RESUMEN
Perovskite-type La:BaSnO3 (LBSO) has been drawing considerable attention due to its high electron mobility and optical transparency. Its thin film electrical properties, however, remain inferior to those of single crystals. This work investigates the thermal post-treatment process of films deposited using the metalorganic chemical vapor deposition method to improve the electrical properties of different stoichiometry films, and demonstrates the modification of thin film's structural properties using short and excessive annealing durations in vacuum conditions. Using vacuum post-treatment, we demonstrate the improvement of electrical properties in Ba-rich, near-stoichiometric, and Sn-rich samples with a maximum electron mobility of 116 cm2V-1s-1 at r.t. However, the improvement of electrical properties causes surface morphology and internal structural changes, which depend on thin film composition. At temperatures of 900 °C-1400 °C the volatile nature of LBSO constituting elements is described, which reveals possible deterioration mechanisms of thin LBSO air. At higher than 1200 °C, LBSO film's decomposition rate increases exponentially. Thin film structure evolution and previously unreported decomposition is demonstrated by Ba and La diffusion to the substrate, and by evaporation of SnO-SnOx species.
RESUMEN
In the present study the advantageous pulsed-injection metal organic chemical vapour deposition (PI-MOCVD) technique was used for the growth of nanostructured La1- x Sr x Mn y O3±Î´ (LSMO) films on ceramic Al2O3 substrates. The compositional, structural and magnetoresistive properties of the nanostructured manganite were changed by variation of the processing conditions: precursor solution concentration, supply frequency and number of supply sources during the PI-MOCVD growth process. The results showed that the thick (≈400 nm) nanostructured LSMO films, grown using an additional supply source of precursor solution in an exponentially decreasing manner, exhibit the highest magnetoresistance and the lowest magnetoresistance anisotropy. The possibility to use these films for the development of magnetic field sensors operating at room temperature is discussed.
RESUMEN
Direct electron transfer between redox enzymes and electrodes is the basis for the third generation biosensors. We established direct electron transfer between quinohemoprotein alcohol dehydrogenase (PQQ-ADH) and modified carbon black (CBs) electrodes. Furthermore, for the first time, this phenomenon was observed for pyrroloquinoline quinone (PQQ)-dependent glucose dehydrogenase (PQQ-GDH). Reagentless enzyme biosensors suitable for the determination of ethanol, glucose and sensors for hydrogen peroxide were designed using CB electrodes and screen-printing technique. Aiming to create an optimal transducing material for biosensors, a set of CB batches was synthesized using the matrix of Plackett-Burman experimental design. Depending on the obtained surface functional groups as well as the nano-scale carbon structures in CBs batches, the maximal direct electron transfer current of glucose and ethanol biosensors can vary from 20 to 300 nA and from 30 to 6300 nA for glucose and ethanol, respectively. Using modified CB electrodes, an electrocatalytic oxidation of H(2)O(2) takes place at more negative potentials (0.1-0.4V versus Ag/AgCl). Moreover, H(2)O(2) oxidation efficiency depends on the amount and morphology of fine fraction in the modified CBs.