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Single-photon detection has emerged as a method of choice for ultra-sensitive measurements of picosecond optical transients. In the short-wave infrared, semiconductor-based single-photon detectors typically exhibit relatively poor performance compared with all-silicon devices operating at shorter wavelengths. Here we show a new generation of planar germanium-on-silicon (Ge-on-Si) single-photon avalanche diode (SPAD) detectors for short-wave infrared operation. This planar geometry has enabled a significant step-change in performance, demonstrating single-photon detection efficiency of 38% at 125 K at a wavelength of 1310 nm, and a fifty-fold improvement in noise equivalent power compared with optimised mesa geometry SPADs. In comparison with InGaAs/InP devices, Ge-on-Si SPADs exhibit considerably reduced afterpulsing effects. These results, utilising the inexpensive Ge-on-Si platform, provide a route towards large arrays of efficient, high data rate Ge-on-Si SPADs for use in eye-safe automotive LIDAR and future quantum technology applications. By incorporating germanium, single-photon avalanche diode detectors using silicon-based platforms are applied to infrared light detection. Here, a cost-effective planar detector geometry is presented yielding high detection efficiency suitable for applications such as sparse photon imaging or LIDAR.

Germanium‐containing short‐wave infrared (SWIR) avalanche photodiode (APD) arrays on silicon platforms have the potential for monolithic integration into complementary metal‐oxide‐semiconductor (CMOS) integrated circuits, making them mass‐manufacturable, high‐performance, arrayed optical detectors operating at wavelengths beyond the silicon cut‐off wavelength. Here, the first high‐performance, surface‐illuminated, 10‐pixel linear array of pseudoplanar geometry germanium‐on‐silicon (Ge‐on‐Si) APDs operating at 1550 nm wavelength and at temperatures up to 378 K are demonstrated. At room temperature, the dark current, avalanche gain, responsivity, and avalanche breakdown of the devices show good uniformity. Array A exhibits a mean dark current density of 198 ± 62 mA cm−2 at 90% of the breakdown voltage. The excess noise factor is less than half that of InP‐based SWIR APD arrays, which allows Ge‐on‐Si devices to operate at a higher avalanche gain. A responsivity of 8.2 A W−1 at a gain of 20 and excess noise of 3.3 is achieved when illuminated with 1550 nm wavelength light. The detector array also demonstrates stable performance at 378 K with a maximum avalanche gain of 24. This device architecture will be applicable for the design of large‐scale APD arrays on Si platforms for SWIR detection which can be used in imaging, sensing, and optical communication applications. The fabrication and characterization of a new type of surface‐illuminated Si‐based avalanche photodiode array operating in the short‐wave infrared region using germanium as the absorber and silicon as the multiplier is reported. The demonstration of an avalanche gain of 24 at a temperature of 378 K allows the devices to operate in outdoor environments.

Germanium-on-silicon (Ge-on-Si) based single-photon avalanche diodes (SPADs) have recently emerged as a promising detector candidate for ultra-sensitive and picosecond resolution timing measurement of short-wave infrared (SWIR) photons. Many applications benefit from operating in the SWIR spectral range, such as long distance light detection and ranging, however, there are few single-photon detectors exhibiting the high-performance levels obtained by all-silicon SPADs commonly used for single-photon detection at wavelengths <1 µ m. This paper first details the advantages of operating at SWIR wavelengths, the current technologies, and associated issues, and describes the potential of Ge-on-Si SPADs as a single-photon detector technology for this wavelength region. The working principles, fabrication and characterisation processes of such devices are subsequently detailed. We review the research in these single-photon detectors and detail the state-of-the-art performance. Finally, the challenges and future opportunities offered by Ge-on-Si SPAD detectors are discussed.

The recently developed precession electron diffraction (PED) technique in scanning transmission electron microscopy (STEM) has been used to elucidate the local strain distribution and crystalline misorientation in CMOS fabricated strained Ge micro disk structure grown on Si substrate. Such structures are considered to be a compact optical source for the future photonics due to the specific undercut for direct bandgap behaviour under strain. In this study, the strain maps are interpreted and compared with a finite element model (FEM) of the strain in the investigated structure. Results demonstrate that the SiN used as a stressor on top of the Ge disk induces an in-plane strain \\(\\epsilon_{xx}\\) of a maximum value of almost 2 % which is also confirmed by FEM simulations. This tensile strain can reduce the difference between the direct and indirect bandgaps leading to direct bandgap radiative transitions, with the potential for applications in strained Ge lasers.

Silicon compatible light sources have been referred to as the grail\" for Si photonics. Such devices would give the potential for a range of applications; from optical interconnects on integrated circuits, to cheap optical gas sensing and spectroscopic devices on a Si platform. Whilst numerous heterogeneous integration schemes for integrating III-V lasers with Si wafers are being pursued, it would be far easier and cheaper to use the epitaxial tools already in complementary-metal-oxide-semiconductor (CMOS) lines, where Ge and SiGe chemical vapour deposition is used in a number of advanced technology nodes. Germanium is an effcient absorber, but a poor emitter due to a band-structure which is narrowly indirect, but by only 140 meV. Through the application of strain, or by alloying with Sn, the Ge bandstructure can be engineered to become direct bandgap, making it an effcient light emitter. In this work, silicon nitride stressor technologies, and CMOS compatible processes are used to produce levels of tensile strain in Ge optical micro-cavities where a transition to direct bandgap is predicted. The strain distribution, and the optical emission of a range of Ge optical cavities are analyzed, with an emphasis on the effect of strain distribution on the material band-structure. Peak levels of strain are reported which are higher than that reported in the literature using comparable techniques. Furthermore, these techniques are applied to GeSn epi-layers and demonstrate that highly compressive GeSn alloys grown pseudomorphically on Ge virtual substrates, can be transformed to direct bandgap materials, with emission >3 m wavelength the longest wavelength emission demonstrated from GeSn alloys. Such emission is modeled to have a good overlap with methane absorption lines, indicating that there is huge potential for the such technologies to be used for low cost, Si compatible gas sensing in the mid-infrared.

The reaction of diallyl ether with nitrogen dioxide in organic solvents yields a mixture of cis and trans 2,3-bis(nitromethyl)-tetrahydrofurans cis and trans 2-nitratomethyl-3-nitromethyl-tetrahydrofurans and a number of straight-chain compounds with one to four nitro groups.

The reaction of diallyl ether with nitrogen dioxide in organic solvents yields a mixture of cis and trans 2,3-bis(nitromethyl)tetrahydrofurans, cis and trans 2-nitratomethyl-3-nitromethyltetrahydrofurans and a number of straight-chain compounds with one to four nitro groups. Under the conditions used, the cyclic compounds form the main products when the solution of nitrogen dioxide is slowly added to the solution of diallyl ether but not when the reverse mode of addition is used. When 15 N-nitrogen dioxide is used, the products show strong 15 N nuclear polarization: the 2,3-di(nitromethyl)tetrahydrofurans give an emission signal, and one straight-chain product with two nonequivalent nitro groups shows both an emission signal and an enhanced absorption signal. For both the cyclic and straight-chain products, the nuclear polarization is consistent with the successive reactions of diallyl ether with two nitrogen dioxide radicals with uncorrelated spins.Key words: diallyl ether, nitrogen dioxide, 15 N nuclear polarization, CIDNP.

The reaction of diallyl ether with nitrogen dioxide in organic solvents yields a mixture of cis and trans 2,3-bis(nitromethyl)tetrahydrofurans, cis and trans 2-nitratomethyl-3-nitromethyltetrahydrofurans and a number of straight-chain compounds with one to four nitro groups. Under the conditions used, the cyclic compounds form the main products when the solution of nitrogen dioxide is slowly added to the solution of diallyl ether but not when the reverse mode of addition is used. When 15 N-nitrogen dioxide is used, the products show strong 15 N nuclear polarization: the 2,3-di(nitromethyl)tetrahydrofurans give an emission signal, and one straight-chain product with two nonequivalent nitro groups shows both an emission signal and an enhanced absorption signal. For both the cyclic and straight-chain products, the nuclear polarization is consistent with the successive reactions of diallyl ether with two nitrogen dioxide radicals with uncorrelated spins.Key words: diallyl ether, nitrogen dioxide, 15 N nuclear polarization, CIDNP.

Background On-the-day surgery cancellations (OTDSCs) have been a longstanding global problem, bringing significant suffering to patients and carers, and substantial waste across healthcare systems. Any cancellation of a surgery that occurs for any reason on the day of the scheduled surgery is defined as an OTDSC. Despite the high prevalence of OTDSCs, little is known about why they happen and how to minimise them. This study aimed to develop Initial Program Theories (IPTs) and share valuable insights that can form the basis for future evaluation of OTDSCs. Method We conducted a study to address the questions, “How do OTDSCs occur, and in what contexts can they be minimised?“. We used a qualitative and multi-stage approach to developing IPTs. Data collection included OTDSC literature ( n  = 35) identified from a systematic search, including feedback sessions with administrators ( n  = 10) from eight NHS trusts, two feedback events with patient expert advisers ( n  = 6), and expert practitioners ( n  = 8). Results The iterative analysis found that OTDSCs are a complex undesired outcome, influenced by many interconnected “variables” at macro-level (e.g., waiting-list policies, austerity measures and workforce shortages) and meso-level (e.g., workload, high emergency admissions and interruptions), as well as healthcare professionals’ (HCPs) and patients’ perceptions and behaviours. The study identified that failures in various aspects of individualised care (such as care planning, communication and resource allocation) in preparing for surgery before admission could also contribute to different types of OTDSCs. Conclusion As a result of the complex and interconnected nature of OTDSCs and the wide variety of causes, it can be hard to reduce their occurrence. OTDSCs can be minimised by carefully considering various aspects of individualisation of care, such as clinical care planning, communication and resource allocation and delivery when preparing patients to undergo surgery. Providing favourable working conditions and creating effective knowledge transfer between the stakeholders initiating OTDSCs and HCPs who prepare patients for surgery can be critical to minimising most OTDSCs. The study developed a taxonomy and novel IPTs that have practical implications for policymakers and practitioners when designing interventions to minimise OTDSCs.

Background Involving groups of community stakeholders (e.g., steering committees) to lead community-wide health interventions appears to support multiple outcomes ranging from policy and systems change to individual biology. While numerous tools are available to measure stakeholder characteristics, many lack detail on reliability and validity, are not context specific, and may not be sensitive enough to capture change over time. This study describes the development and reliability of a novel survey to measure Stakeholder-driven Community Diffusion via assessment of stakeholders’ social networks, knowledge, and engagement about childhood obesity prevention. Methods This study was completed in three phases. Phase 1 included conceptualization and online survey development through literature reviews and expert input. Phase 2 included a retrospective study with stakeholders from two completed whole-of-community interventions. Between May–October 2015, 21 stakeholders from the Shape Up Somerville and Romp & Chomp interventions recalled their social networks, knowledge, and engagement pre-post intervention. We also assessed one-week test-retest reliability of knowledge and engagement survey modules among Shape Up Somerville respondents. Phase 3 included survey modifications and a second prospective reliability assessment. Test-retest reliability was assessed in May 2016 among 13 stakeholders involved in ongoing interventions in Victoria, Australia. Results In Phase 1, we developed a survey with 7, 20 and 50 items for the social networks, knowledge, and engagement survey modules, respectively. In the Phase 2 retrospective study, Shape Up Somerville and Romp & Chomp networks included 99 and 54 individuals. Pre-post Shape Up Somerville and Romp & Chomp mean knowledge scores increased by 3.5 points (95% CI: 0.35–6.72) and (− 0.42–7.42). Engagement scores did not change significantly (Shape Up Somerville: 1.1 points (− 0.55–2.73); Romp & Chomp: 0.7 points (− 0.43–1.73)). Intraclass correlation coefficients (ICCs) for knowledge and engagement were 0.88 (0.67–0.97) and 0.97 (0.89–0.99). In Phase 3, the modified knowledge and engagement survey modules included 18 and 25 items, respectively. Knowledge and engagement ICCs were 0.84 (0.62–0.95) and 0.58 (0.23–0.86). Conclusions The survey measures upstream stakeholder properties—social networks, knowledge, and engagement—with good test-retest reliability. Future research related to Stakeholder-driven Community Diffusion should focus on prospective change and survey validation for intervention effectiveness.