Non-vacuum, single-step conductive transparent ZnO patterning by ultra-short pulsed laser annealing of solution-deposited nanoparticles

Abstract

A solution-processable, high-concentration transparent ZnO nanoparticle (NP) solution was successfully synthesized in a new process. A highly transparent ZnO thin film was fabricated by spin coating without vacuum deposition. Subsequent ultra-short-pulsed laser annealing at room temperature was performed to change the film properties without using a blanket high temperature heating process. Although the as-deposited NP thin film was not electrically conductive, laser annealing imparted a large conductivity increase and furthermore enabled selective annealing to write conductive patterns directly on the NP thin film without a photolithographic process. Conductivity enhancement could be obtained by altering the laser annealing parameters. Parametric studies including the sheet resistance and optical transmittance of the annealed ZnO NP thin film were conducted for various laser powers, scanning speeds and background gas conditions. The lowest resistivity from laser-annealed ZnO thin film was about 4.75 × 10 −2 cm, exhibiting a factor of 10 5 higher conductivity than the previously reported furnace-annealed ZnO NP film and is even comparable to that of vacuum-deposited, impurity-doped ZnO films within a factor of 10. The process developed in this work was applied to the fabrication of a thin film transistor (TFT) device that showed enhanced performance compared with furnace-annealed devices. A ZnO TFT performance test revealed that by just changing the laser parameters, the solution-deposited ZnO thin film can also perform as a semiconductor, demonstrating that laser annealing offers tunability of ZnO thin film properties for both transparent conductors and semiconductors.

Inverter Circuits Using ZnO Nanoparticle Based Thin-Film Transistors for Flexible Electronic Applications

“…Another approach for a punctual annealing of the nanoparticulated film is the employment of pulsed laser exposure. With this technique, the characteristic of the semiconductor can be optimized controlling the parameter of the laser processing or the annealing ambient [29,30]. Even though the annealing of the film is superficial, damaging on the semiconductor film [30] or gate dielectric by excessive laser exposure may lead to instabilities in the transistor operation.…”

“…With this technique, the characteristic of the semiconductor can be optimized controlling the parameter of the laser processing or the annealing ambient [29,30]. Even though the annealing of the film is superficial, damaging on the semiconductor film [30] or gate dielectric by excessive laser exposure may lead to instabilities in the transistor operation. The TFT turn-on voltage ( V ON ) as defined by [14,31] is about 0 V and characterizes the switching point of the transistors.…”

A Review of Low‐Temperature Solution‐Processed Metal Oxide Thin‐Film Transistors for Flexible Electronics

“…Research has been actively conducted to form solution‐processed oxide semiconductors at low‐temperatures using laser irradiation processes . Photoactivation with a laser enables selective processing of localized areas, delivering energy quickly and accurately.…”

Laser wavelength effect on laser-induced photo-thermal sintering of silver nanoparticles

“…Utilizing nanomaterials, low-temperature thermal treatment compatible to flexible substrates [10,11] can be achieved by taking advantage of the significant melting temperature depression due to the thermodynamic size effect [12]. Laser sintering of deposited functional nanoparticle (NP) ink is a promising method since it enables the writing of micron and even submicron conductive patterns [13][14][15][16]. Recently, Lee et al [2] fabricated high-resolution nickel (Ni) patterns from the laser-induced reductive sintering of nickel oxide (NiO) NPs and could demonstrate a touch screen panel (TSP) for display application.…”