RESUMO
Achieving effective polarity control of n- and p-type transistors based on two-dimensional (2D) materials is a critical challenge in the process of integrating transition metal dichalcogenides (TMDC) into complementary metal-oxide semiconductor (CMOS) logic circuits. Herein, we utilized a proficient and nondestructive method of electron-charge transfer to achieve a complete carrier polarity conversion from p-to n-type by depositing a thin layer of aluminum oxide (Al2O3) onto tungsten diselenide (WSe2). By utilizing the Al2O3 passivation layer, we observed precisely tuned n-type behavior in contrast to transistors fabricated on the as-grown WSe2 film without any passivation layer, which display prominent p-type behavior. The polarity-transformed n-type WSe2 transistor from the pristine p-type shows the maximum ON current of â¼0.1 µA accompanied by a high electron mobility of 7 cm2 V-1 s-1 at a drain voltage (VDS) of 1 V. We successfully showcased a homogeneous CMOS inverter utilizing 2D-TMDC which exhibits an impressive voltage gain of 7 at VDD = 5 V. Moreover, this effective polarity control approach was further expanded upon to successfully demonstrate a range of logic circuits such as AND, OR, NAND, NOR logic gates, and SRAM. The proposed methodology possesses significant promise for facilitating the advancement of high-density circuitry components utilizing 2D-TMDC.
RESUMO
Multispectral photodetectors are emerging devices capable of detecting photons in multiple wavelength ranges, such as visible (VIS), near infrared (NIR), etc. Image data acquired with these photodetectors can be used for effective object identification and navigations owing to additional information beyond human vision, including thermal image and night vision. However, these capabilities are hindered by the structural complexity arising from the integration of multiple heterojunctions and selective absorbers. In this paper, we demonstrate a Ge/MoS2 van der Waals heterojunction photodetector for VIS- and IR-selective detection capability under near-photovoltaic and photoconductive modes. The simplified single-polarity bias operation using single pixel could considerably reduce structural complexity and minimize peripheral circuitry for multispectral selective detection. The proposed multispectral photodetector provides a potential pathway for the integration of VIS/NIR vision for application in self-driving, surveillance, computer vision, and biomedical imaging.
RESUMO
Recently, the inherent piezoelectric properties of the 2D transition-metal dichalcogenides (TMDs) tin monosulfide (SnS) and tin disulfide (SnS2) have attracted much attention. Thus the piezoelectricity of these materials has been theoretically and experimentally investigated for energy-harvesting devices. However, the piezoelectric output performance of the SnS2- or SnS-based 2D thin film piezoelectric nanogenerator (PENG) is still relatively low, and the fabrication process is not suitable for practical applications. Here we report the formation of the SnS2/SnS heterostructure thin film for the enhanced output performance of a PENG using atomic layer deposition (ALD). The piezoelectric response of the heterostructure thin film was increased by â¼40% compared with that of the SnS2 thin film, attributed to large band offset induced by the heterojunction formation. Consequently, the output voltage and current density of the heterostructure PENG were 60 mV and 11.4 nA/cm2 at 0.6% tensile strain, respectively. In addition, thickness-controllable large-area uniform thin-film deposition via ALD ensures that the reproducible output performance is achieved and that the output density can be lithographically adjusted depending on the applications. Therefore, the SnS2/SnS heterostructure PENG fabricated in this work can be employed to develop a flexible energy-harvesting device or an attachable self-powered sensor for monitoring pulse and human body movement.