Epitaxial growth of Ge-Sb-Te based phase change materials

Ge-Sb-Te basierte Phasenwechselmaterialen sind vielersprechende Kandidaten für die Anwendung in optischen und elektrischen nicht-flüchtigen Speicheranwendungen. Diese Materialien können mit Hilfe von elektrischen oder optischen Pulsen reversibel zwischen der kristallinen und amorphen Struktur geschaltet werden. Diese stukturellen Phasen zeigen einen großen Unterschied in ihren elektronischen Eigenschaften, der sich in einer starken Änderung der optischen Reflektivität und des elektrischen Widerstands zeigt.Diese Studie befasst sich mit epitaktischem Wachstum und Analyse der epitaktischen Schichten. Der erste Teil der Arbiet befasst sich mir dem epitaktischen Wachstum von GeTe. Dünne GeTe Schichten wurden auf Si(111) und Si(001) Substraten mit einer Gitterfehlanpassung von 10.8% präpariert. Auf beiden Substraten bildet sich in der GeTe Schicht die [111] Oberflächenfacette parallel zur Si(001) und Si(111) Oberfläche aus. Während des inertialen Wachstums findet eine Phasentransformation von amorph zu kristallin statt. Diese Phasentransformation wurde mittels azimuthaler in-situ Beugung hochenergetischer Elektronen sowie in-situ Röntgenbeugung unter streifendem Einfall untersucht. Der zweite Teil der Arbeit wird die Epitaxie sowie die strukturelle Charakterisierung dünner Sb2Te3 Schichten dargestellt. Der dritte Teil umfasst die Epitaxie terniärer Ge-Sb-Te Schichten . Zum Wachstum wurden sowohl die Substrattemperatur als auch die Ge, Sb und Te Flüsse variiert. Es wird gezeigt, dass die Komposition der Schicht stark von der Wachtumstemperatur abhängt und nur entlang der pseudibinären Verbindungslinie von GeTe-Sb2Te3 variiert. Zur Kontrolle des Wachstums wurde dabei die in-situ Quadrupol Massenspektroskopie verwendet. Es zeigen sich diverse inkommensurate Beugungsmaxima entlang der [111] Oberflächennormalen der Schichten, anhand derer die Ausbildung einer Lehrstellen Ordnung in Form einer Überstruktur diskutiert wird.Ge-Sb-Te based phase change materials are considered as a prime candidate for optical and electrical data storage applications. With the application of an optical or electrical pulse, they can be reversibly switched between amorphous and crystalline state, thereby exhibiting large optical and electrical contrast between the two phases, which are then stored as information in the form of binary digits. Single crystalline growth is interesting from both the academic and industrial perspective, as ordered Ge-Sb-Te based metamaterials are known to exhibit switching at reduced energies. The present study deals with the epitaxial growth and analysis of Ge-Sb-Te based thin films. The first part of the thesis deals with the epitaxial growth of GeTe. Thin films of GeTe were grown on highly mismatched Si(111) and (001) substrates. On both the substrate orientations the film grows along [111] direction with an amorphous-to-crystalline transition observed during the initial stages of growth. The amorphous-to-crystalline transition was studied in-vivo using azimuthal reflection high-energy electron diffraction scans and grazing incidence x-ray diffraction. In the second part of the thesis epitaxy and characterization of Sb2Te3 thin films are presented. The third part of the thesis deals with the epitaxy of ternary Ge-Sb-Te alloys. The composition of the films are shown to be highly dependent on growth temperatures and vary along the pseudobinary line from Sb2Te3 to GeTe with increase in growth temperatures. A line-of-sight quadrupole mass spectrometer was used to reliably control the GeSbTe growth temperature. Growth was performed at different Ge, Sb, Te fluxes to study the compositional variation of the films. Incommensurate peaks are observed along the [111] direction by x-ray diffraction. The possibility of superstructural vacancy ordering along the [111] direction is discussed

Molecular authentication of green algae Caulerpa (Caulerpales, Chlorophyta) based on ITS and tufA genes from Andaman Islands, India

109-114Indigenous and non-indigenous invasive algal species introduction or prevalence is one of the major concerns to protect the native coastal environment. Globally, several studies have reported the effect of invasive alga Caulerpa on coral reefs. To establish the genetic variation between indigenous and non-indigenous invasive species, attempts have been made to develop molecular identification of Caulerpa algal species available at the Andaman Islands. In this study, 7 visually and morphologically different species belonging to the genus Caulerpa (Chlorophyta) were collected from the intertidal regions of South and Little Andaman Islands, India. The specimens were preliminarily identified based on the morphological characters and genetically mapped using ITS2 and chloroplast tufA gene markers. Six species of the Caulerpa viz. Caulerpa racemosa, C. racemosa var lamourouxii, C. racemosa var macrophysa, C. serrulata, C. fergusonii and C. microphysa were identified using ITS2 gene, and. C. mexicana var pluriseriata was identified using tufA gene. Two varieties, C. mexicana var. pluriseriata and C. racemosa var lamourouxii were found to be invasive to Indian waters. These were earlier reported in Red sea and in Phillipine waters in the pacific ocean. Further studies are needed to elucidate the genetic divergence of the Caulerpa species present in Andaman waters using different molecular markers

Correlating Photoluminescence and Structural Properties of Uncapped and GaAs-Capped Epitaxial InGaAs Quantum Dots.

The understanding of the correlation between structural and photoluminescence (PL) properties of self-assembled semiconductor quantum dots (QDs), particularly InGaAs QDs grown on (001) GaAs substrates, is crucial for both fundamental research and optoelectronic device applications. So far structural and PL properties have been probed from two different epitaxial layers, namely top-capped and buried layers respectively. Here, we report for the first time both structural and PL measurements from an uncapped layer of InGaAs QDs to correlate directly composition, strain and shape of QDs with the optical properties. Synchrotron X-ray scattering measurements show migration of In atom from the apex of QDs giving systematic reduction of height and enlargement of QDs base in the capping process. The optical transitions show systematic reduction in the energy of ground state and the first excited state transition lines with increase in capping but the energy of the second excited state line remain unchanged. We also found that the excitons are confined at the base region of these elliptically shaped QDs showing an interesting volume-dependent confinement energy scaling of 0.3 instead of 0.67 expected for spherical dots. The presented method will help us tuning the growth of QDs to achieve desired optical properties

Epitaxial growth of Ge-Sb-Te based phase change materials

Ge-Sb-Te basierte Phasenwechselmaterialen sind vielersprechende Kandidaten für die Anwendung in optischen und elektrischen nicht-flüchtigen Speicheranwendungen. Diese Materialien können mit Hilfe von elektrischen oder optischen Pulsen reversibel zwischen der kristallinen und amorphen Struktur geschaltet werden. Diese stukturellen Phasen zeigen einen großen Unterschied in ihren elektronischen Eigenschaften, der sich in einer starken Änderung der optischen Reflektivität und des elektrischen Widerstands zeigt.Diese Studie befasst sich mit epitaktischem Wachstum und Analyse der epitaktischen Schichten. Der erste Teil der Arbiet befasst sich mir dem epitaktischen Wachstum von GeTe. Dünne GeTe Schichten wurden auf Si(111) und Si(001) Substraten mit einer Gitterfehlanpassung von 10.8% präpariert. Auf beiden Substraten bildet sich in der GeTe Schicht die [111] Oberflächenfacette parallel zur Si(001) und Si(111) Oberfläche aus. Während des inertialen Wachstums findet eine Phasentransformation von amorph zu kristallin statt. Diese Phasentransformation wurde mittels azimuthaler in-situ Beugung hochenergetischer Elektronen sowie in-situ Röntgenbeugung unter streifendem Einfall untersucht. Der zweite Teil der Arbeit wird die Epitaxie sowie die strukturelle Charakterisierung dünner Sb2Te3 Schichten dargestellt. Der dritte Teil umfasst die Epitaxie terniärer Ge-Sb-Te Schichten . Zum Wachstum wurden sowohl die Substrattemperatur als auch die Ge, Sb und Te Flüsse variiert. Es wird gezeigt, dass die Komposition der Schicht stark von der Wachtumstemperatur abhängt und nur entlang der pseudibinären Verbindungslinie von GeTe-Sb2Te3 variiert. Zur Kontrolle des Wachstums wurde dabei die in-situ Quadrupol Massenspektroskopie verwendet. Es zeigen sich diverse inkommensurate Beugungsmaxima entlang der [111] Oberflächennormalen der Schichten, anhand derer die Ausbildung einer Lehrstellen Ordnung in Form einer Überstruktur diskutiert wird.Ge-Sb-Te based phase change materials are considered as a prime candidate for optical and electrical data storage applications. With the application of an optical or electrical pulse, they can be reversibly switched between amorphous and crystalline state, thereby exhibiting large optical and electrical contrast between the two phases, which are then stored as information in the form of binary digits. Single crystalline growth is interesting from both the academic and industrial perspective, as ordered Ge-Sb-Te based metamaterials are known to exhibit switching at reduced energies. The present study deals with the epitaxial growth and analysis of Ge-Sb-Te based thin films. The first part of the thesis deals with the epitaxial growth of GeTe. Thin films of GeTe were grown on highly mismatched Si(111) and (001) substrates. On both the substrate orientations the film grows along [111] direction with an amorphous-to-crystalline transition observed during the initial stages of growth. The amorphous-to-crystalline transition was studied in-vivo using azimuthal reflection high-energy electron diffraction scans and grazing incidence x-ray diffraction. In the second part of the thesis epitaxy and characterization of Sb2Te3 thin films are presented. The third part of the thesis deals with the epitaxy of ternary Ge-Sb-Te alloys. The composition of the films are shown to be highly dependent on growth temperatures and vary along the pseudobinary line from Sb2Te3 to GeTe with increase in growth temperatures. A line-of-sight quadrupole mass spectrometer was used to reliably control the GeSbTe growth temperature. Growth was performed at different Ge, Sb, Te fluxes to study the compositional variation of the films. Incommensurate peaks are observed along the [111] direction by x-ray diffraction. The possibility of superstructural vacancy ordering along the [111] direction is discussed

Antimicrobial Potential of Epiphytic Bacteria Associated With Seaweeds of Little Andaman, India

Seaweeds of the intertidal regions are a rich source of surface associated bacteria and are potential source of antimicrobial molecules. In the present study, 77 epiphytic isolates from eight different algae collected from Little Andaman were enumerated. On testing for their antimicrobial activities against certain pathogens twelve isolates showed positive and six of them showed significant antimicrobial inhibition zone against Shigella boydii type 1, Shigella flexneri type 2a, Shigella dysenteriae type 5, Enterotoxigenic Escherichia coli O115, Enteropathogenic E. coli serotype O114, Vibrio cholera; O1 Ogawa, Aeromonas hydrophila, Klebsiella pneumoniae, Staphylococcus aureus. Based on the activity these six isolates (G1C, G2C, G3C, UK, UVAD, and Tor1) were identified by 16S rRNA gene sequence and were found to belong to the phyla Firmicutes and Proteobacteria. Purified antimicrobial compounds obtained from these isolates were identified by GC-MS. Furan derivatives were identified from G2C Pseudomonas stutzeri KJ849834, UVAD Alcanivorax dieselolei KJ849833, UK Vibrio sp. KJ849837, Tor1 Exiguobacterium profundum KJ849838. While 2-Pyrrolidinone, Phenol, 2, 4-bis (1, 1-dimethylethyl) were from G3C Vibrio owensii KJ849836 and (1-Allylcyclopropyl) methanol from the extracts of G1C Bacillus sp. KJ849835. The results of the present study shows that these six potent isolates isolated from the seaweeds are found to be a source of antimicrobial compounds

A Survey on Reducing Costs Vs Improving Outcomes and Opportunities in Health Care Field Using Big Data

In recent years, the total amount of medical data collected has grown exponentially, mainly because of the introduction of new medical technologies and the increased use of IT to manage medical health records of patients. These technologies have been introduced not only to provide higher quality of care but also to help solve some of the major healthcare problems in developed countries%253A the lack of productivity and efficiency, the increasing costs and the relatively low accessibility of the system. Big Data, or the capability to develop, analyze and visualize huge and complex data sets for various research interests and applications, has the promise to radically impact the speed and direction in tackling these problems. Health care field grows tremendously in last few decades. The health care field has generated huge amounts of data that has huge volume, enormous velocity and vast variety. Also it comes from a variety of new sources as hospitals are now tend to implemented electronic health record (EHR) systems. These sources have strained the existing capabilities of existing conventional relational database management systems. In such scenario, Big Data solutions offer to harness these massive, heterogeneous and complex data sets to obtain more meaningful and knowledgeable information. This paper basically studies the impact of implementing the big data solutions on the healthcare field, the potential opportunities, challenges and available platform and tools to implement Big data analytics in health care field

Growth control of epitaxial GeTe–Sb2Te3\mathrm{GeTe–Sb_2Te_3} films using a line-of-sight quadrupole mass spectrometer

A narrow growth window combined with highly temperature dependent compositional variations poses a serious problem for the growth of epitaxial GeTe–Sb2Te3 (GST) thin films. The problems are further aggravated by the weak coupling of the radiatively heated non-contact thermocouples to the substrate. An increase in surface temperature during growth as inferred from the increase in desorption of GeTe heteromolecules and the resulting change in alloy composition are studied. Using the desorption signal as a feedback to control the surface temperature, the thermocouple temperature was varied over the duration of the growth to maintain a constant desorption and hence constant surface temperature. Interestingly, the composition of the grown films varies along the GeTe–Sb2Te3 pseudobinary line just by varying the desorption without changing the supplied flux. The out-of-plane lattice constant of the epitaxially grown GST thin film increases with an increase in Ge concentratio

<span style="font-size:10.0pt;font-family: "Times New Roman";mso-fareast-font-family:"Times New Roman";mso-bidi-font-family: Mangal;mso-ansi-language:EN-US;mso-fareast-language:EN-US;mso-bidi-language: HI" lang="EN-US">Comparative theoretical studies on natural atomic orbitals, natural bond orbitals and simulated UV-visible spectra of N-(methyl)phthalimide and N-(2 bromoethyl)phthalimide</span>

178-184The charge delocalization patterns of phthalimide derivatives such as N-(methyl)phthalimide and N-(2-bromoethyl)-phthalimide have been performed with the help of natural bond orbital (NBO) analyses and simulated UV-visible spectra. The second order perturbation energies of the most interacting NBOs and the population of electrons in core, valance and Rydberg sub-shells have been predicted by density functional theory (DFT) computations in GAUSSIAN 03W software package. In the present study, the natural atomic orbital occupancies showed the presence of charge delocalization within the molecule. The natural hybrid atomic orbital studies enhance us to know about the type of orbitals and its percentage of s-type and <i style="mso-bidi-font-style: normal">p-type character. In addition, the excited electronic transitions along with their absorption wavelengths, oscillator strengths and excitation energies for the gaseous phase of the title molecules have been computed at TD-DFT/B3LYP/6-311++G(d,p) method. <span style="mso-fareast-font-family: Calibri" lang="EN-GB">The energetic behaviour of the compound in different solvent medium (water, ethanol, and methanol) has been examined by applying polarizable continuum model (PCM). The complete molecular orbital simulations and theoretical UV-visible spectra have been carried out in this study which yield better understanding of charge delocalization pattern and stability of the title molecules to a greater extent. </span

DNA barcoding of False stone fish <em>Scorpaenopsis diabolus </em>(Cuvier, 1829), a new record for the Andaman Islands and India

2237-2240A specimen of the false stone fish Scorpaenopsis diabolus(Cuvier, 1829)was captured at the Burmanallah coast in the Andaman Islands, India. Identification was done combining traditional taxonomy, based on the observation and measurement of morphology traits, with DNA barcoding in an integrative taxonomy approach. On this basis, S. diabolus constitutes a new record in the faunal diversity of the Andaman Islands and India

CNN based plant disease identification using PYNQ FPGA

This research presents a novel approach for plant disease identification utilizing Convolutional Neural Networks (CNNs) and the PYNQ FPGA platform. The study leverages the parallel processing capabilities of FPGAs to accelerate CNN inference, aiming to enhance the efficiency of plant disease detection in agricultural settings. The implementation involves optimizing the CNN architecture for deployment on the PYNQ FPGA, considering factors such as image size and learning rates. Through experimentation, the research refines hyper parameters, achieving improved accuracy and F1 scores. Visualizations using heat maps highlight the CNN's reliance on color, shape, and texture for feature extraction in disease identification. The integration of FPGA technology demonstrates promising advancements in real-time, high-performance plant disease classification, offering potential benefits for precision agriculture and crop management. This research contributes to the growing field of FPGA-accelerated deep learning applications in agro technology, addressing challenges in plant health monitoring and fostering sustainable agricultural practices