Silicon is vital to the computing industry due to the high quality of its native oxide and well-established doping technologies. Isotopic purification has enabled quantum coherence times on the order ...of seconds, thereby placing silicon at the forefront of efforts to create a solid state quantum processor. We demonstrate strong coupling of a single electron in a silicon double quantum dot to the photonic field of a microwave cavity, as shown by the observation of vacuum Rabi splitting. Strong coupling of a quantum dot electron to a cavity photon would allow for long-range qubit coupling and the long-range entanglement of electrons in semiconductor quantum dots.
AlGaN p–n junctions were used to fabricate photodetectors operating between 280 and 380 nm. Detector structures were grown on silicon and sapphire substrates by gas source molecular beam epitaxy with ...ammonia. Layers of n‐AlxGa1—xN (0 ≤ xAlN ≤ 0.08) were grown at a temperature of 800 °C on a buffer layer of AlN. The p‐type layers of AlxGa1—xN (0 ≤ xAlN ≤ 0.08) were co‐doped with Mg and oxygen. Hole concentrations as high as 2 × 1018 cm—3 were measured by capacitance voltage profiling. In the p‐Al0.08Ga0.92N layer we measured acceptor activation energy of 195 ± 10 meV. In a comparable layer of p‐GaN, also co‐doped with Mg and O, the acceptor activation energy was 130–165 meV. Low activation energies are attributed to successful co‐doping. In mesa etched diodes we measured zero‐bias leakage currents as low as 6 × 10—13 A cm—2.
Strain relaxation and clustering of Ge thin films grown on Si(111) and Si(100) by molecular beam epitaxy (MBE) have been studied in situ with reflection high energy electron diffraction (RHEED) and ...analyzed by atomic force microscopy (AFM) and Rutherford backscattering spectrometry (RBS). At low temperature, growth is dominated by island nucleation and by strain relief through island formation. The cluster size distribution (measured by AFM) just after the 2D–3D growth mode transition is broader than that for ‘late-stage’ growth (when diffusion gradients dominate cluster growth) and is well fit by a model in which the surface diffusion of adatoms is described by a random walk. At high temperature, growth is dominated by dislocation formation and the aspect ratio of the islands changes. The barrier to dislocation formation is reduced at step bunches; thus, islands nucleate preferentially at the step bunches and grow along them. By understanding Ge island nucleation and evolution, we hope to grow a population of uniformly-sized nanocrystals exhibiting quantum confinement effects.
We measure the interdot charge relaxation time T_1 of a single electron trapped in an accumulation mode Si/SiGe double quantum dot. The energy level structure of the charge qubit is determined using ...photon assisted tunneling, which reveals the presence of a low lying excited state. We systematically measure T_1 as a function of detuning and interdot tunnel coupling and show that it is tunable over four orders of magnitude, with a maximum of 45 microseconds for our device configuration. Measured relaxation times are consistent with a phonon mediated energy relaxation process and indicate that low lying excited states may have important implications in the development of silicon spin qubits.
Inguinal hernia belongs to the most common surgical pathology worldwide. Approximately, one third is asymptomatic. The value of watchful waiting (WW) in patients with asymptomatic or mildly ...symptomatic inguinal hernia has been established in a few randomised controlled trials (RCTs). The aim of this study was to assess long-term outcomes of a RCT comparing WW and elective surgery.
In the original study, men aged ≥50 years with an asymptomatic or mildly symptomatic inguinal hernia were randomly assigned to WW or elective repair. In the present study, the primary outcome was the 12-year crossover rate to surgery, secondary outcomes were time-to-crossover, patient regret, pain, quality of life and incarceration. Dutch Trial Registry: NTR629.
Out of 496 originally analysed patients, 488 (98.4%) were evaluable for chart review (WW: n = 258, surgery: n = 230), and 200 (41.0%) for telephone contact (WW: n = 106, surgery: n = 94) between November 2021 and March 2022 with a median 12 years follow-up (IQR 9–14). After 12 years, the estimated cumulative crossover rate to surgery was 64.2%, which was higher in mildly symptomatic than in asymptomatic patients (71.7% versus 60.4%, HR 1.451, 95% CI: 1.064–1.979). Time-to-crossover was longer in asymptomatic patients (50% after 6.0 years versus 2.0 years, p = 0.019). Patient regret was higher in the WW group (37.7 versus 18.0%, p = 0.002), as well as pain/discomfort (p = 0.031). Quality of life did not differ (p = 0.737). In the WW group, incarceration occurred in 10/255 patients (3.9%).
During 12-year follow-up, most WW patients crossed over to surgery, significantly earlier with mildly symptomatic hernia. Considering the relatively low incarceration rate, WW might still be an option in asymptomatic patients with a clear preference and being well-informed about pros and cons.
The initial trial was funded by the Netherlands Organisation for Health Research and Development (ZonMW). This long-term study did not receive funding.
A membrane reactor is presented for homogeneous catalysis in supercritical carbon dioxide with in situ catalyst separation. This concept offers the advantages of benign high-density gases, i.e., the ...possibility of achieving a high concentration of gaseous reactants in the same phase as the substrates and catalyst as well as easy catalyst localization by means of a membrane. For the separation of the homogeneous catalyst from the products an inorganic microporous membrane is used. The concept is demonstrated for the hydrogenation of 1-butene using a fluorous derivative of Wilkinson's catalyst RhCl{P–(C
6H
4-
p-SiMe
2CH
2CH
2C
8F
17)
3}
3. The size of Wilkinson's catalyst, 2–4 nm, is clearly larger than the pore diameter, 0.5–0.8 nm, of the silica membrane. The membrane will, therefore, retain the catalyst, while the substrates and products diffuse through the membrane. Stable operation and continuous production of
n-butane has been achieved at a temperature of 353 K and a pressure of 20 MPa. A turnover number of 1.2×10
5 has been obtained during 32 h of reaction. The retention of the catalyst was checked using UV–vis spectroscopy and ICP-AAS; no rhodium or phosphorous species were detected at the permeate side of the membrane.
Membrane separation technology is successfully applied for the immobilization of a homogeneous catalyst (a (1H,1H,2H,2H‐perfluoroalkyl)dimethylsilyl‐substituted derivative of Wilkinson's catalyst) in ...a continuous process that uses supercritical carbon dioxide as solvent. The catalyst is separated from the products by a microporous silica membrane (see scheme).
We report development of a novel AlGaN/GaN/AlGaN double heterojunction field effect tansistor (DHFET) with improved device performance over the conventional single heterojunction GaN FET (SHFET). The ...GaN DHFETs with low Al content Al/sub 0.04/Ga/sub 0.96/N buffer layer exhibit three orders of magnitude lower subthreshold drain leakage current and almost three orders of magnitude higher buffer isolation than corresponding SHFET devices (600 M/spl Omega//sq. vs. 1 M/spl Omega//sq.). In GaN DHFET's with 0.15 /spl mu/m conventional T-gates we observed 30% improvement in saturated power density and 10% improvement in PAE at 10 GHz over a corresponding SHFET device.
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