Direct Laser Writing of Crystallized TiO₂ and TiO₂/Carbon Microstructures with Tunable Conductive Properties

Abstract

for use in conductors, semiconductors, and insulators. [5] Electronic properties are indeed closely linked to the nature of the metal and conditions of fabrication, which determine the structure of the final material at the atomic scale. These properties can be modified by doping with different metals, by adjusting the metal to oxygen stoichiometry or by generating an amorphous or crystal phase. [6][7][8][9] Today, integration of MOs as thin films, micropatterns or nanopatterns by convenient and simple means remains a major challenge for the fabrication of electronic and optoelectronic devices. MOs are commonly deposited as thin films by sputtering. Though the sputtered MOs usually exhibit better electrical properties due to the accurate control of the composition and defect concentration at the atomic scale, solution-based processes have gained much attention during the last years due to their simplicity, cost effectiveness, vacuum-free processes, and high versatility.In solution-based processes, thermal annealing is required to eliminate the solvent and organic ligands that are complexed on metal ions and to obtain material and phase compositions with suitable properties. This step is typically conducted at temperatures ranging from 300 to 1000 °C. Thus, such a fabrication strategy can be difficult to apply in the case of multistep integration processes involving different materials.In this context, laser processing of MOs presents many advantages due to the control of the laser-matter interaction in space and time. [9] Laser curing allows a fast treatment that can be confined to a limited volume by focusing the laser beam. Such a laserinduced effect leads to a much lower energy consumption with respect to that of thermal annealing. For example, a pulsed laser in the ultraviolet (UV) or near-infrared (NIR) range has been successfully used for the crystal growth of amorphous MO films [10,11] or the hydrothermal growth of MO nanostructures. [12,13] Recently, laser processing has also been introduced for the direct writing of MO microstructures. For this purpose, UV or deep-UV (DUV) wavelengths are usually used. At the molecular scale, the patterning proceeds according to the photodecomposition of the metal precursors complexed by organic molecules. Patterning can be obtained at room temperature down to the nanoscale using direct laser writing (DLW), but usually, a thermal post-treatment is needed to obtain an MO with suitable Metal oxides are an important class of materials for optoelectronic applications. In this context, developing simple and versatile processes for integrating these materials at the microscale and nanoscale has become increasingly important. One of the major remaining challenges is to control the microstructuration and electro-optical properties in a single step. It is shown here that near-infrared femtosecond laser irradiation can be successfully used to prepare amorphous or crystallized TiO 2 microstructures in a single step using a direct laser writing (DLW) approach from a TiO 2 precursor ...

Laser Irradiation of Electrode Materials for Energy Storage and Conversion

“…The successfully fabricated structures include but are not Figures 7B-7D. [89][90][91][92][93][94] In addition to these achievements, the highly controlled heating enabled by laser irradiation permits intriguing heterostructures ll that have rarely been realized by other methods. A scalable graphene membrane with different carbonization degrees along the vertical direction made by elaborately controlling the lasing process (wavelength: 1,064 nm; CW) contributes to a Janus super-hydrophobic/super-hydrophilic structure.…”

The Fabrication of Micro/Nano Structures by Laser Machining

“…TiO 2 /C nanocomposites exhibited piezoresistive behavior used in pressure sensor devices. Using this method, DLW can be applied to fabricate a miniature pressure sensor [274].…”

Laser‐Patterned Copper Electrodes for Proximity and Tactile Sensors

“…Due to highly focused energy of laser beam, laser direct patterning possesses unparalleled selectivity and high efficiency in precise pattern definition and simultaneous thermal treatment including annealing and sintering. In the process of laser direct patterning, laser beam removes the solvent and ligand, reduces metal ions to form nanoparticles, and in situ anneals nanoparticles to enhance the conductivity of the structure. Due to its compatibility with wide range of materials, laser direct patterning process for many nanomaterials have been reported, including crystallized TiO 2 , graphene, Cu, etc.…”

“…In the process of laser direct patterning, laser beam removes the solvent and ligand, reduces metal ions to form nanoparticles, and in situ anneals nanoparticles to enhance the conductivity of the structure. Due to its compatibility with wide range of materials, laser direct patterning process for many nanomaterials have been reported, including crystallized TiO 2 , graphene, Cu, etc. This provides feasibility for efficiently assembling high‐performance sensors.…”