Interface engineering is essential to enhance the performance and stability of layered devices by resolving the interfacial issues, which dominantly affect the operation of the device. Unlike the interface, the adjoining bulk semiconductor is slightly affected by the interfacial treatment, and it is generally considered negligible in the classical semiconductor device theory. On the other hand, this interfacial effect is no longer trivial at the devices composing ultrathin layers, which are crucial for developing next-generation electronics with high integrity and low power consumption. Even though the semiconductors with tens of nanometers thickness, mainly used in current silicon-based industries, are significantly affected by the surrounding interfaces, however, this prominent interfacial influence is still underestimated. Herein, we show the substantial interfacial impact on the ultrathin semiconductor by the self-assembled monolayer (SAM) deposition, the p- to n-type inversion of the 50 nm silicon. The type and majority carrier density of the 50 nm silicon were determined by the interfacial dipole effect of SAMs according to their direction and strength, which was verified by Hall measurement and surface analysis such as UPS, XPS, and KPFM. As an interface engineering approach, the incorporation and control of SAMs show the potential as a simple alternative to the traditional impurity doping methods, which have difficulty in regulating the randomly distributed dopant in the case of the semiconductors with nanoscale thickness thereby causing unstable performance. Furthermore, we engineer the lateral electronic junction of the 50 nm silicon through the regioselective deposition of SAMs with opposite interfacial dipole, locally inducing p- and n-type silicon at each SAM-deposited region. Due to the presence of a lateral electronic junction, the 50 nm silicon exhibits the rectification behavior, which is reminiscent of a p-n diode. When we modulate the interfacial dipole of each SAMs through the ion pairing method using solutions of varying pH levels, the rectification ratio is sensitively changed. Therefore, the 50 nm silicon treated with the regioselective SAM deposition shows applicability as a pH sensing platform.
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