Gas Sensing Properties of PLD Grown 2D SnS Film: Effect of Film Thickness, Metal Nanoparticle Decoration, and In Situ KPFM Investigation.

This study employs novel growth methodologies and surface sensitization with metal nanoparticles to enhance and manipulate gas sensing behavior of two-dimensional (2D)SnS film. Growth of SnS films is optimized by varying substrate temperature and laser pulses during pulsed laser deposition (PLD). Thereafter, palladium (Pd), gold (Au), and silver (Ag) nanoparticles are decorated on as-grown film using gas-phase synthesis techniques. X-ray diffraction (XRD), Raman spectroscopy, and Field-emission scanning electron microscopy (FESEM) elucidate the growth evolution of SnS and the effect of nanoparticle decoration. X-ray photoelectron spectroscopy (XPS) analyses the chemical state and composition. Pristine SnS, Ag, and Au decorated SnS films are sensitive and selective toward NO2 at room temperature (RT). Ag nanoparticle increases the response of pristine SnS from 48 to 138% toward 2 ppm NO2, which indicates electronic and chemical sensitization effect of Ag. Pd decoration on SnS tunes its selectivity toward H2 gas with a response of 55% toward 70 ppm H2 and limit of detection (LOD) < 1 ppm. In situ Kelvin probe force microscopy (KPFM) maps the work function changes, revealing catalytic effect of Ag toward NO2 in Ag-decorated SnS and direct charge transfer between Pd and SnS during H2 exposure in Pd-decorated SnS.

Synthesis of a large area ReS2 thin film by CVD for in-depth investigation of resistive switching: effects of metal electrodes, channel width and noise behaviour.

The anisotropic crystal structure and layer independent electrical and optical properties of ReS2 make it unique among other two-dimensional materials (2DMs), emphasizing a special need for its synthesis. This work discusses the synthesis and in-depth characterization of a 1 × 1 cm2 large and few layered ReS2 film. Vibrational modes and excitonic peaks observed from the Raman and photoluminescence (PL) spectra corroborated the formation of a ReS2 film with a 1.26 eV bandgap. High resolution transmission electron microscopy (HRTEM) images and selected area electron diffraction (SAED) patterns inferred the polycrystalline nature of the film, while cross-sectional field emission scanning electron microscopy (FESEM) indicated planar growth with ∼10 nm thickness. The chemical composition of the film analysed through X-ray photoelectron spectroscopy (XPS) indicated the formation of a ReS2 film with a Re : S atomic ratio of 1 : 1.75, indicating a small amount of non-stoichiometric RexSy. Following the basic characterization studies, the ReS2 film was tested for resistive switching (RS) device application in which the effects of different metal electrodes (Pt/Au and Ag/Au) and different channel widths (200, 100, and 50 µm) were studied. The highest memory window equal to 108 was obtained for the Ag/Au electrode while Pt/Au showed a memory window of 102. RS for the former was ascribed to the formation of a conducting filament (CF) because of the migration of Ag+ ions, while defect mediated charge carrier transport led to switching in the Pt/Au electrode. Furthermore, the RHRS/RLRS ratio achieved in this work (108) is also of the highest magnitude reported thus far. Furthermore, a comparison of devices with Ag/Au electrodes but with different channel widths (50, 100 and 200 µm) gave insightful results on the existence of multiple resistance states, device endurance and retention. An inverse relationship between the retention time and the device's channel width was observed, where the device with a 50 µm channel width showed a retention time of 48 hours, and the one with a 200 µm width showed stability only up to 3000 s. Furthermore, low frequency noise measurements were performed to understand the effect of defects in the low resistance state (LRS) and the high resistance state (HRS). The HRS exhibited Lorentzian noise behaviour while the LRS exhibited Lorentzian only at low current bias which converged to 1/f noise at higher current bias.

Large-Area Transfer of 2D TMDCs Assisted by a Water-Soluble Layer for Potential Device Applications.

Layer transfer offers enormous potential for the industrial implementation of two-dimensional (2D) material technology platforms. However, the transfer method used must retain the as-grown uniformity and cleanliness in the transferred films for the fabrication of 2D material-based devices. Additionally, the method used must be capable of large-area transfer to maintain wafer-scale fabrication standards. Here, a facile route to transfer centimeter-scale synthesized 2D transition metal dichalcogenides (TMDCs) (3L MoS2, 1L WS2) onto various substrates such as sapphire, SiO2/Si, and flexible substrates (mica, polyimide) has been developed using a water-soluble layer (Na2S/Na2SO4) underneath the as-grown film. The developed transfer process represents a fast, clean, generic, and scalable technique to transfer 2D atomic layers. The key strategy used in this process includes the dissolution of the Na2S/Na2SO4 layer due to the penetration of NaOH solution between the growth substrate and hydrophobic 2D TMDC film. As a proof-of-concept device, a broadband photodetector has been fabricated onto the transferred 3L MoS2, which shows photoresponse behavior for a wide range of wavelengths ranging from near-infrared (NIR) to UV. The enhancement in photocurrent was found to be 100 times and 10 times the dark current in the UV and visible regions, respectively. The fabricated photodetector shows a higher responsivity of 8.6 mA/W even at a low applied voltage (1.5 V) and low power density (0.6 µW/mm2). The detector enables a high detectivity of 2.9 × 1011 Jones. This work opens up the pathway toward flexible electronics and optoelectronics.

Psammocarcinoma of ovary with serous cystadenofibroma of contralateral ovary: a case report.

INTRODUCTION: Psammocarcinoma of ovary is a rare serous neoplasm characterized by extensive formation of psammoma bodies, invasion of ovarian stroma, peritoneum or intraperitoneal viscera, and moderate cytological atypia. Extensive medlar search showed presence of only 28 cases of psammocarcinoma of ovary reported till date. CASE PRESENTATION: We herein report a case of psammocarcinoma of ovary with serous cystadenofibroma of contralateral ovary in a 55 year old Asian Indian female. CONCLUSION: To the best of author's knowledge, ours is the rare case describing coexistence of this very rare malignant serous epithelial tumor with a benign serous cystadenofibroma of contralateral ovary.