This PDF file contains the front matter associated with SPIE Proceedings Volume 12002, including the Title Page, Copyright information, Table of Contents, and Conference Committee listings.

In this paper, III-IV semiconductors are demonstrated as strong candidates for plasmonics applications in the Mid-IR. The perfect absorbers (PA) fabricated with heavily doped semiconductors features strong coupling between Fabry-Perot and localized surface plasmon modes. Also, anisotropic nano-antenna fabricated at the top surface yield a huge anisotropy to the polarized light. The fabricated PA with 2D periodic arrays of rectangular nano-antenna is presented, where the rectangular shape allows one to excite localized surface plasmon resonances (LSPR) at different wavenumbers depending on the polarization of the incident light. Preliminary results of the bio-functionalization through phosphonic acid are shown for the PA aditionnally. Furthermore, it becomes clear that it is possible to detect bio-molecules of interest even far in the infrared on a very small surface and with a few hundreds of nano-antenna.

We show here that Cd(Zn)O can be deposited on GaAs by MOCVD forming nanoparticles with a hemispherical shape. These nanoparticles maintain the key characteristics from a CdO film: very high plasma frequency and very low losses, hence retaining the strong plasmonic character. As a result of this, when illuminated with infrared light, two localized surface plasmon (LSP) modes are excited at 2.7 and 5.3 microns, and the electric field is heavily amplified in the underlying GaAs substrate. Moreover, their hemispherical geometry allows them to partially change the orientation of the field, creating a component perpendicular to the surface. We prove the coupling between the CdO LSPs and the intersubband transitions from a multiple QW structure, where the absorption is largely enhanced for p-polarized electric fields, and it is observed even under normal incidence conditions.

Most recently, electrochromic (EC) oxides, such as WO₃, have transcended far beyond their traditional scope of transmission modulation in smart windows. The ionically facilitated EC effect, leads to an extraordinary increase in excess charge carriers in the host oxide, effectively doping WO₃ up to 10²² cm^-3 electrons. With the protonation doping, the dielectric properties of the given oxide can be altered dynamically and locally. Hence, WO3 changes its refractive index from n = 1.9 to 2.3, and its extinction by Δ𝑘 = 0.5 in the near infrared (NIR). Here, we introduce a plasmonic, EC (‘plasmochromic’) nanowaveguide modulator, for ultrahigh modulation depth. WO3 is integrated into a plasmonic metalinsulator- metal (MIM) waveguide structure with a dual-function waveguide core containing amorphous LiNbO₃ (LN). In this novel architecture, LN provides sufficient ionic conduction for EC switching, while simultaneously supporting optical mode propagation. By decoupling the ionic pathway and the direction of plasmon propagation, the EC waveguide achieves unprecedented modulation speed and depth when compared to traditional EC devices. FDTD simulations predict a maximum modulation depth of 80 dB for 20 μm waveguide length, while measured values show up to 2.5 dB/μm modulation with switching times of a few seconds. The waveguide platform further provides great retention (> 20 h) of the switching state, while allowing very low operating voltages with a figure of merit of 8 dB/V. We envision EC oxide to provide pathways to dynamic photonic devices under low voltage settings, where high modulation is necessary.

Much excitement has surrounded the accelerating development of β-Ga₂O₃ for electronics due to its ultrawide band gap, high breakdown voltage, compatibility with many dopants, and comparative ease of producing large substrates via meltgrowth techniques. Our research has focused on growth and characterization of Czochralski (CZ) and vertical gradient freeze (VGF) single crystals of β-Ga₂O₃ with various dopants, including donors (Zr, Hf, Cr), acceptors (Mg, Zn, Fe, Ni, Cu), and alloying elements (Al). We find in general that doping in CZ and VGF materials can be different and sometimes non-uniform due to the interaction with crucible material (Ir), selective evaporation, and thermal profile. We have also explored the creation and identification of gallium vacancies (V_Ga) through annealing, by using positron annihilation spectroscopy (PAS), hydrogenated Fourier Transform Infrared (FTIR) spectroscopy, and electrical measurements. Different analysis techniques probe different spatial and depth averages, and thus careful consideration must be given to correctly interpret results and significance of defect concentrations determined. Insights from our work to date are offered, in terms of their applicability to devices.

In this paper we analyze the conduction properties, charge trapping and threshold voltage instability of normally-on β-Ga₂O₃ lateral MOSFETs for high power applications by means of threshold voltage transients. We found that a positive bias applied to the gate induces a rightward shift in the threshold voltage, caused by the trapping of electrons at border traps close to the semiconductor-dielectric interface.

The amount of trapped charge was investigated by an innovative fast-CV experimental setup and was found to follow a logarithmic kinetic in time, modeled by a generalization of the inhibition model that takes into account the effect of columbic repulsion in stress conditions.

Then, we developed a model for the gate conduction based on temperature dependent I_G-V_G characteristics. We detected that the gate current characterized in temperature and bias conditions similar to the ones used for the stress is dominated by Poole-Frenkel conduction assisted by a deep level at E_C - 0.12 eV.

Irradiation with high-energy electrons (HEE) at cryogenic temperatures is a subtle tool for shaping matter. Unlike irradiation with heavy particles, e.g. protons, neutrons, or ions, HEE irradiation produces very low local damage generating exclusively point lattice defects. In the interaction process, the primary high-energy electron transfers a minute quantity of energy to a lattice ion, just enough for displacing it from its lattice site. The concentration of induced vacancies depends on the irradiation dose and in this way can be carefully adjusted. Since the lattice defects can act as donor or acceptor states in semiconductors, electron irradiation enables accurately-controlled compensation of electrically-active impurities introduced in a semiconductor crystal during growth. In this article, we present a study of the evolution of electronic properties of β-gallium oxide with step-by-step compensation of initial n-type doping through controlled introduction of point defects (gallium vacancies) produced by a 2.5-MeV electron beam. Our analysis relies on a set of electron paramagnetic resonance, luminescence, and transport data obtained at different temperatures.

A Si-integrated oxide-nitride deep-ultraviolet photodetector with remarkable photosensitivity is demonstrated. The proposed device topology is realized through the disordered nucleation of β-Ga₂O₃ crystals on monocrystalline TiN interlayers forming an oxide-nitride vertical heterostructure stack housed on a Si substrate. Spectral responsivity levels of about 240 A/W at illuminating power density levels of around 7.40 μW/cm² were achieved.

In this paper, we analyze the electrical behavior and the deep levels present in nitrogen-implanted gallium oxide Schottky barrier diodes annealed at increasing temperature from 800 °C to 1200 °C. In gallium oxide, nitrogen implantation is used in order to achieve controlled isolation of parts of the final device, and its stability and performance is therefore of high importance.

The high temperature annealing carried out after implantation causes a reduction in the leakage current flowing in the structure, confirming the feasibility of nitrogen implantation as isolation procedure and the annealing of the defects caused by the implantation process.

Repeated current-voltage measurements show the presence of an electron trapping process in the structure. The involved deep levels were investigated by means of isothermal transient spectroscopy tests, and both current and capacitance were used to monitor the trapping level in the devices. A model was developed to explain the full set of collected data on all the annealing temperatures, based on thermionic injection of electrons into an intermediate deep level and on charge injection into the space charge region.

By means of deep level transient spectroscopy experiments we analyzed the various defects present in the samples. Their concentration correlates with the annealing, decreasing at high temperature. All the detected deep levels are consistent with previous reports in the literature, and are attributed to gallium vacancies, native point defects and extrinsic defects.

In this work, we present our recent results on the applicability of optical microcavities based on Cr doped Ga₂O₃ wires to operate as a nanothermometer in a wide temperature range (at least from 150 up to 550 K) and achieving a temperature precision of around 1 K. To this purpose, DBR (distributed Bragg reflectors) have been used to enhance the reflectivity at the lateral ends of the wires. The transduction mechanism encompasses both the luminescence features of the characteristic R-lines of Cr³⁺ ions in this host as well as the interferometric effects of the Fabry-Perot resonances within the cavity.

We have used first-principles calculations, based on advanced hybrid density functional theory, to accurately model diffusion of point defects and impurities in Ga₂O₃. Control of doping is crucial for devices: it should be possible to control the carrier concentrations all the way from semi-insulating to highly conductive n-type material. I will discuss impurities used for donor doping, deep acceptors, as well as unintentional contaminants such as carbon and hydrogen. The results provide important guidance for incorporating Ga₂O₃ into devices.

Market drivers for the increasing demand for optical interference coatings on planar substrates and lenses include data communication systems and consumer electronics. Magnetron sputtering can deliver environmentally stable coatings with high throughput. Low defect densities combined with high stability of the process and coating system enable complex optical layer designs with very accurate reproducibility. Cylindrical targets are well known for coatings on large area such as window glass, but are rarely used for coating stacks with high layer counts. With the OPTA X, we are introducing a rotary target-based platform that takes advantage of the long-term stable deposition rate and high material utilization of these sputtering sources. Cylindrical targets have almost no re-deposition zone and no deep racetracks due to rotation. This strongly reduces the potential of particle generating arcs that are caused by surface charges in oxidized target areas. We also use substoichiometric target material sputtered in a pure argon atmosphere without the need for further reactive gas process control. Oxidation is performed by a plasma source in a pressure-separated plasma oxidation zone. The platform can be equipped with sputter sources in a sputter-up or sputter-down configuration or in a combination of both. Interesting applications for double-sided filter coatings include beam splitters for aerospace applications or filter deposition on thin glass substrates to compensate for layer stresses and associated geometric deformations. The elimination of substrate flipping for double-sided coatings also enables shorter production times and offers potential for cost savings.

In this paper, we are presenting preliminary optical properties as well as deposition rates of SiO₂ and Nb₂O₅ oxide films. Furthermore, we are showing results of optical single layers as well as examples of filter coatings prepared by broadband transmittance monitoring and process control.

Atomic layer deposition (ALD) has been proven as an excellent method for coating high quality optical films due to its outstanding film quality and precise process control. Unfortunately, batch ALD requires time-consuming purge steps, which lead to low deposition rates and highly time-intensive processes for complex multilayer coatings. Recently, rotary ALD came in focus for optical applications. In this novel process concept, each process step takes place in a separate part of the reactor divided by pressure and nitrogen curtains. The substrates to-be-coated are rotated through these zones. During each rotation, an ALD cycle is completed, thus the deposition rate is mainly dependent on the rotation speed. In this study, the performance of a novel rotary ALD coating tool for optical applications is investigated and characterized with SiO₂ and Ta₂O₅ layers. Low absorption levels of 3.1 ppm for 200 nm thick single layer of Ta₂O₅ and 6.0 ppm for 1032 nm thick single layer of SiO₂ are demonstrated at 1064 nm, respectively, with growth rates up to 0.18 nm/s on fused silica substrates. Furthermore, excellent uniformity is also demonstrated with non-uniformity values reaching as low as 1.55 % and 2.71% for Ta₂O₅ and SiO₂, respectively, over 120 mm on silicon wafers. Seven substrates up to a diameter of 200 mm can be coated in each run. Further investigations on uniformity improvements and multilayer coatings are currently ongoing.

We report enhanced nonlinear optics in nanowires, waveguides, and ring resonators by introducing layered two-dimensional (2D) graphene oxide (GO) films through experimental demonstration. The GO films are integrated on silicon-on-insulator nanowires (SOI), high index doped silica glass, and silicon nitride (SiN) waveguides and microring resonators (MRRs), to demonstrate an improved optical nonlinearity including Kerr nonlinearity and four-wave mixing (FWM). By using a large-area, transfer-free, layer-by-layer GO coating method with photolithography and lift-off processes, we integrate GO films on these complementary metal-oxide-semiconductor (CMOS)-compatible devices. For SOI nanowires, significant spectral broadening of optical pulses in GO-coated SOI nanowires induced by self-phase modulation (SPM) is observed, achieving a high spectral broadening factor of 4.34 for a device with a patterned film including 10 layers of GO. A significant enhancement in the nonlinear figure of merit (FOM) for silicon nanowires by a factor of 20 is also achieved, resulting in a FOM > 5. For Hydex and SiN waveguides, enhanced FWM in the GO-coated waveguides is achieved, where conversion efficiency (CE) enhancements of up to 6.9 dB and 9.1 dB relative to the uncoated waveguides. For MRRs, an increase of up to ~10.3 dB in the FWM CE is achieved due to the resonant enhancement effect. These results reveal the strong potential of GO films to improve the nonlinear optics of nanowires, waveguides, and ring resonators.

The advent of modern devices requires the development of multifunctional nanomaterials with improved performance, while involving low-cost and sustainable processing. In this frame semiconducting oxide nanoparticles and hybrid composites formed by their combination with an organic matrix are gaining increasing attention based on their versatility and wide range of applicability in many fields of technological research. In this work semiconducting oxide nanoparticles (SnO, SnO₂, TiO₂, Ni-Mn-O) and hybrid composites formed with the nanoparticles embedded in Poly(3,4- ethylene-dioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) have been synthesized following diverse chemical routes. The samples have been characterized by using advanced microscopy and spectroscopy techniques and their performance in photovoltaics, thermoelectrics, gas sensing, and energy-related applications have been evaluated. Improvements were achieved by the synergy between the components of the composites.

Surface functionalization of silicon wafers using nanoscale fabrication techniques has attracted a great deal of interest for its promising photonic applications ranging from energy harvesting to sensing and imaging. The surfaces so produced offer also exciting physical properties particularly optical emission and light trapping in a broad spectral range. Several approaches have been used to demonstrate the possibility of producing such functional surfaces using plasma processing, pulsed laser ablation, etc. However, the investigation of a detailed radiative dynamical properties of the recombination processes is still lacking a detailed knowledge. Here, we present the results of the investigation of optical properties of nano sized silicon quantum pillar arrays using advanced characterization techniques.

Zinc manganese oxide (ZnMnO) grown by metal-organic chemical vapor deposition (MOCVD) and atomic layer deposition (ALD) exhibit absorption band edge tunability with Mn incorporation. ZnMnO with good crystal quality oriented in the (002) direction was grown using MOCVD. ALD-grown ZnMnO was amorphous but exhibited high crystallinity after annealing at 800 °C for 1 hour. ZnMnO using both growth techniques showed an overall reduction in band edge with Mn incorporation, but the trend was scattered. The band edge reduction is influenced by energy states and oxidation states of Mn incorporated in ZnMnO rather than the cumulative Mn incorporation. Incorporation of Mn with oxidation states favorable to achieve bandgap tunability could be controlled with growth techniques and growth conditions. Control over energy states introduced by Mn in ZnMnO could enable application of ZnMnO for various areas of interest including spintronics, photovoltaics, photodiodes, and sensing.

We studied polarization-resolved photoluminescence originating from a ZnO-(Mg,Zn)O quantum well heterostucture embedded within an atom probe tip, i.e. a nanoscale needle-shaped sample with apex radius of several tens of nm, prepared by focused ion beam. The study was carried out within a photonic atom probe before the atom probe analysis of the sample. This setup allows for the analysis of the polarization of the photoluminescence emitted by the tip and for its orientation around its axis. While the photoluminescence emitted by bulk ZnO and by the (Mg,Zn)O alloy is strongly polarized along the tip axis, coinciding with the crystal [1-100] axis, the ZnO/(Mg,Zn)O quantum well luminescence appears to be strongly polarized along its in-plane direction, perpendicular to the crystal [1-100] axis. Finite-difference time domain calculations provide a key for the interpretation of these results in terms of selection rules and of effects related to the waveguide effect of the tip.

Ultrasounds are a great tool for defects detection particularly for optically non-transparent materials. Hence, working at very high frequency (#GHz) allows the detection of nanoscale contact defects at the interface between two materials and especially in the presence of air, which has negligible acoustic impedance, making it possible to achieve very high sensitivity.

For several years, we have been using the high frequency acoustic method for the wetting evaluation of nanostructures in our laboratory. In close collaboration with STMicroelectronics company, we deal with the study of wetting state in the context of wet cleaning processes optimization in the microelectronics industry.

Within this perspective and in order to reach these very high frequency ranges, ZnO piezoelectric transducers were developed and integrated on samples to be studied. Thanks to a dedicated workbench, the dynamic of the wetting and drying phenomena have been achieved on high-aspect-ratio nanostructures with liquid solutions having different surface tensions.

Transition metal-doped zinc oxide (ZnTMO) grown using metal-organic chemical vapor deposition exhibited spinrelated properties at room temperature that are driven by secondary phases, defects, transition metal clusters, and extrinsic carrier scattering. ZnTMO has been an interesting material for spintronics and has shown ferromagnetism at room temperature in the literature. However, the mechanism for spin-characteristics is not clear. In this work, Anomalous Hall Effect measurements were performed to investigate these mechanisms. A non-linear trend of transverse Hall resistvity with externally applied field indicated spin polarization in the material. However, variations in transverse resistivity with applied magnetic field follow same trend as four-point Van der Pauw resistivity. Hence, the Anomalous Hall Effect is likely not due to intrinsic free carriers. Spin-related properties of ZnTMO are dominantly influenced by secondary phases, native defects, and other extrinsic carrier-scattering centers such as transition metal clusters. This work contributes towards the understanding of ZnTMO for spintronic applications and provides better clarity regarding the underlying phenomena for its spin-related properties.

The increasing demands for device miniaturization toward energy efficient electronic, optoelectronic, and spintronic applications have led to the advancement of novel material systems such as multiferroics. In this study, we investigated nonlinear optical responses of a (0.275)BaTiO₃-(0.725)BiFeO₃ (BTO-BFO) film and a nanorod arrays, grown on Si substrates. Our results are important for employing these materials for new and improved optical applications.

Pyroelectric detectors are widely used thermal infrared detectors due to their simple construction, robustness, and excellent performance. Most pyroelectric devices are based on monocrystalline lithium tantalate (LT) or pyroelectric lead zirconate titanate (PZT) thin films deposited on silicon (Si) substrate. In comparison, recently discovered pyroelectric doped hafnium oxide (HfO₂) offers the possibility to manufacture completely CMOS-compatible devices on large silicon wafers.

Three-dimensional substrates with trench structures were applied for detectors to multiply the pyroelectric current responsivity of a thin, doped hafnium oxide layer deposited by atomic layer deposition. Micromechanical structuring of the 6” silicon wafers was used to improve the thermal conversion and effective plasmonic absorbers for the spectral range 3 - 5 μm.

An effective pyrocoefficient up to 1300 μC/m²/K was measured, depending on various dopants (Si, Al, La), layer thicknesses and polarization conditions. A high infrared light absorption > 80% of the plasmonic absorber in the relevant spectral range was determined using FTIR reflection measurements. The performance of the sensor element has been evaluated with a conventional analog transimpedance amplifier with a feedback resistance of 5 GΩ. A specific detectivity D* > 1 ∙ 10⁷ cm√Hz/W (black body 1000 K, 3 - 5 μm) was measured for the frequency range 1 - 10 Hz.

Additionally, a new application-specific integrated circuit (ASIC) was used for the electrical signal conditioning to realize the first fully CMOS-compatible pyroelectric detector. This detector offers a flexible configuration, digital communication interface and achieves a similar signal-to-noise performance as the analog detectors.

Within oscillation electron model the superconducting crystal AB is considered consisting of two subsystems for phase separation. During the phase transition in the AB crystal, the valence bond breaking associated with the crystal lattice destruction. It is caused by the balance energies of the AB and A-A, B-B bonds. The basic principle of the phase transition is caused by bonds being broken and dumbbell configurations of atoms are formed.

The pairing of electrons is guided by a plasma mechanism. Free electrons couple to lower system energy. When molecules are formed from individual atoms by dumbbell configuration, energy is released. The energy balance is caused by a change in the distances between atoms A-A and B-B with decreasing temperature. It is necessary, that square electron plasma energy in a local phase was essentially much less, than the one in an initial phase. This is the condition for the superconducting phase transition in the crystal AB.

The equations of the superconducting phase transition curve Tc(q) are derived within the known experimental data and our theoretical parameters Φ (M, ρ, s, q, β), where square Φ (аb), square Φ (а), square Φ (b) is square electron energy in square eV crystal AB, A, B, respectively, Tc is the phase transition temperature, ρ is density, s is valence electron number, M is molecular (atomic) mass, q and β are parameters. The electron plasma parameters of iron selenide FeSe, magnesium diboride MgB2, complex cuprates YBaCuO, mixed compounds of silver Ag2O and gold oxide Ag3AuS2 were calculated.

Calculations for crystals were carried out with the general approach. The phase transition temperature Tc calculated using the equations is obtained for crystals Ag2O, Ag2S, AgJ, RbAg4I5, Ag26I18W4O16, Ag3AuS2. The superconducting or superionic phase transition is described within model by the ratio square plasma energy of the initial crystals and their local sublattices. Interaction parameters for superionic crystals by the equation can be determined.

To avoid foodborne illness, maintaining the prolonged food freshness and real-time food quality/health monitoring are the challenges to be addressed in this era. Development of active food packaging is an advancing research for real-time food health monitoring. In this study, mesoporous silica nanospheres (MSNs) have been synthesized with controlled size (>100nm) and porosity by using modified Stöber method. These MSNs are capable of adsorbing oxygen by physisorption thus can be used as oxygen scavengers for food packaging materials to extend shelf life of the food products. Furthermore, this study aims to incorporate active metal oxide nanoparticles (MNPs) in the pores of synthesized MSNs to extend its applications as oxygen scavenging and detection to avoid oxygen produced food degradation. The MNPs with an average size of <10 nm were successfully synthesized with stable dispersions. The active MNPs including SnO₂, Fe₂O₃, ZnO and TiO₂ (<10 nm) have been incorporated in the pores of MSNs. The MNPs were incorporated in the MSNs using i) Synthesis of MNPs followed by in-situ synthesis of MSNs, ii) synthesis of MSNs first followed by in-situ synthesis of MNPs in the pores of MSNs and, (iii) Synthesis of MSNs and MNPs separately and mixing of stable suspension of both MSNs and MNPs to achieve the best results for oxygen scavenging. The results indicated that first route was more successful for embedding the MNPs in the pores of MSNs. The oxygen scavenging efficiency of the MNPs incorporated MSNs were evaluated.

Tin oxide thin is a promising electron transport layer (ETL) for perovskite solar cells due to its excellent electronic properties and high thermal stability of SnO². In addition, unlike TiO₂ and ZnO, SnO₂ does not have high photocatalytic activity and therefore would improve device stability under illumination compared to devices with titania or ZnO ETLs, and it can be deposited at low temperatures which makes it compatible with flexible devices. However, surface roughness, conformal coating, surface defects of SnO₂, as well as its energy level alignment with the perovskite layer, affect the performance and stability of perovskite solar cells. In this study, we utilized ALD, sol-gel deposition and nanoparticle spin coating method to prepare SnO₂ thin films and apply them as ETLs for planar perovskite solar cells. The obtained results indicate that the method of preparation of SnO₂ significantly affects the solar cell performance. To improve the device performance, we investigated SnO₂ bilayers to attempt to combine advantages of individual coating approaches. For an optimized order of layers to achieve efficient charge extraction across the interface, improved performance can be obtained compared to single layer SnO₂ electron transport layers. Reasons for the performance improvement are discussed.