Engineering Wafer-Scale Epitaxial Two-Dimensional Materials through Sapphire Template Screening for Advanced High-Performance Nanoelectronics

Abstract

In view of its epitaxial seeding capability, c-plane single crystalline sapphire represents one of the most enticing, industry-compatible templates to realize manufacturable deposition of single crystalline two-dimensional transition metal dichalcogenides (MX 2 ) for functional, ultrascaled, nanoelectronic devices beyond silicon. Despite sapphire being atomically flat, the surface topography, structure, and chemical termination vary between sapphire terraces during the fabrication process. To date, it remains poorly understood how these sapphire surface anomalies affect the local epitaxial registry and the intrinsic electrical properties of the deposited MX 2 monolayer. Therefore, molybdenum disulfide (MoS 2 ) is deposited by metal−organic chemical vapor deposition (MOCVD) in an industry-standard epitaxial reactor on two types of c-plane sapphire with distinctly different terrace and step dimensions. Complementary scanning probe microscopy techniques reveal an inhomogeneous conductivity profile in the first epitaxial MoS 2 monolayer on both sapphire templates. MoS 2 regions with poor conductivity correspond to sapphire terraces with uncontrolled topography and surface structure. By intentionally applying a substantial off-axis cut angle (1°in this work), the sapphire terrace width and step heightand thus also surface structurebecome more uniform across the substrate and MoS 2 conducts the current more homogeneously. Moreover, these effects propagate into the extrinsic MoS 2 device performance: the field-effect transistor variability reduces both within and across wafers at higher median electron mobility. Carefully controlling the sapphire surface topography and structure proves an essential prerequisite to systematically study and control the MX 2 growth behavior and capture the influence on its structural and electrical properties.

Standards for the Characterization of Endurance in Resistive Switching Devices

“…g ., FETs) often present data ( i . e ., mobility, subthreshold swing) for >50 devices; − however, in the field of RS, the number of devices analyzed is (in general) strikingly lower, and most publications present data for one or few ( i . e ., < 5) devices, especially in terms of endurance.…”

Detailed study on MOCVD of wafer-scale MoS2 monolayers: From nucleation to coalescence

“…It is clearly visible that the adatoms preferentially accumulate along certain orientations which are roughly perpendicular to the sapphire flat. The intentional substrate off-cut is towards m-plane (perpendicular to the a-plane flat) and therefore these lines are obviously correlated to atomic steps on the sapphire surface [10,11]. As nucleation proceeds (from 15 to 30 min), these oriented nano-nuclei will merge and form chains.…”

“…Despite some valuable theoretical modelling and calculation results [4][5][6][7], it is still challenging to identify the impact of multiple factors and conditions during development and optimization of growth processes. Up to now, a large number of process details and growth parameters have been reported to influence the final output of MOCVD processes, including substrate pre-treatment [8][9][10][11], growth temperature [12][13][14], selection and mass flow rate of precursors [13,[15][16][17][18][19][20]. To complicate things further, strongly different reactor geometries from horizontal [14] and vertical [17] flow, multi-wafer planetary [8,12,15] to showerhead [16,19,20] obviously lead to in part fundamentally contradictory findings, e.g.…”

Modulated Photoluminescence of Single‐Layer MoS2 via Nanostructured SrTiO3 Surface

“…Owing to the unique physicochemical properties as well as the potential applications in frontier technologies, two‐dimensional materials (2DM) have aroused wide concerns from both fundamental and practical researches. [ 1–9 ] Thin MoS 2 films, being one representative member of the 2DM family, have been demonstrated with tunable bandgap, modulatable photoluminescence, superior in‐plane conductivity and wafer‐scale growth possibility, [ 10–14 ] and thus provoked large interests in constructing innovative devices such as synapse transistor, [ 15–17 ] nonvolatile memory, [ 18,19 ] nanopower generators, [ 20 ] and so on. For most application circumstances, a proper support is usually necessary which either holds the transferred MoS 2 thin film or directly serves as the synthetic substrate.…”

“…Owing to the unique physicochemical properties as well as the potential applications in frontier technologies, two-dimensional materials (2DM) have aroused wide concerns from both fundamental and practical researches. [1][2][3][4][5][6][7][8][9] Thin MoS 2 films, being one representative member of the 2DM family, have been demonstrated with tunable bandgap, modulatable photoluminescence, superior in-plane conductivity and wafer-scale growth possibility, [10][11][12][13][14] and thus provoked large interests in constructing Here in this work, we have systematically investigated the morphological effect of the SrTiO 3 substrate over the photoluminescence property of the fabricated MoS 2 adlayer. The SrTiO 3 is an attractive metal oxide material owing to its distinctively layered structure, high dielectric constant, and quantum paraelectricity.…”