Study On The Microstructures And Electronic Properties In Sr_n+1Ru_nO_3n+1 Thin Films

Ruddlesden-Popper(R-P,A_n+1B_nO_3n+1,n=1,2,3…∞)oxide films,due to tunable crystalline structures as well as emergent electronic properties,possess promising applications on storage,sensors,and spin electronics.However,an ultra-high growth temperature（≥1000℃）remains a major challenge for the deposition of high-quality R-P oxide films,which largely restricts their modulations of crystalline and electronic structures and associated applications.In this thesis,strontium ruthenate with R-P structure was grown under different growth atmospheres during pulsed laser depositions（PLD）,which,in turn,notably influences its crystal structure and physical properties.Meanwhile,the structure and physical properties of R-P strontium ruthenate films can be further regulated via non-metallic ions doping,for example,treated by N Plasma and PVDF.These findings shed lights on the developments of high-temperature deposited ruthenate oxide functional films.The main results are as follows:1)In order to systematically study the effects of different atmospheres on the growth of strontium ruthenate films,an additional gas inlet is inserted in a commercial PLD,which is synchronized with the frequency of pulse laser.This adaptable PLD facilitates the deposition of strontium ruthenate film under various gas atmospheres,providing an efficient way to explore atmosphere-sensitive depositions of complex ruthenate oxide films.2)Then,the effects of growth atmosphere on the structure and property of strontium ruthenate films grown with PLD are studied.The growth temperature of high-quality Sr₂RuO₄films has been remarkably declined to 900℃by replacing the deposition atmosphere from oxygen to nitrogen.Meanwhile,a successive SrRuO₃-to-Sr₂RuO₄ structural transformation was realized with growth temperatures ranging from 700℃ to 900℃.It is suggested that the nitrogen atmosphere involved during the deposition results in a relative lower kinetic energy of strontium ruthenate pushed to substrates,and consequently regulates structural and electronic properties of ruthenium oxide films.This unconventional approach offers a new route for developments of high-temperature oxide functional films.3).Plasma treatment is employed to regulate the surface morphology,crystal structure and electronic properties of strontium ruthenate films.Epitaxial SrRuO₃ films,which are grown on different substrates via pulsed laser deposition,are treated by the nitrogen plasma.It is shown that the out-of-plane lattice constant of the treated SrRuO₃ films is increased.Moreover,the magnetic and transport properties of SrRuO₃ films are significantly modulated after the plasma treatment.These observations offer an alternative method to tune crystalline structure and functional properties in complex strontium ruthenate films.4).Compared with traditional metallic ionic doping,herein,the influence of anionic doping on the structure and electrical properties of Sr₂RuO₄films is addressed.After fluorinations via PVDF,it is demonstrated that the F^-is successfully intercalated in Sr₂RuO₄films,resulting in a series of changes in the structures and related electrical transport properties.Thus,a decreased transformation temperature from SrRuO₃ to Sr₂RuO₄ is realized by changing the growth atmosphere.The crystal structure and electronic characteristics of strontium ruthenate films can be effectively regulated by Plasma treatment and fluorination.These results could open up new possibilities for effectively modulating rich structures and functionalities of R-P ruthenate oxide films.