Uesugi Akio, Nakata Shinya, Inoyama Kodai, Sugano Koji, Isono Yoshitada
Department of Mechanical Engineering, Graduate School of Engineering, Kobe University, Kobe, Japan.
Nanotechnology. 2022 Sep 26;33(50). doi: 10.1088/1361-6528/ac8d11.
The effect of surface potential on the carrier mobility and piezoresistance of core-shell silicon carbide nanowires (SiC NWs) was investigated to realize small and sensitive SiC-microelectromechanical systems sensors. The p-type cubic crystalline SiC (3C-SiC) NWs were synthesized via the vapor-liquid-solid method and coated with silicon dioxide (SiO) or aluminum oxide (AlO) dielectric shells to form core-shell structured NWs with different surface potentials. Four-point bending devices (FBDs) with a field-effect transistor (FET) configuration integrating a single core-shell 3C-SiC NW as the FET channel were fabricated to apply an additional electric field and strain to the core-shell 3C-SiC NWs. The fixed oxide charge densities of the SiOand AlOshells showed positive and negative values, respectively, which were equivalent to electric fields of the order of several hundred thousand volt per centimeter in absolute values. In the core-shell 3C-SiC NWs with originally low impurity concentrations, the electric field induced by the fixed oxide charge of the shells can determine not only the electrical conduction but also the charge carriers in the NWs. Bending tests using the FBDs showed that the piezoresistive effect of the SiO-coated NW was almost the same as that of the as-grown 3C-SiC NW reported previously, regardless of the gate voltage, whereas that of the AlO-coated NW was considerably enhanced at negative gate voltages. The enhancement of the piezoresistive effect was attributed to the piezo-pinch effect, which was more pronounced in the NW, where the carrier density at the core-shell interface is enhanced by the electric field of the dielectric.
为了实现小型且灵敏的碳化硅微机电系统传感器，研究了表面电势对核壳结构碳化硅纳米线（SiC NWs）载流子迁移率和压阻的影响。通过气-液-固方法合成了p型立方晶体SiC（3C-SiC）纳米线，并包覆二氧化硅（SiO₂）或氧化铝（Al₂O₃）介电壳，以形成具有不同表面电势的核壳结构纳米线。制作了具有场效应晶体管（FET）配置的四点弯曲器件（FBDs），其中集成了单根核壳3C-SiC纳米线作为FET沟道，以便对核壳3C-SiC纳米线施加额外的电场和应变。SiO₂和Al₂O₃壳层的固定氧化物电荷密度分别显示出正值和负值，其绝对值相当于几十万伏每厘米量级的电场。在原本杂质浓度较低的核壳3C-SiC纳米线中，壳层固定氧化物电荷所诱导的电场不仅可以决定纳米线中的导电情况，还能决定其中的载流子。使用FBDs进行的弯曲测试表明，无论栅极电压如何，SiO₂包覆纳米线的压阻效应与先前报道的生长态3C-SiC纳米线几乎相同，而Al₂O₃包覆纳米线在负栅极电压下的压阻效应则显著增强。压阻效应的增强归因于压挤效应，这种效应在纳米线中更为明显，其中核壳界面处的载流子密度会因电介质的电场而增强。
