Silicon Substrate Research Articles

Synergistic Effects of Nitrogen–Oxygen–Nitrogen, Forming Gas–Oxygen–Forming Gas, and Argon–Oxygen–Argon Annealing Ambient on the Structural and Electrical Characteristics of Thulium Oxide Passivation Layers on Silicon Substrate

A comprehensive probe was conducted to compare the impact of postdeposition annealing at 700°C in different ambient of nitrogen–oxygen–nitrogen (NON), forming gas–oxygen–forming gas (FGOFG), and argon–oxygen–argon (ArOAr) on the passivating characteristics of thulium oxide (Tm2O3) on the silicon (Si) substrate. The nitrogen ions have been incorporated in Tm2O3 passivation layers after annealing in NON and FGOFG ambient, of which NON ambient has impeded the growth of silicon oxide (SiO2) interfacial layer (3.258 nm). Although a thicker SiO2 interfacial layer (4.026 nm) was formed after annealing in FGOFG ambient, the attainment of the highest k value (16.8) indicated that the existence of hydrogen ions has assisted the improvement in the overall k value of Tm2O3 passivation layers. Furthermore, the capacitance–voltage characteristic revealed that the FGOFG ambient was effective in reducing the effective oxide charge (1.32 × 1012 cm−2), while NON ambient was effective in passivating the slow trap density (STD) (3.20 × 1011 cm−2). The Terman, Hill–Coleman, and high–low frequency methods have demonstrated the acquisition of the best interface quality during annealing in FGOFG ambient. As a result, the FGOFG annealing process has led to the maximum breakdown electric field of 4.03 MV/cm and the minimum leakage current density for the Tm2O3 passivation layer.

The peculiarities of direct gallium nitride growth on silicon substrates after surface passivation with gallium atoms and indium as a surfactant

The peculiarities of direct gallium nitride growth on silicon substrates after surface passivation with gallium atoms and indium as a surfactant

Fabrication of high-density vertical CNT arrays using thin porous alumina template for biosensing applications.

This paper explores the process of forming arrays of vertically oriented carbon nanotubes (CNTs) localized on metal electrodes using thin porous anodic alumina (PAA) on a solid substrate. On a silicon substrate, a titanium film served as the electrode layer, and an aluminium film served as the base layer in the initial film structure. A PAA template was formed from the Al film using two-step electrochemical anodizing. Two types of CNT arrays were then synthesized by catalytic chemical vapor deposition. By electrochemically depositing Ni into the PAA pores in two different regimes-constant potential (DC deposition) and alternating current (AC deposition)-catalyst nanoparticles for CNT deposition are formed. It is shown that the size parameters of the CNTs and the proposed CNT growth mechanism depend on the size of the catalyst particles and their localization in the pores of the PAA. Thus, a Ti/PAA/Ni/CNT-based nanocomposite multilayered structure was formed on the Si substrate. Through the use of X-ray diffraction analysis, linear voltammetry, atomic force microscopy, and scanning electron microscopy, the morphological, structural, and electrochemical characteristics of the produced nanocomposite material were investigated. It is shown that the obtained nanostructures can be used for the fabrication of CNT electrodes for biosensing applications.

Unlocking the Performance of Next-generation Non-volatile Capacitive Memory Devices with Ti-doped ZnO Nano Wires via Pulsed Laser Deposition

This paper investigates the impact of titanium (Ti) doping on zinc oxide (ZnO) nano wires (NWs) in non-volatile capacitive memory devices (NVCMDs) through fabrication and characterizations. ZnO NWs were fabricated using pulsed laser deposition (PLD), while Ti thin film (TF) was deposited via electron beam evaporation (e-beam). Field emission gun scanning electron microscopy (FEGSEM) confirmed the formation of ZnO NWs and Ti-doped ZnO NWs (Ti:ZnO NWs) on an n-type silicon (Si) substrates, with elemental compositions determined by energy dispersive X-ray spectroscopy (EDX). Structural characterization was conducted on the samples using high-resolution X-ray diffraction (HRXRD). Gold (Au) interdigitated electrodes (IDE) were employed to fabricate two distinct devices: Au IDE/ZnO NWs and Au IDE/Ti:ZnO NWs. Comparative analysis revealed that the Au IDE/Ti:ZnO NWs device exhibited a lower frequency dispersion fd value (0.025×109 F) compared to Au IDE/ZnO NWs device (0.029×109 F), indicating enhanced signal propagation due to Ti doping. The Au IDE/Ti:ZnO NWs device also demonstrated a high free charge carrier donor concentration ND value of 2.02×1012 /cm3, a significant trap concentration Nt value of 4.44×1011 /cm3 at an 8MHz frequency response. Additionally, it exhibited lower tangent loss (tan(δ)) value of 7430, maximum conductance Gmmax value of 13.40 mS, lower interface trap state density (ITSD) value of 2.05×1014 eV1 cm2, a maximum memory window (∆VMW) of 6.9V at ±15V, improved endurance, and superior data retention, making the Au IDE/Ti:ZnO NWs device a promising candidate for next-generation NVCMDs applications.

Ultrasensitive NO2 Gas Detection using ALD-Grown ZnO-SiO2/Si Thin Film-based UV Sensors

In this study, nitrogen dioxide (NO2) gas sensors based on zinc oxide-silicon (ZnO–Si) and zinc oxide-silicon dioxide-silicon (ZnO–SiO2–Si) configurations were fabricated to study their response to ultraviolet (UV) radiation at room temperature (300K). Single and polycrystalline ZnO layers were deposited using atomic layer deposition (ALD) on silicon and silica substrates. The structure and composition of the films were studied using various characterization techniques. The current-voltage (I-V) characteristics of these sensors’ UV illumination (~365nm) have been investigated. The gas sensing performance of both configurations was analyzed with and without the UV source for varied concentrations of NO2 gas. Exposure to UV light significantly improved the recovery times of the sensors. Specifically, the recovery time for the Si-based sensor decreased from 1578seconds to 24seconds, while for the SiO2-based sensor, it reduced from 540seconds to 5seconds. The response time of ZnO–Si was found to be 2seconds and ZnO–SiO2–Si to be 1second. Under irradiation, the sensitivity factor increased from 8.29 × 107 to 5.79 × 108% ppm-1 for the ZnO–SiO2–Si sensor. It reached a maximum value of 9.12 × 1011% ppm-1, which is extremely high compared to similar devices.

Chemical etching of silicon assisted by graphene oxide under negative electric bias.

Chemical etching of silicon assisted by graphene oxide (GO) has been attracting attention as a new method to fabricate micro- or nano-structures. GO promotes the reduction of an oxidant, and holes are injected into silicon, resulting in the preferential dissolution of the silicon under GO. In the conventional etching method with GO, the selectivity of the etching was low due to the stain etching caused by nitric acid. We developed an etching method that applies a negative bias to the p-type silicon substrate. The silicon under GO was more selectively etched in an etchant consisting of hydrofluoric acid and nitric acid than the silicon uncovered by GO. We assume that this is attributed to the difference in hole concentration in the silicon under GO and in the bare silicon. In addition, the in-plane diffusion of holes in silicon is suppressed by this method, resulting in the formation of highly anisotropic pores. From this study, we found that GO-assisted silicon etching occurs with a similar principle to metal-assisted chemical etching. The negative-bias etching with GO has the potential to be a simple and highly anisotropic microfabrication method.

In-human Nanofluidic Air Transport through Respirators and Masks

During the COVID-19 pandemic, the mandatory use of multiple surgical masks or N95 respirators in public raised concerns about potential health issues associated with the increased breathing force needed to maintain the breathing cycle. To address these concerns, we conducted a comprehensive study investigating the transportation and filtering mechanisms of heterogeneous nanoparticles and virus-like particles through surgical masks and N95 respirators. Our multifaceted approach combined in vitro experiments utilising aerosol spray paints containing nanoparticles and in vivo validation on human volunteer inhaling city air. We employed scanning electron microscopy and transmission electron microscopy to analyse the distribution of nanoparticles across various mask layers and pristine silicon substrates placed on human skin. In addition, we provide analytical insights into the pressure distribution and fluid velocity profiles within the complex polymer fibre network of the masks. Our findings remarkably revealed that both single surgical masks and N95 respirators exhibited similar nanofluidic performance in filtering colloidal and jet-stream nanoparticles in the air. These results have significant implications for policymakers in developing regulations to manage airborne pandemics and air pollution control, ultimately enhancing public health and safety during respiratory health crises.

Fabrication and Electrical Characterization of Low-Temperature Polysilicon Films for Sensor Applications.

The development of low-temperature piezoresistive materials provides compatibility with standard silicon-based MEMS fabrication processes. Additionally, it enables the use of such material in flexible substrates, thereby expanding the potential for various device applications. This work demonstrates, for the first time, the fabrication of a 200 nm polycrystalline silicon thin film through a metal-induced crystallization process mediated by an AlSiCu alloy at temperatures as low as 450 °C on top of silicon and polyimide (PI) substrates. The resulting polycrystalline film structure exhibits crystallites with a size of approximately 58 nm, forming polysilicon (poly-Si) grains with diameters between 1-3 µm for Si substrates and 3-7 µm for flexible PI substrates. The mechanical and electrical properties of the poly-Si were experimentally conducted using microfabricated test structures containing piezoresistors formed by poly-Si with different dimensions. The poly-Si material reveals a longitudinal gauge factor (GF) of 12.31 and a transversal GF of -4.90, evaluated using a four-point bending setup. Additionally, the material has a linear temperature coefficient of resistance (TCR) of -2471 ppm/°C. These results illustrate the potential of using this low-temperature film for pressure, force, or temperature sensors. The developed film also demonstrated sensitivity to light, indicating that the developed material can also be explored in photo-sensitive applications.

Dimethyl Sulfoxide Mixed-Solvent Engineering for Efficient Perovskite/Silicon Tandem Solar Cell

The integration of perovskite with silicon for constructing tandem solar cells (TSCs) represents a promising route in photovoltaic technology. The hybrid sequential deposition (HSD) method, combining thermal evaporation and spin-coating, is crucial for developing perovskite films in textured perovskite/silicon tandem solar cells. However, the process faces challenges due to incomplete reactions caused by the dense perovskite coverage layer (CPCL) formed from high-crystallinity precursors. The CPCL hinders the diffusion of organic salts into the bottom precursor layer, leading to performance degradation and accelerated device aging. Herein, this study explores several polar solvents as additives to n-butanol (nBA) solvent in order to enhance the permeability of organic salts through the CPCL, and we demonstrate that dimethyl sulfoxide (DMSO) as an additive solvent can effectively assist organic salts in rapidly diffusing through the precursor layer, thereby promoting the complete transformation of uniform perovskite crystals. The resulting perovskite films exhibited complete conversion, uniform crystallization, and improved quality. As a result, the target TSCs achieved an increased maximum power conversion efficiency (PCE) of 29.12%. This study offers a robust pathway for depositing high-quality perovskite films on industrial-grade textured silicon substrates, laying a solid foundation for advancing perovskite/silicon tandem solar cells technology.

Selecting the Trajectory of the Laser Beam to Form Vias in the Silicon Substrate

Selecting the Trajectory of the Laser Beam to Form Vias in the Silicon Substrate

Optical Properties of Spin‐Coated Solution Processed MoS2

In this study, the optical and structural properties of solution‐processed molybdenum disulfide (MoS2) thin films are explored. MoS2 is synthesized via chemical exfoliation and deposited on fused silica and silicon substrates using a spin‐coating technique. The morphology and structural properties of the films are characterized using scanning electron microscopy and atomic force microscopy. Optical properties are examined through UV–vis and Raman spectroscopy. In the results, it is shown that the MoS2 thin films exhibit an indirect bandgap of 1.40 eV with over 60% absorption between 400 and 710 nm. Also, physics‐based optical modeling predicts a potential current generation of 25 mA cm−2 with full coverage of MoS2, indicating significant potential for solution‐processed MoS2 as an absorber layer in optoelectronic applications.

Micro-transfer printing of InGaAs/InP avalanche photodiode on Si substrate

Abstract We report on the fabrication and micro-transfer printing of InGaAs/InP avalanche photodiodes (APDs) onto silicon substrates. A process flow was developed to suspend the devices using semiconductor tethers. The developed process reduces the number of fabrication steps required compared to methods based on the use of photoresist tethers. Furthermore, our process is compatible with devices that may be susceptible to damage induced by the photoresist removal process. APDs were characterised in linear mode operation both before suspension and after printing. Despite the additional fabrication steps required to suspend the APD membranes and the physical nature of the micro-transfer printing process, the electrical characteristics of the devices were preserved. No degradation in the optical performance of the devices was measured. Our work represents the first demonstration of micro-transfer printing of InGaAs/InP avalanche photodiodes onto silicon substrates. The results highlight the viability of micro-transfer printing for effective heterogeneous integration of InGaAs/InP avalanche photodiodes with silicon photonic integrated circuits for optical and quantum communication and other light detection applications.

Covalent Grafting of Quaternary Ammonium Salt-Containing Polyurethane onto Silicone Substrates to Enhance Bacterial Contact-Killing Ability

Catheter-associated urinary tract infection (CAUTI) induced by rapid bacterial colonization and biofilm formation on urinary catheters is a key issue that urgently needs to be addressed. To prevent CAUTI, many contact-killing, non-leaching coatings have been developed for the surfaces of silicone catheters. However, due to the chemical inertness of the silicone substrate, most current coatings lack adhesion and are unstable under external forces. Thus, the aim of this study was to develop a surface coating that has both good antibacterial ability and a high affinity toward silicone substrates. To achieve high affinity, a pre-coating layer with abundant surface vinyl groups, named SI-vinyl, was prepared on the silicone substrate by moisture curing using a mixture of α,ω-dihydroxy polydimethylsiloxane and vinyltrimethoxysilane as the painting agent. To endow the surface with contact-killing ability, a series of polyurethanes with different contents of quaternary ammonium salt groups in their main chain and two vinyl end groups were synthesized and covalently grafted onto the surface of SI-vinyl, resulting in corresponding bactericidal coatings with different surface contents of quaternary ammonium salt groups (SI-QAS). Of these bactericidal coatings, SI-QAS-2, with a surface QAS content of 2.1 × 1016 N+ cm−2, was selected as the best coating based on the consideration of stability, compatibility, and antibacterial ability. The SI-QAS-2 coating demonstrated high contact-killing performance, rapidly inactivating 72.8%, 99.9%, and 98.9% of Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa within 30 min. Furthermore, even after being exposed to a high concentration of bacteria (106 CFU/mL) for 4 days, the SI-QAS-2 coating still maintained a high bactericidal ratio of over 80%. In summary, we developed a novel contact-killing coating that reduces the risk of bacterial infections caused by catheter implantation, demonstrating that it has high affinity toward silicone substrates, excellent contact-killing efficiency, a facile preparation method, and potential for further application.

ENHANCEMENT OF POWER CONVERSION EFFICIENCY OF DYE-SENSITIZED SOLAR CELLS VIA INCORPORATION OF GAN SEMICONDUCTOR MATERIAL SYNTHESIZED IN HOT-WALL CHEMICAL VAPOR DEPOSITION FURNACE

This study discusses the results of plasma enhanced chemical vapor deposition synthesis of GaN on sapphire and silicon substrates using specific parameters: a forward output voltage of 150 watts, a N2 gas flow rate of 60 standard cubic centimeters per minute, a chamber pressure of 2.48 mmHg, and a synthesis time of 2hours. Characterization by scanning electron microscope, Raman and energy dispersive X-ray revealed the non-stoichiometric formation of GaN, with Ga clearly predominating in the composition. scanning electron microscope analysis of the substrate surface morphology revealed the presence of small islands, which are considered to be the first step in the chemical vapor deposition process. The research also examined the effects of incorporating GaN into the photoanode of dye-sensitized solar cells. The study investigated the optimal amount of GaN powder in the TiO2 matrix. The initial experiments used commercial GaN powder to determine the optimal weight percentage. Four different weight percentages (wt%) 10 wt%, 20 wt%, 30wt % and 40 wt% GaN were selected for the study. Among them, the 20 wt% GaN had the highest power conversion efficiency of 0.75%. The fill factor values ​​showed a tendency to decrease as the weight fraction of GaN increased.

Multiwire Position-Sensitive Neutron Detector with Two Layers of Boron-10

Multiwire position-sensitive neutron detector with two layers of boron-10 was developed to detect both thermal and fast neutrons. Sensitive dimensions of two coordinate neutron detector are 50 × 50 mm. New detector characteristics are compared with ones of 100 × 100 mm detector built earlier which we used in neutron flux spatial distribution measurement. Plane-parallel design of new detector has symmetrical structure with respect to wire anode and also includes two intermediate grids and two cathodes made of parallel wires with 2 mm pitch and two silicon substrates coated boron-10 layers of 0.003 mm thickness. Detector geometry, working gas mixture and pressure are chosen so as to ensure full absorption of secondary alpha particle from reaction with thermal neutron within detector gas medium half thickness. Neutron coordinates are determined from measured ionization loss pulse heights produced by secondary nucleus. Detector expected efficiency to thermal neutrons is about 5%. The detector can be used in small-angle and diffraction scattering setups in condensed matter physics.

Influence of Sb content on carrier transport and thermoelectric properties of flexible Bi–Sb films

In this study, the Bi–Sb films with different Sb content on silicon and polyimide (PI) substrates were successfully fabricated via high vacuum magnetron sputtering and the carrier transport and thermoelectric properties were studied. As the Sb content increased, the carrier concentration, electrical conductivity, Seebeck coefficient, and power factor of deposited Bi–Sb films initially increased and then decreased at room temperature. The maximum Seebeck coefficient and power factor reached −108.90 μV K−1 and 0.133mW m−1 K−2 for the Bi84Sb16 film at room temperature. The electrical conductivity, Seebeck coefficient, and power factor of deposited Bi–Sb films increased with increasing energy gap. Whether bending toward or bending back toward, the relative electrical conductivity of the films decreased with increasing bending angle. When the bending angle was less than 90°, the electrical conductivity of the films decreased very little. However, the electrical conductivity of the films exhibited an obvious reduction when the bending angle exceeded 90°. The relative electrical conductivity of the deposited films under bending toward and bending back toward decreased by 4% and 8% under 180° bending angle, respectively. Compared with bending toward, the electrical conductivity of the films bending back toward (tensile) decreases even more at the same bending angle. The electrical conductivity of the films bending toward changed little and remained 94.1% after bending 1000 times at the radius of 3 mm. The maximum power density of a flexible thermoelectric generator for Bi84Sb16 film was 0.672 and 0.8644 W m−2 at ΔT = 30 and 39 K, respectively.

Study on ion slicing of iron garnet magneto-optic materials for near and mid-infrared on-chip optical isolators.

Achieving high-crystalline-quality, large-size iron garnet magneto-optic (MO) films on silicon substrates remains a critical challenge for CMOS-compatible on-chip non-reciprocal devices like isolators and circulators. In this study, we explored ion slicing on commercial yttrium iron garnet (YIG) crystals, bismuth-doped iron garnet (BIG), and newly developed YIG ceramics. After He+ ion implantation, wafer bonding and annealing, the BIG film on silicon was successfully fabricated, but its thickness and crystalline phase deviated from expectations. The underlying causes of these discrepancies were systematically investigated. In contrast, the YIG single crystals and ceramics showed blistering during annealing, which demonstrates their ion-slicing viability. Based on the magneto-optical constant dispersion relationships of the two materials, the nonreciprocal phase shift (NRPS) gap between BIG film on silicon and YIG film on silicon narrows significantly as the wavelength increases from 1.55 µm to 2.1 µm, dropping from 399% to 26%. As a proof of concept, we proposed a design for silicon-based TM-mode on-chip isolators at 1.5 µm and 2.1 µm using ion-sliced YIG ceramics, where the simulated insertion loss decreased from 2.78 dB to 0.35 dB due to the substantial reduction in material absorption with increasing wavelength. These results underscore the feasibility and promise of YIG ceramic ion slicing as a practical solution for CMOS-compatible on-chip isolators, particularly in the mid-infrared range.

Effect of nitrogen partial pressure on the structural and mechanical properties of (MoNbTaW)N thin films deposited by DC magnetron sputtering

This study investigates the influence of nitrogen partial pressure on the microstructure, crystal structure, chemical bonding, and mechanical properties of (MoNbTaW)N films deposited on silicon substrates via DC reactive sputtering. The depositions were carried out at room temperature from a MoNbTaW alloy target at 0.6 Pa by varying nitrogen partial pressure between 0% and 50%. The surface morphology, crystal structure, bonding characteristics, and mechanical properties were studied using scanning electron microscopy (SEM), atomic force microscopy (AFM), x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), and nanoindentation. SEM and AFM findings reveal significant morphological changes from lenticularlike structures to fine-grain structures as nitrogen partial pressure increases from 0% to 50%, with feature size decreasing from 12 to 8 nm. XRD analysis confirms a crystalline structure in all films, transforming from body-centred cubic to face-centred cubic, occurring between 16% and 33% nitrogen partial pressure. XPS analysis confirms the formation of metal–nitrogen (Me–N) bonds through binding energy shifts. Despite these structural changes, no significant variations in hardness and film modulus were observed with changes in nitrogen partial pressure, which can be attributed to weaker p(N)-d(TM) interactions. The study underscores nitrogen's crucial role in altering microstructure and crystal structure, while the strength of the Me–N bond limits its effect on mechanical properties.

Effect of ethanol on the structure and aggregation properties of C₆₀ fullerenes

This study investigated the effect of ethanol on the structure and aggregation properties of C₆₀ fullerenes using an atomic force microscope. The fullerenes were dissolved in ethanol with different concentrations (0%, 10%, 25%, 50%, 100%) and deposited on silicon substrate for further analysis. The results showed that the size of molecular aggregates of fullerenes increased significantly with increasing ethanol concentration, starting from 15-20 nm in the absence of ethanol and reaching 80-100 nm at 100% ethanol. At the same time, the structure of the aggregates became more friable, indicating the solvent effect of ethanol. The interaction force measurements showed that the adhesion force of fullerenes to the substrate decreased with increasing ethanol concentration, indicating a weakening of adhesion and molecular interactions. These data confirm the significant effect of ethanol on the physicochemical properties of fullerenes and can be used to develop nanomaterials with variable structural characteristics.

Электрофизические и структурные свойства композитных структур на основе пленок титаната бария стронция и ниобата лития

Ba0.8Sr0.2TiO3 (BST) films were synthesized by high-frequency (HF) sputtering on silicon substrates and silicon substrates with a buffer layer of piezoelectric LiNbO3 (LN) film. Comparative results of electrophysical properties of structures: Ni/BST/SiO2/Si and Ni/BST/LN/SiO2/Si are presented. It is shown that, in contrast to BST/SiO2/Si structures, BST/LN/SiO2/Si objects have a higher breakdown voltage, lower dielectric losses and wider hysteresis loops. Studies using a scanning probe microscope have shown that the effect of the LiNbO3 buffer layer increases the surface roughness of the BST film. The Kelvin probe method has shown that the polarized state in the BST/LN/SiO2/Si structure is stable for several hours.