Screen-printed Ag Research Articles

Specific contact resistance measurements of the screen-printed Ag thick film contacts in the silicon solar cells by three-point probe methodology and TLM method

The specific contact resistance of the screen-printed Ag contacts in the silicon solar cells has been investigated by applying two independent test methodologies such as three-point probe (TPP) and well-known transfer length model (TLM) test structure respectively. This paper presents some comparative results obtained with these two measurement techniques for the screen-printed Ag contacts formed on the porous silicon antireflection coating (ARC) in the crystalline silicon solar cells. The contact structure consists of thick-film Ag metal contacts patterned on the top of the etched porous silicon surface. Five different contact formation temperatures ranging from 725 to 825 °C for few minutes in air ambient followed by a short time annealing step at about 450 °C in nitrogen ambient was applied to the test samples in order to study the specific contact resistance of the screen-printed Ag metal contact structure. The specific contact resistance of the Ag metal contacts extracted based on the TPP as well as TLM test methodologies has been compared and verified. It shows that the extraction procedure based on the TPP method results in specific contact resistance, ρ c = 2.15 × 10−6 Ω-cm2 indicating that screen-printed Ag contacts has excellent ohmic properties whereas in the case of TLM method, the best value of the specific contact resistance was found to be about ρ c = 8.34 × 10−5 Ω-cm2. These results indicate that the ρ c value extracted for the screen-printed Ag contacts by TPP method is one order of magnitude lower than that of the corresponding value of the ρ c extracted by TLM method. The advantages and limitations of each of these techniques for quantitatively evaluating the specific contact resistance of the screen-printed Ag contacts are also discussed.

Transmission Electron Microscope Study of Screen-Printed Ag Contacts on Crystalline Si Solar Cells

Microstructural and chemical properties of screen-printed Ag contacts on an emitter surface in crystalline Si solar cells are investigated using a transmission electron microscope. The Pb-based glass layer, where many Ag precipitates are randomly distributed, is formed between a Ag thick film and textured Si. For both textured and nontextured Si surfaces, the Ag crystallites are epitaxially grown on Si with an abrupt interface along the {111} atomic plane. Based on high resolution electron microscopy images combined with fast Fourier transform patterns, the registry of Ag on Si driven by a geometrical matching condition leads to minimization of the effective lattice mismatch between Ag and Si, resulting in the formation of a Ag/Si epitaxial superlattice near the interface region.

A printing technology combining screen-printing with a wet-etching process for the gate electrodes of organic thin film transistors on a plastic substrate

We have developed a practical printing technology for the gate electrode of organic thin film transistors (OTFTs) by combining screen-printing with a wet-etching process using nano-silver (Ag) ink as a conducting material. An Ag film was deposited onto a PVP (polyvinylphenol)-coated PC (polycarbonate) plastic substrate by screen-printing with nano-Ag ink, where Ag content of 20 wt.% was mixed using a terpineol solvent. Subsequently, the film was cured at 200 °C for 60 min, and then finally wet-etched through patterned positive photo-resist masks. The screen-printed Ag electrode exhibited a minimum line width of ∼5 μm, a thickness of ∼65 nm, and a resistivity of ∼10 −6 Ω cm, producing good geometrical and electrical characteristics for a gate electrode. Additionally, it also provided good step coverage with the PVP dielectric layer, and consequently leakage current between the gate and source/drain electrodes was eliminated. Moreover, the electrical characteristic of the screen-printed Ag electrode was not significantly changed even after a bending test in which the Ag electrodes were bent with a bending radius of 6 mm and 2500 iterations of cyclic bending. OTFTs with the screen-printed Ag electrode produced a saturation mobility of 0.13 cm 2/Vs and a current on/off ratio of 1.79 × 10 6, being comparable to those of an OTFT with a thermally evaporated Al gate electrode.

Specific contact resistance and metallurgical process of the silver-based paste for making ohmic contact structure on the porous silicon/p-Si surface of the silicon solar cell

Porous silicon has been considered as a promising optoelectronic material for developing a variety of optoelectronic devices and sensors. In the present study, the electrical properties and metallurgical process of the screen-printed Ag metallization formed on the porous silicon surface of the silicon solar cell have been investigated. The contact structure consists of thick-film Ag metal contact patterned on the top of the porous silicon surface. The sintering process consists of a rapid firing step at 750–825 °C in air ambient. It results in the formation of a nearly perfect contact structure between the Ag metal and porous silicon/p-Si structure that forms the top metalization for the screen-printed silicon solar cells. The SEM picture shows that Ag metal firmly coalesces with the silicon surface with a relatively smooth interfacial morphology. This implies that high temperature fire-through step has not introduced any signs of adverse effect of junction puncture or excessive Ag indiffusion, etc. The three-point probe (TPP) method was applied to estimate the specific contact resistance, ρc (Ω-cm2) of the contact structure. The TPP measurement shows that contact structure has excellent ohmic properties with ρc = 1.2 × 10−6 Ω-cm2 when the metal contact sintered at 825 °C. This value of the specific contact resistance is almost three orders of magnitude lower than the corresponding value of the ρc = 7.35 × 10−3 Ω-cm2 obtained for the contact structure sintered at 750 °C. This improvement in the specific contact resistance indicates that with increase in the sintering temperature, the barrier properties of the contact structure at the interface of the Ag metal and porous silicon structure improved which in turn results a lower specific contact resistance of the contact structure.

Role of PbO-based glass frit in Ag thick-film contact formation for crystalline Si solar cells

The reactions between Ag pastes containing two types of PbO-based glass frits and an n-type (100) Si wafer during firing in air at 800 °C were investigated in order to understand the mechanism for the formation of inverted pyramidal Ag crystallites at the Si interface as well as the effect of the PbO content of the glass frit on Ag crystallite formation. Inverted pyramidal Ag crystallites were formed by the precipitation of Ag atoms dissolved in fluidized glass during the subsequent cooling process after firing. PbO in the glass frit did not participate directly in the reaction with the Si wafer. However, its content had a strong influence on the reaction rate at the glass/Si interface and, thus, on the size and distribution of the Ag crystallites. The effect of the PbO content in the glass could be understood from the higher Ag solubility and lower viscosity of the glass at the firing temperature with increasing PbO content. Based on the experimental results, a model was proposed for the formation of Ag crystallites at the glass/Si interface during the firing process of screen-printed thick-film Ag metallization.

The ohmic properties and current–voltage characteristics of the screen-printed silicon solar cells with porous silicon surface

The ohmic properties and current–voltage characteristics of the silicon solar cells with fire-through screen-printed Ag metal contacts on the etched porous silicon surface have been investigated. The porous silicon layer of approximately 85 nm thickness was electrochemically etched on the n + -Si surface prior to the deposition of the front Ag grid contacts. Then, Ag contacts are formed by suitably applying a fire-through step at a temperature typically between 700–825 ∘C for 2 min in air ambient followed by annealing step at a lower temperature of 450 ∘C for 5 min in nitrogen ambient. The specific contact resistance ( ρ c ) is one of the important parameters in studying the interfacial properties of the contact metalization system. The value of ρ c of the contact structure is determined using the extrapolation technique based on the three-point probe (TPP) method. It shows that the best value of ρ c is about 8.54×10 −4 Ω cm 2 is obtained for the contact structure which is an order less than the typical value of the ρ c of 3 mΩ cm 2 reported for the sintered Ag metal contacts. The sintering of the Ag contacts on the etched porous silicon at temperature above 800 ∘C in air ambient has resulted in considerable reduction in the value of ρ c of the contact structure. This improvement in ρ c is attributed to the improvement in the barrier properties of the contact structure upon sintering at high temperature. The value of ρ c follows a linear relationship with the surface doping level, N S > 10 19 atoms/cm 3 and improves with an increase in the sintering temperature. The ohmic losses of the fire through Ag contacts are assessed using the power loss algorithm and have shown that relative ohmic losses of the contact structure have improved with higher firing temperatures. These results suggest that fire-through Ag metal contacts on the porous silicon have good ohmic quality and can be expected to provide low ohmic losses.

Detection of Salmonella typhimurium using an electrochemical immunosensor

An electrochemical immunosensor based on screen-printed gold working electrode with onboard carbon counter and silver–silver chloride pseudo-reference electrode for Salmonella typhimurium detection is described in this paper. Monoclonal anti-S. typhimurium antibody was immobilized using physical and covalent immobilization via amine coupling of carboxymethyldextran on the surface of the gold working electrode. A direct sandwich enzyme-linked immunosorbent assays (ELISA) format was then developed and optimized using a polyclonal anti-Salmonella antibodies conjugated to horseradish peroxidase (HRP) as the enzyme label. 3,3′,5,5′-Tetramethylbenzidine dihydrochloride (TMB)/H2O2 was used as the enzyme mediator/substrate system. Electrochemical detection was conducted using chronoamperometry at −200mV vs. onboard screen-printed Ag–AgCl pseudo-reference electrode. The applied potential was selected through the study of the electrochemical behaviour of bare gold electrode with TMB–H2O2–IgG–HRP system. S. typhimurium detection of 5×103cellsml−1 and ∼20cellsml−1 was achieved respectively for physical and covalent antibody immobilization. The developed sensor was then compared to a commercial ELISA kit and a chromogenic agar plating method for meat samples analysis. The sensor format shows a promising technology for simple and sensitive detection system for Salmonella contamination. Rapid detection of Salmonella is a key to the prevention and identification of problems related to health and safety.

Choline oxidase as a selective recognition element for determination of paraoxon

A simple mono-enzyme biosensor has been developed for specific determination of paraoxon (POX). In this biosensor, choline oxidase (ChOx) was introduced and used as a new recognition element. Besides, by application of Prussian blue (PB), as an electron mediator, the necessity of applying oxygen or hydrogen peroxide sensor, as the internal transducer, was abated. The method was based on PB chemically modified screen-printed electrode coupled with ChOx for detection of POX as inhibitor. The concentration of H2O2 produced by ChOx was electrochemically determined by the PB modified electrode at −50mV versus the internal screen-printed Ag pseudo-reference electrode. The decrease in current caused by the addition of inhibitor was used for evaluation of POX concentration. The experimental parameters such as the quantity of enzyme, substrate concentration and incubation time were optimized for ChOx inhibition. At the incubation time of 5min, the biosensor response was linear from 0.1 to 1μM of POX with a detection limit of 0.1μM.

SEM and specific contact resistance analysis of screen-printed Ag contacts formed by fire-through process on the shallow emitters of silicon solar cell

The SEM and specific contact resistance measurements of the Ag metal contact formed by applying a fire-through process on the shallow emitter region of the silicon solar cell have been investigated. The metal contact consists of screen-printed Ag paste patterned on the silicon nitride (Si3N4) deposited over the n+-Si emitter region of the solar cell. The sintering step consists of a rapid firing step at 800 °C or above in air ambient. This is followed by an annealing step at 450 °C in nitrogen ambient. It enables to drive the Ag metal paste onto the Si3N4 layer and facilitates the formation of an Ag metal/p-Si contact structure. It serves as the top metallization for the screen-printed silicon solar cell. The SEM measurement shows that sintering of the Ag metal paste at 800 °C or above causes the Ag metal to firmly coalesce with the underlying n+-Si surface. A thin layer of conductive glassy layer is also presents at the interface of the Ag metal and n+-Si surface. The electrical quality of the contact structure was characterized by measuring the specific contact resistance, ρc (in Ω-cm2) using the iteration technique based on the power loss calculation for the solar cell. It shows that best value of ρc = 2.53 × 10−5 Ω-cm2 is estimated for the Ag metal contact sintered at temperature above 800 °C. This value of ρc is two orders of magnitude lower than the typical value of ρc = 3 × 10−3 Ω-cm2 reported previously for the Ag contacts of the solar cell. Such low value of ρc for the Ag metal contacts indicates that fire-through process results in excellent ohmic properties. The plot of the ρc versus impurity doping level (Ns) shows that measured value of the ρc follows a linear relationship with the Ns as predicted by the theory for the heavily doped semiconductor surface. Hence, carrier injection across the Schottky barrier height is quite appropriate to explain the observed ohmic properties of the Ag metal contacts on the n+-Si surface of the silicon solar cell.

Miniaturized low temperature co-fired ceramics (LTCC) biosensor for amperometric gas sensing

The miniaturization of an amperometric biosensor device by multilayer technique using low temperature co-fired ceramics (LTCC) tapes as construction material was investigated. An internal Ag/AgCl reference electrode of the miniaturized device is prepared by partial chlorination of a screen-printed Ag layer. Different chlorination techniques were evaluated to gain stable electrodes, which obey the Nernst equation. Novel diffusion membranes, compatible with the LTCC process, were developed. Different strategies were evaluated to achieve the necessary degree of hydrophobicity of the ceramic membranes in order to keep buffer/enzyme solution inside the micro-device, and at the same time to conserve the necessary gas diffusion into the device. A well-known formaldehyde dehydrogenase-based system was inserted into the LTCC setup to demonstrate the advantages of the LTCC setup compared to the conventional macro-device. The LTCC micro-device shows a linear response curve in the range of 500 ppb to 10 ppm, a sensitivity of 0.5 μA/ppm (0.5–10 ppm), t90-response times of 6–14 min and a detection limit of 76 ppb (S/N = 3). With this characteristic, the miniaturized enzyme gas sensor achieves the performance of the well-established macro-device while requiring just half of the enzyme and one tenth of the buffer solution.

Demonstration of the Formation of Porous Silicon Films with Superior Properties Formed on Polished (100) Si with Screen-Printed Back Contacts

Porous silicon (PS) layers were formed by anodization on polished substrates of (1 0 0) Si at different current densities for a fixed anodization time of 30 mins. using different screenprinted/ evaporated back contacts (Ag, Al) respectively. The PS films has been characterized by high resolution X-ray diffraction (HRXRD), photoluminescence (PL), Scanning Electron Microscopy (SEM) and Fourier Transform Infrared (FTIR) techniques respectively. Porosity and thickness of PS layers were estimated by gravimetric analysis. The properties of PS formed using screen-printed Ag & Al as the back contacts (SP-(Ag/Al)) was found to be superior as compared to the corresponding films with evaporated back contacts (EV-(Ag/Al)). The PS formed with screenprinted Ag & Al-back contacts shows better crystalline perfection, higher stability, higher PL efficiency and negligible PL decay compared to that formed with evaporated Ag & Al- as the back contact for the same current density and time of anodization.

Power loss calculation as a reliable methodology to assess the ohmic losses of the planar ohmic contacts formed on the photovoltaic devices

The front grid contact is particularly important and requires a low contact resistance which represents the resistance associated with the barrier at the interface of the metal and semiconductor contact structure. Often applied metal contacts are fired at a higher temperature (typically above 700 °C) in air ambient, which produces ohmic contact on both surface of the photovoltaic device. The specific contact resistance is one of the important device parameter on studying the interfacial properties of the metalization system. Therefore, a reliable methodology to assess the ohmic losses of the applied metal contact structure is required. It shows that it is rather simple and reliable to assess the electrical quality of the applied metal contacts by quantifying the total ohmic losses of the solar cell associated with the various resistive components of the solar cell normalized to unit cell area. It has been recently demonstrated that with a new experimental procedure, namely iteration method based on the calculation of power loss (ICPL) associated with the contact resistance of the front Ag thick-film metal contacts, a much reliable value of the specific contact resistance of the order of ≅10−5 Ω cm2 can be extracted for the planar ohmic contacts. In this work, the specific contact resistance of the planar ohmic contacts formed on the heavily doped n+ region of the solar cells were studied on large number of finished cells by two independent methods: (i) standard three-point probe (TPP) and (ii) iteration technique based on the calculation of the power loss (ICPL) associated with the contact resistance of the front Ag contacts of the solar cell normalized to unit cell area. It shows that the value of specific contact resistance measured by both methods are desirably much lower than the expected value of 10−3 Ω cm2 for the screen-printed Ag metal contacts of the photovoltaic cells used for the A.M. 1.5 applications. Using the iteration, each resistive components of the solar cell normalized to unit cell area were directly evaluated. It is shown that by combining the measurements of specific contact resistance of the planar ohmic contacts and ohmic losses of the cell, it gives a direct and non-destructive diagnostic tool to qualitatively check the electrical quality of the applied Ag metal contacts.

Application of power loss calculation to estimate the specific contact resistance of the screen-printed silver ohmic contacts of the large area silicon solar cells

The establishment of a suitable contact formation methodology is a critical part of the technological development of any metal-to-semiconductor contact structure. Many test structures and methodologies have been proposed to estimate the specific contact resistance (ρc) of the planar ohmic contacts formed on the heavily doped semiconductor surface. These test structures are usually processed on the same wafer to monitor a particular process. In this study, new experimental procedure has been evolved to assess the value of ρc of the screen-printed front silver (Ag) thick-film metal contact to the silicon surface. The essential feature of this methodology is that it is an iteration technique based on the calculation of power loss associated with various resistive components of the solar cell normalized to the unit cell area. Therefore, this method avoids the complexity of making the design of any lay out of a standard contact resistance test structure like transmission line model (TLM) or Kelvin resistor, etc. It was shown that value of specific contact resistance of the order of 1.0 × 10−5 Ω−cm2 is measured for the Ag metal contacts formed on the n+ silicon surface. This value is much lower than the ρc data previously reported for the screen-printed Ag contacts. The sintering process of the front metal contact structure at different furnace setting is carried out to understand the possible wet interaction and metal contact formation as a function of the firing. Therefore, the study is further extended to study the peak firing temperature dependence of the ρc of screen-printed Ag metal contacts. It will help to assess the specific contact resistance of the ohmic contacts as a function of firing temperature of sintering process.

Influence of firing temperature on interface adhesion between screen-printed Ag film and BaTiO 3 substrate

Interfaces between porous metal and ceramic are commonly used in many advanced engineering components. The adhesion strength between a porous silver coating and pure barium titanate has been determined here using a blister test. The porous Ag layer was made by screen printing and sintering on a flat dense barium titanate surface. Firing temperature influences the porosity of the silver film and Ag/BaTiO 3 interface strength. A simple graphic procedure was used to subtract the effect of the generalized plastic yielding in the Ag membrane from the total strain energy produced by the pressure application. The average value of the critical interface crack propagation energy G ci at the porous Ag/BaTiO 3 interface ranges between 4.5 and 6.6 J/m 2 while the porosity decreases from 11% to 7%. The observed trend of interfacial fracture energy can offer insights into the interfacial fracture mechanisms between porous metal films and ceramic substrates.

Formation of a low reflective surface on crystalline silicon solar cells by chemical treatment using Ag electrodes as the catalyst

Abstract A new method was developed for making a porous silicon layer as an anti-reflective coating on the top of crystalline silicon solar cells. The porous silicon layer was formed in a mixed solution of H 2 O 2 and HF by using screen-printed Ag front electrodes as the catalyst. With the help of the catalytic effect, porous silicon layers were formed by treatment in a solution chemically milder than conventional solutions. The multi-crystalline silicon solar cell covered with the porous silicon layer showed a surface reflectance below 15% in a wavelength region of 400–800 nm.

Understanding the Formation and Temperature Dependence of Thick-Film Ag Contacts on High-Sheet-Resistance Si Emitters for Solar Cells

Physical and electrical properties of screen-printed Ag thick-film contacts were studied and correlated to understand and achieve good-quality ohmic contacts to high-sheet-resistance emitters for solar cells. Analytical microscopy and surface analysis techniques were used to study the Ag–Si contact interface of three different screen-printed Ag pastes (A, B, and PV168) subjected to high and conventional temperature firing conditions. At firing, all three pastes failed on a emitter because of incomplete etching of the silicon nitride film (PV168), an irregular small distribution of regrown Ag crystallites (paste A), or an excessive diffusion of Ag into the p-n junction (paste B). At a firing temperature of , paste A gave a lower open-circuit voltage because of the diffusion of Al from the glass frit into the emitter region. Paste B failed because of the formation of very large Ag crystallites that shunted the p-n junction. Of the three pastes, the PV168 paste from DuPont gave the best contact quality on a emitter with a solar cell fill factor of 0.782 only after annealing in a hydrogen atmosphere.

Minority-carrier lifetime enhancement in edge-defined film-fed grown Si through rapid thermal processing-assisted reduction of hydrogen-defect dissociation

This paper demonstrates that a very short, 1-s, simultaneous firing of screen-printed Al at the back and SiNx antireflection (AR) coating at the front can significantly enhance the minority-carrier lifetime in edge-defined film-fed grown (EFG) ribbon Si via SiNx-induced hydrogen passivation of defects. It was found that 1-s firing in a rapid thermal processing system at an optimum temperature improved the average minority-carrier lifetime from 3to>80μs, resulting in ∼16% efficient 4-cm2 screen-printed EFG Si cells. It is proposed that rapid thermal firing enhances the retention of hydrogen at defect sites by minimizing the hydrogen-defect dissociation. A combination of simulations and experiments reveals that the dissociation of hydrogen is extremely rapid at conventional firing temperatures of ∼700°C. An activation energy of 2.4–2.6eV was determined for the hydrogen-defect dissociation in EFG Si. This activation energy, in conjunction with the room-temperature photoluminescence data, suggests that the impurity-decorated dislocations are the dominant hydrogenation and dehydrogenation sites in the EFG Si. Based on the above understanding, a manufacturable process, involving rapid co-firing of SiNx AR coating, screen-printed Al-doped back surface field (Al-BSF), and screen-printed Ag front grid, was developed in a conventional belt furnace to minimize the degree of dehydrogenation while producing good Al-BSF and ohmic contacts. This process produced 4-cm2 screen-printed EFG Si cells with an efficiency of 15.9%.

Development of Screen-Printed Silicon Solar Cells With High Fill Factors on 100<tex>$Omega$</tex>/sq Emitters

High-quality DuPont screen-printed Ag contacts were achieved on high sheet-resistance emitters (100 /spl Omega//sq) by rapid alloying of PV168 Ag paste. Excellent specific contact resistance (/spl sim/1 m/spl Omega/-cm/sup 2/) in conjunction with high fill factor (FF) (0.775) were obtained on 100 /spl Omega//sq emitters by a 900/spl deg/C spike firing of the PV168 paste in a belt furnace. The combination of the alloying characteristics of the PV168 Ag paste and optimized single-step rapid low-thermal budget firing resulted in a cost-effective manufacturable process for high-efficiency Si solar cells. In addition, the co-fired 100 /spl Omega//sq cell showed a noticeable improvement of /spl sim/0.5% in absolute efficiency over a conventional co-fired 45 /spl Omega//sq emitter cell. Lighter doping in the 100 /spl Omega//sq emitter cell resulted in better blue-response compared to the conventional cell, contributing to /spl sim/1.3 mA/cm/sup 2/ improvement in short-circuit current. Improved surface passivation on 100 /spl Omega//sq emitter cell resulted in additional 0.6 mA/cm/sup 2/ increase in J/sub sc/, 15-mV higher V/sub oc/, and a 0.6% increase in absolute cell efficiency. Front grid design optimization resulted in a FF of 0.780, and a further improvement in cell efficiency to reach 17.4%.

Rapid thermal technologies for high-efficiency silicon solar cells

This paper shows that rapidly formed emitters in less than 6 min in the hot zone of a conveyor belt furnace or in 3 min in an rapid thermal processing (RTP) system, in conjunction with a screen-printed (SP) RTP Al-BSF and passivating oxide formed simultaneously in 2 min can produce very simple high-efficiency n + -p-p + cells with no surface texturing, point contacts, or selective emitter. It is shown for the first time that an 80Ω/□ emitter and SP Al-back surface field (BSF) formed in a high throughput belt furnace produced 19% FZ cells and greater than 17% CZ cells with photolithography (PL) contacts. Using PL contacts, we also achieved 19% efficient cells on FZ, > 18% on MCZ, and ∼ 17% boron-doped CZ by emitter and SP Al-BSF formation in < 10 min in a single wafer RTP system. Finally, manufacturable cells with 45 Ω/□ emitter and SP Al-BSF and Ag contacts formed in the conveyor belt furnace gave 17% efficient cells on FZ silicon. Compared to the PL cells, the SP cell gave ∼2% lower efficiency along with a decrease in J sc and fill factor. This loss in performance is attributed to a combination of the poor blue response, higher series resistance and higher contact shading in the SP devices.

GROWTH OF CARBON NANOTUBES ON THE GLASS SUBSTRATE FOR FLAT PANEL DISPLAY APPLICATIONS

We have grown carbon nanotubes (CNTs) on the soda-lime glass substrates using chemical vapor deposition of C 2 H 2 gas at 550°C. We used electro-plated Ni thin film as a catalyst and screen-printed Ag thick film as a cathode. The turn-on field was about 2.55 V /μ m with an emission current density of 10 μ A / cm 2, and electric field was about 4.0 V /μ m with an emission current density of 3 mA/cm2. Fowler-Nordheim plot shows good linear fit, indicating that the emission current of CNTs follows the Fowler-Nordheim behavior. This process is suitable for mass production of CNT field emission display(CNT-FED), because of its merits; low temperature (≤ 550° C ) process, easiness of CNT patterning, non-vacuum process, large area uniformity.