Effect of indium doping on the electrical and structural properties of TiO2 thin films used in MOS devices

We investigated the effect of Indium (In) doping on the structural and electrical properties of Ti/Au/ TiO2:In/n-Si metal-oxide-semiconductor (MOS) devices. Sputtering grown TiO2 thin films on Si substrate were doped using two In-films with 15 nm and 50 nm thicknesses leading to two structures named Low Indium Doped (LID) sample and High Indium Doped (HID) sample, respectively. XRD analysis shows no diffraction pattern related to Indium indicating that In has been incorporated into the TiO2 lattice. Current-Voltage (I-V) characteristics show that rectification ratio at 2V is higher for HID sample than for LID sample. Evaluated barrier height, ϕB0 , decreased while the ideality factor, n, increased with decreasing temperature. Such behavior is ascribed to barrier inhomogeneity that was assumed to have a Gaussian Distribution (GD) of barrier heights at interface. Evidence of such GD was confirmed by plotting ϕB0versus n. High value of mean barrier ϕ̅B0 and lower value of standard deviation (σ) of HID structure are due to indium doping which increases the barrier homogeneities. Finally, estimated Richardson constants A* are in good agreement with theoretic values (112 A/cm2K2), particularly, for the HID structure

Atomic-level passivation mechanism of ammonium salts enabling highly efficient perovskite solar cells.

The high conversion efficiency has made metal halide perovskite solar cells a real breakthrough in thin film photovoltaic technology in recent years. Here, we introduce a straightforward strategy to reduce the level of electronic defects present at the interface between the perovskite film and the hole transport layer by treating the perovskite surface with different types of ammonium salts, namely ethylammonium, imidazolium and guanidinium iodide. We use a triple cation perovskite formulation containing primarily formamidinium and small amounts of cesium and methylammonium. We find that this treatment boosts the power conversion efficiency from 20.5% for the control to 22.3%, 22.1%, and 21.0% for the devices treated with ethylammonium, imidazolium and guanidinium iodide, respectively. Best performing devices showed a loss in efficiency of only 5% under full sunlight intensity with maximum power tracking for 550 h. We apply 2D- solid-state NMR to unravel the atomic-level mechanism of this passivation effect

Efficient Triplet Exciton Fusion in Molecularly Doped Polymer Light-Emitting Diodes

Solution-processed polymer organic light-emitting diodes (OLEDs) doped with triplet-triplet annihilation (TTA)upconversion molecules, including 9,10-diphenylanthracene, perylene, rubrene and TIPS-pentacene, are reported. The fraction of triplet-generated electroluminescence approaches the theoretical limit. Record-high efficiencies in solution-processed OLEDs based on these materials are achieved. Unprecedented solid-state TTA-upconversion quantum yield of 23% (TTA-upconversion reaction efficiency of 70%) at electrical excitation well below one-sun equivalent is observed.Department of Physics (University of Cambridge)KACST-Cambridge University Joint Centre of ExcellenceSingapore Agency for Science, Technology and Research (A*STAR)Engineering and Physical Sciences Research Council (EPSRC

Investigation of the structural, optical and electrical properties of indium-doped TiO2 thin films grown by Pulsed Laser Deposition technique on low and high index GaAs planes

© 2020 Elsevier B.V. The properties of In-doped TiO2 grown by Pulsed Laser Deposition on (1 0 0) and (3 1 1)B GaAs substrates have been investigated. X-ray diffraction and photoluminescence results have shown that samples grown on (3 1 1)B GaAs planes have better crystallographic properties than those grown on (1 0 0). Both anatase and rutile phases were detected in samples with lower In-doping (In = 5 nm) while only rutile phase was observed for higher In-doped samples (In = 15 nm). Furthermore, In-doping adversely affected the electrical properties of samples grown on (1 0 0) substrates while it enhanced those of (3 1 1)B samples. Two shallow defects were detected in all samples except for (3 1 1)B sample (In = 15 nm) where three shallow defects were observed. The presence of more shallow defects in this sample is evidenced by a red-shift in the absorption spectrum. It was concluded that sample (3 1 1)B (In = 15 nm) is best among all other samples and makes it more suitable for solar cell applications

Effect of growth techniques on the structural, optical and electrical properties of indium doped TiO2thin films

We have investigated the effect of the growth techniques on the structural, the electrically and optically active defects in Indium doped TiO2 thin films grown by pulsed laser deposition (PLD) and sputtering techniques. X-ray diffraction (XRD) and Raman spectroscopy patterns revealed both rutile and anatase phases for the sputtering samples. On the other hand, only the anatase phase was observed for the PLD samples. The photoluminescence (PL) spectra have unveiled several peaks which were explained by defect related optical transitions. Particularly, the PL bands are fully consistent with anatase/rutile TiO2 phases and the formation of In2O3 during the preparation of our samples. It was also observed that at −4 V reverse bias, the PLD samples have lower leakage currents (∼1.4 × 10−7 A) as compared to the sputtering samples (∼5.9 × 10−7 A). In addition, the PLD samples exhibited lower ideality factors and higher barrier heights as compared to those grown by sputtering. Finally, the Deep Level Transient Spectroscopy (DLTS) measurements have shown only one defect in the PLD samples whereas five defects have been detected in the sputtering samples. Therefore, our results provide strong evidence that the PLD technique is better suited for the growth of In-doped TiO2 thin films

Global overview of the management of acute cholecystitis during the COVID-19 pandemic (CHOLECOVID study)

Background: This study provides a global overview of the management of patients with acute cholecystitis during the initial phase of the COVID-19 pandemic. Methods: CHOLECOVID is an international, multicentre, observational comparative study of patients admitted to hospital with acute cholecystitis during the COVID-19 pandemic. Data on management were collected for a 2-month study interval coincident with the WHO declaration of the SARS-CoV-2 pandemic and compared with an equivalent pre-pandemic time interval. Mediation analysis examined the influence of SARS-COV-2 infection on 30-day mortality. Results: This study collected data on 9783 patients with acute cholecystitis admitted to 247 hospitals across the world. The pandemic was associated with reduced availability of surgical workforce and operating facilities globally, a significant shift to worse severity of disease, and increased use of conservative management. There was a reduction (both absolute and proportionate) in the number of patients undergoing cholecystectomy from 3095 patients (56.2 per cent) pre-pandemic to 1998 patients (46.2 per cent) during the pandemic but there was no difference in 30-day all-cause mortality after cholecystectomy comparing the pre-pandemic interval with the pandemic (13 patients (0.4 per cent) pre-pandemic to 13 patients (0.6 per cent) pandemic; P = 0.355). In mediation analysis, an admission with acute cholecystitis during the pandemic was associated with a non-significant increased risk of death (OR 1.29, 95 per cent c.i. 0.93 to 1.79, P = 0.121). Conclusion: CHOLECOVID provides a unique overview of the treatment of patients with cholecystitis across the globe during the first months of the SARS-CoV-2 pandemic. The study highlights the need for system resilience in retention of elective surgical activity. Cholecystectomy was associated with a low risk of mortality and deferral of treatment results in an increase in avoidable morbidity that represents the non-COVID cost of this pandemic

Direct Growth of III-Nitride Nanowire-Based Yellow Light-Emitting Diode on Amorphous Quartz Using Thin Ti Interlayer

Abstract Consumer electronics have increasingly relied on ultra-thin glass screen due to its transparency, scalability, and cost. In particular, display technology relies on integrating light-emitting diodes with display panel as a source for backlighting. In this study, we undertook the challenge of integrating light emitters onto amorphous quartz by demonstrating the direct growth and fabrication of a III-nitride nanowire-based light-emitting diode. The proof-of-concept device exhibits a low turn-on voltage of 2.6 V, on an amorphous quartz substrate. We achieved ~ 40% transparency across the visible wavelength while maintaining electrical conductivity by employing a TiN/Ti interlayer on quartz as a translucent conducting layer. The nanowire-on-quartz LED emits a broad linewidth spectrum of light centered at true yellow color (~ 590 nm), an important wavelength bridging the green-gap in solid-state lighting technology, with significantly less strain and dislocations compared to conventional planar quantum well nitride structures. Our endeavor highlighted the feasibility of fabricating III-nitride optoelectronic device on a scalable amorphous substrate through facile growth and fabrication steps. For practical demonstration, we demonstrated tunable correlated color temperature white light, leveraging on the broadly tunable nanowire spectral characteristics across red-amber-yellow color regime