivity (TR) measurement. We show that hybrid material displays a unique feature in the TR signal that we attribute to a charge transfer and for which the dynamic matches the hopping time. We then developed a strategy to enhance the photodetection performances of the hybrid material by coupling for the first time intraband absorption to a light resonator. The latter is used to enhance the absorption by a factor 4 and enables an increase of the operating temperature by 80 K compared to the reference device. The obtained device matches the performance of best devices relying on intraband absorption.

Applied Physics Letters, 2021

van der Waals materials offer a large variety of electronic properties depending on chemical comp... more van der Waals materials offer a large variety of electronic properties depending on chemical composition, number of layers, and stacking order. Among them, As2Te3 has attracted attention due to the promise of outstanding electronic properties, and high photo-response. Precise experimental determinations of the electronic properties of As2Te3 are yet sorely needed for better understanding of potential properties and device applications. Here, we study the structural and electronic properties of α-As2Te3. Scanning transmission electron microscopy coupled to energy X-ray dispersion (STEM-EDX), and micro-Raman spectroscopy all confirm that our specimens correspond to α-As2Te3. Scanning tunneling spectroscopy (STS) at 4.2K demonstrates that α-As2Te3 exhibits an electronic band gap of about 0.4 eV. The material can be exfoliated, revealing the (100) anisotropic surface. Transport measurements on a thick exfoliated sample (bulk-like) confirm the STS results. These findings allows for a dee...

HgTe colloidal nanocrystals (NCs) have become a promising building block for infrared optoelectro... more HgTe colloidal nanocrystals (NCs) have become a promising building block for infrared optoelectronics. Despite their cubic zinc blende lattice, HgTe NCs tend to grow in a multipodic fashion, leading to poor shape and size control. Strategies to obtain HgTe NCs with well-controlled sizes and shapes remain limited and sometimes challenging to handle, increasing the need for a new growth process. Here, we explore a synthetic route via seeded growth. In this approach, the small HgTe seeds are nucleated in the first step, and they show narrow and bright photoluminescence with 75% quantum yield in the near infrared region. Once integrated into Light emitting diodes (LEDs), these seeds lead to devices with high radiance up to 20 WSr-1 m-2 and a long lifetime. Heating HgTe seeds formed at the early stage leads to the formation of sphere-shaped HgTe with tunable band edges from 2 to 4 µm. Last, the electronic transport tests conducted on sphere-shaped HgTe NC arrays reveals enhanced mobility and stronger temperature dependence than the multipodic shaped particles.

Journal of Physics: Conference Series, 2020

Photons have been identified early on as a very good candidate for quantum technologies applicati... more Photons have been identified early on as a very good candidate for quantum technologies applications, as carriers of quantum information, either by polarization encoding, time encoding or spatial encoding. Quantum cryptography, quantum communications, quantum networks and quantum computing are some of the applications targeted by the so called quantum photonics. Nevertheless, it was also clear at an early stage that bulk optics for handling quantum states of light would not be the best option for these technologies. More recently, single photons, entangled photons and quantum light in general have been coupled to integrated approaches coming from classical optics in order to meet the requirements of scalability, reliability and efficiency for quantum technologies. In this article, we describe our recent advances using elongated optical nano-fibers. We also present our latest results on nanocrystals made of perovskites and discuss some of their quantum properties. Finally, we will di...

Proceedings of the nanoGe Fall Meeting 2018, 2018

Advanced Optical Materials

Two-dimensional II-VI semiconductor nanoplatelets (NPLs) present exceptionally narrow optical fea... more Two-dimensional II-VI semiconductor nanoplatelets (NPLs) present exceptionally narrow optical features due to their thickness defined at the atomic scale. Since thickness drives the bandedge energy, its control is of paramount importance. Here, we demonstrate that native carboxylate ligands can be replaced by halides that partially dissolve cadmium chalcogenide NPLs at the edges. The released monomers then recrystallize on the wide top and bottom facets, leading to an increase in NPL thickness. This dissolution/recrystallization method is used to increase NPL thickness to 9 MLs while using 3 ML NPLs as the starting material. We also demonstrate that this method is not limited to CdSe and can be extended to CdS and CdTe to grow thick NPLs. When the metal halide precursor is introduced with a chalcogenide precursor on the NPLs, CdSe/CdSe, CdTe/CdTe, CdSe/CdTe core/shell homo-and heterostructures are achieved. Finally, when an incomplete layer is grown, NPLs with steps are synthesized. These stress-free homostructures are comparable to type I heterostructures, leading to recombination of the exciton in the thicker area of the NPLs. Following the growth of core/crown and core/shell NPLs, it affords a new degree of freedom for the growth of structured NPLs with designed band engineering, which has so far been only achievable for heteromaterial nanostructures.

Physical Review B, 2012

, file = rsa-modlock-29dec11.tex, printing time = 6 : 58) The coherent spin dynamics of resident ... more , file = rsa-modlock-29dec11.tex, printing time = 6 : 58) The coherent spin dynamics of resident carriers, electrons and holes, in semiconductor quantum structures is studied by periodical optical excitation using short laser pulses and in an external magnetic field. The generation and dephasing of spin polarization in an ensemble of carrier spins, for which the relaxation time of individual spins exceeds the repetition period of the laser pulses, are analyzed theoretically. Spin polarization accumulation is manifested either as resonant spin amplification or as mode-locking of carrier spin coherences. It is shown that both regimes have the same origin, while their appearance is determined by the optical pump power and the spread of spin precession frequencies in the ensemble.

Arxiv preprint arXiv:1011.1412, 2010

L'imagerie infrarouge bas flux requiert des détecteurs grandes longueurs d'onde de hautes perform... more L'imagerie infrarouge bas flux requiert des détecteurs grandes longueurs d'onde de hautes performances. Les détecteurs à puits quantiques (QWIP), de par la maturité de GaAs, la facilité à ajuster la longueur d'onde détectée sur une très large gamme et la possibilité de réaliser de larges matrices uniformes constituent d'excellents candidats pour ces applications. Afin de confirmer leur intérêt nous avons procédé à la caractérisation électro-optique fine d'un composant QWIP détectant à 15µm. Les performances mesurées ont été utilisées pour simuler celles d'une caméra basée sur ce détecteur et dédiée à un scénario faible flux et ont permis de valider la capacité de la filière QWIP à répondre à de telles missions infrarouges. Ces simulations ont aussi mis en évidence le rôle extrêmement préjudiciable joué par le courant d'obscurité. Nous avons alors mis au point une simulation basée sur un code de diffusion entre états localisés qui nous a permis de mieux appréhender le transport dans ces structures. Un important travail de développement de l'outil de simulation a été nécessaire. Ce code a révélé le rôle déterminant du profil de dopage sur le niveau de courant d'obscurité. Nous avons ainsi pu réaliser de nouvelles structures aux profils de dopage optimisés et dont le niveau de courant d'obscurité est abaissé de 50%. Nous avons par ailleurs pu apporter une interprétation quantique à la forme des courbes I(V) observée. Mais notre code de simulation s'avère plus généralement un outil puissant de simulation du transport dans les hétérostructures. L'influence des défauts de croissance (défauts d'interface et désordre) a pu être quantifiée et nous avons pu apporter les premières prédictions de performances de QCD THz. Enfin l'influence des effets non locaux sur le transport a été étudiée. L'observation de dents de scie sur les courbes I(V) de QWIP a pu être modélisée et son influence sur la détectivité évaluée.

Lead sulfide (PbS) colloidal quantum dots-based photodiodes are remarkable structures obtained vi... more Lead sulfide (PbS) colloidal quantum dots-based photodiodes are remarkable structures obtained via colloidal engineering because of their outstanding optoelectronic performances. They combine surface ligand engineering to design a p-n junction with all solution processability. Here we investigate the PbS diode electronic structure combining static and dynamic photoemissions with transport measurements. We show that the n-type nature of the Icapped PbS CQDs shifts the valence band away from the Fermi level compared to the thiol capped nanocrystals. This change in majority carriers can be probed using time resolved X-ray photoemission spectroscopy (TRXPS). We also prove that the photo-induced binding energy shift depends on the nanoparticle surface chemistry. Finally, we demonstrate the ability of TRXPS to selectively probe the electronic structure of each side of an interface. We explore the PbS/MoO3 interface used as hole extractor in the PbS solar cell, using this method. We demonstrate that the PbS layer photosensitizes the MoO3 layer and that the two layers have a quasi-rigid electrostatic coupling. We identify the band bending occurring on the PbS(EDT)/MoO3 to be a limiting factor for the device performance and suggest strategies to overcome this limitation.

Mercury telluride (HgTe) nanocrystals are among of the most versatile infrared (IR) materials wit... more Mercury telluride (HgTe) nanocrystals are among of the most versatile infrared (IR) materials with the absorption of first optical absorption which can be tuned from visible to the THz range. Therefore, they have been extensively considered as near IR emitters and as absorbers for low-cost IR detectors. However, the electroluminescence of HgTe remains poorly investigated in spite of its ability to go toward longer wavelengths compared to traditional lead sulfide (PbS). Here, we demonstrate a light emitting diode (LED) based on an indium tin oxide (ITO)/zinc oxide (ZnO)/ZnO-HgTe/PbS/gold stacked structure, where the emitting layer consists of a ZnO/HgTe bulk heterojunction which drives the charge balance in the system. This LED has low turn-on voltage, long lifetime, and high brightness. Finally, we conduct short wavelength infrared (SWIR) active imaging, where illumination is obtained from a HgTe NC-based LED, and demonstrate moisture detection.

ACS Applied Nano Materials, 2019

Nanocrystals are often described as interesting materials for the design of low-cost optoelectron... more Nanocrystals are often described as interesting materials for the design of low-cost optoelectronic devices especially in the infrared range. However the driving materials reaching infrared absorption are generally heavy metalcontaining (Pb and Hg) with a high toxicity. An alternative strategy to achieve infrared transition is the use of doped semiconductors presenting intraband or plasmonic transition in the short, mid and long-wave infrared. This strategy may offer more flexibility regarding the range of possible candidate materials. In particular, significant progress have been achieved for the synthesis of doped oxides and for the control of their doping magnitude. Among them, tin doped indium oxide (ITO) is the one providing the broadest spectral tunability. Here we test the potential of such ITO nanoparticles for photoconduction in the infrared. We demonstrate that In2O3 nanoparticles present an intraband absorption in the mid infrared range which is transformed into a plasmonic feature as doping is introduced. We have determined the cross section associated with the plasmonic transition to be in the 1-3x10-13 cm 2 range. We have observed that the nanocrystals can be made conductive and photoconductive due to a ligand exchange using a short carboxylic acid, leading to a dark conduction with n-type character. We bring evidence that the observed photoresponse in the infrared is the result of a bolometric effect.

IEEE Journal of Quantum Electronics, 2012

Sawtooth patterns in the I(V) curves of superlattices result from the bistability induced by the ... more Sawtooth patterns in the I(V) curves of superlattices result from the bistability induced by the negative differential resistance of the local J(F) curve. This behavior has been extensively studied in weakly coupled superlattices from a transport point of view. In this paper, we show that the sawtooth pattern not only affects the dark current but also the noise and responsivity properties of a quantum well infrared photodetector. The impact on the imaging properties of the detector is also quantified.