Plasma Treatment of Ultrathin Layered Semiconductors for Electronic Device Applications

Abstract

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.

Dielectrics for Two-Dimensional Transition-Metal Dichalcogenide Applications

“…Efforts to circumvent this can be broadly classified into (1) surface treatments of the 2D TMD surface − and (2) using seed layers. Surface treatments include UV-O 3 , O 2 plasma, and Ar + ion to generate reactive sites through limited defect or adsorbent introduction but can degrade or alter the 2D TMD properties (Figure d,e).…”

“…However, as the surfaces of most 2D materials are inert without dangling bonds, the precursors are only physically adsorbed on 2D materials which can lead to nonuniform growth. Various approaches have been developed to improve the uniformity of ALD-grown dielectrics, such as creating defects 2D material surfaces through plasma or wet etching − and deposition of metallic or molecular seeding layers − (Figure d). Unfortunately, the deposition of seeding layers can compromise the TMD surface quality, while discrete molecules can make homogeneous film growth challenging …”

Healing Donor Defect States in CVD‐Grown MoS2 Field‐Effect Transistors Using Oxygen Plasma with a Channel‐Protecting Barrier

“…However, such a treatment inevitably damages the TMDC film, thereby degrading its crystallinity and carrier mobility. [18,19] Therefore, herein, we propose a method for healing V s using oxygen plasma, while preventing channel damage via an aluminum oxide (Al 2 O 3 ) barrier layer. As the oxygen plasma treatment time increased, the intrinsic defect density decreased without degrading the electrical characteristics, suggesting that our barrier prevented damage, and O atoms successfully penetrated MoS 2 and healed V s .…”

“…However, such a treatment inevitably damages the TMDC film, thereby degrading its crystallinity and carrier mobility. [ 18,19 ]…”

Near-Infrared Optical Response and Carrier Dynamics for High Photoconversion in Tellurene

“…Semiconductor layered structures are a class of materials with a variety of interesting physical properties that, in turn, could have a wide range of applications in electronics and optoelectronics. − Some of these semiconductors’ outstanding properties stem from their peculiar crystal structure, band gap tunability, and strong light matter interaction. The latter, in particular, is a crucial factor for the enhanced absorption of electromagnetic radiation.…”