M. Aslam Siddiqi

Government College University, Faisalabad

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Burak Atakan

University of Duisburg-Essen

K. Lucas

Laboratoire d'Analyse et d'Architecture des Systèmes

Rehan A. Siddiqui

University of Duisburg-Essen

Jörg Krissmann

University of Duisburg-Essen

P. Svejda

Ruhr University Bochum

Ilona Jipa

Friedrich-Alexander-Universität Erlangen-Nürnberg

Hans‐Peter Steinrück

Friedrich-Alexander-Universität Erlangen-Nürnberg

Ulrich Zenneck

Friedrich-Alexander-Universität Erlangen-Nürnberg

Hubertus Marbach

Carl Zeiss (Germany)

Till Cremer

Incom (United States)

Cooperative Institutions

Friedrich-Alexander-Universität Erlangen-Nürnberg

Ruhr University Bochum

University of Duisburg-Essen

Jeonbuk National University

RWTH Aachen University

University of the Punjab

Chonbuk National University Hospital

Centre National de la Recherche Scientifique

Kiel University

King Saud University

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Methylated [(benzene)(1,3-butadiene)Ru0] Derivatives as Novel MOCVD Precursors with Favorable Properties

Chemical Vapor Deposition (2011)

Ilona Jipa M. Aslam Siddiqi Rehan A. Siddiqui Burak Atakan Hubertus Marbach

Abstract [(Benzene)(2‐methyl‐1,3‐butadiene)Ru 0 ] ( 1 ), [(benzene)(2,3‐dimethyl‐1,3‐butadiene)Ru 0 ] ( 2 ), and [(2,3‐dimethyl‐1,3‐butadiene)(toluene)Ru 0 ] ( 3 ) are prepared and tested as new metal‐organic (MO) ruthenium precursor complexes with favorable deposition properties for the CVD of thin ruthenium films. X‐ray diffraction (XRD) studies of single crystals of the complexes are characteristic for true Ru 0 π‐complexes without molecular structure peculiarities or significant intermolecular interactions in the solid state, which can hinder undecomposed evaporation. Differential thermal analysis (DTA) and vapor pressure data qualify the compounds as almost ideal MOCVD precursors. Thin ruthenium films are deposited successfully on silicon wafers at substrate temperatures between 200 and 400 °C in a nitrogen gas atmosphere. X‐ray photoelectron spectroscopy (XPS), four‐point probe conductivity measurements, and atomic force microscopy (AFM) are used to characterize the films. All films consist of polycrystalline metallic ruthenium with a low surface roughness.

10.1002/cvde.201006853

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Citations (8)

Thermal Stability, Vapor Pressures, and Diffusion Coefficients of Some Metal 2,2,6,6-Tetramethyl-3,5-heptandionate [M(tmhd)_n] Compounds

Journal of Chemical & Engineering Data (2010)

M. Aslam Siddiqi Rehan A. Siddiqui Burak Atakan

Many metal 2,2,6,6-tetramethyl-3,5-heptandionate [M(tmhd)n] compounds are volatile enough to be useful as precursors of the metals in vapor-phase deposition processes, for example, metal organic chemical vapor deposition (MOCVD). The thermal stability, vapor pressures, and gaseous diffusion coefficients of these compounds are, therefore, of fundamental importance for achieving reproducible and effective depositions. The present communication reports the thermal stability, vapor pressures, enthalpies of sublimation, and diffusion coefficients (in nitrogen and/or helium) for some metal 2,2,6,6-tetramethyl-3,5-heptandionate compounds [M(tmhd)n], namely, [Al(tmhd)3], [Cr(tmhd)3], [Cu(tmhd)2], [Fe(tmhd)3], [Mn(tmhd)3], and [Ni(tmhd)2] at temperatures between (341 and 412) K at ambient pressure. All of these are found to be stable under the investigated experimental conditions and thus are suitable precursors for CVD.

Sublimation

Thermal Stability

10.1021/je9006822

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Citations (14)

A novel fibre-optic based technique for the spectrophotometric measurement of phase and chemical equilibrium of (sulphur dioxide+water) at elevated temperatures

The Journal of Chemical Thermodynamics (1997)

M. Aslam Siddiqi Jörg Krissmann K. Lucas

10.1006/jcht.1996.0166

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Citations (8)

A Study of the Effect of Nitrogen Dioxide on the Absorption of Sulfur Dioxide in Wet Flue Gas Cleaning Processes

Industrial & Engineering Chemistry Research (2001)

M. Aslam Siddiqi J. Petersen K. Lucas

The effect of nitrogen dioxide on the physicochemical processes which take place during the absorption of sulfur dioxide in aqueous solution under conditions similar to those of a wet flue gas cleaning process has been studied. The study is done at 298.65, 318.45, and 333.35 K and ambient pressure. The gas phase and the liquid phase could be specified completely. The results show that after a few hours NO2 vanishes from the gas phase. This leads to a reproducible frozen (stable) state in which tetravalent sulfur exists in phase and chemical equilibrium. The simultaneous absorption of SO2 and NO2 in water depends on their initial concentrations and the temperature and is governed by the kinetics of a number of concurrent and consecutive reactions in the liquid phase. The gas phase contains SO2, N2O, and NO. The liquid phase contains a number of nitrogen−sulfur compounds besides tetravalent and hexavalent sulfur and nitrate. A scheme for the reactions that can take place in aqueous solution has been proposed. The analysis results together with the known thermodynamic and kinetic data from the literature have been used to develop a model for the description of the SO2/NO2/N2/H2O system. The model has been used to predict not only the stable state composition at various temperatures but also the time dependence of the system composition. The agreement between the experimental results and model calculations is quite good. The effects of temperature and the initial concentration of the gas mixture on the absorption behavior of SO2 are discussed.

Nitrogen dioxide

Sour gas

10.1021/ie000815g

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Citations (25)

CCDC 769099: Experimental Crystal Structure Determination

The Cambridge Structural Database (2011)

Ilona Jipa K. Danova N. Popovska M. Aslam Siddiqi Rehan A. Siddiqui

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

10.5517/cctt9nk

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Citations (0)

Single- and Double-Strand Break Formation in DNA Irradiated in Aqueous Solution: Dependence on Dose and OH Radical Scavenger Concentration

Radiation Research (1987)

M. Aslam Siddiqi E. Bothe

The yields of single- and double-strand breaks (SSB and DSB) in calf thymus DNA, after 60Co gamma irradiation in dilute aqueous solution, have been determined via molecular weight measurements using a low-angle laser light scattering technique. The irradiations were administered to N2O-containing solutions of DNA in the absence and presence of oxygen and with different concentrations of the OH radical scavengers phenol, tertiary butanol, and methanol. OH radicals were found to produce SSB linearly with dose with a G value of 55 nmol J-1 and 54 nmol J-1 in deoxygenated and oxygenated solutions, respectively. DSB were formed according to a linear-quadratic dose relationship and the G value of linearly formed DSB were GDSB alpha(r.t.) = 3.5 nmol J-1 in deoxygenated and 3.2 nmol J-1 in oxygenated solution. The ratio of GSSB/GDSB alpha(r.t.) = gamma of 19 +/- 6 was independent of the scavenger concentration in the case of tertiary butanol and methanol-containing solutions. GDSB alpha(r.t.) is interpreted to result from a radical site transferred from a sugar moiety of the cleaved strand to the complementary intact strand. This process of radical transfer and subsequent cleavage of the second strand occurs with a probability of about 6 +/- 2% in the presence of oxygen at all scavenger concentrations studied. These data on scavenging capacity on GDSB alpha(r.t.) suggest that the double-strand breakage produced via radical transfer remains higher than that resulting from direct effect, up to scavenging capacities of about 10(9) s-1.

Scavenger

Free radical scavenger

Hydroxyl radical

10.2307/3577098

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Citations (196)

Thermal Stability and Sublimation Pressures of Some Ruthenocene Compounds

Materials (2010)

M. Aslam Siddiqi Rehan A. Siddiqui Burak Atakan Nina Roth Heinrich Lang

We set out to study the use of a series of ruthenocenes as possible and promising sources for ruthenium and/or ruthenium oxide film formation.The thermal stability of a series of ruthenocenes, including (η5-C5H4R)(η5-C5H4R´)Ru (1), R = R´ = H (3), R = H, R´ = CH2NMe2 (5), R = H, R´= C(O)Me (6), R = R´ = C(O)Me (7), R = H, R´ = C(O)(CH2)3CO2H (8), R = H, R´ = C(O)(CH2)2CO2H (9), R = H, R´ = C(O)(CH2)3CO2Me (10), R = H, R´= C(O)(CH2)2CO2Me (11), R = R´ = SiMe3), (η5-C4H3O-2,4-Me2)2Ru (2), and (η5-C5H5-2,4-Me2)2Ru (4) was studied by thermogravimetry. From these studies, it could be concluded that 1–4, 6 and 9–11 are the most thermally stable molecules. The sublimation pressure of these sandwich compounds was measured using a Knudsen cell. Among these, the compound 11 shows the highest vapor pressure.

Ruthenocene

Sublimation

Thermogravimetry

Ruthenium oxide

Thermal Stability

10.3390/ma3021172

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Citations (13)

A Study of the Thermodynamic Behavior of Mercury in a Wet Flue Gas Cleaning Process

Industrial & Engineering Chemistry Research (1998)

Jörg Krissmann M. Aslam Siddiqi P. Peters-Gerth M. Ripke K. Lucas

The behavior of mercury under conditions similar to a wet flue gas cleaning process has been discussed in terms of thermodynamic equilibrium. The spectrophotometric technique developed in our laboratory has been used to study the systems HgCl2 + HCl + H2O, HgCl2 + CaCl2 + H2O, and SO2 + HgCl2 + HCl + H2O at 50 °C and atmospheric pressure in the absence of oxygen. A thermodynamic model presented in earlier communications is developed further. The substance-specific data required were extracted from literature and used without any further adjustment. The experimental results show that the soluble bivalent mercury (HgCl2) is completely reduced to elemental insoluble form through sulfur dioxide, even in the presence of 0.1 M HCl (i.e., also in strongly acidic solutions). This is also confirmed by the calculations done with the thermodynamic model.

Mercury

10.1021/ie970805o

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Citations (11)

Influence of Nitrogen Monoxide on the Complex Phase and Chemical Equilibria in Wet Flue Gas Cleaning Processes

Industrial & Engineering Chemistry Research (2003)

M. Aslam Siddiqi J. Petersen K. Lucas

The present paper reports the absorption behavior of sulfur dioxide in the presence of nitrogen oxides (NO and NO2). The absorption process has been studied at 298.65 and 318.45 K and ambient pressure. The results show that after a few hours NO2 vanishes from the gas phase. This leads to a reproducible frozen (stable) state in which tetravalent sulfur exists in phase and chemical equilibrium. The gas phase contains SO2, N2O, and NO. The liquid phase contains a number of nitrogen−sulfur compounds besides tetravalent and hexavalent sulfur and nitrate. The absorption of NO2 is accelerated by the presence of NO, and the solubility of SO2 increases with the increasing amount of NO. The results of model calculations that give the concentration profile of the species produced in this system as a function of time are presented. The effects of temperature and the initial concentration of the gas mixture on the absorption behavior of SO2 are discussed.

Partial pressure

10.1021/ie020739c

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Citations (10)

A Study of Solute-Solvent Interaction of some Tetraalkylammonium and Common Salts in Formamide from Apparent Molal Volume Data*

Zeitschrift für Physikalische Chemie (1969)

Ram Gopal M. Aslam Siddiqi

Molality

10.1524/zpch.1969.67.1_3.122

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Citations (15)