温度对LaMnO_(3+δ)薄膜材料功函数影响机制研究

Research on influencing mechanism of temperature on work function of LaMnO_(3+δ)thin film materials

通过磁控溅射的方法制备了LaMnO_(3+δ)薄膜材料。掠入射X射线衍射(GIXRD)测试结果表明,薄膜材料为单一相结构的多晶氧化物,结构为正交畸变钙钛矿LaMnO_(3+δ);利用开尔文探针显微镜(KPFM)测得LaMnO_(3+δ)薄膜接触电势差(CPD)的高分辨率图像,并通过CPD结果计算得知,在30~80℃温度范围内,随着温度的升高材料的功函数由4.452 eV升至4.644 eV,这是由于材料内部高价阳离子Mn^(4+)浓度增加所致。该结果在XPS测试中得到进一步验证,Mn^(4+)/Mn^(3+)含量随温度的升高而升高。采用自组装电阻-温度测试系统的测试结果表明,薄膜材料在30~80℃范围内具有一定的负温度系数热敏特性。

LaMnO_(3+δ)thin film material is prepared through magnetron sputtering method.It is verified through grazing incidence X-ray diffraction(GIXRD)tests that the thin film material is a polycrystalline oxide with a single-phase structure,and its structure is orthogonal distortion perovskite LaMnO_(3+δ).Through Kelvin probe microscopy(KPFM)test,the high-resolution images of contact potential difference(CPD)of LaMnO_(3+δ)film are obtained.It is found through CPD result calculation that the work function of the material increases from 4.452 eV to 4.644 eV with the increase of temperature in the range of 30-80℃,which is caused by the increase of the concentration of high-valent cations Mn^(4+)inside the material.This result is further verified in the XPS test,and the content of Mn^(4+)/Mn^(3+)increases with the increasing temperature.Test results from a self-assembled resistance-temperature test system show that the thin-film material has certain negative temperature coefficient thermal properties in the temperature range of 30-80℃.