Steven Molesa

Progress Toward Development of All-Printed RFID Tags: Materials, Processes, and Devices

Printed electronics provides a promising potential pathway toward the realization of ultralow-cost RFID tags for item-level tracking of consumer goods. Here, we report on our progress in developing materials, processes, and devices for the realization of ultralow-cost printed RFID tags. Using printed nanoparticle patterns that are subsequently sintered at plastic-compatible temperatures, low-resistance interconnects and passive components have been realized. Simultaneously, printed transistors with mobilities >10/sup -1/ cm/sup 2//V-s have been realized using novel pentacene and oligothiophene precursors for pMOS and ZnO nanoparticles for nMOS. AC performance of these devices is adequate for 135-kHz RFID, though significant work remains to be done to achieve 13.56-MHz operation.

Plastic-Compatible Low Resistance Printable Gold Nanoparticle Conductors for Flexible Electronics

Low resistance conductors are crucial for the development of ultra-low-cost electronic systems such as radio frequency identification tags. Low resistance conductors are required to enable the fabrication of high- Q inductors, capacitors, tuned circuits, and interconnects. The fabrication of these circuits by printing will enable a dramatic reduction in cost, through the elimination of lithography, vacuum processing, and the need for high-cost substrates. Solutions of organic-encapsulated gold nanoparticles many be printed and subsequently annealed to form low resistance conductor patterns. We describe a process to form the same, and discuss the optimization of the process to demonstrate plastic-compatible gold conductors for the first time. By optimizing both the size of the nanoparticle and the length of the alkanethiol encapsulant, it is possible to produce particles that anneal at low temperatures (,150°C) to form continuous gold films having low resistivity. We demonstrate the printing of these materials using

Printed organic transistors for ultra-low-cost RFID applications

Printed electronics provides a potential pathway toward the realization of ultra-low-cost radio frequency identification (RFID) tags for item-level tracking of consumer goods. Here, we report on our progress in developing materials and processes for the realization of printed transistors for low-cost RFID applications. Using inkjet printing of novel conductors, dielectrics, and organic semiconductors, we have realized printed transistors with mobilities >10/sup -1/cm/sup 2//V-s. AC performance of these devices is adequate for 135-kHz RFID, and, with further optimization, 13.56-MHz RFID appears to be within reach. We review the performance of these devices, and discuss optimization strategies for achieving the ultimate performance goals requisite for realizing ultra-low-cost printed RFID.

Printed electronics for low-cost electronic systems: Technology status and application development

In recent years, printing has received substantial interest as a technique for realizing low cost, large area electronic systems. Printing allows the use of purely additive processing, thus lowering process complexity and material usage. Coupled with the use of low-cost substrates such as plastic, metal foils, etc., it is expected that printed electronics will enable the realization of a wide range of easily deployable electronic systems, including displays, sensors, and RFID tags. We review our work on the development of technologies and applications for printed electronics. By combining synthetically derived inorganic nanoparticles and organic materials, we have realized a range of printable electronic ldquoinksrdquo, and used these to demonstrate printed passive components, multilayer interconnection, diodes, transistors, memories, batteries, and various types of gas and biosensors. By exploiting the ability of printing to cheaply allow for the integration of diverse functionalities and materials onto the same substrate, therefore, it is possible to realize printed systems that exploit the advantages of printing while working around the disadvantages of the same.

High-quality inkjet-printed multilevel interconnects and inductive components on plastic for ultra-low-cost RFID applications

In recent years, there has been tremendous interest in all-printed electronics as a means of achieving ultra-low-cost electronic circuits with uses in displays and disposable electronics applications such as RFID tags. While there have been a few demonstrations of printed organic transistors to date, there has been little work on the associated passive component and interconnection technologies required to enable the development of all-printed RFID circuits. In particular, low-resistance conductors are crucial to achieve the high-Q inductors necessary for RFID. Here, we demonstrate inkjetted nanoparticle-Au conductors on plastic with sheet resistances as low as 0.03 ohms/square. We describe the optimization of the jetting parameters, and their impact on final film morphology and electrical properties. We also demonstrate a bridging technology based on an inkjetted polyimide interlevel dielectric. Using this process, we demonstrate multilevel interconnect and passive component structures including conductor patterns, crossover bridges, and tapped planar spiral inductors. Together, these represent an important step towards the realization of all-printed RFID.

A novel transparent air-stable printable n-type semiconductor technology using ZnO nanoparticles

We report on a novel, air-stable, printable, transparent, NMOS semiconductor technology using soluble ZnO nanoparticles. We demonstrate solution-processed transistors with mobility > 0.1 cm/sup 2//V/spl middot/s, which is the highest solution-processed NMOS mobility reported to date. The air-stability and transparency make this device an ideal candidate for low-cost printed displays and CMOS circuitry.

Inkjetted Organic Transistors using a Novel Pentacene Precursor

Pentacene is one of the most promising organic materials for organic transistor fabrication, since it offers higher mobility, better on-off ratio, improved environmental stability, and better reliability than most other organic semiconductors. However, its severe insolubility renders it useless for the solution-based fabrication of electronic devices. Solution-based processing is the key to enabling ultra-low-cost circuit fabrication, since it eliminates the need for lithography, subtractive processing, and vacuum-based film deposition. Using a recently developed soluble pentacene precursor, we demonstrate the first inkjet-printed pentacene transistor fabricated to date. This is achieved using a substrate-gated transistor structure in conjunction with an inkjetprinted pentacene precursor active layer. After deposition, the precursor is converted to pentacene via heating, through the decomposition of the Diels-Alder product. As the anneal temperature increases above 120°C, performance increases dramatically. The process is therefore compatible with numerous low-temperature plastics. As the anneal time is increased to several minutes, performance likewise increases through increased precursor decomposition. However, exposure to excess temperatures or times tends to degrade performance. This is caused by morphological and chemical changes in the pentacene film. Optimization of the anneal process alone has resulted in the demonstration of transistors with an on-off ratio of >10 5 and field-effect mobility of >0.01cm 2 /V-s, attesting to the great promise of this material.

A high-performance all-inkjetted organic transistor technology

We report on the highest performance all-printed transistors reported to date. Using nanoparticle-based printed contact, polymer dielectrics, and a printed soluble pentacene precursor semiconductor, we demonstrate all-inkjetted devices with mobilities >0.1cm/sup 2//V-s and on-off ratios as high as 10/sup 4/. The performance of these devices is comparable to control devices fabricated on silicon-substrates, and thus, these devices represent a significant step towards the realization of low-cost printed electronics.

Low-voltage inkjetted organic transistors for printed RFID and display applications

We demonstrate printed organic transistors with sub-10V VDD . Using inkjetted nanoparticle conductors, a polymer dielectric, and a pentacene precursor semiconductor, we demonstrate devices on plastic with mobilities >0.05cm2/V-s and on-off ratios >105. Thus, for the first time, we demonstrate devices with operating specifications approaching those required for low-cost electronic systems

All-printed RFID tags: materials, devices, and circuit implications

Printed electronics holds promise for realizing ultra-low-cost RFID tags for item-level tracking of consumer goods. We report on our progress in developing all-printed RFID tags. We review the development of printable materials for these applications, summarize the characteristics of printed devices, and discuss the implications of these on circuit performance limits and needs. Based on this assessment, we discuss the outlook for all-printed RFID tags and identify the problems remaining to be solved and the efforts taking place in this regard.