Gallium nanoparticles colloids synthesis for UV bio-optical sensors

F. Nucciarelli, I. Bravo, L. Vázquez, E. Lorenzo, J. L. Pau, "Gallium nanoparticles colloids synthesis for UV bio-optical sensors", SPIE Optics + Optoelectronics Proc. SPIE 10231 (16 May 2017) Copyright 2017 Society of Photo Optical Instrumentation Engineers. One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited. Proceedings of the Optical Sensors Conference (Prague, Czech Republic) doi: https://doi.org/10.1117/12.2265883A new method for the synthesis of colloidal gallium nanoparticles (Ga NPs) based on the thermal evaporation of Ga on an expendable aluminum zinc oxide (AZO) layer is presented here. The growth of AZO layers was investigated on different substrates at room temperature and 300 °C. By means of physical evaporation process, nanoparticles were deposited with a distribution ranging from 10 nm to 80 nm in diameter. A study of their endurance in acidic environment was carried out in order to assure the NPs shape and size stability during the etching process. Smaller particles start to disappear between 1h and 2h immersion time in a pH=1 solution, while bigger particles reduce their dimension. The NPs were dispersed in tetrahydrofuran (THF) organic solvent and optically characterized, showing strong UV absorption with a band centered at 280 nm. The colloids size distribution of as-evaporated samples was compared with the distribution obtained in droplets of the solution after drop-casting. By Dipole Discrete Approximation simulations, a close relationship between the UV absorption and the NPs with diameter smaller than ∼40 nm was found. Because of the gallium oxide (Ga1-xOx) outer shell that surrounds the Ga NPs, an enhancement of their hydrophobicity occurs. Hence, the low agglomeration state between NPs in tetrahydrofuran allows to obtain narrow absorption band in the optical spectrumWe are also grateful to the international PROMIS project, framed in the Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 641899. This research is supported by the MINECO (CTQ2014-53334-C2-2-R and MAT2016-80394-R) and Comunidad de Madrid (NANOAVANSES ref. S2013/MIT-3029) Projec

Surface modification of optoelectonic devices with gallium nanoparticles

Tesis Doctoral inédita leída en la Universidad Autónoma de Madrid, Facultad de Ciencias, Departamento de Física Aplicada. Fecha de Lectura: 12-07-2019This work aimed to the investigation and develop material surface modification procedures with the use of gallium nanoparticles (Ga NPs). Firstly, a new method to produce Ga colloids in different solvents was designed. The NPs were thermally evaporated on an aluminium zinc oxide (AZO) expendable layer to be transferred later to the solvent such as tetrahydrofuran (THF), deionized water (DIW) or ethanol (EtOH). The sample allowed to investigate the characteristic surface and bulk plasmonic absorptions of the growth NPs. Once determined the intrinsic optical property of the Ga nanostructures, the thesis work focused on the study of plasma and chemical treatment for shaping and tuning NPs arrays. By means of dry etching process, nanocone structures were obtained. The reshaping process was based on the height/diameter (h/d) ratio figure of merit. Comparing to the unmodified NPs, the smaller the h/d, the higher the light absorbed value as also confirmed by far field simulations. Further analytic calculation of different h/d ratios demonstrated up to two fold enhancement of the near field around the modified structure. Additionally, the Ga NPs were also used to fabricate Si nanocolumns with a Ga cap. The exotic shape guaranteed remarkable antireflective coating property, especially in the near infrared range. Since the surface modification strongly depends on the NPs coverage density, our study found that chloridric acid wet etching – a compatible method with many microelectronic processes - can easily control this parameter. Finally, Ga NPs were applied on an InGaAs/InAlAs avalanche photodiode surface jointly to a polymethylmethacrylate (PMMA) passivation layer. The latter helped as a buffer layer between the Ga and the mesa to stop conduction phenomena and reducing the leakage current contribution. Additionally, samples were thermally treated to tune the NPs layer physical composition, hence their effective permittivity. The treatment led to almost 30 % enhancement of the device light current generation. This thesis received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 641899

Gallium nanoparticles colloids synthesis for UV bio-optical sensors

Paper presented at the SPIE Optics + Optoelectronics, held in Prague (Czech Republic) on April 24-27th 2017.A new method for the synthesis of colloidal gallium nanoparticles (Ga NPs) based on the thermal evaporation of Ga on an expendable aluminum zinc oxide (AZO) layer is presented here. The growth of AZO layers was investigated on different substrates at room temperature and 300 °C. By means of physical evaporation process, nanoparticles were deposited with a distribution ranging from 10 nm to 80 nm in diameter. A study of their endurance in acidic environment was carried out in order to assure the NPs shape and size stability during the etching process. Smaller particles start to disappear between 1h and 2h immersion time in a pH=1 solution, while bigger particles reduce their dimension. The NPs were dispersed in tetrahydrofuran (THF) organic solvent and optically characterized, showing strong UV absorption with a band centered at 280 nm. The colloids size distribution of as-evaporated samples was compared with the distribution obtained in droplets of the solution after drop-casting. By Dipole Discrete Approximation simulations, a close relationship between the UV absorption and the NPs with diameter smaller than ~40 nm was found. Because of the gallium oxide (Ga1-xOx) outer shell that surrounds the Ga NPs, an enhancement of their hydrophobicity occurs. Hence, the low agglomeration state between NPs in tetrahydrofuran allows to obtain narrow absorption band in the optical spectrum

High Ultraviolet Absorption in Colloidal Gallium Nanoparticles Prepared from Thermal Evaporation

New methods for the production of colloidal Ga nanoparticles (GaNPs) are introduced based on the evaporation of gallium on expendable aluminum zinc oxide (AZO) layer. The nanoparticles can be prepared in aqueous or organic solvents such as tetrahydrofuran in order to be used in different sensing applications. The particles had a quasi mono-modal distribution with diameters ranging from 10 nm to 80 nm, and their aggregation status depended on the solvent nature. Compared to common chemical synthesis, our method assures higher yield with the possibility of tailoring particles size by adjusting the deposition time. The GaNPs have been studied by spectrophotometry to obtain the absorption spectra. The colloidal solutions exhibit strong plasmonic absorption in the ultra violet (UV) region around 280 nm, whose width and intensity mainly depend on the nanoparticles dimensions and their aggregation state. With regard to the colloidal GaNPs flocculate behavior, the water solvent case has been investigated for different pH values, showing UV-visible absorption because of the formation of NPs clusters. Using discrete dipole approximation (DDA) method simulations, a close connection between the UV absorption and NPs with a diameter smaller than ~40 nm was observed

Photoluminescence enhancement of monolayer MoS2 using plasmonic gallium nanoparticles

[EN] 2D monolayer molybdenum disulphide (MoS) has been the focus of intense research due to its direct bandgap compared with the indirect bandgap of its bulk counterpart; however its photoluminescence (PL) intensity is limited due to its low absorption efficiency. Herein, we use gallium hemispherical nanoparticles (Ga NPs) deposited by thermal evaporation on top of chemical vapour deposited MoS monolayers in order to enhance its luminescence. The influence of the NP radius and the laser wavelength is reported in PL and Raman experiments. In addition, the physics behind the PL enhancement factor is investigated. The results indicate that the prominent enhancement is caused by the localized surface plasmon resonance of the Ga NPs induced by a charge transfer phenomenon. This work sheds light on the use of alternative metals, besides silver and gold, for the improvement of MoS luminescence.The research is supported by the MINECO (CTQ2014-53334-C2-2-R, MAT2015-65356-C3-1-R and CTQ2017-84309-C2-2-R) and Comunidad de Madrid (NANOAVANSENS ref. S2013/MIT-3029) and UAM-Santander (2017/EEUU/14) projects. ARC acknowledges the Ramón y Cajal program (under contract number RYC-2015-18047). FN acknowledges support from the Marie Sklodowska-Curie grant agreement No. 641899 from the European Union's Horizon 2020 research and innovation programme

Photoluminescence enhancement of monolayer MoS2 using plasmonic gallium nanoparticles

2D monolayer molybdenum disulphide (MoS2) has been the focus of intense research due to its direct bandgap compared with the indirect bandgap of its bulk counterpart; however its photoluminescence (PL) intensity is limited due to its low absorption efficiency. Herein, we use gallium hemispherical nanoparticles (Ga NPs) deposited by thermal evaporation on top of chemical vapour deposited MoS2 monolayers in order to enhance its luminescence. The influence of the NP radius and the laser wavelength is reported in PL and Raman experiments. In addition, the physics behind the PL enhancement factor is investigated. The results indicate that the prominent enhancement is caused by the localized surface plasmon resonance of the Ga NPs induced by a charge transfer phenomenon. This work sheds light on the use of alternative metals, besides silver and gold, for the improvement of MoS2 luminescenceThe research is supported by the MINECO (CTQ2014-53334-C2-2-R, MAT2015-65356-C3-1-R and CTQ2017-84309-C2-2-R) and Comunidad de Madrid (NANOAVANSENS) ref. S2013/MIT-3029) and UAM-Santander (2017/EEUU/14) projects. ARC acknowledges the Ramón y Cajal program (under contract number RYC-2015-18047). FN acknowledges support from the Marie Sklodowska-Curie grant agreement No.641899 from the European Union's Horizon 2020 research and innovation programm