Second harmonic generation in two-dimensional transition metal dichalcogenides with growth and post-synthesis defects
- 17 August 2020
- journal article
- research article
- Published by IOP Publishing in 2D Materials
- Vol. 7 (4), 045020
- https://doi.org/10.1088/2053-1583/aba564
Abstract
Strong second harmonic generation (SHG) in monolayer transition metal dichalcogenides demonstrates great promise for nonlinear photonic applications. However, to utilize these materials in photonic applications, it is imperative to investigate the robustness of the nonlinear optical properties against various defects introduced during or post synthesis. Here we study the SHG in hexagonal monolayer WS2 with synthesis defects, in triangular monolayer WS2 with focused ion beam induced structural defects, and in WS2 under ambient and aqueous environmental conditions. We find that WS2 hexagonal monolayers exhibit significantly more uniform SHG intensity across the sample with a coefficient of variation, c(v) = 4.9% than the varying photoluminescence (PL) intensity (c(v) = 32.83%). We also show that introducing structural defects in WS2 monolayers leads to diminishing, but not vanishing SHG. To further explore the robustness of SHG in comparison with PL, we show that aged WS2 monolayers have greatly varying PL across different samples (c(v) = 35.6%), while exhibiting much more uniform SHG (c(v) = 8.31%). Lastly, we find that WS2 monolayers submerged in deionized water shows similar intensity in SHG signal. To understand these experimental results, density functional theory calculations have been performed. Our analysis suggests that potential defects and water introduced to the WS2 monolayers produce relatively little change in the second-order nonlinear susceptibility, whereas nonradiative recombination caused by these defects can significantly affect the PL. These results show a good qualitative agreement with the experimental results.Keywords
Funding Information
- National Science Foundation (EFRI 1433311)
This publication has 44 references indexed in Scilit:
- Identification of individual and few layers of WS2 using Raman SpectroscopyScientific Reports, 2013
- Atomically Thin: A New Direct-Gap SemiconductorPhysical Review Letters, 2010
- Implementation of the projector augmented-wave method in the ABINIT code: Application to the study of iron under pressureComputational Materials Science, 2007
- The rise of grapheneNature Materials, 2007
- Second-Harmonic Optical Response from First PrinciplesPhysica Scripta, 2004
- From ultrasoft pseudopotentials to the projector augmented-wave methodPhysical Review B, 1999
- Projector augmented-wave methodPhysical Review B, 1994
- Full-band-structure calculation of ε(ω) and χ(-2ω;ω,ω) for (GaAs/(GaP (n=1,2) superlattices on GaAs(001) substratesPhysical Review B, 1992
- Full-band-structure calculation of second-harmonic generation in odd-period strained (Si/(GesuperlatticesPhysical Review B, 1991
- Linear and nonlinear optical properties of (GaAs/(AlAssuperlatticesPhysical Review B, 1991