Plasma Treatment of Ultrathin Layered Semiconductors for Electronic Device Applications

The incorporation of two-dimensional (2D) semiconductors into future electronic devices will require electronic-grade, large-scale, and cost-effective means of doping and chemical control over the electronic properties of the utilized materials. In general, the approaches currently employed in the semiconductor industry may prove ineffective or inefficient in the nanofabrication of devices based on large-scale synthetic 2D monolayers. Some reasons for this include low interaction cross-sections with ion beams and the local variability in doping level of as-synthesized 2D materials. Plasma processing has emerged in recent years as a promising candidate to enable this large-scale modification of 2D materials in a time-efficient and cost-effective manner. However, challenges remain in fine-tuning of the chemical functionalization of 2D materials, such that they can act as reliable building blocks for monolithic components in future, low-dimensional circuitry capable of rivaling integrated complementary metal-oxide-semiconductor (CMOS) solutions based on bulk silicon. In this Review, we discuss recent progress in understanding of the chemical and physical etching processes that occur when 2D semiconductors are exposed to reactive plasma. We overview aspects of mobility engineering and doping control in 2D field-effect transistors (FETs) treated with plasma, with a particular focus on contact and gate dielectric interfaces. We also discuss functional devices, such as photodetectors and energy harvesters, based on plasma-activated 2D materials and summarize the operational parameters encountered in the literature for the successful tuning of 2D semiconductor properties with different types of plasma.