Rita Roy

The kinetics of formation of intermetallics in Ag/In thin film couples

Abstract Silver and indium bimetallic thin film couples have been studied by monitoring the contact and composite electrical resistance behaviour with time for both as-deposited and annealed specimens. X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) studies have also been performed on the samples. Silver reacts with indium at room temperature with the formation of e-AgIn 2 phase, which is diffusion controlled, the activation energy being about 0.43 eV in the temperature range 318–401 K. The activation energy of grain boundary diffusion as determined from contact electrical resistance measurements is about 0.34 eV. Both XRD and TEM indicate the growth of e phase, which gradually transforms to δ-Ag 2 In phase for silver-rich films. Indium diffusion through silver grain boundaries has been observed by SEM. A tentative explanation of the first phase formation is proposed.

Low voltage electrodeposition of diamond-like carbon films

Abstract Diamond-like carbon (DLC) films were deposited by electrodeposition technique onto SnO 2 -coated glass substrates by using a mixture of acetic acid and water as electrolyte. The applied voltage between the electrodes was mere 2.1 V. The films have rough surface and distinct broad characteristic peaks at ∼1336 and ∼1601 cm −1 dominated the Raman spectra. Band gap and refractive index of the films varied between 2.3–2.65 eV and 1.25–1.3, respectively. Photoluminscence studies indicate excitonic transition at ∼2.62 eV.

The formation of intermetallics in Cu/In thin films

The kinetics of the formation of intermetallics in the Cu–In bimetallic thin film couple have been studied from room temperature to 432 K by measuring the evolution of composite and contact electrical resistance with time and temperature. The resistivity measurements have been supplemented by x-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Copper reacts with indium even at room temperature to form CuIn intermetallic and assuming a model of defect assisted diffusion into the grains, the activation energy averaged over five different samples is found to be 0.40 eV. The grain boundary diffusion is found to occur with an average activation energy of 0.55 eV. XRD confirms the growth of CuIn intermetallic and on annealing at higher temperature, for copper-rich films copper further reacts with CuIn to form Cu 9 In 4 . Further evidences of solid state reactions and grain boundary diffusion through Cu grain boundaries have been obtained from SEM study. TEM indicates the growth of the grain size on annealing and confirms the presence of the CuIn phase.

Metal complexes of sulphur–nitrogen chelating agents. Part 11. Synthesis, characterisation, and thermodynamics of nucleophilic substitution reactions of monohalogeno nickel(II) complexes of tridentate ligands of the type SNN in solution and the solid state

Square-planar nickel(II) complexes [NiLX](X = Cl, Br, I, or SCN) have been obtained through deprotonation of the ligands methyl 2-(β-aminoethylamino)cyclopent-1-enedithiocarboxylate (HL1), methyl 2-(β-aminoisopropylamino)cyclopent-1-enedithiocarboxylate (HL2), and methyl 2-(β-diethylaminoethylamino)cyclopent-1-enedithiocarboxylate (HL3). Diamagnetic complexes of composition [NiL(MeCN)][ClO4](L = L1–L3) and [Ni2L2(HL)][ClO4]2(L = L1 or L2) have also been synthesised. The equilibrium constants for the nucleophilic substitution reaction [NiL2X]+ B [NiL2(B)]++ X–(X = Cl, Br, or I; B = pyridine and its methyl-substituted derivatives) have been determined spectrophotometrically in the temperature range 25–50 °C. A linear correlation has been obtained between the ΔH⊖ and ΔS⊖ values. The enthalpy changes (ΔH2) and activation energies (Ea*) for the thermal dissociation [NiL2(B)]X(s)→[NiL2X](s)+ B(g) have been determined. A linear correlation has been found between the (ΔS2) and Ea* values.

Metal Complexes of Sulphur-Nitrogen Chelating Agents. Part 14. Nickel(II), Palladium(II), Copper(II), Cobalt(II), and Cobalt(III) Complexes of the Tetradentate Schiff Bases Having ONNS Donor Sites

SummaryComplexes of nickel(II), palladium(II), copper(II), cobalt(II), and cobalt(III) with methyl-2-(β-salicylaldiminoethyl)-cyclopent-1-en-dithiocarboxylate (H2L1) and methyl-2-(β-salicylaldiminoisopropyl)cyclopent-1-en-dithiocarboxylate (H2L2) have been prepared. They contain the donor sites ONNS. The metal(II) ions from neutral, monomeric square planar chelate complexes. The cobalt(III) complexes [CoL1-(H2O)2]X (X=Cl or ClO4) appear to betrans-diaqua-species. All compounds have been characterized by a number of physico-chemical methods.

Metal complexes of sulfur-nitrogen chelating agents. Part 12. The chemistry of nickel(II), palladium(II), cobalt(II) and copper(II) complexes of N2S2 and N3S2 donor systems

SummaryNickel(II), palladium(II), cobalt(II) and copper(II) complexes of the ligandN,N′-1,2-propane-bis(methyl 2-amino-cyclopent-1-ene-dithiocarboxylate) (H2L1),N,N′-1,3-propane-bis(methyl 2-aminocyclopent-1-ene-dithiocarboxylate) (H2L2) andN,N′-[bis(methyl 2-aminocyclopent-1-ene-dithiocarboxylate)] diethylenetriamine (H2L3) have been synthesised. Both H2L1 and H2L2 form complexes of the type ML, and all but the copper(II) complexes, are square planar. In the copper(II) complexes tetrahedral distortion is significantly more with CuL2. From H2L3 square planar complexes of the type [M(HL3)X] (M=Ni, X=Cl, Br, I or SCN; M=Pd, X=Cl or Br) have been obtained in which the donor unit involved is N2SX. The composition of the cobalt(II) and copper(II) complexes is [M(H2L3)X2] (X=Cl or Br) which contain the chromophore [MN3X2].

Electrically conducting polyaniline and polyaniline/polycarbonate composite films: Preparation, characterization and electrical conductivity measurements

Polyanilinc (PAN) films and composites of polyaniline with poly bisphenol A carbonate (PC) have been prepared electrochemically. The electrical conductivity measured from room temperature down to 77 K is larger in air than in vacuum and obeys a ID variable range hopping (VRH) mechanism. From DTA analysis of the composite film, an extra peak at 210 °C apart from the usual peaks of PC and PAN has been identified. It is believed to be the result of a chemical interaction between PAN and PC, that is further confirmed from the shift in the carbonyl peak in the FTIR spectra of the composite films. From XPS studies and electrical conductivity measurements of different films it seems that it is the proportion of ionic chlorine rather than covalent chlorine to nitrogen that is more important in determining the conductivity. SEM pictures clearly indicate the formation of a fibrilar network in the composite film, especially inside the craters seen on the surface.

Structural characterization of the CuIn intermetallic phase produced by interfacial reactions in Cu/In bimetallic films

Abstract The composition, morphology and structure of the new CuIn intermetallic produced by interfacial reaction in Cu/In bimetallic films have been studied by X-ray diffraction and transmission electron microscopy (TEM). Besides development of the CuIn intermetallic, the formation of the Cu 9 In 4 (δ phase) intermetallic has also been noticed on annealing the films at higher temperatures. The CuIn intermetallic has been indexed as a monoclinic lattice with cell dimensions a = 0.8234 nm, b = 1.4490 nm, c = 1.0280 nm and β = 133.79°, and as having a space group P 12 1 1(4) or P 12 1/m 1(11). The film composition shows Cu and In in a 1:1 ratio. TEM study reveals the mechanism of the development of CuIn grains of average size 250 nm, through grain-boundary interstitial diffusion of Cu and In on annealing at 393 K.

X-ray photoelectron spectroscopic studies of conducting polyaniline, poly bisphenol A carbonate and electrochemically synthesized composite of the two

Abstract X-ray photoelectron studies of electrochemically prepared conducting polyaniline (PAN), polycarbonate (PC) and PAN/PC composite films have been studied. The core level spectra of carbon, oxygen, nitrogen and chlorine have been synthesized using Gaussian distribution functions. The analysis of the first two elements indicates the presence of carbonyl group on the surface of PAN samples. The detailed analysis of nitrogen and chlorine spectra show the presence of NCI bonding apart from usual covalent peaks. No major structural modification in the composite film could be detected. Only the presence of covalent chlorine derived from chloroform used to prepare these films have been observed. From the measurement of electrical conductivity of these films it seems that it is the proportion of ionic chlorine, rather than covalent chlorine to nitrogen that is important in determining the conductivities.

The study of diffusion of copper in thin films of silver and AgAl alloys as a function of increasing aluminium concentration

Abstract The diffusion of copper through electron-beam-evaporated silver and AgAl alloy thin films of four different compositions (5.8, 9.2, 15.8 and 18.2 at % Al) has been studied by monitoring the electrical resistance with time in the temperature range 343–543 K. The aim of this work is to determine the extent to which the presence of aluminium affects copper diffusion through silver thin films. It is found that the activation energy Q and the pre-exponential factor D0 determined from the Arrhenius plot decrease in the aluminium content in the alloy film but as a whole the diffusion coefficient increases with increasing aluminium content in the temperature range of interest. Transmission electron microscopy and thin film X-ray diffraction studies with 9.2 and 18.2 at.% Al alloy films indicate that the microstructures and corresponding selected-area diffraction pattern vary as a function of aluminium content. With the addition of aluminium, copper reacts to form Al2Cu (θ phase) precipitates even at room temperature. Precipitation probably occurs along the grain boundaries of copper and along the alloy-Cu interface, thereby reducing grain growth, but, on annealing such films, this retarding effect of the precipitates on the grain growth is removed. The cause of enhancement of diffusion coefficient with increased aluminium content is attributed to the fact that the concentration gradient and accompanying stress gradient at the interface and grain boundaries produce dislocations.