Substrate strain theory

Free-standing semiconductor nanorods grown on lattice-mismatched substrates have become of interest as novel devices, including solar cells. Here, we study the effect of substrate strain on the critical diameter for defect-free growth of free-standing nanorods using continuum elasticity theory. Unlike a thin film, nanorods release strain by relaxing in the lateral direction. We find that substrate relaxation is crucial for defect-free growth of InAs nanorods fabricated on GaAs. The calculation results show that below a critical diameter, the nanorods can grow to infinite length without emitting dislocations. Our findings lend support to the recent experimental efforts to grow defect-free arrays of nanorods providing improved absorption efficiency for next-generation solar cell technology.

• Article • • 02 March 2020 Efficient strain modulation of 2D materials via polymer encapsulation • • • • • • • • • • • • • ORCID: orcid.org/0000-0001-8627-0498 • ORCID: orcid.org/0000-0003-1325-2410 • • ORCID: orcid.org/0000-0002-4321-6288 • … • Show authors Nature Communications volume 11, Article number: 1151 ( 2020) Strain engineering is a promising method to manipulate the electronic and optical properties of two-dimensional (2D) materials. However, with weak van der Waals interaction, severe slippage between 2D material and substrate could dominate the bending or stretching processes, leading to inefficiency strain transfer. To overcome this limitation, we report a simple strain engineering method by encapsulating the monolayer 2D material in the flexible PVA substrate through spin-coating approach. The strong interaction force between spin-coated PVA and 2D material ensures the mechanical strain can be effectively transferred with negligible slippage or decoupling. By applying uniaxial strain to monolayer MoS 2, we observe a higher bandgap modulation up to ~300 meV and a highest modulation rate of ~136 meV/%, which is approximate two times improvement compared to previous results achieved. Moreover, this simple strategy could be well extended to other 2D materials such as WS 2 or WSe 2, leading to enhanced bandgap modulation. The two-dimensional (2D) materials have attracted considerable attention in recent years, owing to their unique electrical, optical, and mecha...

• Article • • 03 November 2021 Substrate strain tunes operando geometric distortion and oxygen reduction activity of CuN 2C 2 single-atom sites • • • • • ORCID: orcid.org/0000-0003-0628-5222 • ORCID: orcid.org/0000-0001-6971-0797 • ORCID: orcid.org/0000-0001-8699-8294 • ORCID: orcid.org/0000-0002-7504-031X • ORCID: orcid.org/0000-0003-0547-7724 • • … • Show authors Nature Communications volume 12, Article number: 6335 ( 2021) Single-atom catalysts are becoming increasingly significant to numerous energy conversion reactions. However, their rational design and construction remain quite challenging due to the poorly understood structure–function relationship. Here we demonstrate the dynamic behavior of CuN 2C 2 site during operando oxygen reduction reaction, revealing a substrate-strain tuned geometry distortion of active sites and its correlation with the activity. Our best CuN 2C 2 site, on carbon nanotube with 8 nm diameter, delivers a sixfold activity promotion relative to graphene. Density functional theory and X-ray absorption spectroscopy reveal that reasonable substrate strain allows the optimized distortion, where Cu bonds strongly with the oxygen species while maintaining intimate coordination with C/N atoms. The optimized distortion facilitates the electron transfer from Cu to the adsorbed O, greatly boosting the oxygen reduction activity. This work uncovers the structure–function relationship of single-atom catalysts in terms of carbon substrate, and provides gui...