Nanotechnological Enhancement of Infrared Detectors by Plasmon Resonance in Transparent Conductive Oxide Nanoparticles

We investigated the use of plasmonic nanotechnology to enhance the performance of semiconductor infrared detectors. An increase of quantum efficiency, responsivity and specific detectivity is obtained by applying transparent conductive oxide (TCO) nanoparticles onto the surface of a photodetector. To this purpose we considered uncooled mercury cadmium telluride (HgCdTe) photoconductive detectors fabricated by isothermal vapor phase epitaxy, but the same procedure can be applied to cryogenically cooled devices, including those of photovoltaic type. The main mechanism of enhancement is light concentration ensured through localized plasmon resonance at the TCO nanoparticles and through enhanced scattering, while the desired wavelength range is reached by a further redshifting through the adjustment of nanoparticle properties. The improvement can be implemented during the final stages of production of the existing photovoltaic and photoconductive detectors. The method is applicable to various practical applications, including updating of high-precision guided ammunition

Nanoplasmonics In Two-dimensional Dirac and Three-dimensional Metallic Nanostructure Systems

Surface plasmons are collective oscillation of electrons which are coupled to the incident electric field. Excitation of surface plasmon is a route to engineer the behavior of light in nanometer length scale and amplifying the light-matter interaction. This interaction is an outcome of near-field enhancement close to the metal surface which leads to plasmon damping through radiative decay to outgoing photons and nonradiative decay inside and on the surface of the material to create an electron-hole pair via interband or intraband Landau damping. Plasmonics in Dirac systems such as graphene show novel features due to massless electrons and holes around the Dirac cones. Linear band structure of Dirac materials in the low-momentum limit gives rise to the unprecedented optical and electrical properties. Electronical tunability of the plasmon resonance frequency through applying a gate voltage, highly confined electric field, and low plasmon damping are the other special propoerties of the Dirac plasmons. In this work, I will summarize the theoretical and experimental aspects of the electrostatical tunable systems made from monolayer graphene working in mid-infrared regime. I will demonstrate how a cavity-coupled nanopatterned graphene excites Dirac plasmons and enhances the light-matter interaction. The resonance frequency of the Dirac plasmons is tunable by applying a gate voltage. I will show how different gate-dielectrics, and the external conditions like the polarization and angle of incident light affect on the optical response of the nanostructure systems. I will then show the application of these nanodevices in infrared detection at room temperature by using plasmon-assisted hot carriers generation. An asymmetric nanopatterned graphene shows a high responsivity at room temperature which is unprecedented. At the end, I will demonstrate the properties of surface plasmons on 3D noble metals and its applications in light-funneling, photodetection, and light-focusing

Optical surfaces for mid-infrared sensing

The mid-infrared (mid-IR) spectral region, with wavelengths between 3 and 15 µm, is known for a wide range of applications ranging from spectroscopic sensing to thermal imaging. However, despite the strong technological interest, optoelectronic devices in the mid-IR are expensive and often inferior in performance compared to their visible and near-IR counterparts. In this thesis, we combine ultrathin materials, e.g. graphene, and novel substrates to develop optical surfaces for applications in the mid-IR.First, we demonstrate a novel uncooled photodetector, combining graphene with a ferroelectric (pyroelectric) substrate. More specifically, we develop a graphene on z-cut lithium niobate (LiNbO3) pyro-resistive platform that supports dynamic tunablity of the responsivity. We also develop a model to identify the key parameters that influence the performance of such detectors and can therefore provide guidelines to improve their performance. Second, we introduce ultra-thin yttria-stabilized zirconia (YSZ), a ceramic material, as a novel platform for IR nano-optics. In particular, we combine YSZ substrates with metallic nanostructures and graphene to demonstrate plasmonic, polarizing and transparent heating devices, which enable high temperature processing and can withstand harsh environments thanks to the high thermal and chemical stabilities of YSZ. Additionally, the mechanical flexibility of YSZ substrates also makes them ideally suited for manufacturing foldable or bendable devices and for low cost large-scale roll-to-roll fabrication processes. Finally, we investigate for the first time electrostatically tunable graphene nano-hole array surfaces by performing a detailed experimental study of structures with periods as low as 100 nm. We obtain a clear plasmonic response from these surfaces in the range 1300-1600 cm-1. We also demonstrated for the first time that these tunable nanostructures can be fabricated by scalable nano-imprint technique. Such large area plasmonic nanostructures are suitable for industrial applications, for example, surface-enhanced infrared absorption (SEIRA) sensing. This is because they combine an easy design, extreme field confinement and the possibility to excite multiple plasmon modes for multiband sensing, a feature not readily available in nanoribbons or other localized resonant geometries. The results contained in this thesis are particularly relevant with regard to extending the use of materials, such as graphene combined with specific substrates (LiNbO3 or zirconia), to mid-IR photodetection, enhanced absorption and molecular sensing.La región espectral del infrarrojo medio (mid-IR), de longitudes de onda entre los 3 y los 15µm, se conoce por su vasto número de aplicaciones: desde la detecciónespectroscópica hasta la imagen térmica. No obstante, a pesar de su gran interéstecnológico, los dispositivos optoelectrónicos en el mid-IR son caros y, a menudo,con rendimientos inferiores al compararlos con sus homólogos en la región visibley en el infrarrojo cercano. En esta tesis, combinamos materiales ultrafinos(e.g. grafeno) con nuevos substratos para desarrollar superficies ópticas conaplicaciones en el mid-IR.Primero, mostramos los resultados de un fotodetector innovador, que nonecesita ser enfriado, fabricado combinando grafeno con un substrato ferroeléc-trico (piroeléctrico). Más específicamente, desarrollamos un artefacto de grafenodispuesto sobre niobato de litio (LiNbO3) cortado en la dirección z, que admiteuna modulación dinámica de su capacidad de respuesta. También desarrollamosun modelo matemático con el propósito de identificar los parámetros claves queinfluyen en el rendimiento de estos fotodetectores y, en consecuencia, propor-cionar una serie de pautas para mejorarlo. En segundo lugar, introducimos la circonita estabilizada con óxido de itrioultrafina (YSZ) como material cerámico vanguardista en el campo de la nanoóp-tica en el IR. En particular, combinamos substratos de YSZ con nanoestructurasmetálicas y grafeno para demostrar la idoneidad de dispositivos plasmónicos,transparentes y polarizadores, que posibilitan el procesamiento a alta temper-atura y que pueden soportar condiciones ambientales más duras gracias a laexcelente estabilidad térmica y química de la YSZ. Además, la flexibilidad delos substratos de YSZ hace de éstas, unas estructuras ideales para la manufactura de dispositivos flexibles y plegables, cuyo proceso rollo-a-rollo de fabricacióna gran escala es de bajo coste. Finalmente, investigamos por vez primera las superficies de grafeno modu-ladas electrostáticamente con patrones de nano-orificios, cuyos periodos llegana distancias tan pequeñas como los 100 nm, por medio de un exhaustivo estudioexperimental. A través del mismo, obtenemos una respuesta plasmónica claraen el rango de los 1300-1600cm-1. También demostramos por primera vez, queestas nanoestrucutras modulables pueden ser fabricadas mediante técnicas es-calables de nanoimpresión. Las grandes dimensiones de dichas nanoestructurasplasmónicas, las hacen plenamente apropiadas para aplicaciones industrialescomo, por ejemplo, la detección por absorción infrarroja amplificada de super-ficie (SEIRA, por sus siglas en inglés). Esto ocurre debido a que combinan undiseño simple, con un confinamiento extremo del campo y con la posibilidad deexcitar diferentes modos plasmónicos, lo que es de gran utilidad para la detec-ción multi-banda, una característica difícil de conseguir con cintas de grafeno uotras geometrías localizadas resonantes. Los resultados integrados en esta tesisson particularmente relevantes con respecto a la extensión de la utilización demateriales como el grafeno en combinación con substratos específicos (LiNbO3o circonita) para la fotodetección en el mir-IR, la absorción amplificada y ladetección molecular.Postprint (published version

Optical surfaces for mid-infrared sensing

The mid-infrared (mid-IR) spectral region, with wavelengths between 3 and 15 µm, is known for a wide range of applications ranging from spectroscopic sensing to thermal imaging. However, despite the strong technological interest, optoelectronic devices in the mid-IR are expensive and often inferior in performance compared to their visible and near-IR counterparts. In this thesis, we combine ultrathin materials, e.g. graphene, and novel substrates to develop optical surfaces for applications in the mid-IR.First, we demonstrate a novel uncooled photodetector, combining graphene with a ferroelectric (pyroelectric) substrate. More specifically, we develop a graphene on z-cut lithium niobate (LiNbO3) pyro-resistive platform that supports dynamic tunablity of the responsivity. We also develop a model to identify the key parameters that influence the performance of such detectors and can therefore provide guidelines to improve their performance. Second, we introduce ultra-thin yttria-stabilized zirconia (YSZ), a ceramic material, as a novel platform for IR nano-optics. In particular, we combine YSZ substrates with metallic nanostructures and graphene to demonstrate plasmonic, polarizing and transparent heating devices, which enable high temperature processing and can withstand harsh environments thanks to the high thermal and chemical stabilities of YSZ. Additionally, the mechanical flexibility of YSZ substrates also makes them ideally suited for manufacturing foldable or bendable devices and for low cost large-scale roll-to-roll fabrication processes. Finally, we investigate for the first time electrostatically tunable graphene nano-hole array surfaces by performing a detailed experimental study of structures with periods as low as 100 nm. We obtain a clear plasmonic response from these surfaces in the range 1300-1600 cm-1. We also demonstrated for the first time that these tunable nanostructures can be fabricated by scalable nano-imprint technique. Such large area plasmonic nanostructures are suitable for industrial applications, for example, surface-enhanced infrared absorption (SEIRA) sensing. This is because they combine an easy design, extreme field confinement and the possibility to excite multiple plasmon modes for multiband sensing, a feature not readily available in nanoribbons or other localized resonant geometries. The results contained in this thesis are particularly relevant with regard to extending the use of materials, such as graphene combined with specific substrates (LiNbO3 or zirconia), to mid-IR photodetection, enhanced absorption and molecular sensing.La región espectral del infrarrojo medio (mid-IR), de longitudes de onda entre los 3 y los 15µm, se conoce por su vasto número de aplicaciones: desde la detecciónespectroscópica hasta la imagen térmica. No obstante, a pesar de su gran interéstecnológico, los dispositivos optoelectrónicos en el mid-IR son caros y, a menudo,con rendimientos inferiores al compararlos con sus homólogos en la región visibley en el infrarrojo cercano. En esta tesis, combinamos materiales ultrafinos(e.g. grafeno) con nuevos substratos para desarrollar superficies ópticas conaplicaciones en el mid-IR.Primero, mostramos los resultados de un fotodetector innovador, que nonecesita ser enfriado, fabricado combinando grafeno con un substrato ferroeléc-trico (piroeléctrico). Más específicamente, desarrollamos un artefacto de grafenodispuesto sobre niobato de litio (LiNbO3) cortado en la dirección z, que admiteuna modulación dinámica de su capacidad de respuesta. También desarrollamosun modelo matemático con el propósito de identificar los parámetros claves queinfluyen en el rendimiento de estos fotodetectores y, en consecuencia, propor-cionar una serie de pautas para mejorarlo. En segundo lugar, introducimos la circonita estabilizada con óxido de itrioultrafina (YSZ) como material cerámico vanguardista en el campo de la nanoóp-tica en el IR. En particular, combinamos substratos de YSZ con nanoestructurasmetálicas y grafeno para demostrar la idoneidad de dispositivos plasmónicos,transparentes y polarizadores, que posibilitan el procesamiento a alta temper-atura y que pueden soportar condiciones ambientales más duras gracias a laexcelente estabilidad térmica y química de la YSZ. Además, la flexibilidad delos substratos de YSZ hace de éstas, unas estructuras ideales para la manufactura de dispositivos flexibles y plegables, cuyo proceso rollo-a-rollo de fabricacióna gran escala es de bajo coste. Finalmente, investigamos por vez primera las superficies de grafeno modu-ladas electrostáticamente con patrones de nano-orificios, cuyos periodos llegana distancias tan pequeñas como los 100 nm, por medio de un exhaustivo estudioexperimental. A través del mismo, obtenemos una respuesta plasmónica claraen el rango de los 1300-1600cm-1. También demostramos por primera vez, queestas nanoestrucutras modulables pueden ser fabricadas mediante técnicas es-calables de nanoimpresión. Las grandes dimensiones de dichas nanoestructurasplasmónicas, las hacen plenamente apropiadas para aplicaciones industrialescomo, por ejemplo, la detección por absorción infrarroja amplificada de super-ficie (SEIRA, por sus siglas en inglés). Esto ocurre debido a que combinan undiseño simple, con un confinamiento extremo del campo y con la posibilidad deexcitar diferentes modos plasmónicos, lo que es de gran utilidad para la detec-ción multi-banda, una característica difícil de conseguir con cintas de grafeno uotras geometrías localizadas resonantes. Los resultados integrados en esta tesisson particularmente relevantes con respecto a la extensión de la utilización demateriales como el grafeno en combinación con substratos específicos (LiNbO3o circonita) para la fotodetección en el mir-IR, la absorción amplificada y ladetección molecular

Frequency Selective Detection of Infrared Radiation in Uncooled Optical Nano-Antenna Array

Mid-infrared (mid-IR) detection and imaging over atmospheric transparent 3-5 μm and 8-12 μm bands are increasingly becoming important for various space, defense and civilian applications. Various kinds of microbolometers offer uncooled detection of IR radiation. However, broadband absorption of microbolometers makes them less sensitive to spectrally resolved detection of infrared radiation and the fabrication is also very tedious involving multiple complex lithography steps. In this study, we designed an optical nano-antenna array based detector with narrow frequency band of operation. The structure consists of a two-element antenna array comprised of a perforated metallic hole array coupled with an underneath disk array which trap incident radiation as dipole currents. The energy is dissipated as electron plasma loss on the hole-disk system inducing close to ~100% absorption of the incident radiation. This near perfect absorption originates from simultaneous zero crossing of real component of permittivity and permeability due to the geometrical arrangement of the two antenna elements which nullifies overall charge and current distributions, prohibiting existence of any propagating electromagnetic modes at resonance. Moreover, the continuous perforated film allows probing of the induced micro-current plasma loss on each nano hole-disk pair via a weak bias current. Such optical antenna design enables flexible scaling of detector response over the entire mid-infrared regime by change in the antenna dimensions. Furthermore, the development of simple nanoimprint lithography based large area optical antenna array fabrication technique facilitates formation of low cost frequency selective infrared detectors

Light-Matter Interactions in Thin-Film Materials and their Optoelectronic Applications

Thin-film layered and traditional materials exhibit distinctive physics properties from their bulk counterparts. Thin-film materials bridges the gap between monolayer two-dimensional (2D) materials and bulk materials and possess the advantages of both, e.g., large tunability and high stability. However, recent research efforts focus on physical properties of monolayer 2D materials while state-of-art commercialized device applications are dominated by conventional bulk materials. Therefore, great potentials remain unexplored in thin-film materials, which host novel physics phenomenon and are promising for advanced device applications. In this work, we investigated the fundamental light-mattering properties of the thin-film materials and further demonstrated thin film devices for optoelectronic applications. The light-matter interactions in thin-film materials exhibit many fascinating physical properties. We first report symmetry-controlled electron-phonon interactions in strong-coupled thin-film layered materials/silicon dioxide (SiO2) vdWs heterostructures. Two optically silent Raman modes in amorphous SiO2 are activated by coupling with electronic transitions in thin-film layered materials, where the chirality and anisotropy are controlled by intrinsic electronic band properties of layered materials. In addition, Raman modes in honeycomb lattice can acquire unique chirality due to its pseudoangular momentum (PAM). We discuss a reduced chirality of Raman G mode with increasing layer number of the honeycomb graphene and hBN, suggesting that the interlayer interaction can significantly influence the symmetry of lattice vibration. Finally, we report a novel valley-selective linear dichroism in thin-film Tin Sulfide (SnS) with orthorhombic lattice. We observe two photoluminescence (PL) peaks, arising from band-edge optical interband transitions from two inequivalent valleys in SnS. The PL emission from Γ-X (Y) valley is completely x (y)-polarized. Thin-film materials also exhibit great potential for mid-infrared light generation, modulation and detection applications. We first report the PL properties of thin-film black phosphorus (BP), whose brightness is comparable to that of an indium arsenide multiple quantum well (MQW) structure. Remarkably, with a moderate displacement field up to 0.48 V/nm, the PL emission from a ~20-layer BP flake is continuously tuned from 3.7 to 7.7 μm, spanning 4 µm in mid-infrared spectral range. Our work provides a comprehensive understanding of mid-infrared light emission properties of thin-film BP, suggesting its promising future in mid-infrared tunable light emitting and lasing applications. In addition, we demonstrate an ultrafast microbolometer for mid-infrared light detection based on ultrathin silicon nanomembrane. In this device, a small heat capacity of approximately 1.9×10^(-11) J⁄K is achieved, which allows for its operation at a speed of over 10 kHz, around 100 times faster than commercial bolometers. Moreover, a compact diabolo antenna is leveraged for efficient mid-infrared light absorption, enabling the downscaling of the active area size to 6.2 µm by 6.2 µm. Due to its CMOS compatible fabrication processes, our demonstration may lead to the future high-resolution and high-speed LWIR imaging solution

High Temperature VO2 based Microbolometer with Enhanced Light Absorption

Department of Materials Science and EngineeringMicrobolometer depends on the change in electrical resistance of material as the temperature of the material changes. As element technology of microbolometer, VOx thin films are widely used due to high temperature resistance coefficients (TCR) and low noise . However, due to the metal insulator transition (MIT) property of the VO2 thin film, it is difficult to fabricate a micro bolometer at 68oC which can operate at high temperatures. Also, high light absorption is required . Here, we developed VO2 thin films a nd nanowires. And we developed a light absorber to increase the responsivity of microbolometer through high light absorption and applied it to various application. In order to obtain high quality of thermal sensitive material, we fabricated the resistor in cluded in micro bolometer which has a low resistance and a high temperature resistance coefficient (TCR) by growing the tetragonal VO2 crystal phase on the oxide thin film of the perovskite structure. In addition, infrared absorber has multilayer structure in which Ti metal layer and an MgF2 dielectric layer are alternately deposited with a several repetition cycle. The absorber layer shows about 70 % infrared absorption in the range of 8 14 ??m. In this paper, we used VO2 for the TCR material and the infrar ed absorber, showing the enhanced performance compared to that of the conventional micro bolometer. The micro bolometer operates even at high temperature of 100??C. The micro bolometer has a responsivity and detectivity of 4.90 x 10^3 V/W and 1.45 x 10^8 cmHz 1/2 /W at 100oC.clos

PbS colloidal quantum dots based photodetectors for integrated SWIR detection

Due to the low water absorption and nightglow, sensing in short wave infrared (SWIR) is very attractive in applications such as; passive night vision, biomedical imaging and remote sensing. The monolithic integration of photodetectors to the readout circuits is desirable in many applications to increase density of detectors and reduce costs, system size and power consumption. Solution-processed semiconductors are a promising alternative to conventional bulk crystalline photodetectors since their production is low cost and easy, their bandgap can be tuned depending on their sizes, and they can be easily integrated on any substrate. In this work, PbS colloidal quantum dot based photodiodes are realized that are compatible with the integration on Read Out Integrated Circuits (ROIC). Various kinds of PbS quantum dots based schottky diodes are designed on glass and silicon substrates. Spin deposition steps and solid state ligand exchange processes are optimized to create pinhole free and high mobility PbS quantum dot layers. In addition to that Integrated Circuit (IC) compatible versions of PbS colloidal quantum dot (CQD) photodiodes are realized. ROIC chip surface is mimicked on Si substrates and fabrication steps are optimized for integration. Special importance is given to optimize highly conductive and transparent indium tin oxide layer using DC magnetron sputtering. Sensitivities of 1.4x1012 Jones, comparable to the conventionally used crystalline, bulk photodetectors is achieved. Also, plasmonic scattering effects of metal nanoparticles in PbS CQD layer are studied. Absorption and responsivity enhancement of 6 fold is presented using gold nanoparticles in PbS CQD based photoconductors