Direct patterned etching of silicon dioxide and silicon nitride dielectric layers by inkjet printing

An inkjet method for the direct patterned etching of silicon dioxide and silicon nitride dielectric is described. The method involves fewer steps, lower chemical usage and generates less hazardous chemical waste than existing resist-based patterning methods (e.g., photolithography), which employ immersion etching. Holes of diameter 40–50 μm and grooves 50–60 μm wide were etched in 300 nm silicon dioxide layers. Grooves were also etched in 75 nm silicon nitride layers formed on textured silicon surfaces. The resulting patterned dielectric layers were used to facilitate masked etching, local diffusions and metal contacting of underlying silicon for solar cell applications.     

纳米导电油墨及其在印刷天线中的应用

文章以印刷RFID天线作为印刷电子技术的应用实例,介绍了利用纳米导电油墨印刷RFID天线的优势、进展与发展展望。     

Controlled Zr doping for inkjet-printed ZTO TFTs

This study examined the effects of controlled Zr doping on the electrical properties of inkjet-printed zinc-tin oxide (ZTO) thin-film transistors (TFTs). In contrast to previous reports, below a certain doping concentration, improved electrical properties were obtained due to the effectively suppressed oxygen vacancies, reduced trapped electrons, and controlled carrier concentrations. The 0.0025 M Zr-doped inkjet-printed ZTO TFTs showed higher mobility, higher on-to-off current ratio, lower threshold voltage, and lower subthreshold slope of 6.43 cm²/V s, 3.72×10⁸, 3.35 V, and 0.53 V/dec, respectively, compared to the un-doped TFTs. The bias stability of the Zr-doped inkjet-printed ZTO TFT was also improved.     

Inkjet Printing of Aqueous Photoluminescent CdSe/CdS Nanorods on Solid Substrates

In order to deposit colloidal nanocrystals on different substrates, a large variety of methodologies have been developed, such as dipcoating, spin coating, or spray coating. The deposition of CdSe/CdS core‐shell nanorods (NRs) with a conventional office printer onto conducting tin‐doped indium oxide glass surfaces is presented. This involves the preparation of water‐based inks containing the NRs. To improve the connection between the CdSe/CdS NRs and the underlying substrates, the glass surfaces were modified by means of silanes. Homogeneous films were obtained by consecutively printing several layers of CdSe/CdS NRs.     

Development,characterization, and processing of thin and thick inkjet-printed dielectric films

This work introduces the material and electrical characterization of two dielectric inks for use with inkjet printing fabrication and the realization of fully-printed multilayer electronic structures. The dielectric inks are categorized by the thickness of their per-layer profiles, where SU-8 polymer and poly(4-vinylphenol)-based solutions are utilized to realize thick (>4 μm) and thin (< 400 nm) inkjet-printed dielectric films, respectively. The material formulations for each ink are outlined in detail in order to achieve the desired viscosity and surface tension for optimal printing with a Dimatix inkjet printing system. Once printability and processing techniques are tuned and established, various material and electrical characterizations are performed, including printed profile measurement, multilayer profile tendencies, thermal reflow processing, UV-ozone surface energy modification, relative permittivity extraction, leakage current density, and dielectric breakdown voltage. Finally, the demonstration of fully-printed post-processed on-chip capacitors utilizing both thin and thick dielectric inks in conjunction with a silver nanoparticle-based metallic ink is presented and compared with other inkjet-printed capacitors.     

Microbes based printing for fabrication of microlenses for organic light emitting diodes

We have demonstrated a novel method to fabricate microlenses for organic light emitting diodes (OLEDs) using templates of patterned microbes. Saccharomyces cerevisiae (Baker’s yeast), generally used in a microbiology laboratory, is allowed or restricted to grow in selected areas on a polyvinylidene fluoride (PVDF) membrane, which acts as a substrate. The process comprises of two autonomous approaches, namely, microbial and antimicrobial approaches, which employ inkjet printing for dispensing a suitable ink. The ink is a culture of microbes in the case of microbial approach and an antimicrobial agent in the antimicrobial approach. Once a three dimensional pattern evolves as a consequence of microbial growth, the substrate serves as a template for casting polydimethyl siloxane (PDMS) microlenses. Among the two approaches, antimicrobial approach presents a pattern with low packing density of microlenses. But, microbial approach results into a densely packed array of microlenses with a significant randomness in the distribution of their diameter and height, as required for efficient light out-coupling. The microlenses obtained from both the approaches are attached to the air side of the glass in all three red, green and blue OLEDs. The luminance was measured with and without these microlenses. A maximum enhancement of 1.24X was attained.     

Thermal inkjet printing of polyaniline on paper

The development of organic devices requires the fabrication of thin films, and inkjet printing has been shown to be a suitable method to reach this goal. This work describes the printing process and characterisation of polyaniline (PANI) printed on bond and photographic papers using a desktop inkjet thermal printer. To enable printing, a solution composed by PANI, n-methyl-2-pyrrolidone, ethylene glycol, alcohol and water must be prepared. PANI is printed on bond and photographic paper and then doping of PANI is performed by hydrochloric acid vapour exposure. Micro-Raman spectroscopy showed that PANI printed on paper keeps its basic characteristics. The results from electrical measurements showed that the surface resistivity of the printed PANI samples decreases by increasing the printing number, i.e. the number of layers that were deposited, and depends slightly on the paper type. A stretched semicircle followed by a linear upward tail, attributed to Warburg impedance combined with other intrinsic mechanisms of PANI on porous media, are always present on the Cole-Cole plots obtained for doped-PANI on bond paper. It was shown that these parameters significantly change with the relative humidity, opening the possibility to apply PANI/paper-based devices as humidity sensors.     

IR-sintering of ink-jet printed metal-nanoparticles on paper

Sintering of printed metal nanoparticles can be made not only by conventional heating, but also by, e.g., electrical, microwave, plasma, laser and flash lamp annealing. We demonstrate sintering by using low-cost incandescent lamps as an effective way of obtaining highly conductive contacts of two types of ink-jet printed metal-nanoparticle inks on paper; both alkanethiol protected gold nanoparticles and a commercially available silver nanoparticle ink. This low-cost roll-to-roll compatible sintering process is especially suitable on paper substrates because of the high diffuse reflectance, relatively high thermal stability and low thermal conductivity of paper. A volume resistivity of around 10 μΩ cm was achieved of the inkjetted silver nanoparticles within 15 s of exposure to an IR lamp, which corresponds to a conductivity of 10-20% of that of bulk silver. Too long exposure time and too high intensity, however, lead to darkening of the paper fibers. Both the crack formation and the coffee ring effect of the inkjet printed gold nanoparticles were, furthermore, found to be reduced on paper as compared to glass or plastic substrates.     

Potentials and challenges in jetting microdroplets onto nonwoven fabrics

Nonwoven fabrics are very diverse in their structural properties. This paper discusses potential opportunities and challenges involved in jetting and depositing microdroplets on such materials. This study reports on the interaction of controlled droplets with the nonwoven substrates. Droplets used had velocities of about 1.8 m/s and diameters of about 90 μm and were produced by using a drop-on-demand (DOD) inkjet printhead. Nonwovens used consisted of two groups of high and low solid volume fraction (SVF) substrates. The results indicate that in the case of low-SVF nonwovens, the local spacing and orientation of the fibres plays a significant role in determining the outcomes of the jetting process. Drops were seen to penetrate deep into a low-SVF nonwoven and deposit on a single fibre or bundle of fibres. Low-SVF nonwovens, therefore, can hold the fluid within their structures—a case of interest in printing electric circuits. The case of jetting on high-SVF nonwovens was found to be primarily dependent on the fibres' surface properties. The drops were found to stay above the surface in the case of hydrophobic fibres and below the surface in the case hydrophilic ones.     

喷墨打印材料的分析技术及质量评价方法

综述了国内外喷墨打印材料的分析技术,包括涂层成分的分析技术和涂层表面结构的表征。其中涂层成分的分析技术主要是利用红外反射-吸收光谱和X射线光电子能谱对其进行分析。涂层表面结构的表征主要是利用扫描电子显微镜和原子力显微镜。另外,综合提出了喷墨打印材料最终质量评价方法,其成品质量评价方法主要有包括：白度、光泽度、色密度、色域、清晰度、图像抗水性和耐光性等。这也是为材料最终的应用提供选择依据,只有综合质量优秀的打印材料才能被更多的消费者接受并应用。对喷墨打印材料的分析技术及质量评价方法优缺点进行了归纳总结。