In contrast to conventional methods for increasing the conductivity of transparent polymer electrodes based on additives, solvent treatment, or hot plate thermal processing, laser heating enables the selective annealing of defined areas of a material on the micrometer scale. This study investigates the spatial conductivity distribution of thin PEDOT:PSS films after selective heating by continuous wave (cw) laser radiation without damaging the material. The sheet resistances of the samples decreased abruptly above a certain threshold intensity and a changed relative permittivity of the irradiated material was detected by imaging ellipsometry. A theoretical model has been derived to estimate the resulting spatial conductivity distribution induced by the inhomogeneous heating with the Gaussian spatial intensity distribution of the applied laser radiation. In combination with the experimental measurements, the model revealed that the conductivity increased proportionally to the intensity above the threshold intensity, but remained unchanged below, resulting also in a Gaussian spatial conductivity distribution. Thus, in contrast to conventional oven annealing where only large-area averaged annealing is possible, laser annealing allows to tailor the spatial distribution of the conductivity on a micrometer scale opening applications for future micro systems.

No abstract

No abstract

Local crystallization of ferromagnetic layers is crucial in the successful realization of miniaturized tunneling magnetoresistance (TMR) devices. In the case of Co–Fe–B TMR devices, used most successfully so far in applications and devices, Co–Fe–B layers are initially deposited in an amorphous state and annealed post-deposition to induce crystallization in Co–Fe, thereby increasing the device performance. In this work, first direct proof of locally triggered crystallization of 10 nm thick Co–Fe–B films by laser irradiation is provided by means of X-ray diffraction (XRD) using synchrotron radiation. A comparison with furnace annealing is performed for benchmarking purposes, covering different annealing parameters, including temperature and duration in the case of furnace annealing, as well as laser intensity and scanning speed for the laser annealing. Films of Co–Fe–B with different stoichiometry sandwiched between a Ru and a Ta or MgO layer were systematically assessed by XRD and SQUID magnetometry in order to elucidate the crystallization mechanisms. The transformation of Co–Fe–B films from amorphous to crystalline is revealed by the presence of pronounced CoFe(110) and/or CoFe(200) reflexes in the XRD θ-2θ scans, depending on the capping layer. For a certain window of parameters, comparable crystallization yields are obtained with furnace and laser annealing. Samples with an MgO capping layer required a slightly lower laser intensity to achieve equivalent Co–Fe crystallization yields, highlighting the potential of laser annealing to locally enhance the TMR ratio.

No abstract