Anisotropic Strain Engineering Research Articles

Uniaxial Strain Engineering via Core Position Control in CdSe/CdS Core/Shell Nanorods and Their Optical Response.

Anisotropic strain engineering has emerged as a powerful strategy for enhancing the optoelectronic performance of semiconductor nanocrystals. Here, we show that CdSe/CdS dot-in-rod structures offer a platform for fine-tuning the optical response of CdSe quantum dots through anisotropic strain. By controlling the spatial position of the CdSe core within a growing CdS nanorod shell, varying degrees of uniaxial strain can be introduced. Placing CdSe cores at the end of the CdS nanorod induces strong asymmetric compression along the c-axis of the wurtzite CdSe core, dramatically altering its absorption and emission characteristics, whereas CdSe cores located near the middle of the nanorod experience a comparatively weak uniaxial strain field. The change in absorption and emission spectra and dynamics for highly strained end-position CdSe/CdS nanorods is explained by (1) relative shifting of the valence band light hole and heavy hole levels and (2) introduction of a strong piezoelectric potential, which spatially separates the electron and hole wave functions. The ability to tune the degree of uniaxial strain through core position control in a nanorod structure creates opportunities for precisely modulating the electronic properties of CdSe nanocrystals while simultaneously taking advantage of dielectric and optical anisotropies intrinsic to 1D nanostructures.

Uniaxial Néel vector control in perovskite oxide thin films by anisotropic strain engineering

Antiferromagnetic (AF) thin films typically exhibit a multidomain state, and control of the AF N\'eel vector is challenging, as AF materials are robust to magnetic perturbations. In this paper, uniaxial N\'eel vector control is demonstrated by relying on anisotropic strain engineering of epitaxial thin films of the prototypical AF material ${\mathrm{LaFeO}}_{3}$ (LFO). Orthorhombic (011)- and (101)-oriented ${\mathrm{DyScO}}_{3}$, ${\mathrm{GdScO}}_{3}$, and ${\mathrm{NdGaO}}_{3}$ substrates are used to engineer different anisotropic in-plane strain states. The anisotropic in-plane strain stabilizes structurally monodomain monoclinic LFO thin films. The uniaxial N\'eel vector is found along the tensile strained $b$ axis, contrary to bulk LFO having the N\'eel vector along the shorter $a$ axis, and no magnetic domains are found. Hence, anisotropic strain engineering is a viable tool for designing unique functional responses, further enabling AF materials for mesoscopic device technology.

Accurate Control of Core–Shell Upconversion Nanoparticles through Anisotropic Strain Engineering

AbstractThe effect of anisotropic interfacial strain on epitaxial growth and optical emission of sodium rare‐earth fluoride core–shell nanoparticles is investigated. A variety of sodium rare‐earth fluoride shells are grown on hexagonal‐phase NaYF4:Yb/Er core for providing anisotropic tuning of interfacial strains. Using high‐resolution transmission electron microscopy and X‐ray diffraction characterizations, the correlations between the epitaxial habits and the interfacial strains are quantitatively addressed. Furthermore, the growth affinity is tuned by controlling precursor concentration in conjunction with Ca2+ doping, which results in accurate regulation of the anisotropic growth. The lattice strain resulting from mismatched epitaxy is found to enhance luminescence response of the nanoparticles to temperature change.

Energy-tunable sources of entangled photons: a viable concept for solid-state-based quantum relays.

We propose a new method of generating triggered entangled photon pairs with wavelength on demand. The method uses a microstructured semiconductor-piezoelectric device capable of dynamically reshaping the electronic properties of self-assembled quantum dots (QDs) via anisotropic strain engineering. Theoretical models based on k·p theory in combination with finite-element calculations show that the energy of the polarization-entangled photons emitted by QDs can be tuned in a range larger than 100meV without affecting the degree of entanglement of the quantum source. These results pave the way towards the deterministic implementation of QD entanglement resources in all-electrically-controlled solid-state-based quantum relays.