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The use of superconducting microresonators together with quantum-limited Josephson parametric amplifiers has enhanced the sensitivity of pulsed electron spin resonance (ESR) measurements by more than four orders of magnitude. So far, the microwave resonators and amplifiers have been designed as separate components due to the incompatibility of Josephson junction–based devices with magnetic fields. This has produced complex spectrometers and raised technical barriers toward adoption of the technique. Here, we circumvent this issue by coupling an ensemble of spins directly to a weakly nonlinear and magnetic field–resilient superconducting microwave resonator. We perform pulsed ESR measurements with a 1-pL mode volume containing 6 × 10 7 spins and amplify the resulting signals within the device. When considering only those spins that contribute to the detected signals, we find a sensitivity of 2.8 × 1 0 3 spins / Hz for a Hahn echo sequence at a temperature of 400 mK. In situ amplification is demonstrated at fields up to 254 mT, highlighting the technique’s potential for application under conventional ESR operating conditions.

The steady-state, space-charge-limited piezoresistance (PZR) of defect-engineered, silicon-on-insulator device layers containing silicon divacancy defects changes sign as a function of applied bias. Above a punch-through voltage ($V_t$) corresponding to the onset of a space-charge-limited hole current, the longitudinal $\langle 110 \rangle$ PZR $\pi$-coefficient is $\pi \approx 65 \times 10^{-11}$~Pa$^{-1}$, similar to the value obtained in charge-neutral, p-type silicon. Below $V_t$, the mechanical stress dependence of the Shockley-Read-Hall (SRH) recombination parameters, specifically the divacancy trap energy $E_T$ which is estimated to vary by $\approx 30$~$\mu$V/MPa, yields $\pi \approx -25 \times 10^{-11}$~Pa$^{-1}$. The combination of space-charge-limited transport and defect engineering which significantly reduces SRH recombination lifetimes makes this work directly relevant to discussions of giant or anomalous PZR at small strains in nano-silicon whose characteristic dimension is larger than a few nanometers. In this limit the reduced electrostatic dimensionality lowers $V_t$ and amplifies space-charge-limited currents and efficient SRH recombination occurs via surface defects. The results reinforce the growing evidence that in steady state, electro-mechanically active defects can result in anomalous, but not giant, PZR., Comment: 9 pages, 8 figures

Electrodes in close proximity to an active area of a device are required for sufficient electrical control. The integration of such electrodes into optical devices can be challenging since low optical losses must be retained to realise high quality operation. Here, we demonstrate that it is possible to place a metallic shallow phosphorus doped layer in a silicon micro-ring cavity that can function at cryogenic temperatures. We verify that the shallow doping layer affects the local refractive index while inducing minimal losses with quality factors up to 10$^5$. This demonstration opens up a pathway to the integration of an electronic device, such as a single-electron transistor, into an optical circuit on the same material platform., Comment: 6 figures

In this paper we use electrically detected optical excitation spectroscopy of individual erbium ions in silicon to determine their optical and paramagnetic properties simultaneously. We demonstrate that this high spectral resolution technique can be exploited to observe interactions typically unresolvable in silicon using conventional spectroscopy techniques due to inhomogeneous broadening. In particular, we resolve the Zeeman splitting of the 4I15/2 ground and 4I13/2 excited state separately and in strong magnetic fields we observe the anti-crossings between Zeeman components of different crystal field levels. We discuss the use of this electronic detection technique in identifying the symmetry and structure of erbium sites in silicon., 6 pages, 4 figures

Silicon chips containing arrays of single dopant atoms could be the material of choice for both classical and quantum devices that exploit single donor spins. For example, group-V-donors implanted in isotopically purified 28 Si crystals are attractive for large-scale quantum computers. Useful attributes include long nuclear and electron spin lifetimes of 31 P, hyperfine clock transitions in 209 Bi or electrically controllable 123 Sb nuclear spins. Promising architectures require the ability to fabricate arrays of individual near-surface dopant atoms with high yield. Here we employ an on-chip detector electrode system with 70 eV r.m.s. noise (∼ 20 electrons) to demonstrate near room temperature implantation of single 14 keV 31 P+ ions. The physics model for the ion-solid interaction shows an unprecedented upper-bound single ion detection confidence of 99.85±0.02% for near-surface implants. As a result, the practical controlled silicon doping yield is limited by materials engineering factors including surface gate oxides in which detected ions may stop. For a device with 6 nm gate oxide and 14 keV 31 P+ implants we demonstrate a yield limit of 98.1%. Thinner gate oxides allow this limit to converge to the upper-bound. Deterministic single ion implantation can therefore be a viable materials engineering strategy for scalable dopant architectures in silicon devices. This article is protected by copyright. All rights reserved.

Spin-qubits based on impurities such as phosphorus in silicon (Si) have attractive attributes for the development of quantum computing devices. Very long coherence times can be achieved for donor-based qubits in Si due to the availability of isotopically pure 28Si layers where the 29Si atoms, which otherwise lead to decoherence, are largely absent in the active region of the device. Well-behaved single donor qubits in Si can routinely be formed using ion implantation, and the key performance criteria needed to demonstrate the basis of a viable platform for quantum computing have been achieved. The crucial next stage of development is to demonstrate suitable pathways for scale-up that allow patterned arrays of donor qubits to be controllably coupled and that are robust against the inherent donor placement tolerances and material processing constraints that exist. Here, we review progress on the fabrication and measurement of donor-based qubits in silicon via the ion implantation pathway and discuss the key developmental milestones that have been achieved. We also provide an overview of the key scale-up strategies that are being actively pursued to take donor-based quantum computing in Si to the next stage.

The bismuth (Bi) substitutional donor in silicon (Si) is an attractive qubit candidate for quantum computing proposals due to its large Hilbert space, clock transitions, and potential to couple to superconducting flux qubits. Single-qubit control, coupling, and readout by surface nanocircuitry requires a Bi depth of ∼20 nm in Si. This can be achieved using ion implantation of ∼25 keV Bi. This work explores the activation properties of Bi implanted at 26 keV with fluences of 1×1014 and 6×1012cm-2 into both crystalline and preamorphized Si. The Bi electrical activation yield was measured over a broad range of annealing conditions using resistivity and Hall effect measurements, enabling optimal annealing strategies to be proposed for the different implant parameters. For the high and low fluences, the maximum Bi activation yields achieved were 64% and 46%, respectively. Above a critical thermal budget, a substantial fraction of Bi forms electrically inactive complexes in the high fluence sample only. The substitutional fraction and diffusion of high fluence Bi was quantified, with diffusion coefficients D0=4.0±0.5 and 7.5±0.5cm2s-1 found for implantation into crystalline and preamorphized Si, respectively, using Rutherford backscattering spectrometry. To demonstrate the successful activation and quantum control of near-surface implanted Bi, the full hyperfine spectrum of these donors is obtained using continuous-wave electron spin resonance at 25 K, supporting the suitability for Bi donor qubits.

Nuclear spins are highly coherent quantum objects. In large ensembles, their control and detection via magnetic resonance is widely exploited, for example, in chemistry, medicine, materials science and mining. Nuclear spins also featured in early proposals for solid-state quantum computers

We analyze the electron spin relaxation rate $1/T_1$ of individual ion-implanted $^{31}$P donors, in a large set of metal-oxide-semiconductor (MOS) silicon nanoscale devices, with the aim of identifying spin relaxation mechanisms peculiar to the environment of the spins. The measurements are conducted at low temperatures ($T\approx 100$~mK), as a function of external magnetic field $B_0$ and donor electrochemical potential $��_{\rm D}$. We observe a magnetic field dependence of the form $1/T_1\propto B_0^5$ for $B_0\gtrsim 3\,$ T, corresponding to the phonon-induced relaxation typical of donors in the bulk. However, the relaxation rate varies by up to two orders of magnitude between different devices. We attribute these differences to variations in lattice strain at the location of the donor. For $B_0\lesssim 3\,$T, the relaxation rate changes to $1/T_1\propto B_0$ for two devices. This is consistent with relaxation induced by evanescent-wave Johnson noise created by the metal structures fabricated above the donors. At such low fields, where $T_1>1\,$s, we also observe and quantify the spurious increase of $1/T_1$ when the electrochemical potential of the spin excited state $|\uparrow\rangle$ comes in proximity to empty states in the charge reservoir, leading to spin-dependent tunneling that resets the spin to $|\downarrow\rangle$. These results give precious insights into the microscopic phenomena that affect spin relaxation in MOS nanoscale devices, and provide strategies for engineering spin qubits with improved spin lifetimes., 14 pages, 8 figures. Version 2 has extensive text revisions, typo corrections, and two extra authors

A giant, anomalous piezo-response of fully-depleted silicon-on-insulator (FD-SOI) devices under mechanical stress is demonstrated using impedance spectroscopy. This piezo-response strongly depends on the measurement frequency, $\omega$, and consists of both a piezoresistance (PZR) and piezocapacitance whose maximum values are $\pi_R = -1100 \times 10^{-11}$ Pa$^{-1}$ and $\pi_C = -900 \times 10^{-11}$ Pa$^{-1}$ respectively. These values should be compared with the usual bulk PZR in p-type silicon, $\pi_R= 70 \times 10^{-11}$ Pa$^{-1}$. The observations are well described using models of space charge limited electron and hole currents in the presence of fast electronic traps having stress-dependent capture ($\omega_c$) and emission rates. Under steady-state conditions (i.e. when $\omega \ll \omega_c$) where the impedance spectroscopy measurements yield results that are directly comparable with previously published reports of PZR in depleted, silicon nano-objects, the overall piezo-response is just the usual, bulk silicon PZR. Anomalous PZR is observed only under non-steady-state conditions when $\omega \approx \omega_c$, with a symmetry suggesting that the electro-mechanically active fast traps are native Pb$_0$ interface defects. The observations suggest new functionalities for FD-SOI, and shed light on the debate over the PZR of carrier depleted nano-silicon., Comment: 14 pages with 10 figures including appendices

We present a scalable strategy to manufacture quantum computer devices, by encoding quantum information in the combined electron-nuclear spin state of individual ion-implanted phosphorus dopant atoms in silicon. Our strategy allows a typical pitch between quantum bits of order 200 nm, and retains compatibility with the standard fabrication processes adopted in classical CMOS nanoelectronic devices. We theoretically predict fast and high-fidelity quantum logic operations, and present preliminary experimental progress towards the realization of a “flip-flop” qubit system.

The rhombohedral phase of Si (r8-Si), a promising semiconducting material, is formed by indentation together with the body-centered cubic phase (bc8-Si). Using a novel sample preparation method, x-ray diffraction is used to determine the relative volume of these phases in indented Si and allow observation of a distorted unit cell along the direction of indentation loading. Theoretical calculations together with these observations suggest the indent contains an intrinsic compression of ∼4 GPa that stabilizes the r8 phase.

Continued dimensional scaling of semiconductor devices has driven information technology into vastly diverse applications. As the size of devices approaches fundamental limits, metrology techniques with nanometre resolution and three-dimensional (3D) capabilities are desired for device optimisation. For example, the performance of an ultra-scaled transistor can be strongly influenced by the local electric field and strain. Here we study the spectral response of single erbium ions to applied electric field and strain in a silicon ultra-scaled transistor. Stark shifts induced by both the overall electric field and the local charge environment are observed. Further, changes in strain smaller than $3\times 10^{-6}$ are detected, which is around two orders of magnitude more sensitive than the standard techniques used in the semiconductor industry. These results open new possibilities for non-destructive 3D mapping of the local strain and electric field in the channel of ultra-scaled transistors, using the single erbium ions as ultra-sensitive atomic probes., 10+5 pages, 4+3 figures

We demonstrate a straightforward way to obtain single crystalline SiGe layers on silicon substrates. Amorphous SiGe layers, deposited by plasma enhanced chemical vapour deposition on Si, are transformed into single crystalline and smooth layers by solid phase epitaxy during annealing in a N2 atmosphere. The SiGe layers relax during the crystallization anneal and become slightly tensile strained during cooldown due to the thermal mismatch. The SiGe layers show excellent structural quality for compositions ranging from Ge- to Si-rich. The Ge content can be accurately estimated from the SiH4 to GeH4 flow ratio. Furthermore, the crystallization temperature decreases linearly with increasing Ge content from 725 °C for a-Si to 475 °C for a-Ge.

Novel phases of Si that are predicted to have industrially desirable properties can be recovered after indentation-induced pressure. However, the thermal stability of these phases is not well understood. Furthermore, in the past, different methods of annealing have resulted in conflicting reports on annealing stability and transformation pathways. This study investigates the thermal stability of several metastable Si phases called r8-Si, bc8-Si, hd-Si, and Si-XIII under furnace annealing, incremental annealing, and laser annealing using Raman microspectroscopy and electron diffraction. The temperature range of stability for these metastable phases is thus determined. Of particular interest, hd-Si is stable to a much higher temperature than previously reported, being the predominant phase observed in this study after annealing at 450 °C. This finding was enabled through a new method for confirming the presence of hd-Si by detailed electron diffraction. This high thermal stability generates renewed interest in exploiting this phase for industrial applications, such as strain-tailored solar absorption.

The diffusion of hydrogen in amorphous silicon formed by ion implantation is studied using real-time elastic recoil detection analysis. An activation energy for H diffusion of 1.82 eV is determined in a single ramped anneal. This activation energy is consistent with diffusion studies in the high H concentration regime. The low beam current employed is found to have a negligible influence on the H diffusion within the sensitivity of the measurement. Further refinements for increased accuracy of this technique are discussed.

The presence of boron in silicon has been shown to have a deleterious effect on the luminescence of interstitial-related centres, particularly the W-centre which is often observed after ion implantation and a low temperature anneal. Competition between silicon-interstitial and boron-interstitial centre formation is considered to be a possible mechanism underlying this dramatic reduction. Previous work on silicon implantation of boron-doped substrates is extended to examine the effect of B implantation itself on W-centre formation. W centres formed via the implantation of B and a low temperature anneal and via a Si implant over an activated B-implant profile followed by low temperature anneal are compared. These studies contrast the effects of boron and silicon implantation and examine the effect of overlapping implantation profiles. Studying the effect of boron on optical centre formation provides insight into defect interactions in silicon and new data for theoretical modelling.

The crystallization of amorphous layers via solid phase epitaxy (SPE) is commonly used in semiconductor device fabrication to activate dopants. The kinetics of SPE depend on temperature, dopant and impurity concentration, hydrostatic pressure and crystallographic orientation. The effect of H on SPE in both Si and Ge is discussed. Numerical simulations are performed to model the H diffusion, the moving amorphous/crystalline interfaces and the refinement of the II profile at these interfaces. Despite the high H concentration involved, a simple Fickian diffusion model results in good agreement with the SIMS data. A significant fraction of the H escapes from the a-Si layer during SPE and becomes trapped at end of range defects. The light-emitting properties of these defects are investigated. Finally, the formation of germanides via SPE is discussed. ©The Electrochemical Society.

A deep level transient spectroscopy (DLTS) study of defects created by low-fluence, low-energy ion implantation for development of ion-implanted silicon field-effect transistors for spin-dependent transport experiments is presented. Standard annealing strategies are considered to activate the implanted dopants and repair the implantation damage in test metal-oxide-semiconductor (MOS) capacitors. Fixed oxide charge, interface trapped charge and the role of minority carriers in DLTS are investigated. A furnace anneal at 950 $\rm ^{o}$C was found to activate the dopants but did not repair the implantation damage as efficiently as a 1000 $\rm ^{o}$C rapid thermal anneal. No evidence of bulk traps was observed after either of these anneals. The ion- implanted spin-dependent transport device is shown to have expected characteristics using the processing strategy determined in this study., 4 pages, 6 figures

In this paper, we present preliminary results of a deep level transient spectroscopy study of the charge traps produced as a function of implantation angle for 70 keV H ions implanted into n-type Si(1 0 0) crystals. The defect types, concentrations and their depth profiles are examined as a function of implantation angle. The experimental results are also compared to the vacancy profiles predicted by the Monte-Carlo binary collision code, Crystal-TRIM. The results of this light ion study are compared and contrasted with those of previous studies.

We have used the classical Hall effect to electrically characterize Indium Tin Oxide (ITO) films grown by two different techniques on silica substrates. ITO films have the unique property that they can be both electrically conducting (and to be used for a gate electrode for example) as well as optically transparent (at least in the visible part of the spectrum). In the near infrared (NIR) the transmission typically reduces. However, the light absorption can in principle be compensated by growing thinner films., 2 pages Optoelectronic and Microelectronic Materials & Devices (COMMAD), 2014 Conference

We review the field of solid-phase epitaxy (SPE), a crystallization process during which atoms undergo bonding rearrangements that allow them to transfer from a metastable amorphous phase to a crystalline phase using the substrate as a template. This process is commonly used to activate an implanted dopant profile on a low thermal budget, often to concentrations much greater than the dopant’s solid solubility limit. Two model systems with great technological importance are used to discuss SPE: silicon and germanium. The well-characterized dependence of SPE on various experimental parameters are considered in detail as well as kinetic models that predict the SPE velocity associated with the crystal-amorphous interface motion. Atomistic models are also reviewed and are shown to provide great insight into the possible mechanisms responsible for the process. Observations of technological interest to current and future semiconductor device fabrication are also discussed, including dopant activation and defect formation.

Silicon has dominated the microelectronics industry for the last 50 years. With its zero nuclear spin isotope (28Si) and low spin orbit coupling, it is believed that silicon can become an excellent host material for an entirely new generation of devices that operate under the laws of quantum mechanics [1}. Semiconductor nanowires however, offer huge potential as the next building blocks of nano-devices due to their one-dimensional structure and properties [2]. We describe a fabrication process to prepare doped vapor-liquid-solid (VLS) grown silicon nanowire samples in a 2- and 4-terminal measurement setup for electrical characterisation., 2 pages Optoelectronic and Microelectronic Materials & Devices (COMMAD), 2014 Conference

Using silicon MOSFETs with thin (5nm) thermally grown SiO2 gate dielectrics, we characterize the density of electrically active traps at low-temperature after 16keV phosphorus ion-implantation through the oxide. We find that, after rapid thermal annealing at 1000oC for 5 seconds, each implanted P ion contributes an additional 0.08 plus/minus 0.03 electrically active traps, whilst no increase in the number of traps is seen for comparable silicon implants. This result shows that the additional traps are ionized P donors, and not damage due to the implantation process. We also find, using the room temperature threshold voltage shift, that the electrical activation of donors at an implant density of 2x10^12 cm^-2 is ~100%.

The kinetics of solid phase epitaxy (SPE) in surface amorphous silicon layers doped with a single arsenic profile have been examined in relation to the generalized Fermi level shifting model of the SPE growth process. The model has been extended to include passivation by hydrogen of the defects responsible for SPE and∕or passivation of dopant atoms. A previous study has suggested that the asymmetry between the dopant-enhanced SPE rate and the arsenic concentration profile is due to the infiltration of hydrogen from the surface oxide. Theoretical calculations of the dopant-enhanced SPE rate compare well with experiment if it is assumed that the indiffusing hydrogen passivates some of the SPE defects and∕or some of the dopant atoms.

The kinetics of intrinsic and arsenic-enhanced solid phase epitaxy (SPE) have been measured in buried amorphous Si (a-Si) layers in which crystallization occurs free from the rate retarding effects of hydrogen. Surface a-Si layers, where H infiltration can occur during crystallization, have also been studied. A single 1.45×1016 As/cm2 implant at 1200 keV was used to form an As concentration profile with a peak concentration of 3×1020 As/cm3 centered at 8000 A beneath the crystal surface, allowing many different enhanced SPE rates to be examined simultaneously. The SPE rate through this profile and its intrinsic counterpart were measured using time-resolved reflectivity. The effects of hydrogen on the SPE rate can be determined by a comparison between the buried and surface a-Si layers. For the surface a-Si layers, it was found that the As-enhanced SPE rate versus depth curve is offset with respect to the concentration profile. We attribute this offset to the H infiltration in the case of the surface a-Si ...

Damage was introduced into Si(100) using 245 keV Si+ ions implanted to a wide range of doses with implant temperatures of −195, 25 or 100 °C. The accumulation of this damage was monitored with Rutherford backscattering and ion channeling (RBS-C) and by following the intensity and lineshape variation of the first-order (1-O) Raman peak of silicon. For all implant temperatures the RBS-C data showed the expected trend with dose. For −195 °C and room temperature implants, the decrease in intensity of the 1-O Raman peak shows a similar trend to the RBS-C data, but in each case the threshold dose is about a decade lower than its RBS-C counterpart. On implantation at 100 °C the sensitivity of the Raman spectra to low damage concentrations is more dramatic and decreases continuously over the full dose range, from 5×1012 to 2×1016 Si/cm2, examined in this study. This suggests that the intensity of the 1-O Raman peak is particularly sensitive to the types of defect structures that are stable in silicon during irrad...

The effect of implantation angle on the profile of the vacancy-phosphorus and divacancy centres (VP/V 2 − ) in n-type 0.7–1.1 Ω cm Cz-grown (1 0 0) Si has been examined using depth profiling with deep-level transient spectroscopy. Samples were mounted with 10° twists from the [1 1 0] direction and various tilts from the [1 0 0] direction then implanted with 600 keV P to a dose of 5×10 8 cm −2 . The peak depth of the VP/V 2 − profile exhibits a systematic variation with the implantation angle: narrowing and increasing in peak concentration as the implantation angle is progressively varied from the aligned direction. The defect profiles are approximately 0.3 μm deeper than the peak in the vacancy profile predicted using the binary collision code Crystal-TRIM. Surface-enhanced annihilation of migrating defects has been considered as the cause of this.

Rutherford backscattering spectroscopy and ion channeling and secondary ion mass spectroscopy have been used to study the evolution of a potassium profile in amorphous silicon during solid phase epitaxial crystallisation. The potassium profile exhibits some propensity for refinement in front of the crystallising interface for the concentrations used in this experiment. Also, the potassium is partially substitutional in the crystallised layer. Preliminary studies on the influence of potassium on the rate of solid phase epitaxy (SPE) in silicon are presented. Surface amorphous films doped with potassium were crystallised and the rate of epitaxy was monitored using time resolved reflectivity. The inclusion of potassium was found to retard the rate of SPE. These results indicate that potassium doped amorphous films may be helpful in efforts to further refine present models of SPE in silicon.

Solid-phase epitaxy was examined in deep amorphous volumes formed in silicon wafers by multi-energy self-implantation through a mask. Crystallization was effected at elevated temperatures with the amorphous volume being transformed at both lateral and vertical interfaces. Sample topology was mapped using an atomic force microscope. Details of the process were clarified with both plan-view and cross-sectional transmission electron microscopy analyses. Crystallization of the amorphous volumes resulted in the incorporation of a surprisingly large number of dislocations. These arose from a variety of sources. Some of the secondary structures were identified to occur uniquely from the crystallization of volumes in this particular geometry.

Vanadium Dioxide is an optically dense phase change material that has been applied to modulating the resonances of plasmonic structures resonant in the THz, infrared and optical ranges. It has been shown previously that fabrication of optical antennas on thin films of Vanadium Dioxide can result in a resonance shift of more than 10% across the phase change. This post-fabrication, dynamic tuning mechanism has the potential to significantly increase the possible applications of plasmonic devices. Here, we show that optical antenna arrays fabricated on differing thicknesses of Vanadium Dioxide supported by a silicon substrate show a dependence of their resonant wavelengths on this thickness. Along with the geometry of the antennas in the arrays this constitutes an additional degree of freedom in the design of the tuning range of these devices, offering further potential for optimisation of this mechanism. The potential extra blue-shift provided by optimising this thickness may be used, for example, in lieu of reducing antenna dimensions to avoid increasing antenna absorption and the additional plasmonic heating that can result.

The kinetics of intrinsic and dopant-enhanced solid phase epitaxy (SPE) have been measured in the H-free environment provided by buried amorphous Si layers formed by MeV ion implantation. The dopant-enhanced SPE kinetics were studied in buried a-Si layers containing uniform As concentration profiles produced by multiple energy ion implantation to doses spanning the concentration range 1–28×1019 As/cm3 and the crystallisation rates were measured over the temperature range 460–660°C using time-resolved reflectivity. The dopant-enhanced SPE data can be modelled by an extension of the Generalised Fermi Level Shifting model (GFLS) to take into account the degenerate semiconductor statistics on the crystalline Si side of the interface and by estimating the effect of band bending at the amorphous/crystalline (a/c) interface.

The detection of electron spins associated with single defects in solids is a critical operation for a range of quantum information and measurement applications currently under development. To date, it has only been accomplished for two centres in crystalline solids: phosphorus in silicon using electrical readout based on a single electron transistor (SET) and nitrogen-vacancy centres in diamond using optical readout. A spin readout fidelity of about 90% has been demonstrated with both electrical readout and optical readout, however, the thermal limitations of the electrical readout and the poor photon collection efficiency of the optical readout hinder achieving the high fidelity required for quantum information applications. Here we demonstrate a hybrid approach using optical excitation to change the charge state of the defect centre in a silicon-based SET, conditional on its spin state, and then detecting this change electrically. The optical frequency addressing in high spectral resolution conquers the thermal broadening limitation of the previous electrical readout and charge sensing avoids the difficulties of efficient photon collection. This is done with erbium in silicon and has the potential to enable new architectures for quantum information processing devices and to dramatically increase the range of defect centres that can be exploited. Further, the efficient electrical detection of the optical excitation of single sites in silicon is a major step in developing an interconnect between silicon and optical based quantum computing technologies., Corrected the third affiliation. Corrected one cross-reference of "Fig. 3b" to "Fig. 3c". Corrected the caption of Fig. 3a by changing (+-)1 to 0

The formation of R8 germanium is reported. The β-Sn phase is first induced by the indentation of amorphous germanium (a-Ge) and the resultant phases on pressure release are characterized by Raman scattering. The expected Raman line frequencies for the various phases of Ge are determined from first-principles calculations using density functional perturbation theory of the zone-center phonons in the diamond, ST12, BC8, and R8 Ge phases. In addition to the R8 phase, traces of BC8 may also be present following pressure release.

Raman scattering is used to investigate the metastable Si phases formed by indentation. The indent strain, phase distribution and the kinetics of the phase transformations are examined.

We show the photo-ionisation of an individual erbium centre in silicon. A single-electron transistor is used as a charge detector to observe the resonant ionization as a function of photon energy. This allows for optical addressing and electrical detection of individual erbium centres with exceptionally narrow line width.

We have utilised ion implantation to fabricate silicon nanocrystal sensitised erbium-doped slot waveguide structures in a Si/SiO2/Si layered configuration and photoluminescence (PL) and Rutherford backscat-tering spectrometry (RBS) to analyse these structures. Slot waveguide structures in which light is confined to a nanometre-scale low-index region between two high-index regions potentially offer significant advantages for realisation of electrically-pumped Si devices with optical gain and possibly quantum optical devices. We are currently investigating an alternative pathway in which high quality thermal oxides are grown on silicon and ion implantation is used to introduce the Er and Si-ncs into the SiO2 layer. This approach provides considerable control over the Er and Si-nc concentrations and depth profiles which is important for exploring the available parameter space and developing optimised structures. RBS is well-suited to compositional analysis of these layered structures. To improve the depth sensitivity we have used a 1 MeV α beam and results indicate that a layered silicon-Er:SiO 2/silicon structure has been fabricated as desired. In this paper structural results will be compared to Er photoluminescence profiles for samples processed under a range of conditions. © Owned by the authors 2012.

In this work, we present the creation and characterisation of single photon emitters at the surface of 4H-and 6H-SiC, and of 3C-SiC epitaxially grown on silicon. These emitters can be created by annealing in an oxygen atmosphere at temperatures above 550 degrees C. By using standard confocal microscopy techniques, we find characteristic spectral signatures in the visible region. The excited state lifetimes are found to be in the nanosecond regime in all three polytypes, and the emission dipoles are aligned with the lattice. HF-etching is shown to effectively annihilate the defects and to restore an optically clean surface. The defects described in this work have ideal characteristics for broadband single photon generation in the visible spectral region at room temperature and for integration into nanophotonic devices. (C) 2016 AIP Publishing LLC.

Hydrogen blister rates in Si (100), Si (111) and Ge (100) substrates are compared as a function of annealing temperature and time, for a range of implant energies and fluences. For each material, the rate of blister formation was found to exhibit Arrhenius behavior and to be characterised by a single activation energy over the temperature range examined. The extracted activation energies were 2.28±0.03 eV, 2.17±0.06 eV and 1.4±0.03 eV for (100) Si; (111) Si and (100) Ge, respectively. These results are compared with reported measurements and discussed in relation to proposed models of hydrogen blistering.

The effect of intrinsic and applied stress on hydrogen diffusion and trapping are studied by elastic-recoil detection (ERD), Rutherford backscattering and channelling (RBS-C) and transmission electron microscopy (TEM).

The photoluminescence of self-interstitials in silicon produced by ion implantation is investigated. A range of annealing temperatures have been used to follow the evolution of these defects. The effect on the formation of these defects in the presence of B and P dopants is considered. As expected, boron is found to reduce the W-line. Phosphorous also reduces the luminescence but to a lesser extent.

The effect of boron and phosphorous doping and co-doping on the optical properties of silicon nanocrystals formed in fused-silica by ion implantation is being studied. Boron-phosphorus pairs in silicon nanocrystals are of interest for possible applications in optical quantum computing.

Boron ions will be implanted at 150 keV down the axis of n-type silicon. Deep-level transient spectroscopy will be used to study the range, concentration and species of the created defects. A comparison to crystal-TRIM results will be made in order to refine model parameters.

The properties of traps at SiO2/Si and Si3N4/Si interfaces were examined and compared using deep level transient spectroscopy (DLTS). Small pulse DLTS was used to determine the effective electron capture cross-section of the interface states. Similar trends are found for both systems with the capture cross-section decreasing rapidly towards the band edge. The effective capture cross-section and energy level is also given for the Si≡Si3 defect at the Si3N4/Si interface.

We review an ongoing effort to demonstrate technologies required for quantum computing with phosphorus donors in silicon. The main aspect of our research is to achieve control over charge and spin states of individual dopant atoms. This work has required the development of new techniques for engineering silicon nanodevices at the atomic level. We follow an approach for implanting single phosphorus ions into silicon substrates with integrated p–i–n detectors. Configuring our devices with radio-frequency single-electron transistors (RF-SETs) allows for charge sensing at low temperatures. In this context, we perform measurements of single-electron charge transfer between individual phosphorus donors. In a parallel effort, we employ nanoscale Schottky contacts for populating and depopulating individual dopant atoms. Of particular interest is coherent manipulation of single-electron charge and spin states on individual dopant atoms. Charge manipulation between coupled donor states may be achieved by either external microwave pumping or intrinsic tunnel coupling. Spin manipulation, on the other hand, involves magnetic resonance. In this context, we pursue electrically detected spin resonance in phosphorus-doped devices with a decreasing number of dopant atoms.

This letter demonstrates that, whereas nanocavities are quite stable in crystalline Si (c-Si), they are unstable in amorphous Si (a-Si). This behavior is illustrated by introducing a band of nanocavities into c-Si by H implantation, followed by annealing at 850 °C. Amorphization of the c-Si surrounding the nanocavities led to their disappearance. Transmission electron microscopy, Rutherford backscattering, and channeling and time resolved (optical) reflectivity were used to provide details of the cavity instability process by studying the amorphous Si after implantation and subsequent crystallization. Two possible reasons are suggested for the instability of nanocavities in a-Si.

The kinetics of intrinsic and dopant-enhanced solid phase epitaxy (SPE) is stud- ied in amorphous germanium (a-Ge) layers formed by ion implantation on Ge substrates. The SPE rates were measured with a time-resolved reflectivity (TRR) system between 300 and 540 degC and found to have an activation energy of (2.15 +/- 0.04) eV. To interpret the TRR measurements the refractive indices of the a-Ge layers were measured at the two wavelengths used, 1.152 and 1.532 ��m. For the first time, SPE rate measurements on thick a-Ge layers (>3 ��m) have also been performed to distinguish between bulk and near-surface SPE growth rate behavior. Possible effects of explosive crystallization on thick a-Ge layers are considered. When H is present in a-Ge it is found to have a considerably greater retarding affect on the SPE rate than for similar concentrations in a-Si layers. Hydrogen is found to reduce the pre-exponential SPE velocity factor but not the activation energy of SPE. However, the extent of H indiffusion into a-Ge surface layers during SPE is about one order of magnitude less that that observed for a-Si layers. This is thought to be due to the lack of a stable surface oxide on a-Ge. Dopant enhanced kinetics were measured in a-Ge layers containing uniform concentration profiles of implanted As or Al spanning the concentration regime 1-10 x1019 /cm-3. Dopant compensation effects are also observed in a-Ge layers containing equal concentrations of As and Al, where the SPE rate is similar to the intrinsic rate. Various SPE models are considered in light of these data., 42 pages, 10 figures, 1 table, accepted for publication in Physical Review B

Preliminary findings from a photoluminescence (PL) study of 30 keV boron implanted and furnace annealed silicon are presented. When different laser excitation wavelengths were used: namely, 1064 nm, and 532 nm; the observed PL emission yield changed substantially. Since the excitation volumes of these two wavelengths are significantly different in silicon due to sample absorption, they provide a means of probing defect related luminescence as a function of the excitation depth. An additional advantage of using the 1064 nm excitation is the inclusion of the phononic silicon (Raman) band which overlaps with the PL spectrum allowing it to be used as a scattering quantum counter. This provides a means of normalising the luminescence yield for samples prepared under different conditions.

Boron enhanced H diffusion in amorphous Si (a-Si) layers formed by ion implantation is observed using secondary ion mass spectroscopy (SIMS). Constant concentrations of B were achieved using multiple energy B implantations into thick a-Si layers. The evolution of single H implanted profiles centered on the uniformly B-implanted regions was studied for partial anneals at temperatures in the range 380 – 640 °C. Boron enhanced diffusion is observed and the enhanced diffusion coefficient shows trends with temperature typically associated with a Fermi level shifting dependence. A modified form of the generalized Fermi level shifting model is considered in light of these results.

The kinetics of intrinsic and dopant-enhanced solid phase epitaxy (SPE) are studied in thick amorphous germanium (a-Ge) layers formed by ion implantation on Ge substrates. The SPE rates for H-free Ge were measured with a time-resolved reflectivity (TRR) system in the temperature range 300 – 540 °C and found to have an activation energy of (2.15 ± 0.04) eV. Dopant enhanced SPE was measured in a-Ge layers containing a uniform concentration profile of implanted As spanning the concentration regime 1 – 10 × 1019 cm3. The generalized Fermi level shifting model shows excellent fits to the data.