Monolithically Integrable Si-Compatible Light Sources

On the road to integrated optical circuits, the light emitting device is considered the bottleneck preventing us from arriving to the fully monolithic photonic system. While the development of silicon photonics keeps building momentum, the indirect bandgap nature of silicon represents a major problem for obtaining an integrated light source. Novel nanostructured materials based on silicon, such as silicon-rich oxide (SRO) containing silicon nanoparticles, present intense luminescence due to quantum phenomena. Using this material, electroluminescent devices have already been fabricated and even integrated in monolithic photonic circuits by fully complementary metal oxide semiconductor (CMOS) compatible techniques, opening the door to seamless electronic and photonic integration. The present work discusses some of the strategies used to improve the performance of SRO-based electroluminescent devices fully compatible with CMOS technology. Results from the characterization of devices obtained using different approaches are presented and compared

Luminescent Devices Based on Silicon-Rich Dielectric Materials

Luminescent silicon‐rich dielectric materials have been under intensive research due to their potential applications in optoelectronic devices. Silicon‐rich nitride (SRN) and silicon‐rich oxide (SRO) films have been mostly studied because of their high luminescence and compatibility with the silicon-based technology. In this chapter, the luminescent characteristics of SRN and SRO films deposited by low‐pressure chemical vapor deposition are reviewed and discussed. SRN and SRO films, which exhibit the strongest photoluminescence (PL), were chosen to analyze their electrical and electroluminescent (EL) properties, including SRN/SRO bilayers. Light emitting capacitors (LECs) were fabricated with the SRN, SRO, and SRN/SRO films as the dielectric layer. SRN‐LECs emit broad EL spectra where the maximum emission peak blueshifts when the polarity is changed. On the other hand, SRO‐LECs with low silicon content (~39 at.%) exhibit a resistive switching (RS) behavior from a high conduction state to a low conduction state, which produce a long spectrum blueshift (~227 nm) between the EL and PL emission. When the silicon content increases, red emission is observed at both EL and PL spectra. The RS behavior is also observed in all SRN/SRO‐LECs enhancing an intense ultraviolet EL. The carrier transport in all LECs is analyzed to understand their EL mechanism

Synthesis and Luminescent Properties of Silicon Nanocrystals

Nowadays, study of silicon-based visible light-emitting devices has increased due to large-scale microelectronic integration. Since then different physical and chemical processes have been performed to convert bulk silicon (Si) into a light-emitting material. From discovery of Photoluminescence (PL) in porous Silicon by Canham, a new field of research was opened in optical properties of the Si nanocrystals (Si-NCs) embedded in a dielectric matrix, such as SRO (silicon-rich oxide) and SRN (silicon-rich nitride). In this respect, SRO films obtained by sputtering technique have proved to be an option for light-emitting capacitors (LECs). For the synthesis of SRO films, growth parameters should be considered; Si-excess, growth temperature and annealing temperature. Such parameters affect generation of radiative defects, distribution of Si-NCs and luminescent properties. In this chapter, we report synthesis, structural and luminescent properties of SRO monolayers and SRO/SiO2 multilayers (MLs) obtained by sputtering technique modifying Si-excess, thickness and thermal treatments

Study of the Effect of Nitric Acid in Electrochemically Synthesized Silicon Nanocrystals: Tunability of Bright and Uniform Photoluminescence

In this work, we show a correlation between the composition and the microstructural and optical properties of bright and uniform luminescent porous silicon (PSi) films. PSi films were synthesized by electrochemical etching using nitric acid in an electrolyte solution. PSi samples synthesized with nitric acid emit stronger (up to six-fold greater) photoluminescence (PL) as compared to those obtained without it. The PL peak is shifted from 630 to 570 nm by changing the concentration ratio of the HF:HNO3:(EtOH-H2O) electrolyte solution, but also shifts with the excitation energy, indicating quantum confinement effects in the silicon nanocrystals (Si-NCs). X-ray photoelectron spectroscopy analysis shows a uniform silicon content in the PSi samples that emit the strongest PL. High-resolution transmission electron microscopy reveals that the Si-NCs in these PSi samples are about ~2.9 ± 0.76 nm in size and are embedded in a dense and stoichiometric SiO2 matrix, as indicated by the Fourier transform infrared analysis. On the other hand, the PSi films that show PL of low intensity present an abrupt change in the silicon content depth and the formation of non-bridging oxygen hole center defects

Effect of the Graded Silicon Content in SRN/SRO Multilayer Structures on the Si Nanocrystals and Si Nanopyramids Formation and Their Photoluminescence Response

Two multilayer (ML) structures, composed of five layers of silicon-rich oxide (SRO) with different Si contents and a sixth layer of silicon-rich nitride (SRN), were deposited by low pressure chemical vapor deposition. These SRN/SRO MLs were thermally annealed at 1100 °C for 180 min in ambient N2 to induce the formation of Si nanostructures. For the first ML structure (MLA), the excess Si in each SRO layer was about 10.7 ± 0.6, 9.1 ± 0.4, 8.0 ± 0.2, 9.1 ± 0.3 and 9.7 ± 0.4 at.%, respectively. For the second ML structure (MLB), the excess Si was about 8.3 ± 0.2, 10.8 ± 0.4, 13.6 ± 1.2, 9.8 ± 0.4 and 8.7 ± 0.1 at.%, respectively. Si nanopyramids (Si-NPs) were formed in the SRO/Si substrate interface when the SRO layer with the highest excess silicon (10.7 at.%) was deposited next to the MLA substrate. The height, base and density of the Si-NPs was about 2–8 nm, 8–26 nm and ~6 × 1011 cm−2, respectively. In addition, Si nanocrystals (Si-ncs) with a mean size of between 3.95 ± 0.20 nm and 2.86 ± 0.81 nm were observed for the subsequent SRO layers. Meanwhile, Si-NPs were not observed when the excess Si in the SRO film next to the Si-substrate decreased to 8.3 ± 0.2 at.% (MLB), indicating that there existed a specific amount of excess Si for their formation. Si-ncs with mean size of 2.87 ± 0.73 nm and 3.72 ± 1.03 nm were observed for MLB, depending on the amount of excess Si in the SRO film. An enhanced photoluminescence (PL) emission (eight-fold more) was observed in MLA as compared to MLB due to the presence of the Si-NPs. Therefore, the influence of graded silicon content in SRN/SRO multilayer structures on the formation of Si-NPs and Si-ncs, and their relation to the PL emission, was analyzed

Experiencias de Aprendizaje-Servicio en la UPM: 2021 y 2022

La Oficina de Aprendizaje-Servicio (ApS) de la UPM, constituida en sesión del Consejo de Gobierno de diciembre de 2019 tiene, como misión fundamental, promover en el ámbito de las enseñanzas de esta universidad la metodología ApS. Con esta finalidad se vienen realizando convocatorias de proyectos de impacto social alineados con los ODS como un mecanismo más para la contribución a la Agenda 2030, y se colabora intensamente con las diversas oficinas constituidas con el mismo objetivo en otras universidades. Nuestra oficina pretende impulsar progresivamente la colaboración con entidades ajenas a la UPM, y atender demandas y necesidades sociales en las que nuestros estudiantes y profesores brinden sus conocimientos para la construcción de una mejor y más justa sociedad. Con este propósito, se han puesto en marcha numerosas iniciativas y colaboraciones con Ayuntamientos, Asociaciones, ONG, Fundaciones y centros de enseñanza, con el fin común de plantear mejoras y trabajar con entornos desfavorecidos, y colectivos vulnerables de nuestro entorno. Cabe destacar la muy positiva acogida que, progresivamente se está logrando, en lo relativo a la diseminación de estas iniciativas en el ámbito de la UPM, viéndose incrementada la participación e interés de nuestros docentes y estudiantes en los llamamientos que se realizan desde la oficina. Desde la constitución de la oficina, son ya más de 100 actividades desarrolladas con la participación de más de 500 profesores. Uno de los compromisos de la Oficina ApS de la UPM es dar visibilidad por su carácter meritorio a las experiencias realizadas por el profesorado y los estudiantes de nuestra universidad y, es por ello, que nos complace la presentación de esta primera edición del ebook, en el que se recogen algunas de las experiencias realizadas en nuestra universidad y que confiamos ampliar periódicamente con futuras ediciones. Nuestro más sincero agradecimiento a todos los profesores que habéis hecho posible esta primera publicación con vuestras contribuciones