Bulletin of the American Physical Society
APS March Meeting 2017
Volume 62, Number 4
Monday–Friday, March 13–17, 2017; New Orleans, Louisiana
Session S42: Spins and Defects in Si and SiCFocus
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Sponsoring Units: GQI Chair: Pratibha Dev, Howard University Room: 389 |
Thursday, March 16, 2017 11:15AM - 11:51AM |
S42.00001: Creating and Controlling Single Spins in Silicon Carbide Invited Speaker: David Christle Silicon carbide (SiC) is a well-established commercial semiconductor used in high-power electronics, optoelectronics, and nanomechanical devices, and has recently shown promise for semiconductor-based implementations of quantum information technologies. In particular, a set of divacancy-related point defects have improved coherence properties relative to the prominent nitrogen-vacancy center in diamond, are addressable at near-telecom wavelengths, and reside in a material for which there already exist advanced growth, doping, and microfabrication capabilities. These properties suggest divacancies in SiC have compelling advantages for photonics and micromechanical applications, yet their relatively recent discovery means crucial aspects of their fundamental physics for these applications are not well understood. \newline \newline I will review our progress on manipulating spin defects in SiC, and discuss efforts towards isolating and controlling them at the single defect limit[1]. In particular, our most recent experimental results demonstrate isolation and control of long-lived ($\mathrm{T}_2 = 0.9\,\mathrm{ms}$) divacancies in a form of SiC that can be grown epitaxially on silicon. By studying the time-resolved photoluminescence of a single divacancy, we reveal its fundamental orbital structure and characterize in detail the dynamics of its special optical cycle. Finally, we probe individual divacancies using resonant laser techniques and reveal an efficient spin-photon interface with figures of merit comparable to those reported for NV centers in diamond. These results suggest a pathway towards photon-mediated entanglement of SiC defect spins over long distances. \newline \newline [1] D. J. Christle, A. L. Falk, P. Andrich, P. V. Klimov, J. ul Hassan, N. T. Son, E. Janz\'{e}n, T. Ohshima, and D. D. Awschalom, Nature Materials \textbf{14}, 160–163 (2015). [Preview Abstract] |
Thursday, March 16, 2017 11:51AM - 12:03PM |
S42.00002: Spin-photon entanglement interfaces based on silicon carbide defects Sophia Economou, Pratibha Dev There is currently a strong interest in silicon carbide defects, as they emit very close to the telecommunication wavelength, making them excellent candidates for long-range quantum communications. In this work we develop explicit protocols for spin-photon entanglement interfaces in several SiC defects: the silicon monovacancy, the silicon divacancy, and the NV center. Distinct approaches are given for (i) single-photon and spin entanglement and (ii) the generation of long strings of entangled photons. The latter are known as graph states and comprise a resource for measurement based quantum information processing. [Preview Abstract] |
Thursday, March 16, 2017 12:03PM - 12:15PM |
S42.00003: Deterministic generation of all-photonic quantum repeaters Donovan Buterakos, Edwin Barnes, Sophia Economou Quantum repeaters are nodes in a quantum communication network that allow reliable transmission of entanglement over large distances. It was recently shown that highly entangled photons in so-called graph states can be used for all-photonic quantum repeaters, which overcome some of the challenges of atomic-memory based repeaters.~We present a protocol for the deterministic generation of large repeater graph states using quantum emitters such as semiconductor quantum dots and defect centers in solids. Our protocol has a built-in redundancy which makes it resilient to photon loss. [Preview Abstract] |
Thursday, March 16, 2017 12:15PM - 12:27PM |
S42.00004: Spin and Optical Properties of the V1 Silicon Vacancy Defect in Silicon Carbide at Low Temperature Roland Nagy, Matthias Widmann, Matthias Niethammer, Ilja Gerhardt, Takeshi Oshima, Nguyen Tien Son, Ivan G. Ivanov, Sophia Economou, Cristian Bonato, Sang Yun Lee, J\"org Wrachtrup Silicon carbide (SiC), a technologically-relevant wide-bandgap semiconductor, offers spin-active color-centers and features very long electronic spin coherence times [1,2] which potentially can be applied for sensing [3]. According to Kramers theorem, the degeneracy of S$=$3/2 spin sublevels cannot be broken by strain and electric fields, thereby providing a robust spin-photon interface [4]. In this study, we will investigate the properties of the silicon vacancy in 4H-SiC. In particular, we will present optical spectroscopic study for the two zero phonon lines known as V1 and V1'. Additionally, we will show coherent optical and spin properties of the V1 and V1' line and discuss the possibility of the V1-defect as a qubit for quantum computing and communication. [1] Luke Gordon et al., MRS Bulletin, 38, 802 (2013) [2] M. Widmann et al., Nat. Mater. 14, 164 (2015) [3] B. Grotz et al., New J. Phys. 13, (2011) [4] O. O. Soykal et al., Phys. Rev. B 93, 081207(R) (2016)) [Preview Abstract] |
Thursday, March 16, 2017 12:27PM - 1:03PM |
S42.00005: Resonant optical spectroscopy and coherent control of Cr$^{\mathrm{4+}}$ spin ensembles in SiC and GaN Invited Speaker: William Koehl Spins bound to point defects have emerged as an important resource in quantum information and spintronic technologies, especially as new materials systems have been developed that enable robust and precise quantum state control via optical, electronic, or mechanical degrees of freedom. In an effort to broaden the range of materials platforms available to such defect-based quantum technologies, we have recently begun exploring optically active transition metal ion spins doped into common wide-bandgap semiconductors. The spins of such ions are derived in part from unpaired $d$ orbital electron states, suggesting in some cases that they may be portable across multiple materials systems. This in contrast to many vacancy-related defect spins such as the diamond nitrogen vacancy center or silicon carbide divacancy, which are formed primarily from the dangling bond states of the host. Here we demonstrate ensemble optical spin polarization and time-resolved optically detected magnetic resonance (ODMR) of the $S=$ 1 electronic ground state of chromium (Cr$^{\mathrm{4+}})$ impurities in silicon carbide (SiC) and gallium nitride (GaN) [1]. We find that these impurities possess narrow optical linewidths (\textless 8.5 GHz at cryogenic temperatures) that allow us to optically resolve the magnetic sublevels of the spins even when probing a large ensemble of many ions simultaneously. This enables us to directly polarize and probe the Cr$^{\mathrm{4+}}$ spins using straightforward optical techniques, which we then combine with coherent microwave excitation in order to characterize the dynamical properties of the ensemble. Significantly, these near-infrared emitters also possess exceptionally weak phonon sidebands, ensuring that \textgreater 73{\%} of the overall optical emission is contained within the defects' zero-phonon lines. These characteristics make the Cr$^{\mathrm{4+}}$ ion system a promising target for further study in the ongoing effort to integrate optically active quantum states within common optoelectronic materials. [1] W. F. Koehl, B. Diler, S. J. Whiteley, A. Bourassa, N. T. Son, E. Janz\'{e}n, and D. D. Awschalom, arXiv:1608.08255. [Preview Abstract] |
Thursday, March 16, 2017 1:03PM - 1:15PM |
S42.00006: Electrical Excitation of Silicon Vacancies in 4H SiC Jordan Stroman, Evelyn Hu, Gary Harris The Silicon Vacancy in 4H Silicon Carbide (SiC) can serve as a single photon source. In this presentation I will describe my work to electrically excite an ensemble of Silicon Vacancies. A 4H SiC pn junction was irradiated with electrons and then a mesa structure was fabricated to probe this junction. I will describe the effects of this irradiation on the electroluminescence spectrum of this junction under forward and reverse bias conditions, as well as after annealing the junction at 200C, 500C, and 1000C. [Preview Abstract] |
Thursday, March 16, 2017 1:15PM - 1:27PM |
S42.00007: Charge state control of divacancy spin defects in 4H-SiC Gary Wolfowicz, Andrew L. Yeats, David D. Awschalom Defect spin states in silicon carbide (SiC) offer a platform for exploring quantum information science in a technologically-relevant material amenable to wafer-scale fabrication. Neutral divacancies ($VV^0$) are particularly attractive for their optically-addressable spin states and long spin coherence times. We investigate the charge state dynamics of ensemble divacancies in 4H-SiC using a wide range of optical excitations between the $VV^0$ zero-phonon line ($\approx$ 1 eV) and the bulk bandgap ($\approx$ 3.2 eV). At short wavelengths we observe a strong enhancement of the $VV^0$ population through both PL and ODMR measurements, which we ascribe to charge conversion. In addition, we also probe the charge state dynamics and lifetimes using two- and three-color pulsed experiments. In the dark, charge state conversion persists on a timescale of hours, increasing the ODMR intensity without any effect on the spin coherence time. Under illumination, the charge state is reshuffled to a wavelength-dependent steady state on a timescale between milliseconds and minutes, depending on the optical power. [Preview Abstract] |
Thursday, March 16, 2017 1:27PM - 1:39PM |
S42.00008: Studying the surface diffusion of Al on H:Si(100) for STM lithography Hyun-Soo Kim, A.N. Ramanayaka, Ke Tang, J.M. Pomeroy The surface diffusion of elemental Al on hydrogen passivated Si(100) (H:Si(100)) is studied to identify a process window for acceptor-based nano-devices using scanning tunneling microscope (STM). Previous study and our work on elemental Al show high density of undesirable Al nuclei on hydrogen masking that may cause current paths through the outside of the STM defined regime. The removal of Al nuclei on H:Si(100) by desorbing the hydrogen mask (liftoff) is not successful due to low vapor pressure of Al. In order to fabricate acceptor-based nano-devices with Al using STM lithography, we are examining an alternative approach to reduce the number density of Al nuclei on H:Si(100) surface. We are studying the Al diffusion on H:Si(100) to reduce the number density of Al nuclei by decreasing the Al deposition rate. With low enough density of undesirable Al nucleus on H:Si(100) to isolate STM patterned devices, STM lithography with Al could enable fabrication and study of acceptor-based nano-devices with atomic precision. [Preview Abstract] |
Thursday, March 16, 2017 1:39PM - 1:51PM |
S42.00009: Development of Atomically Precise Low Dimensional Wires and Tunnel Junctions for Quantum Information and Metrology M. D. Stewart, Jr., J. M. Pomeroy, Curt A. Richter, Richard M. Silver, Neil M. Zimmerman, K. J. Dwyer, Joseph A. Hagmann, Binhui Hu, Hyun-soo Kim, Roy Murray, Pradeep Namboodiri, A. N. Ramanayaka, Ryan Stein, Ke Tang, Xiqiao Wang, Johnathon Wyrick Devices consisting of precisely placed phosphorus atoms in silicon fabricated through STM lithography show great promise for quantum information applications due to the intrinsic reproducibility of using single atoms as qubits and the long coherence times measured in the system. Moreover, these devices have applications in traditional computation, dimensional, and electrical metrology. However, fabrication of these devices remains challenging, requiring extremely clean surfaces, high STM pattern fidelity, restricted thermal budgets coupled with high-quality Si epitaxy, accurate alignment between STM and ex-situ fabrication for robust electrical contact, and device modeling. As an initial step toward our goal of fabricating atomically precise devices completely encased in enriched $^{\mathrm{28}}$Si, we present electrical measurements of STM patterned, phosphorus wires of different widths as well as tunnel junctions of differing geometry. We will discuss these results in the context of the materials, fabrication, and metrology challenges above and our methods for overcoming them. [Preview Abstract] |
Thursday, March 16, 2017 1:51PM - 2:03PM |
S42.00010: Optimizing silicon locking layer overgrowth for high-quality phosphorus-doped delta layers Xiqiao Wang, Joseph Hagmann, Pradeep Namboodiri, Jonathan Wyrick, Kai Li, Roy Murray, M.D. Stewart, Jr, Curt Richter, Richard Silver Doped semiconductor structures with ultra-sharp dopant confinement, minimal lattice defect density, and high carrier concentrations are highly desirable in the development of both ultra-scaled conventional semiconductor devices and emerging all-silicon quantum computer architectures. We present a systematic investigation using low temperature locking layers to suppress dopant segregation and diffusion while optimizing dopant confinement, epitaxial growth quality, and transport properties of 2D phosphorus-doped layers. We use secondary ion mass spectroscopy (SIMS), scanning tunneling spectroscopy (STM), transmission electron spectroscopy (TEM), and low-temperature transport measurements to fine-tune the locking layer thickness, growth rate, and thermal anneal to elucidate their respective roles in optimizing the delta layer quality. The dopant segregation and diffusion properties under different locking layer growth conditions were further studied in detail by modeling dopant segregation and diffusion along with implementing a convolution procedure to correct SIMS profiles. [Preview Abstract] |
Thursday, March 16, 2017 2:03PM - 2:15PM |
S42.00011: Quantum metrology with a single spin-3/2 defect in silicon carbide Oney O. Soykal, Thomas L. Reinecke We show that implementations for quantum sensing with exceptional sensitivity and spatial resolution can be made using the novel features of semiconductor high half-spin multiplet defects with easy-to-implement optical detection protocols. To achieve this, we use the spin-$3/2$ silicon monovacancy deep center in hexagonal silicon carbide based on our rigorous derivation of this defect's ground state and of its electronic and optical properties. For a single $\textrm{V}_{\textrm{Si}}^-$ defect, we obtain magnetic field sensitivities capable of detecting individual nuclear magnetic moments. We also show that its zero-field splitting has an exceptional strain and temperature sensitivity within the technologically desirable near-infrared window of biological systems. Other point defects, i.e. 3d transition metal or rare-earth impurities in semiconductors, may also provide similar opportunities in quantum sensing due to their similar high spin ($S\geq 3/2$) configurations. [Preview Abstract] |
Thursday, March 16, 2017 2:15PM - 2:27PM |
S42.00012: Electron Paramagnetic Resonance Spectroscopy of Hyperfine Structure of Er:YSO using Josephson Bifurcation Amplifier Rangga P Budoyo, Kosuke Kakuyanagi, Hiraku Toida, Yuichiro Matsuzaki, William J Munro, Hiroshi Yamaguchi, Shiro Saito We introduce a scheme to perform electron paramagnetic resonance (EPR) spectroscopy by measuring the induced magnetization using a tunable Josephson Bifurcation Amplifier (JBA). This scheme allows us to perform EPR spectroscopy over a relatively wide range of frequency and magnetic field. Using this scheme, we perfomed continuous wave EPR spectroscopy of an erbium-doped yttrium orthosilicate crystal (Er:YSO) at 200 mK for magnetic fields between 0.3 and 6.5 mT and frequencies between 0.1 and 5.2 GHz. We observed multiple transitions within the range of measurement. The observed spectra agree well with the simulated spectrum, taking into account the hyperfine and quadrupole interactions of $^{167}$Er. The sensitivity and sensing volume of this scheme is estimated to be about $\approx 7000$ spins$/\sqrt{Hz}$ and $\approx 0.15$ pl, respectively. [Preview Abstract] |
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