Samit K. Ray

Bio: Samit K. Ray is an academic researcher from Indian Institute of Technology Kharagpur. The author has contributed to research in topics: Photoluminescence & Thin film. The author has an hindex of 44, co-authored 507 publications receiving 8085 citations. Previous affiliations of Samit K. Ray include University of Delaware & Indian Institute of Technology Kanpur.

Studies on carbon dots embedded Tamm plasmon polariton structures

Abstract: Tamm plasmon polaritons (TPPs) are excellent candidates for photonic device application for their intriguing properties and simple fabrication design. In this study, optical Tamm structures are fabricated by depositing silver thin film on onedimensional photonic crystals (1DPhCs), constituting twelve pairs of alternating quarter wave thick SiO2 and TiO2 thin films. Carbon quantum dots (CQDs) were incorporated in the TiO2 matrix of the final four pairs of the 1DPhCs. TPPs are observed in the reflectance spectra of the samples with and without CQDs. With the help of transfer matrix method electric field intensity distribution profile is obtained. It is observed that the electric field is confined and enhanced at the metal-1DPhC interface and decays within the 1DPhC. Comparison of PL emission from samples with and without CQDs in the last four layers are presented. Enhanced PL emission from CQDs corresponding to the TPP mode and suppression of emission within the photonic stop band is demonstrated.

Charge transfer mediated giant photo-amplification in air-stable $\alpha$-CsPbI$_3$ nanocrystals decorated 2D-WS$_2$ photo-FET with asymmetric contacts

Abstract: Hybrid heterostructure based phototransistors are attractive owing to their high gain induced by photogating effect. However, the absence of an in-plane built-in electric field in the single channel layer transistor results in a relatively higher dark current and require a large operating gate voltage of the device. Here, we report novel air-stable cesium lead iodide/tungsten di-sulfide (CsPbI 3 /WS 2 ) mixed dimensional heterostructure based photo-field-effect-transistors (photo-FETs) with asymmetric metal electrodes (Cr/WS 2 /Au), exhibiting extremely low dark current (~10 -12 A) with a responsivity of ~ 10 2 A/W at zero gate bias. The Schottky barrier (WS 2 /Au interface) induced rectification characteristics in the channel accompanied by the excellent photogating effect from solution-processed α-phase CsPbI 3 NCs sensitizers, resulting in gate-tunable broadband photodetection with a very high responsivity (~10 4 A/W) and excellent sensitivity (~10 6 ). Most interestingly, the device shows superior performance even under high humidity (50-65%) conditions owing to the formation of cubic α-phase CsPbI 3 nanocrystals with a relatively smaller lattice constant ( a = 6.2315 Å) and filling of surface vacancies (Pb 2+ centres) with the sulfur atoms from WS 2 layer, thus protecting it from environmental degradation. These results emphasise a novel strategy for developing mixed dimensional hybrid heterostructure based phototransistors for futuristic integrated nano-optoelectronic systems.

High Performance CsPbI3 NCs Decorated Few-layer WS2 Hybrid Photodetectors

Abstract: A promising device architecture that can achieve high response in photodetector devices can be consists of an effective semiconductor layer with high carrier mobility and highly photoabsorbing material. Here, we report a superior broadband visible photodetector with a few-layer tungsten disulfide (WS2) decorated with cesium lead iodide (CsPbI3) nano-crystals (NCs) in hybrid heterojunctions. An enhancement in photocurrent is demonstrated in the CsPbI3 NCs decorated WS2 0D/2D hybrid nanostructure compared to pristine WS2, revealing the potential of hybrid systems in next generation optoelectronic devices.

Integration of Au-SnO 2 nanocomposites with power efficient MEMS substrate for acetone sensing

Abstract: In this paper we report synthesis of Au-SnO 2 nanocomposites, and their integration on micro-hotplates through dip pen nano-lithography to realize a resistive acetone sensor device. The devices are power efficient (8.2°C temperature increase requires for 1 milli watt of power). The devices were characterized exposing acetone in presence of both dry and humid (40% RH) air. The response varies between 3.8 times (with 250 ppm) and 5.5 times (1000 ppm), and did not show much deterioration in presence of humidity.

Structural and electrical characterizations of oxynitride films on solid phase epitaxially grown silicon carbide

Abstract: We have investigated the structural and electrical properties of as-prepared and rapid thermal oxynitride films on C+ implanted solid phase epitaxially grown SiC. The oxynitride was grown using N2O. The C concentration of the samples was estimated to be 1, 2 and 5 at. %. From the infrared spectra, samples with 1 and 2 at. % carbon showed that the carbon was substitutionally incorporated into the silicon. No precipitation of SiC was detected. However, for the 5 at. % C sample, some precipitation was observed as indicated by a broad peak at ∼800 cm−1. The oxynitride films showed the Si-O-Si stretching mode at ∼1100 cm−1. The shoulder at 980–1067 cm−1 was due to the O-Si-N bond. The peak at 830 cm−1 was due to the Si-N and Si-C bonds and C-O complex vibrational mode was observed at 663 cm−1. Electrical characterization of the oxynitride films was carried out using the MOS capacitor structure. The interface state density was found to range between 5.7×1011 to 3.35×1012 cm−2eV−1 and increased with an increase in the C concentration. The electrical breakdown field was found to be in the range of 5–7 MV cm−1 and reduced with an increase in C concentration. The charge-to-breakdown value was measured and decreased with an increase in C concentration.

Prospects of Colloidal Nanocrystals for Electronic and Optoelectronic Applications

Abstract: Nanocrystals (NCs) discussed in this Review are tiny crystals of metals, semiconductors, and magnetic material consisting of hundreds to a few thousand atoms each. Their size ranges from 2-3 to about 20 nm. What is special about this size regime that placed NCs among the hottest research topics of the last decades? The quantum mechanical coupling * To whom correspondence should be addressed. E-mail: dvtalapin@uchicago.edu. † The University of Chicago. ‡ Argonne National Lab. Chem. Rev. 2010, 110, 389–458 389

Principles Of Fluorescence Spectroscopy

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Nanoscale metal oxide-based heterojunctions for gas sensing: A review

Abstract: Metal oxide-based resistive-type gas sensors are solid-state devices which are widely used in a number of applications from health and safety to energy efficiency and emission control. Nanomaterials such as nanowires, nanorods, and nanoparticles have dominated the research focus in this field due to their large number of surface sites facilitating surface reactions. Previous studies have shown that incorporating two or more metal oxides to form a heterojunction interface can have drastic effects on gas sensor performance, especially the selectivity. Recently, these effects have been amplified by designing heterojunctions on the nano-scale. These designs have evolved from mixed commercial powders and bi-layer films to finely-tuned core–shell and hierarchical brush-like nanocomposites. This review details the various morphological classes currently available for nanostructured metal-oxide based heterojunctions and then presents the dominant electronic and chemical mechanisms that influence the performance of these materials as resistive-type gas sensors. Mechanisms explored include p–n and n–n potential barrier manipulation, n–p–n response type inversions, spill-over effects, synergistic catalytic behavior, and microstructure enhancement. Tables are presented summarizing these works specifically for SnO2, ZnO, TiO2, In2O3, Fe2O3, MoO3, Co3O4, and CdO-based nanocomposites. Recent developments are highlighted and likely future trends are explored.

Diversity of life

Abstract: It is clear that the above can lead to confusion when scientists of different countries are trying to communicate with each other. Another example is the burrowing rodent called a gopher found throughout the western United States. In the southeastern United States the term gopher refers to a burrowing turtle very similar to the desert tortoise found in the American southwest. One final example; two North American mammals known as the elk and the caribou are known in Europe as the reindeer and the elk. We never sing “Rudolph the Red-nosed elk”! Confused? This was the reason for creating an internationally recognized system of naming organisms. To avoid confusion, living organisms are assigned a scientific name based on Latin or Latinized words. The English sparrow is Passer domesticus or Passer domesticus (italics or underlining these two names is the official written representation of a scientific name). Using a uniform naming system allows scientists from all over the world to recognize exactly which life form a scientist is referring to. The naming process is called the binomial system of nomenclature. Passer is comparable to a surname and is called the genus, while domesticus is the specific or species name (like your given name) of the English sparrow. Now scientists can give all sparrow-like birds the genus Passer but the species name will vary. All similar genera (plural for genus) can be grouped into another, “higher” category (see below). Study the following for a more through understanding of taxonomy. Taxonomy Analogy Kingdom: Animalia Country

Environmental applications of graphene-based nanomaterials.

Abstract: Graphene-based materials are gaining heightened attention as novel materials for environmental applications The unique physicochemical properties of graphene, notably its exceptionally high surface area, electron mobility, thermal conductivity, and mechanical strength, can lead to novel or improved technologies to address the pressing global environmental challenges This critical review assesses the recent developments in the use of graphene-based materials as sorbent or photocatalytic materials for environmental decontamination, as building blocks for next generation water treatment and desalination membranes, and as electrode materials for contaminant monitoring or removal The most promising areas of research are highlighted, with a discussion of the main challenges that we need to overcome in order to fully realize the exceptional properties of graphene in environmental applications