Item Open AccessHigh external quantum efficiency light-emitting diodes enabled by advanced heterostructures of type-ii nanoplatelets(American Chemical Society, 2023-03-13) Durmusoglu, Emek G.; Hu, Sujuan; Hernandez-Martinez, Pedro Ludwig; Izmir, Merve; Shabani,Farzan; Guo, Min; Gao, Huayu; Isik, Furkan; Delikanli, Savas; Sharma, Vijay Kumar; Liu, Baiquan; Demir, Hilmi Volkan; Demir, Hilmi Volkan; Shabani, Farzan; Işık, Furkan; Delikanli, SavaşColloidal quantum wells (CQWs), also known as nanoplatelets (NPLs), are exciting material systems for numerous photonic applications, including lasers and light-emitting diodes (LEDs). Although many successful type-I NPL-LEDs with high device performance have been demonstrated, type-II NPLs are not fully exploited for LED applications, even with alloyed type-II NPLs with enhanced optical properties. Here, we present the development of CdSe/CdTe/CdSe core/crown/crown (multi-crowned) type-II NPLs and systematic investigation of their optical properties, including their comparison with the traditional core/crown counterparts. Unlike traditional type-II NPLs such as CdSe/CdTe, CdTe/CdSe, and CdSe/CdSexTe1–x core/crown heterostructures, here the proposed advanced heterostructure reaps the benefits of having two type-II transition channels, resulting in a high quantum yield (QY) of 83% and a long fluorescence lifetime of 73.3 ns. These type-II transitions were confirmed experimentally by optical measurements and theoretically using electron and hole wave function modeling. Computational study shows that the multi-crowned NPLs provide a better-distributed hole wave function along the CdTe crown, while the electron wave function is delocalized in the CdSe core and CdSe crown layers. As a proof-of-concept demonstration, NPL-LEDs based on these multi-crowned NPLs were designed and fabricated with a record high external quantum efficiency (EQE) of 7.83% among type-II NPL-LEDs. These findings are expected to induce advanced designs of NPL heterostructures to reach a fascinating level of performance, especially in LEDs and lasers. Item Open AccessTailoring vibrational signature and functionality of 2d-ordered linear-chain carbon-based nanocarriers for predictive performance enhancement of high-end energetic materials(MDPI, 2022-04-01) Lukin, Alexander; Gülseren, Oğuz; Gülseren, OğuzA recently proposed, game-changing transformative energetics concept based on predictive synthesis and preprocessing at the nanoscale is considered as a pathway towards the development of the next generation of high-end nanoenergetic materials for future multimode solid propulsion systems and deep-space-capable small satellites. As a new door for the further performance enhancement of transformative energetic materials, we propose the predictive ion-assisted pulse-plasma-driven assembling of the various carbon-based allotropes, used as catalytic nanoadditives, by the 2D-ordered linear-chained carbon-based multicavity nanomatrices serving as functionalizing nanocarriers of multiple heteroatom clusters. The vacant functional nanocavities of the nanomatrices available for heteroatom doping, including various catalytic nanoagents, promote heat transfer enhancement within the reaction zones. We propose the innovative concept of fine-tuning the vibrational sig-natures, functionalities and nanoarchitectures of the mentioned nanocarriers by using the surface acoustic waves-assisted micro/nanomanipulation by the pulse-plasma growth zone combined with the data-driven carbon nanomaterials genome approach, which is a deep materials informatics-based toolkit belonging to the fourth scientific paradigm. For the predictive manipulation by the micro-and mesoscale, and the spatial distribution of the induction and energy release domains in the reaction zones, we propose the activation of the functionalizing nanocarriers, assembled by the heteroatom clusters, through the earlier proposed plasma-acoustic coupling-based technique, as well as by the Teslaphoresis force field, thus inducing the directed self-assembly of the mentioned nanocarbon-based additives and nanocarriers. © 2022 by the authors. Licensee MDPI, Basel, Switzerland. Item Open AccessUncovering the non-radiative thermal characteristics of a passive radiative cooler under real operating conditions(Institute of Physics Publishing Ltd., 2022-12-12) Koçer, Hasan; Durna, Yılmaz; Işık, Halil; Soydan, Mahmut Can; Khalichi, Bahram; Ghobadi, Amir; Kurt, H.; Özbay, Ekmel; Koçer, Hasan; Durna, Yılmaz; Işık, Halil; Soydan, Mahmut Can; Khalichi, Bahram; Ghobadi, Amir; Özbay, EkmelPassive radiative cooling (PasRadCool), which emits thermal energy from objects to deep cold space through atmospheric transparency, offers complementary and alternative green energy solutions for passive cooling of buildings, clothing, and renewable energy harvesting. Depending on the spectral emissive/absorptive properties of the unit under test (UUT), radiative heat exchanges occur between the UUT, atmosphere, and sun, while at the same time non-radiative heat exchange occurs. The performance of the PasRadCool is determined by the combined thermal and thermodynamic effects of both exchange mechanisms. Although the non-radiative heat exchange, which consists of conductive and convective processes to the outer surfaces of the UUT and the surrounding air fluid, is very sensitive to environmental changes, the actual performance is not fully determined since this feature is considered statically in many studies. Herein, we propose a method that reveals the non-radiative thermal characteristics of the PasRadCool under real operating conditions. With a photonic radiative cooler structure, which we manufacture as a proof of concept, we perform nighttime field test measurements in varying non-radiative thermal conditions. The proposed method extracts the time-dependent non-radiative heat transfer coefficient of the UUT as accurately as possible. We also confirm that our experimental result shows good agreement with both numerical and analytical methods. The proposed approach, which highlights the realistic thermal management of PasRadCool, is not specific to the circumstances of our study and can be applied to all PasRadCool situations with different geometry, material, and environmental conditions. Item Open AccessAzimuthal correlations of high transverse momentum jets at next-to-leading order in the parton branching method(Springer Science and Business Media Deutschland GmbH, 2022-01-13) Abdulhamid, M.I.; Al-Mashad, M.A.; Martinez, A. Bermudez; Bonomelli, G.; Bubanja, I.; Crnković, N.; Colombina, F.; D’Anzi, B.; Cerci, S.; Davydov, M.; Banos, L. I. Estevez; Forzano, N.; Hautmann, F.; Jung, H.; Kim, S.; Quirós, A. León; Martins, D.E.; Mendizabal, M.; Figueroa, K. Moral; Prestel, S.; Monfared, S. Taheri; Süslü, C.; Cerci, D. Sunar; van Kampen, A.M.; Van Mechelen, P.; Verbytskyi, A.; Wang, Q.; Yang, H.; Zhou, Y.; Süslü, C.The azimuthal correlation, Δ ϕ12, of high transverse momentum jets in pp collisions at s=13 TeV is studied by applying PB-TMD distributions to NLO calculations via MCatNLO together with the PB-TMD parton shower. A very good description of the cross section as a function of Δ ϕ12 is observed. In the back-to-back region of Δ ϕ12→ π, a very good agreement is observed with the PB-TMD Set 2 distributions while significant deviations are obtained with the PB-TMD Set 1 distributions. Set 1 uses the evolution scale while Set 2 uses transverse momentum as an argument in αs, and the above observation therefore confirms the importance of an appropriate soft-gluon coupling in angular ordered parton evolution. The total uncertainties of the predictions are dominated by the scale uncertainties of the matrix element, while the uncertainties coming from the PB-TMDs and the corresponding PB-TMD shower are very small. The Δ ϕ12 measurements are also compared with predictions using MCatNLO together Pythia8, illustrating the importance of details of the parton shower evolution. © 2022, The Author(s). Item Open AccessSubwavelength densely packed disordered semiconductor metasurface units for photoelectrochemical hydrogen generation(American Chemical Society, 2022-03-10) Ulusoy Ghobadi, T. Gamze; Ghobadi, Amir; Odabaşı, Oğuz; Karadaş, Ferdi; Özbay, Ekmel; Ulusoy Ghobadi, T. Gamze; Ghobadi, Amir; Karadaş, Ferdi; Özbay, EkmelFor most semiconductors, especially the visible-light-absorbing ones, the carrier diffusion length is significantly shorter than the light penetration depth, limiting their photoactivities. This limitation could be mitigated through the use of subwavelength semiconductor-based metasurfaces and metamaterials. In this paper, a large-scale compatible metasurface photocathode, made of densely packed disordered p-type chromium oxide (CrOX), is developed to be utilized in photoelectrochemical (PEC) hydrogen generation. For this purpose, first, tightly packed random Cr nanorods are fabricated using an oblique angle deposition technique. Afterward, an annealing step is applied to the sample to transform these metallic units into a semiconducting p-type CrOX-based metasurface. Based on the experimental characterization results and numerical simulations, the proposed design can provide strong light-matter interactions in an ultra-broadband-wavelength range, mainly due to its multidimensional random geometry and ultrasmall gap sizes. Finally, to substantiate the activity of the CrOXnanorods, a core-crown geometry is developed where the NiOXcapping layer catalyzes the hydrogen evolution reaction (HER). The proposed heterostructure metasurface absorber can impose photocurrent values as large as 50 μA cm-2with a photocurrent spectral response extended up to 500 nm. Moreover, the electrode shows outstanding operation under light irradiation for 9 hours. This work demonstrates a simple, scalable design strategy to fabricate low-cost and stable photocathodes for PEC hydrogen evolution. © 2022 American Chemical Society. All rights reserved. Item Open AccessDesign and robustness improvement of high-performance LNA using 0.15 μm GaN technology for X-band applications(John Wiley & Sons Ltd., 2022-07) Zafar, Salahuddin; Çankaya Akoğlu, Büşra; Aras, Erdem; Yılmaz, Doğan; Nawaz, Muhammad İmran; Kashif, Ahsanullah; Özbay, Ekmel; Zafar, Salahuddin; Çankaya Akoğlu, Büşra; Aras, Erdem; Yılmaz, Doğan; Nawaz, Muhammad İmran; Kashif, Ahsanullah; Özbay, EkmelIn this paper, we present a highly robust GaN-based X-band low-noise amplifier (LNA) showing promising small-signal and noise performance as well as good linearity. The LNA is fabricated using in-house 0.15 μm AlGaN/GaN on a SiC HEMT process. Owing to the optimum choice of HEMT topologies and simultaneous matching technique, LNA achieves a noise figure better than 2 dB, output power at 1 dB gain compression higher than 19 dB, input and output reflection coefficients better than −9 and −11 dB, respectively. The small-signal gain of LNA is more than 19 dB for the whole band, and NF has a minimum of 1.74 dB at 10.2 GHz. LNA obtains an OIP3 up to 34.2 dBm and survives input power as high as 42 dBm. Survivability is investigated in terms of gain compression and forward gate current. Reverse recovery time (RRT), a crucial parameter for radar front-ends, is explored with respect to the RC time constant and trap phenomenon. The analysis shows that the significant contribution in RRT is due to traps while the RC time constant is in the nanoseconds range. Moreover, this study also addresses the requirement and choice of a DC gate feed resistor for the subsequent stages in a multi-stage design. The size of the designed LNA chip is 3 mm (Formula presented.) 1.2 mm only. Item Open AccessPolarization insensitive phase change material-based nanoantenna array for thermally tunable infrared applications(Institute of Electrical and Electronics Engineers, 2022-09-21) Khalichi, Bahram; Omam, Zahra Rahimian; Osgouei, Ataollah Kalantari; Ghobadi, Amir; Özbay, Ekmel; Khalichi, Bahram; Omam, Zahra Rahimian; Osgouei, Ataollah Kalantari; Ghobadi, Amir; Özbay, EkmelThermal radiation management is an emerging application of metamaterials owing to their exotic electromagnetic radiative properties. Herein, a thermally tunable phase change material-based nanoantenna array is reported to manipulate electromagnetic waves for potential applications in radiative cooling and multispectral camouflage from thermal infrared detectors. The simulation results show that the proposed nanoantenna array possesses high reflectance exceeding at least 60% within the 3−5 µm and 8−12 µm wavelength ranges, indicating low thermal emissivity, while the reflectance value increases as the temperature rises. Additionally, the wavelength-selective nanoantenna emitter operates with high absorption and therefore emission within the non-atmospheric window (5−8 µm). The thermally tuning feature leads to further controlling the absorption and, therefore, the emission performance of the nanoantenna and corresponding infrared signatures detected by thermal cameras. Item Open AccessA Transmissive all-dielectric metasurface-based nanoantenna array for selectively manipulation of thermal radiation(Institute of Electrical and Electronics Engineers, 2022-09-21) Khalichi, Bahram; Omam, Zahra Rahimian; Osgouei, Ataollah Kalantari; Ghobadi, Amir; Özbay, Ekmel; Khalichi, Bahram; Omam, Zahra Rahimian; Osgouei, Ataollah Kalantari; Ghobadi, Amir; Özbay, EkmelIn this study, a wavelength-selective thermal nanoantenna emitter based on metamaterial design with heat radiation signature management and radiative cooling property is proposed. The design can be considered as a multifunctional window by reducing the heat signature and releasing the heat energy within the non-atmospheric window. The approach relies on the indium tin oxide cubic-shaped unit cell coated on a flexible and transparent substrate (polystyrene). The spectral behaviors of the proposed structure are obtained using the finite difference time domain method, where the power calculation model is utilized to demonstrate the radiative cooling efficiency and low power detection on infrared cameras. Item Open AccessTransmissive terahertz metasurfaces with vanadium dioxide split-rings and grids for switchable asymmetric polarization manipulation(Nature Research, 2022-12) Serebryannikov, Andriy E.; Lakhtakia, Akhlesh; Vandenbosch, Guy A. E.; Özbay, Ekmel; Özbay, EkmelMetasurfaces containing arrays of thermally tunable metal-free (double-)split-ring meta-atoms and metal-free grids made of vanadium dioxide (VO2), a phase-change material can deliver switching between (1) polarization manipulation in transmission mode as well as related asymmetric transmission and (2) other functionalities in the terahertz regime, especially when operation in the transmission mode is needed to be conserved for both phases of VO2. As the meta-atom arrays function as arrays of metallic subwavelength resonators for the metallic phase of VO2, but as transmissive phase screens for the insulator phase of VO2, numerical simulations of double- and triple-array metasurfaces strongly indicate extreme scenarios of functionality switching also when the resulting structure comprises only VO2 meta-atoms and VO2 grids. More switching scenarios are achievable when only one meta-atom array or one grid is made of VO2 components. They are enabled by the efficient coupling of the geometrically identical resonator arrays/grids that are made of the materials that strongly differ in terms of conductivity, i.e. Cu and VO2 in the metallic phase. © 2022, The Author(s). Item Open AccessA study on GaN-based betavoltaic batteries(Institute of Physics Publishing Ltd., 2022-10-27) Toprak, Ahmet; Yılmaz, Doğan; Özbay, Ekmel; Toprak, Ahmet; Yılmaz, Doğan; Özbay, EkmelIn this paper, a GaN-based betavoltaic epitaxial structure was grown by metal–organic chemical vapor deposition and a p-type ohmic contact was studied for different Ni/Au metal thickness ratios, temperature dependent in N2:O2 (1:1) gas atmosphere and different surface treatments for this epitaxial structure. Transfer length method measurements were done after each different process condition in order to check specific contact resistivities. GaN-based betavoltaic batteries were fabricated and a scanning electron microscope (SEM) was used as an electron source to test these devices. For this purpose, devices connected to a printed circuit board were exposed to an electron current of 1.5 nA with 17 keV energy in the SEM. For 1 × 1 mm2 devices, a dark current value of 2.8 pA at 0 V, fill factor of 0.35, maximum power conversion efficiency of 3.92%, and maximum output power of 1 µW were obtained. Item Open AccessSilicene dynamic optical response in the presence of external electric and exchange fields(Institute of Physics Publishing Ltd., 2022-01-04) Mirzaei, M.; Vazifehshenas, T.; Salavati-fard, T.; Tanatar, Bilal; Tanatar, BilalWe investigate the dynamic optical transition of monolayer silicene in the presence of external electric and exchange fields within the low-energy tight-binding model. Applying external electric and exchange fields breaks the silicene band structure spin and valley degeneracies. Three phases of silicene corresponding to different strengths of perpendicular electric field with respect to the spin–orbit coupling (Δz < Δso, Δz = Δso and Δz > Δso) are considered. We obtain the spin-valley-dependent optical responses to the incoming circularly polarized light using the Kubo formula. We show and discuss how the magnitude and direction of the transverse and longitudinal optical responses of such a system change with the electric and exchange fields. Our calculations suggest that the intraband part of the longitudinal optical response as well as the initial point of the interband part have strong dependencies on the exchange field. Furthermore, we show that one of the spin subbands plays a dominant role in the response to polarized light. Depending on the type of incident light polarization, the dominant subband may change. Our results shed light on the relation between silicene dynamic optical responses and externally applied fields. Item Open AccessManagement of electroluminescence from silver-doped colloidal quantum well light-emitting diodes(Cell Press, 2022-05-18) Liu, Baiquan; Sharma, Manoj; Yu, Junhong; Wang, Lin; Shendre, Sushant; Sharma, Ashma; Izmir, Merve; Delikanlı, Savaş; Altıntaş, Yemliha; Dang, Cuong; Sun, Handong; Demir, Hilmi Volkan; Delikanlı, Savaş; Altıntaş, Yemliha; Demir, Hilmi VolkanImpurity doping is a promising strategy to afford colloidal nanocrystals exhibiting novel optical, catalytic, and electronic characteristics. However, some significant properties of noble metal-doped nanocrystals (NMD-NCs) remain unknown. Here, we report the electroluminescence (EL) from NMD-NCs. By doping silver impurity into cadmium selenide colloidal quantum wells (CQWs), dual-emission emitters are achieved and a light-emitting diode (LED) with a luminance of 1,339 cd m−2 is reported. In addition, the proposed energy gap engineering to manage exciton recombination is a feasible scheme for tunable EL emissions (e.g., the dopant emission is tuned from 606 to 761 nm). Furthermore, an organic-inorganic hybrid white LED based on CQWs is realized, reaching a color rendering index of 82. Moreover, flexible CQW-LEDs are reported. The findings present a step to unveil the EL property of NMD-NCs, which can be extended to other noble metal impurities, and pave the pathway for NMD-NCs as a class of electronic materials for EL applications. © 2022 The Authors Item Open AccessSelective glucose sensing under physiological pH with flexible and binder-free prussian blue coated carbon cloth electrodes(Wiley-VCH Verlag GmbH & Co. KGaA, 2022-01-27) Oglou, Ramadan Chalil; Ulusoy Ghobadi, T. Gamze; Özbay, Ekmel; Karadaş, Ferdi; Oglou, Ramadan Chalil; Ulusoy Ghobadi, T. Gamze; Özbay, Ekmel; Karadaş, FerdiThe frequent detection of physiological glucose levels from human blood or sweat requires the development of low-cost electrodes with high sensitivity and selectivity. In this work, we prepared a series of Prussian blue (PB) modified carbon cloth (CC) electrodes with different cyanoferrate groups. We achieved a sensitivity as high as 145.43 μA mm−1cm−2 in a 0.1–6.5 mm concentration range with a response time below 2 s under physiological pH. The electrodes exhibited a superior selectivity of glucose in the presence of interfering agents, including sucrose, lactose, NaCl, ascorbic acid, and uric acid. The electrodes also showed outstanding long-term stability over 15 days. Furthermore, we performed comprehensive electrochemical and characterization studies to elucidate the role of the cyanoferrate group on the morphologic and electronic properties of non-enzymatic glucose sensors. Item Open AccessLIPSS for SERS: Metal coated direct laser written periodic nanostructures for surface enhanced raman spectroscopy(Wiley-VCH Verlag GmbH & Co. KGaA, 2022-11-18) Erkızan, S. N.; İdikut, F.; Demirtaş, Ö.; Goodarzi, A.; Demir, Ahmet Kemal; Borra, M.; Pavlov, I.; Bek, A.; Demir, Ahmet KemalA novel method of fabricating large-area, low-cost surface-enhanced Raman spectroscopy (SERS) substrates is introduced which yields densely nanostructured surfaces utilizing laser-induced periodic surface structuring (LIPSS) of crystalline silicon (Si). Two different interaction regimes yield low spatial frequency (LSFL) and high spatial frequency (HSFL) LIPSS patterns. Nanostructuring of Si surface is followed by deposition of a thin noble metal layer to complete the fabrication procedure. A 50–70 nm thick Ag layer is shown to maximize the SERS performance. The SERS effect is attributed to the electromagnetic field enhancement originating from the nanoscale surface roughness of Si that can be controlled by LSFL and HSFL nature of the structure. The SERS substrates are found to be capable of detecting a Raman analyte down to 10−11 m. SERS performance of the Ag deposited substrates at 532, 660, and 785 nm excitation wavelengths is compared. Both LSFL and HSFL Si surfaces with 70 nm thick Ag are found to exhibit the strongest SERS under 660 nm excitation exhibiting Raman enhancement factors (EFs) as high as 109. The Raman EFs are calculated both by SERS spectra experimentally, and using finite-elements method simulation of the electric field enhancement where a good agreement is found. Item Open AccessColor enrichment solids of spectrally pure colloidal quantum wells for wide color Span in displays(Wiley-VCH Verlag GmbH & Co. KGaA, 2022-07-18) Erdem, T.; Soran Erdem, Z.; Işık, Furkan; Shabani, Farzan; Yazici, A. F.; Mutlugün, E.; Gaponik, N.; Demir, H. V.; Işık, Furkan; Shabani, FarzanColloidal quantum wells (CQWs) are excellent candidates for lighting and display applications owing to their narrow emission linewidths (<30 nm). However, realizing their efficient and stable light-emitting solids remains a challenge. To address this problem, stable, efficient solids of CQWs incorporated into crystal matrices are shown. Green-emitting CdSe/CdS core/crown and red-emitting CdSe/CdS core/shell CQWs wrapped into these crystal solids are employed as proof-of-concept demonstrations of light-emitting diode (LED) integration targeting a wide color span in display backlighting. The quantum yield of the green- and red-emitting CQW-containing solids of sucrose reach ≈20% and ≈55%, respectively, while emission linewidths and peak wavelengths remain almost unaltered. Furthermore, sucrose matrix preserves ≈70% and ≈45% of the initial emission intensity of the green- and red-emitting CQWs after >60 h, respectively, which is ≈4× and ≈2× better than the drop-casted CQW films and reference (KCl) host. Color-converting LEDs of these green- and red-emitting CQWs in sucrose possess luminous efficiencies 122 and 189 lm W−1elect, respectively. With the liquid crystal display filters, this becomes 39 and 86 lm W−1elect, respectively, providing with a color gamut 25% broader than the National Television Standards Committee standard. These results prove that CQW solids enable efficient and stable color converters for display and lighting applications. Item Open AccessImpact of the low temperature ohmic contact process on DC and forward gate bias stress operation of GaN HEMT devices(Institute of Electrical and Electronics Engineers, 2022-08-17) Odabaşı, Oğuz; Ghobadi, Amir; Ghobadi, Türkan Gamze Ulusoy; Ünal, Yakup; Salkım, Gurur; Başar, Güneş; Bütün, Bayram; Özbay, Ekmel; Odabaşı, Oğuz; Ghobadi, Amir; Ghobadi, Türkan Gamze Ulusoy; Ünal, Yakup; Salkım, Gurur; Başar, Güneş; Bütün, Bayram; Özbay, EkmelIn AlGaN/GaN high electron mobility transistors (HEMTs), high temperature processes (such as ohmic annealing with >800°C value) could deform the crystal structure and induce trap states within the bulk and surface. Expanded defect densities cause crucial problems, such as threshold voltage ( Vth ) instability, current collapse, and high leakages. In this work, a low temperature ohmic contact process (630°C, 10 minutes) is adopted with recess etch, and contact resistances <0.1Ω ⋅ mm with low sheet resistances are achieved. The positive impact of this low thermal budget process on surface morphology, DC operation, long-term stability, and forward gate bias stress of the device is studied. Item Open AccessTuning the spatially controlled growth, structural self-organizing and cluster-assembling of the carbyne-enriched nano-matrix during ion-assisted pulse-plasma deposition(Tech Science Press, 2022-06-27) Lukin, Alexander; Gülseren, Oğuz; Gülseren, OğuzRevise and shorten the abstract as follows: Carbyne-enriched nanomaterials are of current interest in nanotechnology-related applications. The properties of these nanomaterials greatly depend on their production process. In particular, structural self-organization and auto-synchronization of nanostructures are typical phenomena observed during the growth and heteroatom-doping of carbyne-enriched nanostructured metamaterials by the ion-assisted pulse-plasma deposition method. Accordingly, fine tuning of these processes may be seen as the key step to the predictive designing of carbyne-enriched nano-matrices with improved properties. In particular, we propose an innovative concept, connected with application of the vibrational-acoustic effects and based on universal Cymatics mechanisms. These effects are used to induce vibration-assisted self-organized wave patterns together with the simultaneous manipulation of their properties through an electric field. Interaction between the inhomogeneous electric field distribution generated on the vibrating layer and the plasma ions serves as the additional energizing factor controlling the local pattern formation and self-organization of the nano-structures. © This work is licensed under a Creative Commons Attribution 4.0 International License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Item Open AccessLithography-free metamaterial absorbers: Opinion(The Optical Society, 2022-02-01) Ghobadi, Amir; Ulusoy Ghobadi, Türkan Gamze; Özbay, Ekmel; Ghobadi, Amir; Ulusoy Ghobadi, Türkan Gamze; Özbay, EkmelAlthough advancement in nanofabrication provides the opportunity to realize nanoscale geometries with high resolutions, the scalability and repeatability issues limit their large-scale applications. Lithography-free metamaterial absorbers (LFMAs) are a potential route for the upscaling of these designs. With restricted freedom in their synthesis, the importance of the proper material choice is emphasized. Herein, we provide a comprehensive overview of the recently developed LFMAs, from both design and material perspectives, while considering their most promising applications. © 2022 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement Item Open AccessA wavelength-selective multilayer absorber for heat signature control(Institute of Electrical and Electronics Engineers, 2022-09-28) Osgouei, Ataollah Kalantari; Khalichi, Bahram; Omam, Zahra Rahimian; Ghobadi, Amir; Özbay, Ekmel; Osgouei, Ataollah Kalantari; Khalichi, Bahram; Omam, Zahra Rahimian; Ghobadi, Amir; Özbay, EkmelEngineering the thermal radiation using wavelength-selective thermal emitters is of great importance in the field of thermophotovoltaics, radiative cooling, and heat signature control. In this paper, a wavelength-selective Vanadium/Germanium (V/Ge) multilayer absorber is demonstrated. The proposed design realizes a perfect absorption at the resonance wavelength of 5870 nm, placed within the nonatmospheric window (5-8 μ m) while maintaining low absorptivity within the atmospheric windows. It is verified that the proposed emitter represents angle insensitive feature for oblique incidence up to 60° for both transverse magnetic (TM) and transverse electric (TE) polarizations. Item Open AccessMulti-band light-matter interaction in hBN-based metasurface absorber(Institute of Electrical and Electronics Engineers, 2022-09-28) Omam, Zahra Rahimian; Khalichi, Bahram; Osgouei, Ataollah Kalantari; Ghobadi, Amir; Özbay, Ekmel; Omam, Zahra Rahimian; Khalichi, Bahram; Osgouei, Ataollah Kalantari; Ghobadi, Amir; Özbay, EkmelThis paper presents a multi-band metamaterial-based absorber using phononic two-dimensional (2D) material. The structure consists of a top hexagonal boron nitride (hBN) layer on an aluminum nanograting structure deposited on a dielectric slab waveguide and a thick metallic reflector forming an MIM (metal-insulator-metal) configuration. The proposed absorber exhibits a hyperbolic phonon polariton (HPPs) in hBN, surface plasmon (SP) modes in the spacer (ZnTe: zinc telluride), and Fabry-Perot resonances in the MIM configuration, resulting in five sharp, high absorption peaks in the mid-infrared (MIR) spectral range. The proposed multi-band absorber can be utilized in various applications, ranging from optical detection devices to multispectral thermoelectric volt.