Due to their low cost, chemical and thermal stability, and unique electronic, optical or bioresponsive properties, metal-oxides (MeO) have become almost irreplaceable materials in an impressive range of modern technologies, such as (photo)catalysis, sensing, detection, or energy harvesting. In many cases, the functional properties of MeO may be enhanced by their nanostructuring that increases the specific surface and facilitates physicochemical phenomena like adsorption and diffusion of chemical species. One possibility of producing these materials relies on the deposition of highly porous transition metal (e.g. Ti, V, Nb, W) nanoparticle films by magnetron-based gas aggregation sources followed by the subsequent annealing of such formed nanoparticle films that assures their controllable oxidation and crystallization. The aim of this study is to demonstrate that further improvement of the functional properties of MeO nanoparticle-based films may be achieved if they are decorated with sputter-deposited noble metal nanostructures. In this way, different functionalities intrinsic to metal-oxide and metal components may be successfully combined or enhanced. As shown in this study, such metal/MeO nanomaterials are highly interesting as novel platforms for surface-enhanced Raman spectroscopy (SERS), in which the noble metals act as highly SERS-active component, while the transition MeO due to its photocatalytic characteristics provides the possibility of highly effective re-cycling of the platforms after cleaning them with UV light irradiation.

This work was supported by the grant GAČR 21-05030K from the Grant Agency of the Czech Republic.

Carbon nanotubes (CNTs) have been used as gas-sensing material owing to their high specific surface areas and structural porosities that enable rapid responses and high sensitivity at room temperature. Fully inkjet printing technology promotes the green process using by digital controlled pattern in required location to offer fast, material saving, low cost, high substrate selectivity, and low annealing temperature. In this work, Inkjet-printed CNT films can be conferred with the appropriate resistance for embedding into transmission-type resonators for gas sensing by controlling droplet spacing (DS) and layer number. CNTs films as sensing layers and silver films as conductive layers to realize gas sensors using fully inkjet printing technology. Gas sensors, including resistive and microwave resonator sensors, were inkjet-printed on CLTE-MW to measure their response in the presence of ammonia. Gas responses of CNT films with regular electrode and interdigital electrode patterns were compared by resistive-type gas sensors. CNTs with the IDE pattern can provide large contact areas between the silver film and CNTs for the provision of more effective conductive paths, this resulting in stable sheet resistance and high response. The resistance of the sensing films embedded into the transmission-type microwave resonators should be as low as possible to avoid affecting loss. A microwave resonator consisting of two open-loop ring resonators coupled to each other by an interdigital structure was proposed as a microwave gas sensor. CNT films with the IDE pattern were embedded at the edge of the interdigital structure. The repeatability of the resonator under exposure to 700 ppm NH₃ for 20 cycles was examined. The exposure time to NH₃ gas at each step was 60 s and then, pure N₂ was injected into test chamber for 90 s at the recovery step. The average sensitivities of insertion loss and resonant frequency were 9.5 mdB and 353 kHz for 20 cycles, respectively. The results demonstrated that the CNT films with IDE pattern embedded in transmission-type microwave resonator provided two-dimensional response values in NH₃ sensing through electromagnetic transduction, thereby providing wireless sensor applications.

Across a wide range of application areas, understanding the chemistry and structure of surfaces and interfaces is crucial. In the last fifty years, X-ray photoelectron spectroscopy (XPS) has become established as a one of the key techniques for measuring surface and interface chemistry, and advances in instrumentation have enabled it to keep pace with the requirements for both academia and industry. XPS can deliver quantified surface chemistry measurements, and by using depth profiling, an understanding of layer and interfacial chemistry, but the limit on spatial resolution for XPS can prevent it from determining how the surface structure is related to the measured chemical properties. For example, how the changing morphology of the surface during a depth profile could influence the measured composition would be challenging to determine using just XPS.

Other experimental techniques which are unable to match the surface selectivity of XPS are able to provide complementary information to extend the data from XPS. Electron microscopy can provide high resolution imaging, with elemental composition provided by energy dispersive X-ray microanalysis, but without the same surface selectivity seen with XPS or Auger electron spectroscopy (AES). This can be a perfect complement to XPS analysis, so long as the same points of interest can be identified. Molecular spectroscopy, such as FTIR or Raman, can also provide complementary information to XPS, albeit with different sampling depths, which can be extremely useful to validate measurements or confirm particular molecular structures using the wide range of spectral libraries available for those techniques.

In this poster, we will describe how a correlative approach using both surface analysis instrumentation and scanning electron microscopy can be used to characterize 2D nanomaterials. Samples of MoS₂ grown on Si substrates have been investigated using XPS, Raman and SEM to determine their composition and structure. To facilitate co-alignment of the analysis positions when moving between the instruments, special sample carriers and software alignment routines have been developed.

High-entropy alloy coating feature high hardness, excellent thermal stability, and corrosion resistance. They have been considered as promising candidates for next-generation surface coating material because of their advantageous properties.In recent years, the popular high power impulse magnetron sputtering (HIPIMS) surface technology has attracted considerable attention due to the ability to produce coatings with excellent properties. It is preferable to replace high entropy alloy target with a co-sputtering method involving the use of more targets(single element metal target) simultaneously, which can greatly reduce the process cost.

ZnO is a common semiconductor material recently, due to its piezoelectric property, it can be used to fabricate the piezoelectric devicessuch as pressure sensor for monitoring the human health. Beside, doping vanadium(V) into ZnO can boost up the device performance because of increasing the piezoelectric coefficientandthe p-type carrier concentration. In our research, we will prepare the thin film V doped ZnO piezoelectric pressure sensor by RF magnetron sputtering system with different working power. After deposition, we will annealing the sample at Ar atmosphere. XRD,SEM&EDS were observed the structure, surface morphology and doping concentration. XPS results show the V⁵⁺ amount will reduce with higher doping concentration, and these trends were similar with the piezoelectric coefficient. The optical measurement will analysis by UV-vis, UPS, PL&RAMAN, these suggest the defect properties and energy level. When we enhance the doping concentration, the intrinsic defect will decrease, however, the lattice arrangement becomes disorder because the zinc sites were replaced by the vanadium. Finally, the sensor current sensitivity will discus by the I-V curve. when the V concentration is about 0.24 at%, piezoelectric coefficient and carrier concentration can reach the balance, promoting the device’s sensitivity significantly.

Thin film catalyst, giving a different morphology, provides a significant advantage over catalyst particles for gas evolution reaction.Taking the advantages of sputter deposition, we hereby report high entropy alloy (HEA) thin film electrocatalyst for oxygen evolution reaction (OER).We investigate the catalyst characteristics not only in its as-deposited state but also during and after the OER.For comparison, unary, binary, ternary, and quaternary thin film catalysts were prepared and characterized.The surface electronic structure modification due the addition of a metal is studied experimentally and theoretically using density function theory calculation.We demonstrate that sputtered FeNiMoCrAl HEA thin film exhibits OER performance superior to all the reported HEA catalysts with robust electrocatalytic activity having a low overpotential of 220 mV at 10 mA cm^-2, and excellent electrochemical stability at different constant current densities of 10 and 100 mA cm^-2 for 50 h.Furthermore, we have investigated the microstructure transformation during the OER, which is important for the understanding of the OER mechanism provided by HEA electrocatalyst.Such finding would contribute to future catalyst design.

Anti-reflective (AR) coatings are of high importance for our everyday lives in the field of optics, for example in visual aids and photography equipment. Lesser known, those coatings are also essential in the realm of photovoltaics like solar cells, because they are able to reduce the reflectivity of the material surface. There is a plethora of different design approaches to this topic. Within our work, we want to change the optical properties of hard TiC/TaC superlattice protective coatings without sacrificing superior mechanical properties. Using DC magnetron sputtering, we create nano-scale transition metal nitride-based (AlN and ZrN) thin films exhibiting different material characteristics. We investigate the influence of deposition parameters and film thickness on the optical properties of our materials system. Apart from structural and morphological investigations and the determination and comparison of mechanical properties of our material systems, we conduct optical investigations using differential reflectance spectroscopy (DRS).

Sn-based perovskites exhibit compelling properties such as reduced toxicity and lowered band gaps over those purely based on Pb. As a result, they are of increasing interest for photovoltaic applications in single-junction and all-perovskite tandem applications.^[1]

For high performances, control of the oxidation state and interfacial chemistry is paramount, which can be determined using X-Ray photoelectron spectroscopy (XPS). However, the minor chemistry related shifts of the Sn core level emission complicate the analysis, especially for semiconducting materials. Here, surface band-bending as well as differences in the work function can be particularly pronounced.

In this presentation, we demonstrate that studies based on the modified Auger parameter α′ provide a robust method to resolve different chemical states in Sn-based perovskites. Using a set of reference samples, we identified a high sensitivity to the halide, resulting in a shift of up to Δα ′ = 2 eV between ASnI₃ and ASnBr₃-type polycrystalline perovskite thin-films.^[2] Observed dependencies of α ′ on the Sn oxidation state and local chemistry provide a framework that enables reliable tracking of degradation as well as X-site composition for Sn-based perovskites and related compounds. Recently, we successfully applied this framework on Sn-based perovskite nanocrystals to ensure the absence of Sn(IV) impurities upon optimized synthesis procedures.^[3]

The higher robustness and sensitivity of such studies not only enables more in-depth surface analysis of Sn-based perovskites than previously performed, but also increases reproducibility across laboratories. Due to the facile data analysis, this method is ideal for high-throughput studies that are increasingly being adopted in the development of new semiconducting materials.^[4]

[1] H. Lai, J. Luo, Y. Zwirner, S. Olthof, A. Wieczorek, F. Ye, Q. Jeangros, X. Yin, F. Akhundova, T. Ma, R. He, R. K. Kothandaraman, X. Chin, E. Gilshtein, A. Müller, C. Wang, J. Thiesbrummel, S. Siol, J. M. Prieto, T. Unold, M. Stolterfoht, C. Chen, A. N. Tiwari, D. Zhao, F. Fu, Adv. Energy Mater. 2022, 12, 2202438.

[2] A. Wieczorek, H. Lai, J. Pious, F. Fu, S. Siol, Adv. Mater. Interfaces 2023, 10, 2201828.

[3] D. N. Dirin, A. Vivani, M. Zacharias, T. V. Sekh, I. Cherniukh, S. Yakunin, F. Bertolotti, M. Aebli, R. D. Schaller, A. Wieczorek, S. Siol, C. Cancellieri, L. P. H. Jeurgens, N. Masciocchi, A. Guagliardi, L. Pedesseau, J. Even, M. V. Kovalenko, M. I. Bodnarchuk, Nano Lett. 2023, 23, 1914.

[4] S. Zhuk, A. Wieczorek, A. Sharma, J. Patidar, K. Thorwarth, J. Michler, S. Siol, Chem. Mater. 2023, 35, 7069.

The multipactor phenomenon is a critical issue that can occur in particle accelerators. To improve the performance of components used in particle accelerators, we have chosen to develop a materials approach with innovative coatings.

The SEY is the ratio of the number of secondary electrons to the number of incident electrons (primary electrons). To avoid the multipactor effect, the ratio must be less than 1. Currently, most materials have an SEY greater than 1 [1].The investigated coatings based on nitride or carbide titanium because the SEY ratio is intrinsically low [2,3]. My work consists to elaborate based TiN (TiO_xN_y, TiN, TiN_xC_y) thin films and study their properties. Another approach concerns the investigation of thin layers consisting of alternating layers of NbN and TiN. The preferred deposition method is PVD (Physical Vapor Deposition) by cathodic pulverisation. We will present the results obtained as a function of coating nature: (i) firstly, the physical properties (such as electrical properties by 4-point measurements) and chemical characterisations (such as the layer composition determined by XPS analysis); (ii) the values of secondary electron emission yields at the fully conditioned state (see Table, the surface was conditioned by electron bombardment). In this work, we study the SEY without the effects of roughness, which is known to significantly influence the SEY.

Table: SEY values of different thin films obtained PVD

REFERENCES

[1] N. Hilleret, SPS & LEP Performance Workshop, Chamonix, 2000.

[2] P. C. Pinto et al., Particle Accelerator Conference, New York, 2011.

[3] I. Montero, et al., Journal of Applied Physics, vol. 101, n^o 11, p. 113306, juin 2007, doi: 10.1063/1.2736861 [https://doi.org/10.1063/1.2736861].

Nickel oxide (NiO_x) thin films were deposited by r.f. magnetron sputtering on n-type silicon and corning glass substrates. The deposition conditions were 60 W of power during 6 minutes, a pressure of 5 mTorr and different substrate temperatures in the range of 25-200 °C. The partial pressure between O/Ar was varied between 0 and 4 %. Prior to deposition, the substrates were cleaned in an ultrasonic bath with acetone, isopropyl alcohol and deionized water for 5 min each and dried with high-purity nitrogen after each step. Besides, the target was pre-sputtered for 15 min. MOS capacitors were fabricated by deposition of gold and aluminum as top and back contacts using thermal evaporation.The thickness and optical constants of the films were obtained by spectroscopic ellipsometry. Measurements of current-voltage (I-V) and capacitance-voltage (C-V) dependences were carried out to study the effect of temperature and oxygen partial pressure on the electrical properties of the NiO_x thin films. The obtained results indicate that it is possible to obtained high quality films at low r.f. power that are viable for applications in electronic devices.

NiO_x thin films were deposited by RF sputtering in Ar atmosphere on n-Si and glass substrates. During the deposition the RF power was varied between 5 W and 60 W, while the deposition time was fixed at 9 min. Three deposition temperature of 25 ^oC, 50 ^oC and 100 ^oC were used. The samples deposited on Si were separated in three groups. The first group was furnace annealed at 450 ^oC in N₂ atmosphere for 1 h. The second one was treated by Rapid Thermal Annealing (6 min, 550 ^oC), while the third group was kept as control. Metal/NiO_x/n–Si heterostructures were prepared by deposition of Au electrodes through a mask.

The thicknesses and optical constants of the layers were determined by spectroscopic ellipsometry. XRD measurements were used to determine the effect of deposition temperature and thermal annealing on the crystallinity of the films. The Au/NiO_x/c-Si structures were electrically characterized by current-voltage (I-V) and capacitance-voltage (C-V) measurements. The I-V dependences showed formation of p-n heterojunction diodes with properties, which depend on the r.f. power, deposition temperature and annealing.

The nano-scaled mechanics for the hexagonal 4H SiC single-crystal surface (with a bandgap of 3.26 eV) is examined by using nanoindentation testing on the {0001} basal plane. The 4H SiC material was prepared by Prof. M. C. Chou’s lab via the Czochralski process. The as-grown crystal surface has been examined carefully by X-Ray diffraction (XRD) to confirm the 4H hexagonal structure, with the basal plane lying on the horizon plane and the c-axis parallel to the growth direction. The (0004) peak at 2q=35.5° is the only peak appeared, ensuring the well-grown surface orientation with minimum defects. The lattice parameters, a and c, are determined to be 0.3073 and 0.1006 nm, respectively. Through the analysis of XRD rocking curves, it is confirmed that there should be minimum defects inside the as-grown SiC surface.

Nanoindentation tests were performed using the continuous stiffness method (CSM), up to a maximum depth of ~950 nm on the (0001) basal plane surface. The average elastic modulus and hardness calculated from depth ranging from 300~800 nm over nine indents were ~500 GPa and ~42.5 GPa, respectively. In addition, the first few pop-in loads and displacements are captured from the deviations from a perfect Hertizian contact curve fitted to the load-displacement curve. By using rough estimation for the yield stress from hardenss by a factor about 2.5 (Tabor’s assumption), we estimate the yield stress to be about 42.5/2.5 ~ 17.0 GPa. The first pop-in loads, pop-in hardness, and pop-in stresses can all be measured. The first pop-in stress is usually termed as the incipient stress, associated with the first initiation of the activation of dislocations (nucleation or gliding of diloscations). The average incipient stress for the first dislocation activity is about 16.1 GPa, slightly below the overall yield stress. From the first pop-in displacement, about 10 nm, it is likely to be a result of the micropipe threading screw dislocations (with a Burger’s vector of c-axis, namely, ~1 nm). This suggests that the first pop-in could be caused by these screw dislocations gliding for 10 Burger’s vectors. The understanding of dislocation incipient pop-in as a function of applied load would give the insight for subsequent influence for various functional properties of 4H SiC.

Soft x-ray nanoscopy employing the scanning transmission x-ray microscope (STXM), which can provide chemical structural information of materials at tens of nanometer scale, has become a powerful study in analytical microscopic research. The nanoscopy beamline in the Pohang Light Source is operating currently at the optimum condition in its focused beam size ~30 nm and photon energy resolution < 0.1 eV in the soft x-ray energy range (200-1650 eV).

Basically, based on different x-ray absorption contrast depending on chemical states, we have studied structural and electronic properties of nanoscale defects or domains formed on various two-dimensional (2D) materials including graphene, hBN, MoS₂, WSe₂, and topological insulators such as Bi₂Se₃ thin film as well as energy materials. We will here introduce briefly the 2D nanoscale chemical mapping of such functional materials.

Moreover, as for Li-ion batteries, we investigated in-situ annealing effect on Ni-rich NCM cathode materials from RT to high temperature by measuring Ni, Co, Mn L₃-, and O K-edge absorption spectra. In-situ thermal degradation is induced by annealing. And oxygen reduction is preferentially observed on the edges of smaller particles at 400 ^oC.

KEYWORDS: 2D chemical mapping, soft x-ray nanoscopy, STXM, 2D materials, energy materials

In plastic processing, the use of sensor thin films is gaining interest for inline measurement to ensure stable process control. However, due to the corrosive and abrasive characteristics of molten plastics, the application of an appropriate protective coating becomes imperative to ensure the functionality of the sensor films. AlCrON thin films demonstrate favorable protective attributes for this purpose. The tribo-mechanical and electrical properties are inherently influenced by the oxygen content. Therefore, a systematic variation of O₂ gas flow rates (10 to 30 sccm in steps of five) during the mid-frequency magnetron sputtering process was employed resulting in the O contents rise from 12.2 at.-% for 10 mln O₂ to 57.6 at.–% for 30 mln O₂. Simultaneously, a change of a polycrystalline structure containing CrN, Cr₂N, and hexagonal AlN to an amorphous structure with increasing O content for AlCrON is observed. This affects the tribo-mechanical properties. The highest polycrystallinity was reached at 25.2 at.–% O resulting in a H/E maximum, with a maximum in hardness of (37.6 ± 2.8) GPa and an elastic modulus of (361.2 ± 20.7) GPa. Here, also the lowest coefficient of friction (CoF) at elevated temperatures was reached with 0.43 against polypropylene (PP) and 0.23 against polyamide (PA). The low CoF correlates with a lower wetting ability of the AlCrON thin film. Regarding the electrical properties AlCrON thin films show insulating characteristics dependent on the O content. The electrical resistance increases with higher O content while the dielectric stregth tends to increase with higher crystallinity.

A first attempt to apply a functional copper layer within an Al₂O₃ and AlCrON system was successful, showing promise for enhanced functionality. However, further investigation is needed to fully understand its potential and optimize its performance.

The results show that AlCrON thin films offer promising protective qualities for sensor applications in plastic processing. By adjusting the oxygen content, their tribo-mechanical properties can be optimized for reduced friction and enhanced durability, while their insulating properties are promising for maintaining the functionality of the sensors.

Gallium oxide (Ga₂O₃) is an emerging ultrawide-bandgap semiconductor for high power electronics and ultraviolet photonics. Among various Ga₂O₃ crystal structures, a α-Ga₂O₃ has gained a great interest because its bandgap (>5.3 eV) is far wider than that of common β-Ga₂O₃ (4.5 – 5.3eV). Thermodynamically stable β-Ga₂O₃ thin films have been successfully synthesized by various deposition techniques. However, the growth of metastable α-Ga₂O₃ thin films is more challenging process because the formation of α-Ga₂O₃ is only stable for the first few monolayers and easily converted from α-Ga₂O₃ to β-Ga₂O₃ during high temperature post growth treatment. In this work, we have explored an effective route for growing relatively thick epitaxial α-Ga₂O₃ films on m-plane and a-plane sapphire substrates by pulsed laser deposition (PLD). First, we have grown Ga₂O₃ films at various substrate temperatures (560 – 720 °C) while the background pressure was kept at 3 mTorr of oxygen. Second, the effect of oxygen background pressure was investigated in an oxygen pressure range between 1 and 50 mTorr while the substrate temperature was fixed at 720 °C. The crystal structure and film quality of all Ga₂O₃ thin films were then investigated by high-resolution X-ray diffraction (XRD). For films grown on a-plane sapphires, pure α-Ga₂O₃ films can be obtained at only high growth temperatures (> 720°C) while the β-Ga₂O₃peaks are appeared as the growth temperature is lowered below 720 °C. For films grown on m-plane sapphires, pure α-Ga₂O₃ film can be obtained at all temperature ranges (560 – 720 °C) while the film crystallinity improved as the growth temperature increases. We will present details of optimization processes to grow pure α-Ga₂O₃ films along with structural and optical properties of Ga₂O₃ films.

This work was supported by the Office of Naval Research (ONR) through the Naval Research Laboratory basic research program.

Two-dimensional GaS is an important member of group III_A–VI_A semiconductors possessing exceptional optoelectronic properties. In this work, 2D GaS nanobelts (NBs) were successfully synthesized via the vaper-liquid-solid (VLS) method and the structure, morphology, and chemical composition of the as-prepared nanobelts are extensively investigated. Furthermore, GaS nanobelts are fabricated into photodetector with Ni contacts through electron beam lithography (EBL), electron beam evaporation and lift-off processes. The photodetector determines the photodetectors exhibited a dark current smaller than 500 fA while demonstrating remarkably high responsivity, external quantum efficiency (EQE) and detectivity is tens mAW⁻¹, ~10⁴ % and ~10¹³ Jones, respectively. Moreover, they displayed repeatable ON−OFF switching behavior, which with a fast response time is ~60 ms under the 405 nm excitation. Given the very low dark current, the GaS nanobelts were characterized as p-type semiconductors via MOSFET measurements under 405 nm excitation, with a measured mobility of ~10^-3 cm² V⁻¹ s⁻¹.

To further enhance the performance of the devices,GaS/Ni heterostructure devices were formed through rapid thermal annealing (RTA). Post-annealing,the devices exhibited metallic behavior with a conductivity of ~10³ Ω^-1cm^-1 with high annealing temperature. On the other hand, low-temperature annealing resulted in the formation of Ni_xGaS/GaS heterostructures. These findings present a novel approach to enhancing the responsivity of GaS photodetectors with Ni contacts, offering promise for future high-performance optoelectronic systems.

For the decade, it has been shown that diamond-like carbon (DLC) coatings are very promising anti-reflection (AR) and protective coatings for solar cell.However, tetrahedral amorphous carbon (ta-C) coatings with extremely high hardness, smooth surface, excellent wear resistance, and better thermal stability than DLC have been paid much attention to an alternative protective coating materials. Additionally, optical properties of the taC coating could be improved by various metals doping. In this study, various contents of Si were doped in the taC coating to improve the mechanical and optical properties of tacC coatings. A filtered cathodic vacuum arc (FCVA) and magnetron sputter hybrid system was used to synthesize the metal doped taC coating. As the Ti concentration increased, the mechanical properties of the coatings decreased. The hardness and elastic modulus of the taC coating (50 and 435 GPa)decrease down to 14 and ~223 GPa. Xray photoelectron spectroscopy (XPS) C 1 s spectra showed that both the Ti atomic percent and TiC bond percent increased with sputtering power. In addition, Tidoped taCcoatings showed an improved transmittance in all wavelength ranges when the sputtering powers were relatively low, comparing with undoped taC coating. Tribological behaviors of the Tidoped taC coatings were ubvestigagted and the results showed that with increasing sliding distance, the CoF and the wear rate increased regadless of the Ti and Ti-C contendt in the Ti-doped taC coatings. Experimental details and further results will be presented.

Optical sensors using zero-reflection points (ZRPs) enable excellent sensitivity due to accompanying phase singularities and the steepest slope of the reflectivity curve. Reflection zeros have been demonstrated at different spectral regions under very specific conditions in the angle of incidence (AoI) and polarization state. However, manipulation of the darkness points for multiple spectral positions and polarizations has not been achieved yet. Here, we report the collaborative and synergic operation of three ZRPs in a simple platform formed by a lithography-free, three-layer, metal-dielectric-metal structure where careful design and efficient manipulation of these ZRPs results in an optical sensor with unsurpassed, experimentally demonstrated, limit of detection ~2x10^-8 RIU. The synergic operation of the proposed sensor relies on: i) strong coupling between p-pol surface plasmon polariton and p-pol photonic waveguide modes with experimentally demonstrated reflection suppression, Rabi splitting and phase singularities; ii) simultaneous implementation of two orthogonally polarized ZRPs and wavelength-interrogation mode of operation leads to spectral overlap of s-pol photonic modes with the coupled, p-pol resonances; and iii) ellipsometry-based sensing where the relatively insensitive s-pol ZRPs provide internal references to boost the sensor performance in terms of the amplitude ratio (ψ) and phase difference (Δ) of the s- and p-polarized reflectance thereby naturally forming a refinement measuring scale akin to a Vernier scale. Remarkably, the precise manipulation of the double dark points via the AoI control enables a second metric that yields ultrahigh sensitivity and can be reset to the original spot over a large dynamic range, thereby avoiding the trade-off between sensitivity and dynamic range. This occurs because the AoI acts an additional degree of freedom to tune and reset the sensor to its original ZRPs while keeping track of the total accumulated change. The strength of these capabilities has been demonstrated for a biosensor of SARS-CoV-2 spike (S2) protein that can track the full functionalization process of the chip surface and then reset to its best sensing conditions to perform real-time dose-dependent detection of the S2 spike protein. Our work provides a new and powerful strategy for the development of optical sensors, perfect light absorbers, pyroelectric detectors, and phase modulators.

This work was supported by the Research Grants Council of Hong Kong, SAR, Project number CityU 11219919.

The consortium of Opti-Reve project is composed by Surcotec and He-arc for the Swiss part and Gaggionne and UTBM for the French part. This project aims to develop a new technological solution (optical and protective coatings) in order to improve the quality of optical polymer components thanks to new functionalities brought to the surface by PVD technology, notably the corrosion resistance and the wear, as well as the brightness.

As part of this study, we first theoretically defined the material presenting the best reflection for the application but also its thickness. Based on the theoretical results, an adequate protective coating is determined. From the experimental point of view, the films were sputtered by magnetron sputtering from metallic targets in a neutral argon atmosphere for the reflective layer, then in a reactive atmosphere for the protective layer. The thin films were characterized by SEM, XRD for the morphological and structural parameters, the optical properties were determined by spectrophotometry. The first results obtained will be presented as well as future work.

Funding:

This project is carried out within the framework of the INTERREG VI France‐Switzerland 2021-2027 European territorial cooperation program. The total cost of the project amounts to €571 663.57. It benefits from financial support from the EU through the European Regional Development Fund (ERDF) for €186 634.06, from the Swiss Federal INTERREG for €105 547.65 and from Swiss cantonal funds for an amount of €105 547.65 (Canton of Geneva = €40 322.58 and canton of Neuchâtel = €65 225.07)

In recent years, two-dimensional(2D) materials have garnered significant attention and research due to their exceptional material properties, including atomic layer thickness, high mobility, making them a prime candidate for next-generation semiconductor. Among them, molybdenum disulfide (MoS₂) has been extensively studied. MoS₂ can be synthesized on various substrates using chemical vapor deposition (CVD) and has found applications in energy storage, photodetectors, and two-dimensional field-effect transistors.However, conventional CVD methods suffer from limitations such as uncontrollable growth locations, irregular material dimensions, and the need for additional post-processing steps like transfer and etching. These post-processing steps introduce defects, leading to a reduction in material performance. Moreover, etching steps increase processing costs and introduce metal contamination issues.

In this study, we propose a highly controllable and crystalline growth method for MoS₂ arrays directly grown on SiO₂ substrate by using seeds as heterogeneous nucleation sites. Due to the lower surface energy of seed material, MoS₂ preferentially grows on pre-deposited seed arrays. MoS₂ grown using this approach exhibits excellent uniformity, with a 95.2% yield and consistent crystal sizes in a 50x50 array. Raman spectroscopy analysis indicates a single-layer structure with an E_2g-A_1g peak separation of 19.59 cm^-1, while photoluminescence analysis demonstrates high crystallinity. Mapping analysis of photoluminescence and Raman spectra proves the high consistency of crystal quality and thickness uniformity. In addition, we can see from the peak position that the gold seeds cause almost no strain effect. This synthetic approach eliminates the need for etching and transfer processes, reducing process complexity and costs, which is beneficial for compatibility with today's IC fabrication procedures.

Keywords: monolayer MoS₂, positioning and patterning, chemical vapor deposition