Probing post-growth hydrogen intercalation and H2 nanobubbles formation in graphene on Ge (110)

Solar fuels offer a promising approach to provide sustainable fuels by harnessing sunlight. Following a decade of advancement, Cu2O photocathodes are capable of delivering a performance comparable to that of photoelectrodes with established photovoltaic materials. However, considerable bulk charge carrier recombination that is poorly understood still limits further advances in performance. Here we demonstrate performance of Cu2O photocathodes beyond the state-of-the-art by exploiting a new conceptual understanding of carrier recombination and transport in single-crystal Cu2O thin films. Using ambient liquid-phase epitaxy, we present a new method to grow single-crystal Cu2O samples with three crystal orientations. Broadband femtosecond transient reflection spectroscopy measurements were used to quantify anisotropic optoelectronic properties, through which the carrier mobility along the [111] orientation was found to be an order of magnitude higher than those along other orientations. Driven by these findings, we developed a polycrystalline Cu2O photocathode with an extraordinarily pure (111) orientation and (111) terminating facets using a simple and low-cost method, which delivers 7 mA cm− 2 current density (more than 70% improvement compared to that of state-of-the-art electrodeposited devices) at 0.5 V versus a reversible hydrogen electrode under air mass 1.5 G illumination, and stable operation over at least 120 h.

Science Advances

In two-dimensional semiconductors, cooperative and correlated interactions determine the material’s excitonic properties and can even lead to the creation of correlated states of matter. Here, we study the fundamental two-particle correlated exciton state formed by the Coulomb interaction between single-particle holes and electrons. We find that the ultrafast transfer of an exciton’s hole across a type II band-aligned semiconductor heterostructure leads to an unexpected sub-200-femtosecond upshift of the single-particle energy of the electron being photoemitted from the two-particle exciton state. While energy relaxation usually leads to an energetic downshift of the spectroscopic signature, we show that this upshift is a clear fingerprint of the correlated interaction of the electron and hole parts of the exciton. In this way, time-resolved photoelectron spectroscopy is straightforwardly established as a powerful method to …

Nanophotonics

We present a theoretical investigation of guided second harmonic generation at THz frequencies in SiGe waveguides embedding n-type Ge/SiGe asymmetric coupled quantum wells to engineer a giant second order nonlinear susceptibility. A characteristic of the chosen material system is the existence of large off-diagonal elements in the χ 2 tensor, coupling optical modes with different polarization. To account for this effect, we generalize the coupled-mode theory, proposing a theoretical model suitable for concurrently resolving every second harmonic generation interaction among guide-sustained modes, regardless of which χ 2 tensor elements it originates from. Furthermore, we exploit the presence of off-diagonal χ 2 elements and the peculiarity of the SiGe material system to develop a simple and novel approach to achieve perfect phase matching without requiring any fabrication process. For a realistic design …

bioRxiv

Simultaneously recording network activity and ultrastructural changes of the synapse is essential for advancing our understanding of the basis of neuronal functions. However, the rapid millisecond-scale fluctuations in neuronal activity and the subtle sub-diffraction resolution changes of synaptic morphology pose significant challenges to this endeavour. Here, we use graphene microelectrode arrays (G-MEAs) to address these challenges, as they are compatible with high spatial resolution imaging across various scales as well as high temporal resolution electrophysiological recordings. Furthermore, alongside G-MEAs, we deploy an easy-to-implement machine learning-based algorithm to efficiently process the large datasets collected from MEA recordings. We demonstrate that the combined use of G-MEAs, machine learning (ML)-based spike analysis, and four-dimensional (4D) structured illumination microscopy (SIM) enables the monitoring of the impact of disease progression on hippocampal neurons which have been treated with an intracellular cholesterol transport inhibitor mimicking Niemann-Pick disease type C (NPC) and show that synaptic boutons, compared to untreated controls, significantly increase in size, which leads to a loss in neuronal signalling capacity.

Figure 1cd-ψ and Δ as a function of λ: Data contains measured data for monolayer graphene, bilayer graphene and resonant bilayer, and their respective fitted models. The model fitting was performed using the graphene/SiO2/silicon model as constructed from Accurion EP4 software dielectric function data for selected materials. We initially measured the bare substrate to determine the thickness of the SiO2 (tSiO2= 90.5 nm) to use as a fixed parameter when fitting the graphene layer. The Gaussian resonance term is defined by ???????? (????)= ???? (exp (−(????− ????????) 2 ????2

Nanophotonics

A parabolic potential that confines charge carriers along the growth direction of quantum wells semiconductor systems is characterized by a single resonance frequency, associated to intersubband transitions. Motivated by fascinating quantum optics applications leveraging on this property, we use the technologically relevant SiGe material system to design, grow, and characterize n-type doped parabolic quantum wells realized by continuously grading Ge-rich Si1−x Ge x alloys, deposited on silicon wafers. An extensive structural analysis highlights the capability of the ultra-high-vacuum chemical vapor deposition technique here used to precisely control the quadratic confining potential and the target doping profile. The absorption spectrum, measured by means of Fourier transform infrared spectroscopy, revealed a single peak with a full width at half maximum at low and room temperature of about 2 and 5 meV …

Nature

Solar fuels offer a promising approach to provide sustainable fuels by harnessing sunlight,. Following a decade of advancement, Cu2O photocathodes are capable of delivering a performance comparable to that of photoelectrodes with established photovoltaic materials, –. However, considerable bulk charge carrier recombination that is poorly understood still limits further advances in performance. Here we demonstrate performance of Cu2O photocathodes beyond the state-of-the-art by exploiting a new conceptual understanding of carrier recombination and transport in single-crystal Cu2O thin films. Using ambient liquid-phase epitaxy, we present a new method to grow single-crystal Cu2O samples with three crystal orientations. Broadband femtosecond transient reflection spectroscopy measurements were used to quantify anisotropic optoelectronic properties, through which the carrier mobility along the [111 …

ACS Applied Materials & Interfaces

Interfaces play an essential role in the performance of ever-shrinking semiconductor devices, making comprehensive determination of their three-dimensional (3D) structural properties increasingly important. This becomes even more relevant in compositional interfaces, as is the case for Ge/GeSi heterostructures, where chemical intermixing is pronounced in addition to their morphology. We use the electron tomography method to reconstruct buried interfaces and layers of asymmetric coupled Ge/Ge0.8Si0.2 multiquantum wells, which are considered a potential building block in THz quantum cascade lasers. The three-dimensional reconstruction is based on a series of high-angle annular dark-field scanning transmission electron microscopy images. It allows chemically sensitive investigation of a relatively large interfacial area of about (80 × 80) nm2 with subnanometer resolution as well as the analysis of several …

The growth of machine learning, combined with the approaching limits of conventional digital computing, are driving a search for alternative and complementary forms of computation, but few novel devices have been adopted by mainstream computing systems. The development of such computer technology requires advances in both computational devices and computer architectures. However, a disconnect exists between the device community and the computer architecture community, which limits progress. Here we explore this disconnect with a focus on machine learning hardware accelerators. We argue that the direct mapping of computational problems to materials and device properties provides a powerful route forwards. We examine novel materials and devices that have been successfully applied as solutions to computational problems: non-volatile memories for matrix-vector multiplication, magnetic …

Advanced Materials

In recent years, halide perovskite materials have been used to make high‐performance solar cells and light‐emitting devices. However, material defects still limit device performance and stability. Here, synchrotron‐based Bragg coherent diffraction imaging is used to visualize nanoscale strain fields, such as those local to defects, in halide perovskite microcrystals. Significant strain heterogeneity within MAPbBr3 (MA = CH3NH3+) crystals is found in spite of their high optoelectronic quality, and both 〈100〉 and 〈110〉 edge dislocations are identified through analysis of their local strain fields. By imaging these defects and strain fields in situ under continuous illumination, dramatic light‐induced dislocation migration across hundreds of nanometers is uncovered. Further, by selectively studying crystals that are damaged by the X‐ray beam, large dislocation densities and increased nanoscale strains are correlated with …

Physical Review Applied

The fabrication of complex low-dimensional quantum devices requires the control of the heteroepitaxial growth at the subnanometer scale. This is particularly challenging when the total thickness of stacked layers of device-active material becomes extremely large and exceeds the multi-μ m limit, as in the case of quantum cascade structures. Here, we use the ultrahigh-vacuum chemical vapor deposition technique for the growth of multi-μ m-thick stacks of high Ge content strain-balanced Ge/Si-Ge tunneling heterostructures on Si substrates, designed to serve as the active material in a THz quantum cascade laser. By combining thorough structural investigation with THz spectroscopy absorption experiments and numerical simulations we show that the optimized deposition process can produce state-of-the-art threading dislocation density, ultrasharp interfaces, control of dopant atom position at the nanoscale, and …

Nanotechnology

The fabrication and characterization of steep slope transistor devices based on low-dimensional materials requires precise electrostatic doping profiles with steep spatial gradients in order to maintain maximum control over the channel. In this proof-of-concept study we present a versatile graphene heterostructure platform with three buried individually addressable gate electrodes. The platform is based on a vertical stack of embedded titanium and graphene separated by an intermediate oxide to provide an almost planar surface. We demonstrate the functionality and advantages of the platform by exploring transfer and output characteristics at different temperatures of carbon nanotube field-effect transistors with different electrostatic doping configurations. Furthermore, we back up the concept with finite element simulations to investigate the surface potential. The presented heterostructure is an ideal platform for …

ACS nano

Reliable, clean transfer and interfacing of 2D material layers are technologically as important as their growth. Bringing both together remains a challenge due to the vast, interconnected parameter space. We introduce a fast-screening descriptor approach to demonstrate holistic data-driven optimization across the entirety of process steps for the graphene–Cu model system. We map the crystallographic dependences of graphene chemical vapor deposition, interfacial Cu oxidation to decouple graphene, and its dry delamination across inverse pole figures. Their overlay enables us to identify hitherto unexplored (168) higher index Cu orientations as overall optimal orientations. We show the effective preparation of such Cu orientations via epitaxial close-space sublimation and achieve mechanical transfer with a very high yield (>95%) and quality of graphene domains, with room-temperature electron mobilities in the …

Environmental Science and Pollution Research

In decentralized systems, adsorption-based strategies offer inherent advantages for the treatment of drinking water contaminated with oxoanion. However, these strategies only involve phase transfer and not the transformation to an innocuous state. The requirement for an after-treatment procedure to manage the hazardous adsorbent further complicates the process. Here we formulate green bifunctional ZnO composites for the simultaneous adsorption and photoreduction of Cr(VI) to Cr(III). Three non-metal-ZnO composites based on raw charcoal- ZnO, modified charcoal- ZnO charcoal, and chicken feather- ZnO were prepared from the combination of ZnO with non-metal precursors. The composites were characterized and both the adsorption and photocatalyst features were studied, separately, in synthetic feedwater and groundwater contaminated with Cr(VI). The adsorption efficiency of the composites for Cr(VI) at …

The discovery of graphene has opened novel exciting opportunities in terms of functionalities and performances for spintronics devices. To date, it is mainly graphene properties for efficient in-plane spin transport which have been put forward. [1] We will present here experimental results concerning integration of graphene and other 2D Materials in vertical Magnetic Tunnel Junctions (MTJ), with strong technological potential. [2]We will show that a thin graphene passivation layer, directly integrated by low temperature catalyzed chemical vapor deposition (CVD), [3] allows to preserve a highly surface sensitive spin current polarizer/analyzer behavior. Characterizations of complete spin valves making use of graphene grown by CVD will be presented. The graphene layer prevents the oxidation of ferromagnets, unlocking in turn the exploration of spin filtering phenomena at graphene/ferromagnet interfaces, [4] as well as the …

arXiv preprint arXiv:2303.17886

Excitons are two-particle correlated bound states that are formed due to Coulomb interaction between single-particle holes and electrons. In the solid-state, cooperative interactions with surrounding quasiparticles can strongly tailor the exciton properties and potentially even create new correlated states of matter. It is thus highly desirable to access such cooperative and correlated exciton behavior on a fundamental level. Here, we find that the ultrafast transfer of an exciton's hole across a type-II band-aligned moir\'e heterostructure leads to a surprising sub-200-fs upshift of the single-particle energy of the electron being photoemitted from the two-particle exciton state. While energy relaxation usually leads to an energetic downshift of the spectroscopic signature, we show that this unusual upshift is a clear fingerprint of the correlated interactions of the electron and hole parts of the exciton quasiparticle. In this way, time-resolved photoelectron spectroscopy is straightforwardly established as a powerful method to access exciton correlations and cooperative behavior in two-dimensional quantum materials. Our work highlights this new capability and motivates the future study of optically inaccessible correlated excitonic and electronic states in moir\'e heterostructures.

Nanoscale

Identification of non-amplified DNA sequences and single-base mutations is essential for molecular biology and genetic diagnostics. This paper reports a novel sensor consisting of electrochemically-gated graphene coplanar waveguides coupled with a microfluidic channel. Upon exposure to analytes, propagation of electromagnetic waves in the waveguides is modified as a result of interactions with the fringing field and modulation of graphene dynamic conductivity resulting from electrostatic gating. Probe DNA sequences are immobilised on the graphene surface, and the sensor is exposed to DNA sequences which either perfectly match the probe, contain a single-base mismatch or are unrelated. By monitoring the scattering parameters at frequencies between 50 MHz and 50 GHz, unambiguous and reproducible discrimination of the different strands is achieved at concentrations as low as one attomole per litre …

Materials Science in Semiconductor Processing

The challenge of Fermi-level pinning significantly complicates the establishment of Ohmic, low-resistance contacts for lightly doped n-type crystalline silicon (c-Si), a critical requirement for economically feasible device development. In this novel study, we present an innovative approach by introducing an ultra-thin zirconium oxide (ZrOx) film to achieve an Ohmic contact in n-type c-Si. The ZrOx films are deposited through e-beam evaporation at room temperature, and their properties are characterized using spectroscopic ellipsometry (SE), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and contact resistivity (ρc) measurements. Our investigation unveiled a pronounced dependence of the contact resistivity on the thickness of the ZrOx layer, with the lowest ρc value of 22 mΩ cm2 achieved with an ultrathin 1 nm ZrOx film. To demonstrate our study's feasibility, we applied ZrOx as an electron-selective …

Materials Science in Semiconductor Processing

M-type Sr nanohexaferrite, SrFe12-2xCrxInxO19, samples were synthesized using the conventional solid-state reaction technique with concentration ratios x (wt.%) = 0.00 wt%, 0.05 wt%, 0.10 wt%, 0.15 wt% and 0.20 wt%. Cr2O3 and In2O3 were used in the substitution process as impurities embedded within the M-type Sr nanohexaferrite composition. The X-ray diffraction (XRD) technique characterized the samples' structure, where the formation of hexagonal SrFe12O19 nanohexaferrite structure with the space group (P63/mmc) was confirmed. Field Emission Scanning Electron Microscope (FESEM) and Transmission Electron Microscope (TEM) techniques were used to investigate the morphology of the samples. The X-ray photoelectron spectroscopy (XPS), ensured the presence of Fe2+ and Cr3+, which was interpreted as a result of electron transfer between Fe3+ and Cr6+. Moreover, the Vibrating Sample …

Materials Science in Semiconductor Processing

The impact of gamma irradiation and subsequent recovery at room temperature on the device performance of commercial 4H–SiC Schottky barrier diodes (SBDs) was investigated through the analysis of the electrical properties and the deep level transient spectroscopy (DLTS). The ideality factor (n) of the SBDs increased from 1.01 to 1.13 with an increasing irradiation dose, but recovered after 7 days of room temperature annealing. To determine Schottky barrier heights (ΦB), both current-voltage (I–V) and capacitance-voltage (C–V) measurements were performed. The results of the combined I–V and C–V analysis showed that a little variations in ΦB were consistent with the variations in irradiation dose, except for the ΦB calculated by C–V measurement at 30 kGy. Similarly, the ΦB recovered after 7 days at room temperature. DLTS analysis revealed the presence of Z1/Z2 traps in the samples after 7 days at room …

Materials Science in Semiconductor Processing

This paper presents microfabrication, characterization, optical sensing and memory testing using nanostructured tungsten trioxide (WO3). Different experiments were performed to realize the integrated sensing and computing memory (ISCM) functionality on the same device. These ISCM devices were fabricated using standard wafer-scale microfabrication processes on 2-inch silicon (Si) substrate. First, the devices were tested to detect the broad wavelength spectrum ranging ultraviolet (UV) to near infrared (NIR). These photosensing devices were shown repeatable, reproducible and reliable results with fast switching speed (rise time (0.05 s)/fall time (0.08 s)) at 880 nm. Further, the memory functionality was realized using the electrical and optical stimuli at room temperature. The optically stimulated device has shown higher sensitivity for 880 nm and mimics the human brain's functional characteristics. The …

Materials Science in Semiconductor Processing

The aim of this study is to investigate the effects of various process parameters (the grinding-wheel speed, feed rate, workpiece speed, spark-out grinding time, and grinding-wheel granularity) on the surface quality of single-crystal SiC during nanogrinding while concurrently analysing the grinding mechanism and optimising the overall process. Experiments are performed to investigate the macrotexture and micromorphology of the single-crystal SiC surface. By employing image-processing technology, the proportion of brittle and plastic removal components is determined, thus facilitating a comprehensive analysis into the removal mechanism and the subsequent establishment of a material-removal model. The findings indicate that after grinding, the surface of single-crystal SiC exhibits a distinct grinding trajectory that radiates outwards from the centre, the density of the grinding trajectory is higher in the central area …

Materials Science in Semiconductor Processing

The epitaxial growth of a strained Ge layer, which is a promising candidate for the channel material of a hole spin qubit, has been demonstrated on 300 mm Si wafers using commercially available Si0.3Ge0.7 strain relaxed buffer (SRB) layers. The assessment of the layer and the interface qualities for a buried strained Ge layer embedded in Si0.3Ge0.7 layers is reported. The XRD reciprocal space mapping confirmed that the reduction of the growth temperature enables the 2-dimensional growth of the Ge layer fully strained with respect to the Si0.3Ge0.7. Nevertheless, dislocations at the top and/or bottom interface of the Ge layer were observed by means of electron channeling contrast imaging, suggesting the importance of the careful dislocation assessment. The interface abruptness does not depend on the selection of the precursor gases, but it is strongly influenced by the growth temperature which affects the …

Materials Science in Semiconductor Processing

Thin film microstructure and its properties can be effectively altered with post deposition heat treatments. In this respect, CdTe thin films were deposited on glass substrates at a substrate temperature of 200 °C using thermal evaporation technique, followed by air annealing at different temperatures from 200 to 500 °C. Structural analysis reveals that CdTe thin films have a cubic zincblend structure with two oxide phases related to CdTe2O5 and CdTeO3 at annealing temperature of 400 and 500 °C respectively. Regardless of the annealing temperature, the plane (111) was found to be the preferred orientation for all films. The crystallite size was observed to increase with annealing temperature. All films were found to display higher lattice parameters than the standard, and hence found to carry a compressive stress. Optical measurements suggest high uniformity of films both before and after post deposition heat …

Materials Science in Semiconductor Processing

The optimization of magnetron sputter epitaxy (MSE) for the high-volume production of high-quality GaN films is increasingly important. This study concerns the influence of key MSE process parameters - including the partial pressure of process gas, target-to-substrate distance (TSD), and growth temperature (TG) - for the synthesis of GaN thin films using a liquid Ga target. It is observed that the effective Ga/N ratio on the substrate surface determines the film's growth behavior and affects material's composition and luminescence properties. A lower Ar/N2 partial pressure ratio substantially enhances the crystalline quality, evidenced by the reduction in peak width of x-ray rocking curves from approximately 1.25° (N-rich regime) to 0.35° (Ga-rich regime) and improved GaN bandgap emission. While target sputtered in a highly Ga-rich condition significantly reduces the GaN growth rate (R), primarily due to Ga desorption …

Materials Science in Semiconductor Processing

We demonstrate the fabrication of unpatterned and nanohole patterned AlGaN/GaN High electron mobility transistor-based metal-semiconductor-metal UV photodetectors. Device with shallow, non-dense periodic arrays of 200 nm diameter and 20 nm deep nanoholes on the AlGaN barrier surface shows∼ 10 3 photo-to-dark current ratio and responsivity of 1.3× 10 5 A/W for 325 nm wavelength at 5 V bias. Nanohole etching on AlGaN barrier surface is shown to enhance the spectral response of the devices in the near UV (NUV) range, with clear UV/Visible cut-off. The enhancement is attributed to light trapping in nanoholes which prolonged light path and enhanced absorption in the active region. External quantum efficiency of the devices exceeded 100%, due to internal gain mechanism of the device. Two spectral responsivity peaks occurred at wavelengths correspond to AlGaN and GaN bandgaps. The device …

Materials Science in Semiconductor Processing

This study employed density functional theory calculations to provide predictions regarding the optoelectronic and thermoelectric properties of both pristine and defective CsSnCl3 in their respective cubic and tetragonal phases. In this study, we provide novel findings about the influence of spin-orbit coupling (SOC) on the optical and thermoelectric characteristics of these systems. When considering the phenomenon of SOC, it is noticed that these materials have enhanced absorption capabilities in the visible range compared to their counterparts without SOC, owing to their unique band characteristics. The compounds, regardless of the inclusion of SOC, exhibit a figure of merit that is approximately equal to unity. This characteristic suggests that these materials hold promise as possible candidates for use in photovoltaics and thermoelectrics.

Materials Science in Semiconductor Processing

High quality CdSₓSe₁₋ₓ thin films were deposited by Aerosol Assisted Chemical Vapor Deposition (AACVD) at 450 °C using the dual source approach on quartz substrates. Cd mole solutions of C₁:C₂ and C₃:C₄ homoleptic precursors, [Cd(iPr₂P(X)NC(Y)NC₅H₁₀-κ2-X,Y)₂] with X = Y = S (C₁); X = Se, Y = S (C₂); X = S, Y = O (C₃) and the dinuclear complex [Cd(iPr₂P(Se)NC(O)NC₅H₁₀-κ2-Se,O)₂(μ₂-O)]₂ (C₄), were used to deposit two sets of thin films, 2F–6F and 7F–9F, respectively. The morphology was studied by scanning electron microscopy (SEM), showing uniform deposition of the materials over the whole film with spherical particles assembled in columns for 2F–5F and 7F, while 8F–9F films showed dense flake-like structures. The elemental composition was confirmed by energy dispersive X-ray analysis (EDXA), revealing additional homogeneous P content between 2.5 % and 7.5 …

Materials Science in Semiconductor Processing

Organic solar cells are a promising new technology for the generation of renewable energy. However, their efficiency is still relatively low and therefore, demand for designing new materials and strategies to improve their performance is growing. Herein, the structural, optical, and electrical properties are calculated and estimated of a set of 8 molecules based on pyrrole framework as organic material designed for application as visible light materials in organic solar cells using Density Functional Theory approach. We changed the original reference molecule to SD1−SD8 molecules to enhance optoelectronic properties of these materials. The fundamental gap was reduced from 2.25 eV to 1.55 eV by altering the donor part of the molecule. The designed materials were fully relaxed and their various properties, like HOMO-LUMO, density of states, molecular electrostatic potential, and transition density matrix were …

Materials Science in Semiconductor Processing

This study investigates methods to modulate the effective work function (EWF) and control the multiple threshold voltages (VTHs) of metal-oxide-semiconductor (MOS) devices by applying metal electrodes with different work function materials (WFMs), including a single layer of n-type (TaAlC) and p-type (TaAlN) as well as their stacked structures, through atomic layer deposition (ALD). Dual-Work-Function-Metal (DWFM) gate is a crucial aspect of confirming the feasibility of metal gate stacks in MOS devices for a complementary metal-oxide-semiconductor (CMOS) integration scheme. The gate stack structure of p-Si/IL (Inter layer)/HfO2/DWFM (p/n-type compatible metal stack)/W exhibits good adhesion and even chemical composition distribution, as evidenced by transmission electron microscope (TEM) and energy dispersive spectrometer (EDS) analysis. By fabricating MOS capacitors using this WFM structure and …

Materials Science in Semiconductor Processing

Semiconductor-based photocatalytic processes are widely applied as ecofriendly technology for degrading organic pollutants. Establishing photocatalytic heterojunctions with Z-type photocarriers transfer pathways is projected to be a superb strategy to enhance photocatalytic behavior. In this paper, novel and stable (0D/2D) heterojunctions of CoS-embedded boron-doped g-C3N4 (CoS/BCN) with a high rate of charges transfer/separation were assembled for degradation of malachite green dye (MG). The CoS/BCN photocatalyst achieves a photodegradation efficiency of 96.9 % within 1 h of LED illumination, which is 2.5 and 1.4-fold enhancement compared with bare g-C3N4 and BCN, respectively. Besides, the results of species-trapping trials exhibited that •O2− and at a lower degree, photogenerated holes were mainly in charge of the boosted performance. In light of the above results of the trapping experiments …

Materials Science in Semiconductor Processing

Among various titanium(IV) oxide (TiO2, titania) structures, 1D nanotubes (TiO2 NTs) produced during the two-electrode anodization process, are extensively utilized in sensors or supercapacitors as well as in photo(electro)catalytic water splitting. However, due to wide bandgap and fast electron-hole recombination additional modifications, mostly concerned on materials surface, are required. According to the recent research, TiO2 NTs photo(electro)catalytic characteristic were markedly improved by the combination of surface decoration with transition metal nanoparticles further treated with the laser beam. Nevertheless, until recently, the photocatalytic ability of laser-treated TiO2 NTs for recalcitrant chemicals degradation were hardly described. In this regard, our work focuses on obtaining long, about 7.3 μm TiO2 NTs (L-TiO2 NTs), together with their photoactivity and physicochemical characteristics, as well as …

Materials Science in Semiconductor Processing

In this paper, an efficient hexagonal micro-ring resonator is proposed to improve the cancer biosensor performance. The sensor is based on a two-dimensional photonic crystal lattice with a horizontal waveguide. Finite-difference time-domain method is used to calculate the response of the sensor. The simulations show that by using the optimum hexagonal micro-ring resonator, the sensor performance parameters such as full width half maximum, absorption/transmittance, quality factor & sensitivity have been improved. Various parameters are involved in the design of a micro-ring resonator, which include; the coupling area length, the side length, the inner and outer radius of the micro-ring resonator and the waveguide gap width. This study not only unveils the obscure effect of some kind of symmetries in the design of micro-ring resonators on the final device performance, but also brings important perspectives to …

Materials Science in Semiconductor Processing

Acceptor dopants in 4H-SiC exhibit energy levels that are located deeper in the band gap than the thermal energy at room temperature (RT), resulting in incomplete ionization at RT. Therefore, a comprehensive understanding of the defect energetics and how the impurities are introduced into the material is imperative. Herein, we study impurity related defect levels in 4H-SiC epitaxial layers (epi-layers) grown by chemical vapor deposition (CVD) under various conditions using minority carrier transient spectroscopy (MCTS). We find two trap levels assigned to boron impurities, B and D, which are introduced to varying degrees depending on the growth conditions. A second acceptor level that was labeled X in the literature and attributed to impurity related defects is also observed. Importantly, both the B and X levels exhibit fine structure revealed by MCTS measurements. We attribute the fine structure to acceptor …

Materials Science in Semiconductor Processing

The switching dynamics of TiN/Ti/HfO2/W-based resistive memories is investigated. The analysis consisted in the systematic application of voltage sweeps with different ramp rates and temperatures. The obtained results give clear insight into the role played by transient and thermal effects on the device operation. Both kinetic Monte Carlo simulations and a compact modeling approach based on the Dynamic Memdiode Model are considered in this work with the aim of assessing, in terms of their respective scopes, the nature of the physical processes that characterize the formation and rupture of the filamentary conducting channel spanning the oxide film. As a result of this study, a better understanding of the different facets of the resistive switching dynamics is achieved. It is shown that the temperature and, mainly, the applied electric field, control the switching mechanism of our devices. The Dynamic Memdiode …

Materials Science in Semiconductor Processing

In this study, a surfactant assisted wet-chemical method was used to synthesize manganese and neodymium co-doped cobalt ferrite [Co1-xFe2-y O4 (x = Mn, y = Nd)]. The co-doping strategy was adopted to enhance the magnetic properties, tune the band gap, and hamper charge–recombination in the spinel ferrite during the photocatalytic application. Different dopant concentrations, namely Mn = Nd = 1.1 %, 2.2 %, 3.3 %, and, 4.4 %, were used to synthesize MNCF-1, MNCF-2, MNCF-3, and MNCF-4 samples, respectively. The pristine (CF) and co-doped samples (MNCF) were characterized via TGA, PXRD, Raman, FTIR, and UV/Vis techniques to examine the impact of co-doping on the various physicochemical and thermal properties. The optical study proposed the MNCF-4 sample with a band gap value of 2.88 eV as most suitable for visible-light harvesting. A dielectric study showed that co-doped ferrite with a …

Materials Science in Semiconductor Processing

In the present research, the two dicyanomethylene-4H-pyran derivatives M4 and M5 have been synthesized and characterized for nonlinear optical response. The photophysical properties were investigated through UV–Vis absorption and emission studies. The polarity-dependent salvatochromic study has been performed to confirm intramolecular charge transfer (ICT) occurring in both compounds. The third-order optical nonlinearities have been enumerated using Z–scan techniques with a diode laser (520 nm) and both the compounds exhibit self-defocusing behavior and saturable absorption behavior. The rare phenomenon i.e. nonlinear absorption switching from saturable to reverse saturable has also been highlighted in both compounds, this inherent property makes the material an effective component for optical limiters. The nonlinear optical susceptibility (χ (3)), absorption coefficient (β), and refractive index …