Layer-controlled epitaxy of 2D semiconductors: bridging nanoscale phenomena to wafer-scale uniformity

Abstract

The rapid cadence of MOSFET scaling is stimulating the development of new technologies and accelerating the introduction of new semiconducting materials as silicon alternative. In this context, 2D materials with a unique layered structure have attracted tremendous interest in recent years, mainly motivated by their ultra-thin body nature and unique optoelectronic and mechanical properties. The development of scalable synthesis techniques is obviously a fundamental step towards the development of a manufacturable technology. Metal-organic chemical vapor deposition has recently been used for the synthesis of large area TMDs, however, an important milestone still needs to be achieved: the ability to precisely control the number of layers and surface uniformity at the nano-to micro-length scale to obtain an atomically flat, self-passivated surface. In this work, we explore various fundamental aspects involved in the chemical vapor deposition process and we provide important insights on the layer-dependence of epitaxial MoS film's structural properties. Based on these observations, we propose an original method to achieve a layer-controlled epitaxy of wafer-scale TMDs.

Determination of energy thresholds of electron excitations at semiconductor/insulator interfaces using trap-related displacement currents

“…The GaN/Al2O3 samples were prepared on heavily doped n-type (n≈1x10 18 cm -3 ) 2 m precursors, respectively, following the chemical vapor deposition (CVD) process described elsewhere [5]. Electrical contact to the disulfide semiconductor layers was done either by using non-transparent contact pads (Au or Al, 100 nm thick) [4,6] or by evaporation of semitransparent (15 nm) Au or Al electrodes of 0.5 mm 2 area.…”

A roadmap for electronic grade 2D materials

“…137 Recent progress in this area has been made via manipulation of metal:chalcogen ratios and delineation of strategic growth steps in MOCVD. 79,81,138,139 However, for further improvement, in-situ characterization techniques are needed to provide real-time insight into nucleation and growth. The higher pressures used in CVD chambers render electron diffraction techniques ineffective; consequently, optical methods such as spectroscopic ellipsometry, laser reflectance, infrared absorption, and Raman spectroscopy are potential candidates for in-situ characterization.…”

Surface analysis in the semiconductor industry: Present use and future possibilities

“…While C-AFM and the closely related scanning spreading resistance microscopy (SSRM) used to measure surface resistivity (from which dopant-induced carrier distributions can be mapped) have long since been valuable tools in materials research, 5,11 conductive probe techniques have been found to be particularly useful for the investigation of two-dimensional (2D) materials, 5,[12][13][14][15][16][17][18][19] . As one of the leading candidates to replacing Si as a channel material in logic devices, it is critical that the electrical properties of such materials be characterized without impact of the surrounding environment.…”

“…The influence of the ambient environment on the 2D layer can, however, be mitigated by performing conductive probe measurements in high vacuum (HV) conditions. As an example, C-AFM was performed on a three-to four-layer (1.8-2.4 nm) thick MoS 2 sample grown by chemical vapor deposition (CVD) on a 2 00 c-sapphire substrate (details of the sample and growth can be found in previous works [18,19] ). The experimental setup is shown schematically in the inset of Figure 4E.…”