Optical And Electrical Properties Of Flexible Transparent Conducting Ba_1-x La_x SnO₃ Thin Films

Transparent conductive film（TCO）is a kind of important optoelectronic information material with high transmittance and low resistivity in visible light band.This study focused on the perovskite structure stannate oxide BaLaSnO₃ system,which is a new inorganic transparent conductive material with high electron mobility and light transmission.Due to its excellent photoelectric properties and highly stable chemical properties,it is expected to be widely used in the fields of liquid crystal displays,solar panels and ultraviolet detectors.The parent BaSnO₃（BSO）is a typical n-type semiconductor material with extremely high light transmittance.When a small amount of La³⁺partially replaces Ba²⁺,its conductivity is greatly improved.The results show that the electron mobility in the single crystal of Ba_0.96La_0.04SnO₃ can reach 320 cm2v^-1s^-1,the forbidden band width exceeds 4 eV,and the performance is obviously better than that of the general transparent conductive oxide.Therefore,BaLaSnO₃ material has great application value in the field of transparent conductivity^[1].At present,most transparent conductive films are grown on hard substrates,but with the development of semiconductor technology,in order to realize the portability,bendability and external impact resistance of electronic products,the preparation of various thin films with flexible substrates has become a development trend in the field of material physics.Ba_1-xLa_x SnO₃ thin films were prepared by using Mica as substrate.Ba_0.96La_0.04SnO₃ thin films with different thickness were prepared,Ba_1-xLa_xSnO₃ thin films with different concentration of La doping were deposited,and different preparation processes were tried to obtain the best photoelectric performance of BaLaSO₃thin films.The specific work is as follows:1.First,Ba_0.96La_0.04SnO₃ thin films were epitaxially grown on SrTiO₃ substrates with different orientations,to study the influence of different substrate orientations on the photoelectric properties of thin films.We selected two comparative studies of（001）and（111）.The structure of the epitaxial crystal was analyzed by XRD.The flatness of the thin films surface was analyzed by atomic force microscopy（AFM）.The effects of substrate growth orientation on the photoelectric properties of the films were analyzed by measuring the light transmittance and temperature varying resistivity.At the same time,the source of the difference in conductivity between the（001）and（111）directions is clarified theoretically by using the first-principles calculation.2.Ba_0.96La_0.04SnO₃ films with different thickness were prepared on flexible substrate Mica.The crystal structure and surface of the films were analyzed by XRD and AFM.The measurement of electronic transport at a variable temperature shows that the resistivity decreases with the increase of film thickness while the transmittance does not change obviously with the increase of film thickness.The Mica substrate was stripped to a bending state of about 0.02mm by physical stripping method,and the light transmittance test showed that the thin film still maintained more than 80%of the light transmittance under the bending state of visible range,indicating that the flexible thin film had no great influence on the transparency under the condition of deformation.3.Despite the Ba_0.96La_0.04SnO₃ films grown on the mica substrate having a high resistance and a semiconductor conductivity,the same thin films grown on the SrTiO₃ substrate have a small resistance and show a metallic conductivity.In order to reduce the resistance of BaLaSnO₃ thin films grown on mica substrates,on one hand,misfit dislocation and interface resistance are reduced by high temperature nitrogen annealing.On the other hand,by increasing the doping ratio of La ions,the carrier concentration is increased and the resistance is reduced.Finally,the resistance of the films grown on Mica substrates was improved and a metal insulation transitions similar to those present on SrTiO₃ substrates were observed.