arXiv subjects

J. David Carey

Publications and source records attributed to J. David Carey.

3 recordsLinked to original sources

arXiv2021

Spin echo from erbium implanted silicon

Erbium implanted silicon as a quantum technology platform has both telecommunications and integrated circuit processing compatibility. In Si implanted with Er to a concentration of 3x10^17 cm^3 and O to a concentration of 10^20 cm^3, the electron spin coherence time, T2, and the spin-lattice relaxation time, T1, were measured to be 7.5 ls and ~1 ms, respectively, at 5 K. The spin echo decay profile displayed strong modulation, which was consistent with the super-hyperfine interaction between Er3þ and a spin bath of 29Si nuclei. The calculated spectral diffusion time was similar to the measured T2, which indicated that T2 was limited by spectral diffusion due to T1-induced flips of neighboring Er3þ spins. The origin of the echo is an Er center surrounded by six O atoms with monoclinic C1h site symmetry.

cond-mat.mtrl-sci↗

arXiv2020

Erbium implanted silicon for solid-state quantum technologies

Erbium implanted silicon as a quantum technology platform has both telecommunications and integrated circuit (IC) processing compatibility. The electron spin coherence time of Er implanted Si with an Er concentration of 3X1017 cm-3 is measured to be ~10 μs at 5 K and the spin echo decay profile displays strong modulation due to super-hyperfine interaction with 29Si nuclei. Three independent measurements: temperature quenching of photoluminescence (PL), PL lifetime and photo-illuminated electron spin resonance (ESR) all indicate the presence of a previously unreported Er related defect state which can facilitate non-radiative relaxation from the Er exited state. This gives an energy level scheme analogous to that of the diamond NV centre, and implies that optical spin polarisation of the Zeeman ground state and high temperature operation of Er qubits in Er implanted Si may be feasible. The collective coupling strength between a superconducting NbN lumped-element microresonator and Er implanted Si with an Er concentration of 1017 cm-3 at 20 mK was ~ 1 MHz.

cond-mat.mes-hall↗

arXiv2018

Controlled Inertial Cavitation as a Route to High Yield Liquid Phase Exfoliation of Graphene

Ultrasonication is widely used to exfoliate two dimensional (2D) van der Waals layered materials such as graphene. Its fundamental mechanism, inertial cavitation, is poorly understood and often ignored in ultrasonication strategies resulting in low exfoliation rates, low material yields and wide flake size distributions, making the graphene dispersions produced by ultrasonication less economically viable. Here we report that few-layer graphene yields of up to 18% in three hours without introduction of basal plane defects can be achieved by optimising inertial cavitation during ultrasonication. We demonstrate that the yield and the graphene flake dimensions exhibit a power law relationship with inertial cavitation dose. Furthermore, inertial cavitation is shown to preferentially exfoliate larger graphene flakes which causes the exfoliation rate to decrease as a function of sonication time. This study demonstrates that measurement and control of inertial cavitation is critical in optimising the high yield sonication-assisted aqueous liquid phase exfoliation of size-selected nanomaterials. Future development of this method should lead to the development of high volume flow cell production of 2D van der Waals layered nanomaterials.

cond-mat.mtrl-sci↗