Fabrication Of Electrical Devices Research Articles

Fabrication of electrical devices on conformal surfaces based on array nozzle and five-axis motion mechanism

It has been known that conformal printing with a single nozzle has low efficiency. This study proposes a novel non-expandable curved surface printing method that could realize high-efficiency printing with array nozzles. First, based on the non-uniform rational B-splines curved surface reconstruction method, the parameter equation of the stereolithography format curved surface model is obtained. An equidistant parallel curve filling method is proposed based on the parameter equation. According to the filling accuracy, a spatial equidistant curve network model is established by fitting the surface. Using each node on the curve network as the filling pixel increases the filling rate of the non-expandable surface and improves the printing accuracy. Compared with that of the traditional equidistant filling, the droplet filling rate could be increased by 13.05 % in this study. Finally, based on the self-developed five-axis curved surface inkjet printing system and normal vector printing method, samples of concave, convex, and multi-material conformal surfaces are sequentially printed. Our research finding lays the foundation for high-efficiency integrated molding of electronic devices with complex conformal surfaces.

Tin Oxide Nanoparticles: A Review

Abstract: The aim of this review article is an overview of the tin oxide (SnO2) nanoparticles, and the literature addresses the existing research related to the various modifications and characterization of SnO2 nanoparticles with their physicochemical investigations. Among various metal-oxide nanoparticles, SnO2 nanoparticles are considered one of the potential candidates for electronic and electrical device fabrication, sensors, display devices, gas sensing, photovoltaic devices, LIBs (Lithium-ion batteries), photocatalysis and optoelectronic devices, supercapacitors, SnO2 nanowires would provide electrolyte channels for effective transport, catalyst, and anode materials. Apart from their technological supremacy, SnO2 nanoparticles have demonstrated their compatibility with human cervical cancer cells and have successfully achieved hyperthermia temperature when subjected to an alternating current magnetic field. Doping with some of the potential rare-earth dopants via various synthesis methods such as Chemical co-precipitation, sol-gel, polymeric precursor method, and nebulizer spray pyrolysis method is the major highlight of this review article. As per the requirement of the system, SnO2 nanoparticles can be tuned by size, shape, and functionality.

Single step synthesis of amine functionalized graphene oxide/Cu-Ni bimetallic nanocomposite and tuning its electrical properties

A facile chemical method was adopted for the synthesis of bimetallic Cu-Ni particles supported on amine-functionalized graphene oxide (AGO). The amine functionalized graphene oxide (AGO) and different nanocomposites were characterized by X-ray photoelectron spectroscopy,which indicated that Cu and Ni nanoparticles were partially oxidized on the surface layer AGO.The optical direct bandgap of AGO and its nanocomposite were in the range of 5.1–5.6 eV. The PL emission spectra of these nanocomposites showed different defects related to PL emission peaks.The interaction between the metal oxide and GO was calculated from the Perdew-Becke-Ernzeroff density functional theory and from the results it is observed thatmetal oxides were adsorbed on the GO surface, and the cation-π interaction was responsible for the most stable orientation. Electrical conductivity and relaxation were significantly pronounced in low/mid-temperature zones. Moreover, AGO-Cu/Ni (1:0) showed the highest conductivity and excellent efficiency and may be used as potential candidate for smart electrical device fabrication.

Magnetizable Membranes Based on Cotton Microfibers, Honey, Carbonyl Iron, and Silver Nanoparticles: Effects of Static Magnetic Fields and Medium-Frequency Electric Fields on Electrical Properties

In this work, we present the manufacturing process of magnetizable membranes based on cotton microfibers, honey, carbonyl iron, and three different concentrations of silver microparticles. Each membrane is used as a dielectric material for the fabrication of electrical devices. By using the plane capacitor method, the electrical capacitance and dielectric loss tangent are measured in a medium-frequency alternating field superimposed on a static magnetic field. From the obtained data, the time constants of the devices, the components of complex dielectric permittivity, and the electrical conductivity of the membranes as a function of the electric field frequency and magnetic flux density can be extracted. The results show that the obtained membranes can be useful for the fabrication of low-cost and environmentally friendly magneto-active membranes that are required for various technical and biomedical applications.

Utilization of counter anions for charge transportation in the electrical device fabrication of Zn(II) metal-organic frameworks.

The present work reports the fabrication of anion-induced electrical devices with Zn(ii) metal-organic frameworks. The essence of our electronic device fabrication is to utilize the anionic species entrapped inside of the three-dimensional network of the MOFs for charge transportation. The idea is to generate MOFs as a host-guest system with encapsulated anions or anion-solvent clusters as guests and a cationic yet insulating three-dimensional framework as the host. Accordingly, we have synthesized two Zn(ii) MOFs using a neutral bispyrazole-based ligand, which results in a cationic chassis with substantial void space and porous channels inside the network. For both MOFs, the porous channels are occupied by infinitely hydrogen bonded networks of anions and anion-solvent clusters. This provides an excellent platform for anionic species-induced charge transportation and improved electrical conductivity. Indeed, the impedance spectroscopy data and current density-voltage (J-V) characteristics of the fabricated electrical devices further vindicate our idea. The current-voltage measurements clearly indicate the usefulness of modified host-guest-type MOFs for electronic device fabrication with corroborating conductivity values of 8.71 × 10-5 S m-1 and 5.79 × 10-4 S m-1 for compound 1 and compound 2, respectively.

Fabrication of Soft Sensor Using Laser Processing Techniques: For the Alternative 3D Printing Process.

Recently, the rapid prototyping process was actively studied in industry and academia. The rapid prototyping process has various advantages such as a rapid processing speed, high processing freedom, high efficiency, and eco-friendly process compared to the conventional etching process. However, in general, it is difficult to directly apply to the fabrication of electric devices, as the molding made by the rapid prototyping process is usually a nonconductive polymer. Even when a conductive material is used for the rapid prototyping process, the molding is made by a single material; thus, its application is limited. In this study, we introduce a simple alternative process for the fabrication of a soft sensor using laser processing techniques. The UV laser curing of polymer resin and laser welding of nanowires are conducted and analyzed. Through the laser processing techniques, we can easily fabricate soft sensors, which is considered an alternative 3D printing process for the fabrication of soft sensors.

Direct 3D Printing of Hybrid Nanofiber-Based Nanocomposites for Highly Conductive and Shape Memory Applications

Three-dimensional (3D) printing with conductive polymer nanocomposites provides an attractive strategy for the "on-demand" fabrication of electrical devices. This paper demonstrates a family of highly conductive multimaterial composites that can be directly printed into ready-to-use multifunctional electrical devices using a flexible solvent-cast 3D printing technique. The new material design leverages the high aspect ratio and low contact resistance of the hybrid silver-coated carbon nanofibers (Ag@CNFs) with the excellent 3D printability of the thermoplastic polymer. The achieved nanocomposites are capable of printing in open air under ambient conditions, meanwhile presenting a low percolation threshold (i.e., <6 vol %) and high electrical conductivity (i.e., >2.1 × 105 S/m) without any post-treatments. We further find that this hybrid Ag@CNF-based nanocomposite shows a quick and low-voltage-triggered electrical-responsive shape memory behavior, making it a great candidate for printing electroactive devices. Multiple different as-printed Ag@CNF-based highly conductive nanocomposite structures used as high-performance electrical devices (e.g., ambient-printable conductive components, microstructured fiber sensors, flexible and lightweight scaffolds for electromagnetic interference shielding, and low-voltage-triggered smart grippers) are successfully demonstrated herein. This simple additive manufacturing approach combined with the synergic effects of the multimaterial nanocomposite paves new ways for further development of advanced and smart electrical devices in areas of soft robotics, sensors, wearable electronics, etc.

Fundamentals of the Local Anodic Oxidation of Graphene for Scalable Applications

Using a novel instrument previously reported by our group [1], we have been able to perform Local Anodic Oxidation (LAO) over monolayer graphene to create unprecedented large areas (larger than mm2) of single layer Graphene Oxide (GO) with any shape and in a very short time (a few minutes). Our instrument is equipped with three electromechanical steppers with 0.05 µm accuracy and 1 µm precision, and each stepper with a linear piezoactuator. It operates at speeds up to 15 mm/s, and includes a steel/Ni spring probe of typically 6 µm radius to work in tapping or contact mode. The equipment is provided with a humidity control system that allows maintaining a stable Relative Humidity (RH) environment, together with a system of supply and electrical monitoring. Thus, electrical signal coming from the tip-sample interaction is continuously monitored (by means of a high speed oscilloscope). When the tip approaches to graphene on a wet atmosphere (RH higher than 40%), it is commonly accepted that a water bridge is created between them. When a negative bias is applied to the tip respect to the grounded graphene (in our case we operate between 20V - 40 V), the LAO phenomena takes place [2] (Fig. 1a). The process firstly consists on electrical water ionization in H+ and OH- ions. Hydroxyl anions are then conducted to the graphene surface, which is thus oxidized. Within a specific RH range, the oxide patterns created show a good reproducibility and regular shape (Fig. 1b). Controlling the movement of the tip, we can draw the desired patterns over the graphene or any other 2D-substrate (Fig. 1c). We have extensively studied and optimized the influence of the experimental variables affecting the process, like applied bias, contact time or relative humidity. This LAO procedure is so a very powerful tool for the fabrication of electrical devices. Also, the possibility of chemical functionalization of GO allow us to design a large variety of utilities like (bio)chemical sensors, supported catalysts, etc. In addition, we have been able to record the electrochemical trace generated during the oxidation reaction of graphene. To our knowledge, it is the first time these records have been reported. Moreover, based on these data, we have formulated a theoretical model based just on classical first principles that predicts the behavior of the LAO process over graphene. This model shows a very accurate fit for the dependence of the oxide pattern expansion with the applied voltage (Fig. 2a), with the contact time (Fig. 2b), and also for the evolution of the recorded transient electric current (Fig. 2c). This model reveals very relevant information about the processes governing LAO. First, at the beginning (< 20 ms), most of the total current I(t) passing through the tip-substrate junction does not come from the electrochemical reaction but from residual conductance of the non-oxidized graphene. We call this component drift current, IT(t). Second, for longer times (>200 ms), the total current becomes dominated just by the electrochemical reaction, and the drift component almost vanishes. We call this component electrochemical current, IEC(t) (Fig. 2c). Third, the process is mainly driven by the electric field increase at the edge of the pattern. And fourth, the GO generated has a very high oxidation degree. This work opens new promising fields for development of extensive fabrication methods, technical applications and the study of anodic oxidation processes of conducting and any 2d material at large scales.

Ultrafast and low-temperature synthesis of patternable MoS2 using laser irradiation

The fascinating properties of transition metal dichalcogenides have been studied for a decade to broaden their promising applications as flexible electronics. However, conventional mass production of 2D materials is carried out at relatively high temperatures over 600 °C, which typical flexible substrates cannot withstand. For this reason, proper low-temperature synthesis methods must be developed. Here, we propose a fast and low-temperature synthesis method for metallic MoS2, which can be achieved on a flexible polyethylene terephthalate (PET) substrate. A precursor solution was prepared by a mixture of (NH4)2MoS4 powder and dimethylformamide. This solution was then coated on the silicon or PET substrate and an MoS2 film can be fabricated in unconstrained patterns such as lines or a continuous film at micro scale. The necessary laser power and exposure time were confirmed from systematic Raman spectroscopy measurements. The metallic behavior of the synthesized film was demonstrated by the electrical device fabrication and these excellent metallic properties show the feasibility of using MoS2 as a patternable electrode material on flexible substrates.

Synthesis and characterization of graphene nanoribbons on hexagonal boron nitride

Graphene, as a typical representative of the two-dimensional material family, has received a wide attention due to its excellent physical and chemical properties. Graphene nanoribbon (GNR) is graphene in a width of several to a few tens of nanometers. GNRs not only inherit most of the excellent properties of graphene, but also have their own specific properties such as band gap opening and spin-polarized edge states, which make it the potential candidate in graphene based electronics in the future. Hexagonal boron nitride (h-BN), which has similar lattice constant with graphene, normally serves as an ideal substrate for graphene and GNRs. It can not only effectively preserve their intrinsic properties, but also benefit for the fabrication of electrical devices via popular semiconductor processes. In this paper, we reviewed the development history of research of graphene and GNRs on h-BN in recent years. The recent progress of physical properties is also discussed. In order to realize the large scale production of graphene and GNRs on h-BN, high quality h-BN multilayer is necessary. In addition, recent progresses about h-BN preparation methods are presented, and the progresses could pave the way for the further application of GNRs in the electronics. Finally, the research direction of graphene and GNRs on h-BN in the future is discussed.

Ultraquantum magnetoresistance in the Kramers-Weyl semimetal candidateβ−Ag2Se

In the history of condensed matter physics, reinvestigation of a well-studied material with enhanced quality sometimes led to important scientific discoveries. A well-known example is the discovery of fractional quantum Hall effect in high quality GaAs/AlGaAs heterojunctions. Here we report the first single crystal growth and magnetoresistance (MR) measurements of the silver chalcogenide $\beta $-Ag$_2$Se (Naumannite), a compound has been known for the unusual, linear-field-dependent MR in its polycrystalline form for over a decade. With the quantum limit (QL) as low as 3 Tesla, a moderate field produced by a superconductor magnet available in many laboratories can easily drive the electrons in Ag$_2$Se to an unprecedented state. We observed significant negative longitudinal MR beyond the QL, which was understood as a `charge-pumping' effect between the novel fermions with opposite chiralities. Characterization of the single-crystalline Ag$_2$Se and the fabrication of electric devices working above the QL, will represent a new direction for the study of these exotic electrons.

Large-Area, Highly Ordered Array of Graphitic Carbon Materials Using Surface Active Chitosan Prepatterns.

We demonstrate that chitosan prepatterns can generate not only highly periodic DNA pattern but also various types of graphitic carbon materials such as single-walled carbon nanotubes (SWNTs), graphene oxide (GO) and reduced graphene oxide (RGO). Scanning electron microscopy (SEM), fluorescence imaging and Raman spectroscopic results revealed that the graphitic carbon materials were selectively deposited on the surface of the periodic chitosan patterns by the electrostatic interaction between protonated amine groups of chitosan and the negative charged carbon materials. One proof-of-concept application of the system to the fabrication of electrical devices based on the micropatterns of SWNTs and RGO was also demonstrated. The strategy to use highly surface active chitosan pattern that can easily fabricate highly periodic pattern via a variety of lithographic tools may pave the way for the production of periodic arrays of graphitic carbon materials for large area device integration.

Direct CVD Growth of High Quality Single Layer Graphene on Dielectric Substrates

Many applications of graphene especially for the fabrication of electrical devices require physical placement of graphene on dielectric substrates. Several strategies developed for the graphene device fabrication include 1) mechanical exfoliation of graphene on a dielectric substrate followed by fabrication, 2) graphene growth on metal catalysts by chemical vapor deposition (CVD) process followed by transferring it onto dielectric substrates and fabrication, 3) dispersion of reduced graphene oxides (RGOs) on dielectric substrates followed by fabrication, etc. To utilize the intrinsic high charge carrier mobility of graphene, however, a direct synthesis of graphene by CVD on dielectric substrates is highly demanding. In this presentation, I will introduce our recent experimental results demonstrating successful direct growth of graphene on various dielectric substrates, such as hexagonal boron nitride (h-BN), sapphire, quartz, and amorphous SiO2/Si, thus excluding complex transfer process to secure the quality of graphene by excluding impurities that are accompanied during the transfer process. The detailed growth mechanism involved in graphene nucleation and growth propagation on various substrates will be also discussed.

Chemically exfoliated large-area two-dimensional flakes of molybdenum disulfide for device applications

A solution-based exfoliation method for obtaining large-area two-dimensional flakes of molybdenum disulfide, followed by the fabrication of electrical devices is presented in this manuscript. The exfoliation method is based on the use of an aprotic solvent, namely, acetonitrile under mild sonication steps. In order to fabricate devices, a dielectrophoresis technique is used for transferring MoS2 flakes site-specifically on to the electrode pairs pre-written on the glass chips. The devices fabricated thus can be operated as chemical sensor in liquids while investigations under photo illumination indicate that such devices can also efficiently function as photodetectors.

Gold catalytic Growth of Germanium Nanowires by chemical vapour deposition method

Germanium nanowires (GeNWs) were synthesized using chemical vapor deposition (CVD) based on vapor–liquid–solid (VLS) mechanism with Au nanoparticles as catalyst and germanium tetrachloride (GeCl4) as a precursor of germanium. Au catalysts were deposited on silicon wafer as a thin film, firstly by sputtering technique and secondly by submerging the silicon substrates in Au colloidal solution, which resulted in Au nanoparticles with different sizes. GeNWs were synthesized at 400 °C, which is a low temperature for electrical device fabrication. Effect of different parameters such as Au nanoparticles size, carrier gas (Ar) flow and mixture of H2 with the carrier gas on GeNWs diameter and shape was studied by SEM images. The chemical composition of the nanostructure was also examined by energy dispersive X-ray spectroscopy (EDS).

Synthesis of linear ZnO structures by a thermal decomposition method and their characterisation

The semiconductor zinc oxide (ZnO) is a promising material for applications in optoelectronics, photochemistry and chemical sensing. Furthermore, ZnO structures can be grown with a large variety of sizes and shapes. Devices with ZnO rods or wires as their core elements can be used in solar cells, gas sensors or biosensors. In this article, an easy approach for the non-aqueous wet chemical synthesis of ZnO structures is presented that employs the solvent trioctylamine (TOA) and the surfactant hexamethylenetetramine (HMTA). Using the thermal decomposition method, rod-shaped structures were grown that are suitable for the fabrication of electrical devices. A detailed study was carried out to investigate the effects of various reaction parameters on the growth process. Both the concentration of the surfactant HMTA and the zinc precursor zincacetylacetonate (Zn(acac)2) were found to show strong effects on the resulting morphology. In addition to structural characterisation using XRD, SEM and TEM, also optical properties of rod-shaped ZnO structures were measured. Rod-shaped structures were obtained for the following conditions: reaction time 4 h, reaction temperature 70 °C, 1 mmol of Zn(acac)2, 4 mmol of HMTA and 25 mL of the solvent TOA. Photoluminescence and photoluminescence excitation spectroscopy of samples grown under these conditions provided information on levels of defect states that could be critical for chemical sensing applications. Two narrow peaks around 254 and 264 nm were found that are well above the band gap of ZnO.

INTEGRATION OF N- AND P-CONTACTS TO GaN-BASED LIGHT EMITTING DIODES

Low-resistance Ohmic contacts are essential for the fabrication of electrical devices. While low contact resistance has been achieved to p -type layers or n -type layers separately, contacts are likely to degrade when both types need to be integrated into a single fabrication process, in particular when prior mesa etching is required. We present a solution to the problem, resulting in low-resistance Ohmic contacts on n -type GaN layers without post-deposition thermal anneal, while maintaining the quality of typical p -type contacts. We implement an integrated process for both, n - and p -contacts, involving an oxygen pretreatment to fabricate light emitting diodes with lower series resistance in the contacts and lower voltage drop at high current when compared to separately optimized contacts.

Electrical properties of polysilicon nanowires for device applications

AbstractPolysilicon nanowires are synthesized using the well known and low cost technique commonly used in microelectronic industry: the sidewall spacer formation technique. Polysilicon layer is deposited by Low Pressure Chemical Vapour Deposition technique on SiO2 wall patterned by conventional UV lithography technique. Polysilicon film is then plasma etched. Accurate control of the etching rate leads to the formation of nanometric size sidewall spacers with a curvature radius as low as 100 nm used as polysilicon nanowires. These polysilicon nanowires are first integrated into the fabrication of electrical devices as resistors and electrical properties are studied in function of in situ phosphorus doping levels. I(T) measurements show that polysilicon nanowires dark conductivity is thermally activated according to the Seto's theory. In addition, field effect transistors made with such polysilicon nanowires used as channel region highlight promising field effect behaviour. (© 2011 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Fabrication of a Patterned Assembly of Semiconducting Organic Nanowires

The current interest in organic semiconductors arises from their synthetic facility, their solution processability, and their potential applications for the fabrication of electrical devices. Among semiconductors of this type, those based on organic nanowires are particularly interesting because of their outstanding self-assembly characteristics and anisotropic optical properties. Several research groups have reported various kinds of functional organic nanowires. While some of these wires exhibit electrical conductivity and mobility, others emit polarized photoluminescence (PL). In spite of these special characteristics, nanowires often form entangled coil-like structures. Therefore, much effort has been made to align the wires in a better way. Various methods, such as electric-field assembly, Langmuir–Blodgett process, and soft lithography have been applied for this purpose. However, it is still difficult to manipulate these randomly generated nanowires one-dimensionally and direct them to the desired position, for example, toward electrode channels for fabricating electrical or optical devices with polarized emission. Among these methods, soft lithography is considered one of the most promising patterning tools because of its simplicity and high efficiency. While inorganic nanowires are frequently patterned by means of soft lithography, only a few organic semiconducting nanowires have been aligned using this process due to their unsatisfactory fluidic selfassembling and structure-forming characteristics. Thus, the kernel of organic nanowire patterning via soft lithography is the development of nanowires with high self-assembly capability. It should be meaningful to align these developed semiconducting nanowires for measuring their electrical and optical properties by the MIMIC (micromolding in capillaries) method, which is one of the effective soft lithography processes. In the present study, we used 1-cyano-trans-1,2-bis-(30,50bis-trifluoromethyl-biphenyl)ethylene (CN-TFMBE) for nanowire patterning. CN-TFMBE was chosen because some of

Study on LCD Micro Stereolithography using Silver Particles Photosensitive Resin

In order to apply the LCD micro stereolithography to the fabrication of electric devices, we developed silver particles photosensitive resins, which were made by mixing micro-sized silver particles into an acrylic photosensitive resin. In this report, 3D microelectrode with high electrical conductivity was typically fabricated as a test piece. Electrical conductivity was then examined as a function of silver mixing rates by the use of four-terminal micro resistance patterns before and after heat treatment under the condition of 200±10°C for 1hour. After the heat treatment, micro resistance patterns with silver mixing rates of 50wt% showed a low electrical resistance less than 3×10-5Ω·cm. Our results indicated that the electrical conductivity was improved with an increase of conductive path equivalent to the mixing rate of silver particles. Consequently, 100 numbers of microelectrodes with the high electrical conductivity were able to fabricate in the high speed of 1.3second by using the LCD mask designed with four grayscale levels of 255, 170, 130 and 80. Also, the good fabrication accuracy could be accomplished within the error rate of 2.8% or 1.4% in height or width after the heat treatment.