Nanoparticle Deposition System Research Articles

Energy harvesting of flexible and translucent dye-sensitized solar cell fabricated by laser assisted nano particle deposition system

A cost-effective way of fabricating flexible and translucent dye-sensitized solar cell (DSSC) was demonstrated by forming TiO2 layer for photo-electrode via laser assisted nano particle deposition system (La-NPDS). In the La-NPDS, TiO2 particles are accelerated through a nozzle toward the substrate beyond the speed of sound while sintering is being induced concurrently with laser treatment. A uniform and 10.55μm-thick TiO2 film was deposited onto indium tin oxide-polyethylene terephthalate (ITO-PET) substrate via La-NPDS using 15nm-diameter TiO2 particles. In situ laser sintering of TiO2 was found to improve the efficiency of DSSC from 1.05% to 1.92%. Moreover, short circuit current and fill factor of DSSC are significantly increased by laser treatment due to close linking among adjacent particles. The necking among particles decreases the surface area of the laser treated TiO2 layer, resulting in decrease of the series resistance and higher short circuit current.The feasibility of the fabricated DSSC as an energy harvesting unit for wireless sensor network was evaluated. Three 1cm×1cm DSSC modules successfully demonstrated as a stable power supply when combined with maximum power management unit under dim light down to 130mW/cm2.

Photovoltaic Characteristics of a Dye-Sensitized Solar Cell (DSSC) Fabricated by a Nano-Particle Deposition System (NPDS)

Nano particle deposition system (NPDS) was evaluated for the potential photoelectrode fabrication method for dye-sensitized solar cell (DSSC). TiO2 powders as a photoelectrode for DSSC, were fabricated via NPDS and screen printing methods to compare its photovoltaic characteristics. The NPDS is a novel system for depositing ceramic and metallic powders on substrates at room temperature without using solvents by accelerating particles to supersonic velocity. The conventional method for preparing working electrodes uses TiO2 paste where poor adhesion to the substrate and numerous steps to properly disperse the powders are the main problems. To overcome these issues, TiO2 powders were directly sprayed onto ITO glass using the NPDS. The nano-sized TiO2 particles were densely deposited, no adhesion problems were noted and the solar-cell properties were improved. The photovoltaic performance of a cell having TiO2 layers first deposited by the NPDS method and then deposited by the paste method was compared to a cell fabricated only using the NPDS and only using the paste. A light conversion efficiency of 3.5% was obtained for the former cell, which indicates synergy effect of using these two methods. The screen-printing step right after NPDS deposition served to densify the TiO2 film, which decreased the series resistance. Therefore, NPDS was found to be a promising approach for improving DSSC properties and efficiencies. [doi:10.2320/matertrans.M2013220]

Effect of Scanning Speed on Copper Line Deposition Using Nanoparticle Deposition System (NPDS) for Direct Printing Technology

Cu nanoparticles (100 nm) were deposited on a silicon substrate using Nanoparticle Deposition System (NPDS) at 300 μm of stand-off distance (SoD). It was found that the lines deposited at a scanning speed below 5 μm/s showed ohmic contact; their resistivities were 1.68 × 10−4 Ω·cm at 5 μm/s, 3.91 × 10−5 Ω·cm at 2 μm/s, 1.70 × 10−5 Ω·cm at 1 μm/s, and 1.28 × 10−5 Ω·cm at 0.5 μm/s, respectively. However, samples fabricated at scanning speed of 8 and 10 μm/s showed schottky contact behavior. To study relationship between resistances of the deposited copper lines at various scanning speeds and density of the line, porosity of the deposited copper lines and SEM images of Cu lines were studied. As a result, average porosity of the copper lines was found to be 16% at 5 μm/s, 8% at 2 μm/s, 2% at 1 μm/s, and 6% at 0.5 μm/s. The porosity values are closely related to the resistance of the deposited copper lines. Therefore, the deposited copper line at 1 μm/s of scanning speed was shown to be the best one with the l...

Nano-particle deposition system (NPDS): Low energy solvent-free dry spray process for direct patterning of metals and ceramics at room temperature

With increasing concerns of environmental issues in manufacturing process, energy efficient and waste free manufacturing processes have been widely studied. In the field of nano/micro manufacturing, many research results of direct writing processes such as ink jet printing, gravure printing, and rapid prototyping processes have been reported to remove waste-producing conventional lift-off process for patterning. In addition, the use of toxic solvents such as acetone, toluene, xylene and so on has been decreased. At the same time, energy efficiency becomes one of environmental issues in manufacturing process. In this research, Nano particle deposition system (NPDS), a dry spray deposition process for fabrication of meta and ceramic direct patterning at room temperature, was introduced according to the environmental aspects. In previous studies, NPDS has shown the feasibility of the depositions of metals such as Sn and Ni, and the depositions of ceramics such as Al2O3, and TiO2 by spraying powders under low vacuum condition. The advantages of NPDS are 1) solvent free dry deposition process, 2) relatively low energy consumption with room temperature and low vacuum process condition, and 3) direct patterning process. The energy consumption in NPDS was briefly compared with similar processes including aerosol deposition and cold spray. The direct patterning results with 200μm width line pattern using micro-nozzle were fabricated without any post-processes. These results confirmed NPDS can become a solvent-free energy efficient direct patterning process for metals and ceramics.

Fabrication of Dye-Sensitized Solar Cell (DSSC) Using Different Particle Sizes of TiO2 Deposited via Nano-Particle Deposition System (NPDS)

TiO2 layers were fabricated using a nano-particle deposition system (NPDS) on transparent conductive oxide (TCO) glass for dye sensitized solar cells (DSSCs). Conventionally, TiO2 paste for working electrodes has been fabricated using paste type methods. The fabricated paste composed of a mixture of nano-sized TiO2 powders, binders and solutions is then painted on TCO glass. After drying, the TiO2 layer on TCO glass is sintered to make a path for electron transfer. TiO2 layers formed by this paste type method require numerous steps, which can be time consuming. In this study, TiO2 powders were sprayed directly on TCO glass using NPDS in order to simplify the fabrication steps. To improve porosity and produce scattering layers, commercial nanocrystalline TiO, powders with different sizes were alternately deposited. Moreover, powders with different sizes were mixed and deposited on the TCO glass. The results indicate that the DSSCs with a TiO2 layer composed of different particle sizes had better cell performance than the cells assembled with single-sized TiO2 particles. Therefore, this study shows that a dry TiO2 coating process is possible for DSSC fabrication to improve its cell efficiencies, and this method can easily be applied on flexible substrates since NPDS is a room-temperature deposition process.

Dry-Spray Deposition of TiO<SUB>2</SUB> for a Flexible Dye-Sensitized Solar Cell (DSSC) Using a Nanoparticle Deposition System (NPDS)

TiO2 powders were deposited on indium tin oxide (ITO) coated polyethylene terephthalate (PET) substrates for application to the photoelectrode of a dye-sensitized solar cell (DSSC). In the conventional DSSC manufacturing process, a semiconductor oxide such as TiO2 powder requires a sintering process at higher temperature than the glass transition temperature (T(g)) of polymers, and thus utilization of flexible polymer substrates in DSSC research has been constrained. To overcome this restriction related to sintering, we used a nanoparticle deposition system (NPDS) that could produce a thin coating layer through a dry-spray method under atmospheric pressure at room temperature. The powder was sprayed through a slit-type nozzle having a 0.4 x 10 mm2 rectangular outlet. In order to determine the deposited TiO2 thickness, five kinds of TiO2 layered specimens were prepared, where the specimens have single and double layer structures. Deposited powders on the ITO coated PET substrates were observed using FE-SEM and a scan profiler The thicker TiO2 photoelectrode with a DSSC having a double layer structure showed higher energy efficiency than the single layer case. The highest fabricated flexible DSSC displayed a short circuit current density J(sc) = 1.99 mA cm(-2), open circuit voltage V(oc) = 0.71 V, and energy efficiency eta = 0.94%. These results demonstrate the possibility of utilizing the dry-spray method to fabricate a TiO2 layer on flexible polymer substrates at room temperature under atmospheric pressure.

Laser-assisted nano particle deposition system and its application for dye sensitized solar cell fabrication

A novel fabrication process called laser-assisted nano particle deposition system (LaNPDS) was developed by integrating in situ laser irradiation process with the nano particle deposition system (NPDS). Energy is transferred from the 355nm diode laser beam to nano particles flying through the supersonic nozzle before deposition. The laser helps local sintering of nano powders to form films free from thermal damage on the substrate. Nanoparticles of TiO2 were deposited on glass and polymer substrates using LaNPDS for the dye sensitized solar cell (DSSC), and their surface morphologies, cross-sections, crystallographic changes and mechanical properties (hardness and elastic modulus) were characterized by using various analytical methods. Finally, the cell efficiency was approximately doubled compared with the one without laser assistance.

Effect of stand-off distance for cold gas spraying of fine ceramic particles (< 5 μm) under low vacuum and room temperature using nano-particle deposition system (NPDS)

The nano-particle deposition system (NPDS) is a novel fabrication method for metallic and ceramic coatings at room temperature that sprays dry nano-sized powder or micro-sized powder without binders or additives. NPDS has been used to coat metal, ceramic, and polymer substrates with various metal and ceramic powders such as TiO 2, Al 2O 3, Ni, and Sn. Deposition results have been reported, but the process parameters have not been evaluated in detail. The effect of the stand-off distance (SoD), which is an important process parameter and is easily controlled during fabrication, was evaluated in this study to better understand the process. Numerical analysis of the impact velocity of particles using the commercially available ANSYS CFX software package and experiments examining Al 2O 3 deposition on sapphire wafers (Al 2O 3) using NPDS was carried out. In NPDS, the impact velocity of particles is one of the most important deposition parameters because the sole energy source for bonding is the kinetic energy of the particles. The SoD range was set from 1 to 7 mm in 2-mm increments. Numerical analysis showed that the impact velocity of particles increased with increasing SoD. The impact velocity of particles correlated with the mechanical properties of the deposited layers. High impact velocity resulted in high mechanical properties for the deposited layer within the range of SoD tested. SoDs longer than 7 mm were not evaluated because the width and thickness of deposited layer were not suitable for patterning. Additionally, numerical analysis also helped explain the deposition geometry, especially the width of the deposited pattern under the 1-mm SoD condition. The numerical analysis used in this study can be applied to research on the effects of other process parameters.

Room temperature deposition of TiO2 using nano particle deposition system (NPDS): Application to dye-sensitized solar cell (DSSC)

To apply for the working electrode of dye-sensitized solar cell (DSSC), semiconducting TiO2 powder is deposited on indium tin oxide (ITO)-coated glass. In conventional DSSC fabrication, the high-temperature sintering process should be contained to make the necking of powders, and to assemble powders and substrate. In this research, dry TiO2 powder is deposited using a nano particle deposition system (NPDS) to make photoelectrode layer through spraying at room temperature conditions. The powder is sprayed through a slit-type nozzle having a 0.4×10mm2 rectangular outlet under atmospheric chamber pressure. Through XRD analysis and FE-SEM observation, the deposition of the semiconductor oxide powder is confirmed and the thickness (7.6μm) is measured. The fabricated DSSC has a short circuit current density JSC = 3.077mA/cm2, open circuit voltage VOC = 0.709V, and energy efficiency η = 1.24%.

Deposition mechanism of dry sprayed ceramic particles at room temperature using a nano-particle deposition system

The nano-particle deposition system (NPDS) is a new dry spray process used to deposit metal and ceramic particles at room temperature. Low temperature deposition techniques for metals and ceramics that involve particle spraying include the NPDS, cold spray, and aerosol deposition methods. These are widely used to minimize thermal damage to the substrate when fabricating metal or ceramic layers. To optimize the process conditions for the intended applications and improve the deposition quality one must understand the mechanism of particle deposition at room temperature. The bonding mechanism in metal particle deposition by the cold spray method has already been researched. Adiabatic shear instability near the particle/substrate interface due to plastic deformation was reported to be the bonding mechanism for metal particles below the melting temperature. However, the bonding mechanism of ceramic particles has not been fully determined. This study assessed the bonding of ceramic particles by NPDS using numerical analysis and experimental results. A bonding mechanism is suggested after considering the experimental results for shock compaction, which is a process similar to that of the NPDS. The suggested deposition mechanism for ceramics involves the fragmentation of submicron ceramic particles into nanoparticles and the successive impact of submicron particles, which provides sufficient bonding energy, with heat and high pressure, to nanoparticles fragmented by the shock wave.

Nanoscale hybrid manufacturing process by nano particle deposition system (NPDS) and focused ion beam (FIB)

A novel nanoscale hybrid manufacturing process was developed by integrating the nano particle deposition system and focused ion beam. Thin films of metals and ceramics were deposited by NPDS which sprays nanosized particles at supersonic speed. FIB was adopted as a nanostructuring, i.e., profile cutting, tool of these thin films. By repeating the deposition and the profile cutting, multi-layered-nano-structures with thickness of 500 nm were made of different materials at room temperature. The room temperature deposition of various materials without using binders and controlled-nanoscale profile cutting provides two unique features of this technology in manufacturing of multi-layer 3D nanostructures.

Deposition of TiO 2 layers for dye-sensitized solar cells using nano-particle deposition system

A novel method was applied for the deposition of TiO 2 powders using Nano-Particle Deposition System (NPDS) for a dye-sensitized solar cell (DSSC). NPDS is a method used to deposit ceramic and metallic powders on substrates at room temperature by accelerating particles to subsonic speeds. In this study, TiO 2 powders were directly sprayed on transparent conductive oxide (TCO) glass at room temperature. TiO 2 powder deposition resolved problems common to conventional pastes of TiO 2 powders, such as crack formation and poor adhesion on substrates. Using this dry-coating method, the maximum light-conversion efficiency of the fabricated cell was 2.86% with a photocurrent density of 7.72 mA cm −2. The cell efficiency improved when the sealing-sheet thickness was 25 μm because the amount of electrolyte in the cell was optimized to prevent unnecessary recombination of electrons and holes. Therefore, sealing-sheet thickness is crucial in maximizing photovoltaic efficiency. Overall, this study proved that dry-coating of TiO 2 is possible for DSSC, and this method can also be applied on flexible substrates.

Coating of Ni powders through micronozzle in a nano particle deposition system

Nano particle deposition system (NPDS) is a novel method to deposit ceramic and metal powders at room temperature. Nickel powders with a size of 3 μm in diameter were sprayed through the fabricated micro nozzle, varying stand-off distance (SoD), which is a gap between the end of the nozzle and the substrate. Injection time for Ni powders was set to 1 min and the flow rate of air-powder was kept to 10 l/min. When SoD was 300 μm, the average deposition thickness was measured to be 2.49 μm, whereas the average deposition thickness was 300 nm for SoD being 500 μm. Therefore, Ni powder deposition at a SoD of 300 μm was successful compared to a SoD of 500 μm with minimal deposition. Moreover, electrical resistance of the deposited film was measured to study its characteristics. Resistivity of the film deposited at a SOD of 300 μm was substantially lower than that of the film deposited at a SoD of 500 μm, confirming the successful deposition at a SoD of 300 μm. Finally, heated treatment of the deposited Ni powders to 150 °C improved the electrical conductivity significantly by lowering its resistivity to 4.4 × 10−7 Ωm.

Nickel Line Patterning Using Silicon Supersonic Micronozzle Integrated with a Nanoparticle Deposition System

In this study, 3-µm- and 20-nm nickel powders were deposited on Si substrates to pattern a metal line using a nanoparticle deposition system (NPDS) at room temperature. The stand-off distance (SoD), the distance between the substrate and the end of nozzle, was varied from 300 to 1000 µm to determine its effect on deposition properties. A Ni line was successfully formed on the Si substrate. When 3-µm Ni powders were used, the thickness of the deposited layer on the Si substrate was measured to be 5.4 µm, and its width was 176.4 µm at a SoD of 300 µm. In contrast, the deposited average thickness at a SoD of 500 µm was 1.1 µm, with a width of 190.6 µm. Moreover, the deposited thickness was measured to be 6.4 µm using 20-nm Ni powders at a SoD of 300 µm. Thus, it was found that the deposited thickness decreased as SoD increased, indicating an inversely proportional relationship. For deposition behavior, depending on the size of powders, it was found that 20-nm Ni powders resulted in a thicker deposition than did 3-µm Ni powders, as momentum transfer between carrier gas and powders is inversely proportional to the powder size. Thus, as the powder size decreased, its spray velocity increased; hence, it is more effective to use nano powders for Ni line patterning. Surface resistivity of the deposited Ni line was 1.83 ×10-7 Ω·m using 20-nm powders and 1.61 ×10-7 Ω·m using 3-µm powders. These values are close to the standard resistivity value for bulk Ni, which is 6.9 ×10-8 Ω·m, making NPDS a promising technique for metal line-fabrication equipment.

DEPOSITION OF Al2O3 POWDERS USING NANO-PARTICLE DEPOSITION SYSTEM

In this paper, alumina film was deposited using supersonic micronozzle in nano-particle deposition System (NPDS). Powder deposition at room temperature is important in the field of film deposition since high processing temperature can be a serious limitation for the deposition on flexible substrate. Previously, many studies have been reported on particle deposition, such as aerosol deposition method (ADM) or cold spray method. However, these deposition methods cannot be applied to various types of powders. Recently, NPDS using aluminum nozzle was designed to resolve these problems but it cannot deposit precise patterns less than 1 mm. In this study, alumina particles were deposited using Silicon-based micronozzle in NPDS. Three-dimensional silicon micronozzle was fabricated using semiconductor processing method, specifically deep reactive ion etching (DRIE) method. The silicon micronozzle fabricated by Bosch process is advantageous over the conventionally used nozzle, since the hardness of silicon is higher than that of aluminum and the lifetime can be increased. In this study, alumina nano-particles were accelerated to supersonic level at the neck of micronozzle and deposited on the substrate in a low vacuum condition. The film characteristics were evaluated using field-emission scanning electronic microscope (FE-SEM) and alpha step to measure its thickness of the deposited layer. The deposition result showed that alumina powders were successfully deposited using the fabricated micronozzle by means of NPDS.

COMPUTATIONAL FLUID DYNAMICS ANALYSIS OF FABRICATED MICRONOZZLE FOR SUPERSONIC PARTICLE DEPOSITION

A micronozzle was applied in nanoparticle deposition system (NPDS) for supersonic deposition. To determine whether suitable behavior of supersonic fluid can be produced or not, computational fluid dynamics (CFD) flow analysis was used. Ni particles were successfully deposited using the fabricated micronozzle in NPDS at room temperature. It was found that shorter micronozzle with larger side profile deposits wide and thick film compared to the deposition using long micronozzle with smaller side profile. These experimental results agree with the simulation results.

Fine-Sized Etching of Flexible Substrates Using Nano Particle Deposition System (NPDS)

Nano Particle Deposition System (NPDS) was used to etch flexible substrates, such as SU-8 and indium tin oxide (ITO) substrates using nickel powders using micronozzles. The stand-off distance (SoD) was changed in order to find out the optimal distance on etching behavior. The results showed that the etching capability was influenced by the SoD and the types of substrate. Especially, the etching depth of the substrate was the largest when the SoD was 500 mm. This phenomenon related to the variation of SoD can be explained by the flow behavior at which the powder-gas mixture injected from the nozzle where the particles are most highly accelerated at that point. The etching capability is also affected by the types of substrates. Especially, the hardness of the substrate mainly determines the etching depth. The result suggests that the NPDS gives an alternative way of micromachining suitable for fine-sized etching on flexible substrates. [doi:10.2320/matertrans.M2010221]

Continuous nanoparticle generation and assembly by atmospheric pressure arc discharge

This letter describes a nanoparticle generation and deposition system which combines aspects of high temperature plasmas with room temperature aerosols. The process works at atmospheric pressure and produces nanoparticles of Au or ZnO through cathode erosion inside a dc arc discharge plasma. The particles are positively charged by the arc and form a room temperature aerosol. From the aerosol, nanoparticles assemble on conductive sample surfaces through openings in patterned resist with resolution enhanced by electrodynamic nanolenses. We report that continued operation of the system results in funneled deposition of nanoparticles into well positioned three dimensional nanostructures.

TiO 2 coating on metal and polymer substrates by nano-particle deposition system (NPDS)

TiO 2 thin films have been widely used in corrosion protection, solar cells, self-cleaning surfaces, photocatalysis, capacitors, etc. In this research, TiO 2 thin films were deposited on metal substrates (stainless steel, Cu alloy, Al alloy) and polymer substrates (PET, PMMA) by nano-particle deposition system (NPDS) at room temperature and low vacuum condition. Submicron size TiO 2 powders were sprayed through the supersonic nozzle and deposited at high deposition rate without thermal damage on the substrates. Material properties such as hardness, modulus, chemical composition, adhesion and morphology were measured. The test results showed that the NPDS provides a good coating method of TiO 2 material for applications requiring large surface areas.

Design and development of a nanoparticle deposition system

This paper outlines the development process of a pneumatic projection device to fire particles into substrates at a range of high speeds. An alternate approach to the existing cold gas dynamic spray device is taken in an effort to seek a simple and cost-effective method for research and industrial purposes. Initially, a large-scale vacuum cannon is used to obtain data and compare velocity results to analytical methods and numerical simulations using computational fluid flow software. A system to precisely measure muzzle velocity is then developed for use on a smaller-scale pneumatic device operating at relatively low pressures (95 psi) and at subsonic velocities. The device is then redesigned and developed for use with a high-pressure (up to 1000 psi) air supply to accelerate particles to supersonic muzzle velocities. The objectives of this study are to develop a device capable of accelerating particles to supersonic speeds in a simple and cost-effective manner when compared to similar existing technologies and to develop a device suitable for the investigation of the effect of impacts on substrate materials.