| Laser-induced thermoelectric voltage (LITV) effects in oxides have been widely studied due to their great potential applications in the field of photo detectors and micro-cooling. A great many high-temperature superconductor oxide (HTSC) and colossal magneto-resistance (CMR) films which possess perovskite structure could be detected LITV signals. In order to improve the accuracy and sensitivity of detector, a variety of methods were implemented to optimize performance of LITV signal, such as exploring new materials, preparing multilayer thin films and superlattice structure films etc. While LITV effect based on thermoelectric effect is sensitive to temperature. The temperature variation in films mainly comes from laser and external environment, which both influence on the performance of LITV signal. And the substrate temperature plays a very important role which transferred from external environment. It will result in the serious reduction of precision in energy measurement as detector without taking substrate temperature into account. However, few researches about the dependence of LITV effect on substrate temperature have been reported.This thesis sets out to use typical cubic structure perovskite materials LaFeO3. To increase the anisotropic structure, this paper takes La0.8Sr0.2Fe03with0.2doping content of Sr as the object of a series of studies. The specific contents are as follows.1. La0.8Sr0.2FeO3polycrystalline target was synthesized by conventional solid-state reaction method, which was characterized by XRD. Subsequently, La0.8Sr0.2Fe03films were deposited on LaAlO3(100) single substrate by pulsed laser deposition technique (PLD) technology. La0.8Sr0.2FeO3films were characterized by XRD and AFM. It can be observed that these films, which have good crystalline and grown oriented along the direction (220), is smooth, compact, and uniform. It indicates that above films belong to high quality films.2. Firstly, LITV effect is observed firstly in Lao.8Sro.2Fe03thin films grown on the vicinal cut LaAIO3(LAO) substrates by pulse laser deposition (PLD), when the pulsed ultraviolet (UV) laser beam from KrF excimer with wavelength of248nm lights on the films. Secondly, the effect of the growth temperature of films and tilt angle of substrate on LITV signal of La0.8Sr0.2Fe03films were researched. Thirdly, the paper also explores the influence of number of film layers onperformance of LITV signals.3. The influence of substrate temperature on Laser-induced thermoelectric voltage signalsin La0.8Sro.2Fe03film grown on vicinal cut LaAlO3single crystal substrate was studied. With theincrease of substrate temperature, the peak voltages (Vp) were obviously increased and FWHMsdecreased. That determined by dependence of carrier concentration on temperature. It isnotable that there is an abrupt point appeared both in Vp-Ts and FWHM-Ts curves in255K-27OKand300K-315K respectively, and in R-T curve as well, which are demonstrated to be the phasetransition of La0.8Sr0.2FeO3film by in situ photoluminescence spectroscopy. These seriouslydecrease the precision in energy measurement as a detector.4. In the research of electromagnetic characteristics of La0.8Sr0.2Fe03films, which weregrown on LaAlO3, Si and SiO2substrate respectively, abrupt points were all detected in R-Tcurves in a certain temperature range. Therefore, the further explorations of this paper will aimat the electromagnetic characteristics of La0.8Sr0.2FeO3films. |
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