Currently the most widely graphene production technique is growth via Chemical Vapor Deposition (CVD) on copper thin films previously deposited by evaporation on sapphire substrates, which can yield high-quality monolayer graphene coatings. However, the transfer of graphene from the growth substrate via conventional methods making use of support/protective layers (e.g., organic polymers), lithographic masking layers and chemical etching, is a multi-step complex procedure. Here, we report the use of laser-based transfer technique, namely, Laser-Induced Forward Transfer (LIFT) for the reliable, reproducible and high-quality transfer of graphene pixels at designated areas on SiO2/Si substrates, directly from the growth substrate. LIFT is an environmentally friendly, mask-less technique and offers high resolution with high throughput. The quality of the transferred films has been inspected via SEM, Raman spectroscopy, and AFM characterization. Electrical characterization for mobility measurement will also be performed. The aim of this study is the process optimization of LIFT process parameters, such as the laser fluence. The reported results highlight the advantages of the laser-based monolayer graphene deposition methods for the on-chip integration of graphene-based photodetectors.
Laser induced forward transfer (LIFT) and laser sintering of metal nanoparticle inks constitute a two-step digital fabrication technique which has been proven a key enabling technology for the fabrication of flexible microelectronic devices. In this work we will present the investigation of the laser printing and sintering process of Ag nanoparticle inks for the production of a conductive grid comprised of parallel lines as replacement for the bottom Indium Tin Oxide (ITO) electrode in organic photovoltaics (OPVs). We study the effect of a range of laser parameters and their impact on the morphological characteristics and the electrical performance of the laser printed conductive grid. The electrical conductivity of the laser printed lines is calculated by means of electrical measurements in a 4-point probe IV station while their morphological characteristics are assessed with profilometry measurements. As a result, flexible ITO-free OPVs incorporating laser-printed Ag grids as a bottom electrode on PET substrates will be presented. The results confirm that the laser printing and sintering combination is an advantageous technique, which can offer a distinguishing solution for applications in highly efficient ITO-free OPVs.
In this work, we report on the conformal laser printing and sintering of Ag nanoparticle inks applied on particularly sensitive substrates and structures. The latter involve challenging patterns with periodicity and aspect ratio in the nano to 100-micron scale. We investigate the effect of a number of essential to the laser sintering technique parameters, such as the laser wavelength, repetition rate, pulse duration and the pulse to pulse spatial and temporal overlap. The demonstrated results show that laser printing and sintering can offer specific solutions to particularly challenging use cases and applications in flexible electronics.
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