E-beam synthesized fast-switching TiO2/SnO2 type-II heterostructure photodetector.

A fast-switching T i O 2/S n O 2 heterostructure thin-film (TF) photodetector synthesized by electron beam evaporation technique is analyzed in this study. The substrate utilized is n-type silicon (Si), while gold (Au) is employed as the top electrode. To assess sample morphology and confirm elemental composition, field emission scanning electron microscopy (FESEM), energy dispersive x-ray spectroscopy (EDS), and chemical mapping were conducted. Structural characteristics were determined using X-ray diffraction (XRD) analysis. The XRD analysis confirmed the presence of various phases of T i O 2 (anatase and rutile) and S n O 2 (rutile). UV-Vis spectroscopy revealed multiple absorption peaks, at 447 nm, 495 nm, 560 nm, and 673 nm, within the visible spectrum. The device demonstrates high detectivity (D ∗) of 1.737×109 Jones and a low noise equivalent power (NEP) of 0.765×10-10 W. Evaluation of the device's switching response through current-time characteristic (I-T) analysis indicates rapid switching with a rise time and fall time of 0.33 s and 0.36 s, respectively.

Enhanced Photodetection in Glancing Angle Deposited One-Dimensional In2O3 Nanorod Array.

Glancing angle deposition (GLAD) oriented electron beam (e-beam) evaporation process has been employed to develop 1D In2O3 nanorod array over n-Si substrate. The morphology of as-deposited In2O3 thin film (∼70 nm) and GLAD 1D In2O3 nanorod array (∼400 nm) were explored using field emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS) and high resolution transmission electron microscopy (HRTEM) analysis. The structural analysis were perceived by high-resolution X-ray diffraction (HRXRD) and atomic force microscopy (AFM) techniques. The clampdown of ∼4.4 fold photoluminescence (PL) emission intensity was observed for In2O3 nanorod array. Metallization were done to measure the current (I)-voltage (V) characteristics for n-Si/In2O3 thin film and n-Si/In2O3 nanorod devices. The In2O3 nanorod device displayed ∼2.2 fold enhancement in current conduction at -4.6 V and an averagely ∼1.1 fold augmentation in photosensitivity were also observed. The photoresponsivity of ∼28 µA/W, maximum specific detectivity of ∼9.9×107 Jones and low NEP of ∼4.5×10-12 W/√Hz was achieved for the In2O3 nanorod-based photodetectors. The maximum ∼2.5 fold high detectivity and ∼2.4 fold low noise equivalent power (NEP) were perceived for the 1D In2O3 nanorod array detector as compared to the bare In2O3 thin film detector.

Bandgap Modulation of Glancing Angle Deposition Aided Ag Nanoparticles Covered TiO2 Thin Film by High Temperature Annealing.

Glancing Angle Deposition (GLAD) technique has been used to fabricate the Ag nanoparticles (NPs) over TiO2 thin film (TF) on the n-Si substrate. The deposited Ag NPs are in the size of 3-5 nm. Open-air annealing has been done at 500 °C and 600 °C for the n-Si/TiO2 TF/Ag NP samples. High Resolution X-ray Diffraction (HRXRD) peaks were identified to calculate the crystalline size of the NPs and rutile phase of the annealed sample were exhibited. Morphological analysis has been done for the sample using Field Emission Scanning Electron Microscopy (FESEM), Energy Dispersive Spectroscopy (EDS) and Atomic Force Microscopy (AFM). The enhancement of plasmonic absorption and modulation in the bandgap for the annealed Ag NPs surrounded TiO2 TF has been verified by UV-Vis Spectroscopy and the bandgap has been calculated using Tauc plot. An overall 2.5 fold and 3 fold enhancement has been observed in the UV region and visible region for n-Si/TiO2 TF/Ag NP annealed at 500 °C and 600 °C samples as compared to the n-Si/TiO2 TF/Ag NP as-deposited samples. The modulation of bandgap due to the sub-band transition and Localized Surface Plasmon Resonance (LSPR) effect of Ag NPs and relevant sub-band transition due to change in annealing temperature has been reported.

Enhanced Photodetection with Crystalline Si Nanoclusters.

SiOx nanodots were fabricated on a TiO2 thin film using glancing angle deposition technique. The fabricated samples were annealed at 950 °C in open air configuration to obtain Si nanoclusters resulting from phase separation of SiOx nanodots. Field Emission Gun Scanning electron microscopy and atomic force microscopy were used to examine the topography of the samples. The elemental composition of the samples was analyzed using energy dispersive X-ray mapping and their crystallinity was confirmed by analyzing the bandgap determined from the Tauc plots. The annealed samples show a broadband absorption which is about two folds in magnitude as compared to the as deposited (unannealed) samples. The photoluminescence spectra confirms the quantum confinement effect in the annealed samples. A photodetector was fabricated from an annealed sample by depositing gold contacts on top of it. This photodetector showed a two-fold increase in dark current and a 1.5-fold increase in light current compared to a photodetector made from the as-deposited SiOx samples-which is due to the increased crystallinity in Si nanoclusters. Finally, the rise and fall times of the device were measured through a switching experiment.

Improved UV Photodetection by Indium Doped TiO2 Thin Film Based Photodetector.

Indium (In) was doped into TiO2 thin film (TF) using the electron beam evaporation technique followed by an annealing process. The high resolution X-ray diffraction (HRXRD) analysis revealed lower angle diffraction peak (2) shifting of Rutile (002) phases of TiO2 from 61.9 to 61.56 for an increased In doped samples. Calculated average grain size from FESEM (field emission scanning electron microscope) gradually decreased from 21.12 nm to 17.03 mm with an increase in In content ranging from 1.45~17.30 at%. HRXRD data revealed that crystallite sizes also reduced from 21.79 nm to 16.93 nm with an increased In doping concentration. Doping of In leads to the formation of inhomogeneous InxTiy O2 alloy that enhances the transition between 3.3-3.42 eV energy levels with variation in doping concentration. The photo-efficiencies for increased doping concentration of In with 3.47 at% and 17.30 at% were enhanced by 2.56 and 2.76 times, respectively, compared to the undoped TiO2 TF detector and both were larger than low doped In with 1.45 at% sample. The ratio of main band detection intensity to oxygen defect level was also increased from 0.22 to 2.22 with the gradual increase in In content.

Pilot study of essential drug quality in two major cities in India.

BACKGROUND: India is an increasingly influential player in the global pharmaceutical market. Key parts of the drug regulatory system are controlled by the states, each of which applies its own standards for enforcement, not always consistent with others. A pilot study was conducted in two major cities in India, Delhi and Chennai, to explore the question/hypothesis/extent of substandard and counterfeit drugs available in the market and to discuss how the Indian state and federal governments could improve drug regulation and more importantly regulatory enforcement to combat these drugs. METHODOLOGY/PRINCIPAL FINDINGS: Random samples of antimalarial, antibiotic, and antimycobacterial drugs were collected from pharmacies in urban and peri-urban areas of Delhi and Chennai, India. Semi-quantitative thin-layer chromatography and disintegration testing were used to measure the concentration of active ingredients against internationally acceptable standards. 12% of all samples tested from Delhi failed either one or both tests, and were substandard. 5% of all samples tested from Chennai failed either one or both tests, and were substandard. Spatial heterogeneity between pharmacies was observed, with some having more or less substandard drugs (30% and 0% respectively), as was product heterogeneity, with some drugs being more or less frequently substandard (12% and 7% respectively). CONCLUSIONS/SIGNIFICANCE: In a study using basic field-deployable techniques of lesser sensitivity rather than the most advanced laboratory-based techniques, the prevalence of substandard drugs in Delhi and Chennai is confirmed to be roughly in accordance with the Indian government's current estimates. However, important spatial and product heterogeneity exists, which suggests that India's substandard drug problem is not ubiquitous, but driven by a subset of manufacturers and pharmacies which thrive in an inadequately regulated environment. It is likely that the drug regulatory system in India needs to be improved for domestic consumption, and because India is an increasingly important exporter of drugs for both developed and developing countries. Some poor countries with high burdens of disease have weak drug regulatory systems and import many HIV/AIDS, tuberculosis and malaria drugs from India.