Analysis of current ‐ voltage ‐ temperature characteristics of In and Cu contacts on n‐type MoSe2 single crystals

The current voltage characteristics of In / Cu with n‐type MoSe₂ Schottky diodes were measured over a wide temperature range 50 < T < 300 K. The interface formed by In and MoSe₂ shows ohmic behavior after annealing the contact at 100 °C for 12 h. The ohmic nature was retained at all the measured temperatures. The Cu ‐ nMoSe2 interface formed a Schottky junction diode with a good rectification ratio. The Schottky barrier height and the ideality factor thereby obtained were 0.72 eV and 1.45, respectively, at room temperature. Below room temperature, the barrier height and the ideality factor vary with decreasing temperature. The changes are significant at low temperatures. Barrier height inhomogeneities at the interface cause deviation in the zero‐bias barrier height and the ideality factor at low temperatures, and produce extra current such that I‐V characteristics remain consistent with the thermionic emission mechanism. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Reversal of stability on metalation of pentagonal-bipyramidal (1-MB6H7(2-) 1-M-2-CB5H7(1-) and 1-M-2,4-C2B4H7) and Icosahedral (1-MB11H12(2-) 1-M-2-CB10H12(1-) and 1-M-2,4-C2B9H12) boranes (M = Al, Ga, In, and Tl): energetics of condensation and relationship to binuclear metallocenes

The usual assumption of the extra stability of icosahedral boranes (2) over pentagonal-bipyramidal boranes (1) is reversed by substitution of a vertex by a group 13 metal. This preference is a result of the geometrical requirements for optimum overlap between the five-membered face of the ligand and the metal fragment. Isodesmic equations calculated at the B3LYP/LANL2DZ level indicate that the extra stability of 1-M-2,4-C(2)B(4)H(7) varies from 14.44 kcal/mol (M = Al) to 15.30 kcal/mol (M = Tl). Similarly, M(2,4-C(2)B(4)H(6))(2)(1-) is more stable than M(2,4-C(2)B(9)H(11))(2)(1-) by 9.26 kcal/mol (M = Al) and by 6.75 kcal/mol (M = Tl). The preference for (MC(2)B(4)H(6))(2) over (MC(2)B(9)H(11))(2) at the same level is 30.54 kcal/mol (M = Al), 33.16 kcal/ mol (M = Ga) and 37.77 kcal/mol (M = In). The metal-metal bonding here is comparable to those in CpZn-ZnCp and H(2)M-MH(2) (M= Al, Ga, and In).     

Effect of additional hydrogen peroxide to H2O2...(H2O)n, n=1 and 2 complexes: quantum chemical study

Hydrogen peroxide, H2O2, acts as a particularly strong reactant in aqueous environment. It has been demonstrated earlier that agglomerates with a single peroxide interacting with one and two water molecules manifest in several stable conformers within a narrow energy range. In the present study we seek structural changes brought out by adding an extra H2O2 to these systems at molecular level employing ab initio quantum chemical methods, viz., restricted Hartree-Fock and the second order Moller-Plesset perturbation theory. These clusters exhibit consistent trends in energy hierarchy at both the levels. Further, a many body interaction energy analysis quantifies the strength and cooperativity of hydrogen bonding in the (H2O2)2...(H2O)n, (n=1 and 2) clusters, bringing out structuring/destructuring effects attributed to attachment of water and hydrogen peroxide molecules.     

Neptunium estimation in the spent fuel dissolver solution by inductively coupled plasma-atomic emission spectroscopy

This paper deals with the optimization of experimental conditions for the estimation of Np in spent fuel dissolver solution using 2-thenoyltrifluoroacetone (HTTA) as extractant. The quantitative extraction of Np from the dissolver solution employing 0.5 M HTTA/xylene was followed by its estimation by Inductively Coupled Plasma-Atomic Emission Spectroscopy (ICP-AES) after stripping it from the organic phase with 8 M HNO₃. The reliability of the method was checked by standard addition technique. The method is precise and accurate yielding Np analytical recovery of 99 ± 1%.     

Comparative extraction efficiencies of tri-<Emphasis Type="Italic">n</Emphasis>-butyl phosphate and <Emphasis Type="Italic">N,N</Emphasis>-dihexyloctanamide for uranium recovery using supercritical CO<Subscript>2</Subscript>

Extraction of uranium from tissue paper, synthetic soil, and from its oxides (UO₂, UO₃ and U₃O₈) was carried out using supercritical carbon dioxide modified with methanol solutions of extractants such as tri-n-butyl phosphate (TBP) or N,N-dihexyl octanamide (DHOA). The effects of temperature, pressure, extractant/nitric acid (nitrate) concentration, and of hydrogen peroxide on uranium extraction were investigated. The dissolution and extraction of uranium in supercritical CO₂ modified with TBP, from oxide samples followed the order: UO₃ ≫ UO₂ > U₃O₈. Addition of hydrogen peroxide in the modifier solution enhanced the dissolution/extraction of uranium in dynamic mode. DHOA appeared better than TBP for recovery of uranium from different oxide samples. Similar enhancement in uranium extraction was observed in static mode experiments in the presence of hydrogen peroxide. Uranium estimation in the extracted fraction was carried out by spectrophotometry employing 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (Br-PADAP) as the chromophore.     

Fixed point results for generalized quasicontraction mappings in abstract metric spaces

In this paper, we introduce the concept of generalized quasicontraction mappings in an abstract metric space. By using this concept, we construct an iterative process which converges to a unique fixed point of these mappings. The result presented in this paper generalizes the Banach contraction principle in the setting of metric space and a recent result of Huang-Zhang for contractions. We also validate our main result by an example.     

Is high electric field capable of selectively inducing a covalent-like bond between polar and non-polar molecular species?

It is demonstrated through the present ab initio theoretical investigation that an external electric field can bring about a phenomenal enhancement in the strength of the bond between water and carbon-dioxide molecules from a van der Waals type (binding energy ~0.085 eV), to strong covalent type (binding energy ~7.45 eV), resulting in an exotic molecular complex. The onset of this effect is characterized by an abrupt change in the dipole moment of the composite system at a particular field-value, concomitant with the O–C=O ? O=C–O resonance in the CO₂ moiety of the complex. This field-induced bond formation is further confirmed by the emergence of a characteristic intermolecular stretching mode (~317 cm^?1) in the vibrational response of the system. This exotic bond that exhibits a covalent-like character, which accompanied by a charge-transfer, renders the carbon atom a substantial negative charge.     

Syntheses and antibacterial studies of some 2-[5-(Aryl)-[1,3,4]oxadiazole-2-ylsulfanyl] alkanoic Acids

Some new 2-[5-(aryl)-[1,3,4]oxadiazole-2-ylsulfanyl]alkanoic acids were synthesized and studied for their antibacterial activity. These compounds were prepared from aromatic carboxylic acid hydrazides. Aromatic carboxylic acid hydrazides 1 on refluxing with carbon disulfide and methanolic potassium hydroxide and then on subsequent acidification with hydrochloric acid furnish 5-aryl-1,3,4-oxadiazole-2-thiones 2. 2-Chloro alkanoic acids react with 2 in alkaline media and on acidification yield the title compounds 3. These compounds were characterised by CHN analyses, IR, mass and ¹H NMR spectral data. All the compounds were evaluated for their in vitro antibacterial activity against two Gram negative strains (Escherichia coli and Pseudomonas aeruginosa) and two Gram positive strains (Bacillus subtilis and Staphylococcus aureus) and their minimum inhibitory concentration (MIC) were determined.     

Exchange and correlation effects on density excitation spectra of metallic quantum wires at finite temperature

We have studied the effect of exchange and correlations on the density excitation spectra of metallic quantum wires at finite temperature. The correlations are treated by incorporating the first-order self and exchange contributions into the random-phase approximation (RPA). Numerical results are presented for the spectra of the density response function and the plasmon dispersion for the gold wire on Si(557) substrate-a system studied recently by Nagao et al. (2006 Phys. Rev. Lett. 97 116802) for plasmons using electron energy loss spectroscopy. Our results for plasmons are found to agree with the experimental data. Though the first-order correction is small at currently accessible wire parameters, it becomes significant with increasing coupling parameter r(s). The effect of temperature on plasmons is found to be small for the wire system investigated experimentally. However, temperature has a significant effect on the spectra of the response function. We have also calculated the static structure factor, the pair-correlation function and the correlation energy at zero temperature in the first-order theory to check its applicability in dealing with correlations. Results are compared directly with the available Monte Carlo simulation data. It is found that the static correlation functions improve significantly over the RPA with the increase of r(s). On the other hand, the correlation energy shows very good agreement for r(s) ≤ 5 and wire widths b ≥ a(0). For smaller b, the agreement is good up to relatively smaller r(s).     

Investigation of carrier scattering mechanisms in molybdenum diselenide single crystals by hall effect measurements

Molybdenum diselenide (MoSe₂) belong to the large family of layered transition metal dichalcogenides. It consists of weakly coupled sandwiched layers i.e. Se – Mo – Se in which a Mo atom layer is enclosed within two Se layers. This structure makes MoSe₂ extremely anisotropic in character and leads to unusual structural properties. In addition, MoSe₂ possess flexible nature along with good carrier mobility to make them potential candidate for fabricating flexible high mobility electronic devices such as Schottky barrier devices, FETs, solar cell etc. In context of this authors made an effort to study the low temperature (12 < T < 300 K) electronic transport properties of Molybdenum diselenide (MoSe₂). Through the investigation the temperature dependent Hall mobility study revealed that the grown crystals of MoSe₂possess a mixed scattering mechanism. It has been found that observed temperature dependant mobility has at least two transitions from lattice to impurity scatterings showing an imprint of multicarrier nature of this semiconductor originating from its complex band structure. It has been observed that the studied crystals have at least two group of carriers of differing origins in which transition between dominant scattering mechanisms occur at different temperatures. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)