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.

Electrical characteristics of plasma oxidized Si1−x−yGexCy metal–oxide–semiconductor capacitors

Abstract: Microwave plasma oxidation (below 200 °C) of partially strain-compensated Si1−x−yGexCy (Ge:C=20:1 and 40:1) with and without a Si cap layer is reported The electrical properties of grown oxides have been characterized using a metal–oxide–semiconductor structure Fixed oxide charge density and mid-gap interface trap density are found to be 29×1011/cm2 and 88×1011/cm2/eV, respectively, for directly oxidized Si079Ge02C001 film The oxide on samples with low C (05%) concentration, exhibits hole trapping, whereas electron trapping is observed for oxides on alloys containing 1% C

Qualitative behavior of three species food chain around inner equilibrium point: spectral analysis

Abstract: This work deals with analytical investigation of local qualitative temporal behavior around inner equilibrium point of a model for three species food chain, studied earlier by Hastings and Powel and others. As an initial step towards the spectral analysis of the model, the governing equations have been split into linear and nonlinear parts around arbitrary equilibrium point. The explicit parameter dependence of eigenvalues of Jacobi matrix associated to the linear part have been derived. Analyzing these expressions in conjunction with some pedagogical analysis, a lot of predictions on stable, unstable or chaotic change of species have been highlighted. Agreement of predictions of this work with available numerical or semi-analytical studies suggest the utility of analytical results derived here for further investigation/analysis of the model as desired by earlier works.

Superior optical (λ ∼ 1550 nm) emission and detection characteristics of Ge microdisks grown on virtual Si0.5Ge0.5/Si substrates using molecular beam epitaxy.

Abstract: We report the optical characteristics of relatively larger sized (~7.0 – 8.0 μm) but low aspect ratio Ge microdisks grown on a virtual Si0.5Ge0.5 substrate using molecular beam epitaxy following Stranski–Krastanov growth mechanism. Grown microdisks with a very low aspect ratio Ge islands, exhibit direct band gap (~ 0.8 eV) photoluminescence emission sustainable up to room temperature, enabled by the confinement of carriers into the microdisks. p-i-n diodes with an intrinsic layer containing Ge microdisks have been fabricated to study their emission and photo-response characteristics at optical communication wavelength of ~ 1550 nm. A strong electroluminescence at 1550 nm has been achieved at low temperatures in the device for a very low threshold current density of 2.56 μA/cm2 due to strong confinement of injected holes. The emission characteristics of the fabricated device with respect to injected current density and temperature have been studied. Novel emission and optical modulation characteristics at 1550 nm of the fabricated p-i-n device containing Ge microdisks grown on a virtual SiGe substrate indicate its potential for Si CMOS compatible on-chip optical communications.

Comparative study of mangrove litter nitrogen cycling to the adjacent estuary through modelling in pristine and reclaimed islands of Sundarban mangrove ecosystem, India

Abstract: Sundarban mangrove ecosystem is consisted of many islands both virgin and reclaimed in nature. A seven compartment model featuring different forms of nitrogen in soil and water is applied on virgin island in order to compare for estimating several parameters with reclaimed island. The physical, chemical factors and other rate parameters are retained same as in reclaimed island model, published before. The study is carried out for over two years, primary and secondary data are used in the model belong to same time scale for both the islands. Loss rate of soil organic nitrogen as humic acid and fulvic acids is very sensitive parameter for both the systems. Model results depict that virgin island is detritus based system governed by leaching and microbial processes.

Properties of Si1-x-yGexCy Epitaxial Films Grown by Ultrahigh Vacuum Chemical Vapor Deposition

Abstract: We have studied the deposition of Si 1-x-y Ge x C y epitaxial films using ultrahigh vacuum chemical vapor deposition at temperatures from 475 to 600°C. The growth rate is found to decrease substantially with the addition of methylsilane. Incorporation of C, as measured by secondary ion mass spectroscopy (SIMS ), is found to increase linearly with flow for low C concentration (∼2%) but the dependence becomes sublinear at higher CH 3 SiH 3 flow rates. The substitutional incorporation of C, determined using X-ray diffraction is found to increase with decreasing temperature. For the films studied here we find substitutional incorporation up to 1.8% in Si 1-y C y films This is for a total incorporation of 2.5%, as measured by SIMS. Complete substitutional incorporation of C is obtained for up to 1.2%. For Si 1-x-y Ge x C y films, we find that the amount of substitutional C that can be incorporated decreases with increasing temperature. At 550°C we find a maximum of 0.7% C can be incorporated substitutionally, whereas at 475°C we are able to incorporate higher concentrations, similar to that for Si 1-y C y layers. Morphology studies also indicate that lower growth temperatures are preferable in the growth of Si 1-y C y films.

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