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Peter A. Dowben - One of the best experts on this subject based on the ideXlab platform.
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Characterization of boron carbide thin films fabricated by plasma enhanced chemical vapor deposition from boranes
Journal of Applied Physics, 1992Co-Authors: Sunwoo Lee, G. Ramseyer, John Mazurowski, Peter A. DowbenAbstract:We have fabricated boron carbide thin films on Si( 111) and other substrates by plasma-enhanced chemical-vapor deposition (PECVD). The PECVD of boron carbides from nido-cage boranes, specially nido-pentaborane( 9) (B,H,), and methane ( CH4) is demonstrated. The band gap is closely correlated with the boron to carbon ratio and can range from 0.77 to 1.80 eV and is consistent with the thermal activation barrier of 1.25 eV for conductivity. We have made boron carbide by PECVD from pentaborane and methane that is sufficiently isotropic to obtain resistivities as large as 10” n cm at room temperature. This material is also shown to be suitable for photoactive p-n heterojunction diode fabrication in combination with Si( 111).
Dowben, Peter A. - One of the best experts on this subject based on the ideXlab platform.
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Forming B\u3csub\u3e1-x\u3c/sub\u3eC\u3csub\u3ex\u3c/sub\u3e Semiconductor Layers by Chemical Vapor Deposition
DigitalCommons@University of Nebraska - Lincoln, 1997Co-Authors: Dowben, Peter A.Abstract:Active semiconductor devices including heterojunction diodes and thin film transistors are formed by PECVD deposition of a boron carbide thin film on an N-type substrate. The boron to carbon ratio of the deposited material is controlled so that the film has a suitable band gap energy. Boron carbides such as B4.7C, B7.2C and B19C have suitable band gap energies between 0.8 and 1.7 eV. The stoichiometry of the film can be selected by varying the partial pressure of precursor gases, such as nido pentaborane and methane. The precursor gas or gases are energized. e.g., in a plasma reactor. The heterojunction diodes retain good rectifying properties at elevated temperature, e.g., up to 400° C
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Forming B\u3csub\u3e1-x\u3c/sub\u3eC\u3csub\u3ex\u3c/sub\u3e Semiconductor Devices By Chemical Vapor Deposition
DigitalCommons@University of Nebraska - Lincoln, 1995Co-Authors: Dowben, Peter A.Abstract:Active semiconductor devices including heterojunction diodes and thin film transistors are formed by PECVD deposition of a boron carbide thin film on an N-type substrate. The boron to carbon ratio of the deposited material is controlled so that the film has a suitable band gap energy. Boron carbides such as B4.7C, B7.2C and B19C have suitable band gap energies between 0.8 and 1.7 eV. The stoichiometry of the film can be selected by varying the partial pressure of precursor gases, such as nido pentaborane and methane. The precursor gas or gases are energized, e.g., in a plasma reactor. The heterojunction diodes retain good rectifying properties at elevated temperature, e.g., up to 400° C
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The structural homogeneity of boron carbide thin films fabricated using plasma-enhanced chemical vapor deposition from B\u3csub\u3e5\u3c/sub\u3eH\u3csub\u3e9\u3csup\u3e+\u3c/sup\u3e\u3c/sub\u3eCH\u3csub\u3e4\u3c/sub\u3e
DigitalCommons@University of Nebraska - Lincoln, 1993Co-Authors: Lee Sunwoo, Mazurowski J., O\u27brien W.l., Dong Q.y., Jia J.j., Callcott T.a., Miyano K.e., Ederer D.l., Mueller D.r., Dowben, Peter A.Abstract:Boron carbide thin films of several B/C ratios have been deposited on Si(111) using plasma-enhanced chemical vapor deposition from nido-pentaborane(9) (B5H9) and methane (CH4). X-ray diffraction studies of boron carbide thin films on Si(111) exhibited characteristic microcrystalline diffraction lines. Soft x-ray emission spectroscopy was used to verify that the local electronic structure and composition of each sample corresponded to a homogeneous solid solution boron carbide phase
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Structures of selected boranes and carboranes
DigitalCommons@University of Nebraska - Lincoln, 1992Co-Authors: Lee Sunwoo, Dowben, Peter A., Wen A.t., Hitchcock A.p., Glass, John A., Spencer, James T.Abstract:Nido-pentaborane(9) (B5H9), 1, nido-2,3-diethyl-2,3-dicarbahexaborane(8)[( C2H5)2C2B4H6], 2, nido-decaborane (14) (B10H14), 3, closo- 1,2-dicarbadodecaborane(12) (H2C2B10H10), 4, can be used as possible source compounds for boron and boron carbide thin film deposition. Inner shell electron energy-loss spectroscopy (ISEELS) studies of the boron Is and carbon Is core excitations of gas phase species have been undertaken so as to characterize these molecular precursors at solid surfaces. The near edge structure of ISEELS provides a good fingerprint for the identification of these molecular species. A comparison is made between calculated [modified neglect of differential overlap (MNDO)] bond lengths for molecular clusters and the x-ray or electron diffraction bond lengths, bond lengths determined from extended energy-loss fine structure
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NOVEL METHODS FOR DEPOSITION OF BORON CARBIDE FILMS
DigitalCommons@University of Nebraska - Lincoln, 1991Co-Authors: Mazurowski J., Baral-tosh S., Ramseyer G., Spencer J.t., Kim Yoon-gi, Dowben, Peter A.Abstract:By combining pentaborane (B5H9) and decarborane (B10H14) with methane in a plasma reactor, a variety of boron-carbides can be made over a wide range of compositions. The resulting thin films have uniform composition and appear to be polycrystalline
Sundargopal Ghosh - One of the best experts on this subject based on the ideXlab platform.
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Homometallic Cubane Clusters: Participation of Three-Coordinated Hydrogen in 60-Valence Electron Cubane Core
2015Co-Authors: K. Yuvaraj, Dipak Kumar Roy, Bijan Mondal, Babu Varghese, Sundargopal GhoshAbstract:This work describes the synthesis, structural characterizations, and electronic structures of a series of novel homometallic cubane clusters [(Cp*Ru)2{Ru(CO)2}2BH(μ3-E)(μ-H)B(μ-H)3M], (2, M = Cp*Ru, E = CO; 3, M = Ru(Cp*Ru)2(μ-CO)3(μ-H)BH), E = BH), [(Cp*Ru)3(μ3-CO)(BH)3(μ3-H)3], 4, and [(Cp*Ru)2(μ3-CO){Ru(CO)3}2(BH)2(μ-H)B], 5 (Cp* = η5-C5Me5). These cubane clusters have been isolated from a thermally driven reaction of diruthenium analogue of pentaborane(9) [(Cp*RuH)2B3H7], 1, and [Ru3(CO)12]. Structural and spectroscopic studies revealed the existence of triply bridged hydrogen (μ3-H) atoms that participate as a vertex in the cubane core formation for compounds 2, 3, and 4. In addition, the crystal structure of these clusters clearly confirms the presence of an electron precise borane ligand (borylene fragment) which is triply bridged to the trimetallic units. Bonding of these novel complexes has been studied computationally by DFT methods, and the studies demonstrate that the cubane clusters 2 and 3 possess 60 cluster valence electrons (cves) with six metal–metal bonds. All the new compounds have been characterized in solution by mass spectrometry; IR; and 1H, 11B, and 13C NMR studies, and the structural types were unequivocally established by crystallographic analysis of compounds 2–5
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In search for new bonding modes of the methylenedithiolato ligand: novel tri- and tetra-metallic clusters
Dalton Transactions, 2015Co-Authors: R. S. Anju, Bijan Mondal, Koushik Saha, Thierry Roisnel, Jean-françois Halet, Sundargopal GhoshAbstract:Building upon our earlier results on the chemistry of diruthenium analogue of pentaborane (9) with heterocumulenes, we continued to investigate the reactivity of arachno-[(Cp*Ru)2(B3H8)(CS2H)], 1, (Cp* = η5-C5Me5) towards group 7 and 8 transition metal carbonyl compounds under photolytic and thermolytic conditions. The metal carbonyl compounds show diverse reactivity pattern with arachno-1. For example, the photolysis of arachno-1 with [Re2(CO)10] yielded [(Cp*Ru)2B3H5(CH2S2)\Re(CO)4\2], 2, [(Cp*RuCO)2(μ-H)2(CH2S2)\Re(CO)4\\Re(CO)3\], 3 and [(Cp*Ru)2(μ-CO)(μ-H)(CH2S2)\Re(CO)3\], 4. The geometry of 2 with a nearly planar eight-membered ring containing heavier transition metals rhenium, ruthenium is unprecedented. Compounds 3 and 4 can be considered as M4-quadrilateral and M3-triangle with a methylenedithiolato ligand attached to the metal centres, respectively. [Mn2(CO)10], on the other hand, reacts with arachno-1 to yield heterometallic binuclear [(Cp*RuCO)\Mn(CO)4\(μ-H)(SCH3)], 5 and homocubane [(Cp*Ru)2\Mn(CO)3\-(CS2H2)B3H4], 6. In an attempt to generate group 8 analogues of 2–5, we performed the reaction of arachno-1 with [Fe2(CO)9] and [Ru3(CO)12]. Although, the objective of isolating analogous compounds was not achieved, the reaction with [Fe2(CO)9] led to novel tetrahedral cluster [(Cp*RuCO)\(Fe(CO)3\2S(μ-H)], 7. [Ru3(CO)12], in contrast, yielded known compounds [\Cp*Ru(CO)\2B2H6], 9 and [Cp*Ru(CO)2]2, 10. All the cluster compounds have been characterized by mass spectrometry, IR, and 1H, 11B, and 13C NMR spectroscopy, and the geometric structures were unequivocally established by crystallographic analysis of 2–5 and 7
Ghosh Sundargopal - One of the best experts on this subject based on the ideXlab platform.
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Chemistry of diruthenium and dirhodium analogues of pentaborane(9): synthesis and characterization of metal N,S-heterocyclic carbene and B-agostic complexes
John Wiley & Sons Inc, 2015Co-Authors: Roy, Dipak Kumar, Anju R. S., Mondal Bijan, Ghosh SundargopalAbstract:Building upon our earlier results on the synthesis of electron-precise transition-metal–boron complexes, we continue to investigate the reactivity of pentaborane(9) and tetraborane(10) analogues of ruthenium and rhodium towards thiazolyl and oxazolyl ligands. Thus, mild thermolysis of nido-[(Cp*RuH)2B3H7] (1) with 2-mercaptobenzothiazole (2-mbtz) and 2-mercaptobenzoxazole (2-mboz) led to the isolation of Cp*-based (Cp*=η5-C5Me5) borate complexes 5 a,b [Cp*RuBH3L] (5 a: L=C7H4NS2; 5 b: L=C7H4NOS)) and agostic complexes 7 a,b [Cp*RuBH2(L)2], (7 a: L=C7H4NS2; 7 b: L=C7H4NOS). In a similar fashion, a rhodium analogue of pentaborane(9), nido-[(Cp*Rh2B3H7] (2) yielded rhodaboratrane [Cp*RhBH(L)2], 10 (L=C7H4NS2). Interestingly, when the reaction was performed with an excess of 2-mbtz, it led to the formation of the first structurally characterized N,S-heterocyclic rhodium-carbene complex [(Cp*Rh)(L2)(1-benzothiazol-2-ylidene)] (11) (L=C7H4NS2). Furthermore, to evaluate the scope of this new route, we extended this chemistry towards the diruthenium analogue of tetraborane(10), arachno-[(Cp*RuCO2B2H6] (3), in which the metal center possesses different ancillary ligands
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Diruthenium analogues of Hexaborane(12) and Pentaborane(9): synthesis and structural characterization of [(1,2-Cp*Ru)2B2H6S2] and [(2,3-Cp*Ru)2B3H6 (μ-η1-EPh)], (E = S, Se and Te) (Cp* = η5-C5Me5)
'Elsevier BV', 2015Co-Authors: Rao, Chokkapu Eswara, Yuvaraj K., Ghosh SundargopalAbstract:In an objective to synthesize metallaheteroboranes containing heavier chalcogen atoms, we performed the reaction of dimetallaborane analogues of pentaborane(9) with various chalcogen sources. As a result, the thermolysis of nido-[1,2-(Cp*RuH)2B3H7], 1 (Cp* = η5-C5Me5) with mixture of S and Se powder was carried out, that led to the isolation of half sandwich dimetallaheteroborane arachno-[(1,2-Cp*Ru)2B2H6S2], 2. On the other hand, the reaction of nido-1 with diorganyldichalcogenide ligands, [Ph2E2] afforded chalcogen bridged half sandwich complexes [(2,3-Cp*Ru)2B3H6 (μ-η1-EPh)], 4a-c (4a: E = S; 4b: E = Se and 4c: E = Te). Compound 2 can be derived from a closo-snub disphenoid by removing a 5-connect vertex followed by the removal of a 3-connect vertex. Compound 4a–c can be described as nido-square pyramidal structures, isoelectronic and isostructural with nido-1. All the compounds have been characterized by mass spectrometry, 1H, 11B, 13C spectroscopy. Further, the geometry of compounds 2, 3, 4b and 4c were unequivocally established by crystallographic analysis
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Homometallic cubane clusters: participation of three-coordinated hydrogen in 60-valence electron cubane core
American Chemical Society, 2015Co-Authors: Yuvaraj K., Roy, Dipak Kumar, Mondal Bijan, Varghese Babu, Ghosh SundargopalAbstract:This work describes the synthesis, structural characterizations, and electronic structures of a series of novel homometallic cubane clusters [(Cp*Ru)2{Ru(CO)2}2BH(μ3-E)(μ-H)B(μ-H)3M], (2, M = Cp*Ru, E = CO; 3, M = Ru(Cp*Ru)2(μ-CO)3(μ-H)BH), E = BH), [(Cp*Ru)3(μ3-CO)(BH)3(μ3-H)3], 4, and [(Cp*Ru)2(μ3-CO){Ru(CO)3}2(BH)2(μ-H)B], 5 (Cp* = η5-C5Me5). These cubane clusters have been isolated from a thermally driven reaction of diruthenium analogue of pentaborane(9) [(Cp*RuH)2B3H7], 1, and [Ru3(CO)12]. Structural and spectroscopic studies revealed the existence of triply bridged hydrogen (μ3-H) atoms that participate as a vertex in the cubane core formation for compounds 2, 3, and 4. In addition, the crystal structure of these clusters clearly confirms the presence of an electron precise borane ligand (borylene fragment) which is triply bridged to the trimetallic units. Bonding of these novel complexes has been studied computationally by DFT methods, and the studies demonstrate that the cubane clusters 2 and 3 possess 60 cluster valence electrons (cves) with six metal–metal bonds. All the new compounds have been characterized in solution by mass spectrometry; IR; and 1H, 11B, and 13C NMR studies, and the structural types were unequivocally established by crystallographic analysis of compounds 2–5
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In search for new bonding modes of the methylenedithiolato ligand: novel tri- and tetra-metallic clusters
'Royal Society of Chemistry (RSC)', 2015Co-Authors: Anju R. S., Mondal Bijan, Saha Koushik, Roisnel Thierry, Halet Jean-françois, Ghosh SundargopalAbstract:International audienceBuilding upon our earlier results on the chemistry of diruthenium analogue of pentaborane (9) with heterocumulenes, we continued to investigate the reactivity of arachno-[(Cp*Ru)2(B3H8)(CS2H)], 1, (Cp* = η5-C5Me5) towards group 7 and 8 transition metal carbonyl compounds under photolytic and thermolytic conditions. The metal carbonyl compounds show diverse reactivity pattern with arachno-1. For example, the photolysis of arachno-1 with [Re2(CO)10] yielded [(Cp*Ru)2B3H5(CH2S2)\Re(CO)4\2], 2, [(Cp*RuCO)2(μ-H)2(CH2S2)\Re(CO)4\\Re(CO)3\], 3 and [(Cp*Ru)2(μ-CO)(μ-H)(CH2S2)\Re(CO)3\], 4. The geometry of 2 with a nearly planar eight-membered ring containing heavier transition metals rhenium, ruthenium is unprecedented. Compounds 3 and 4 can be considered as M4-quadrilateral and M3-triangle with a methylenedithiolato ligand attached to the metal centres, respectively. [Mn2(CO)10], on the other hand, reacts with arachno-1 to yield heterometallic binuclear [(Cp*RuCO)\Mn(CO)4\(μ-H)(SCH3)], 5 and homocubane [(Cp*Ru)2\Mn(CO)3\-(CS2H2)B3H4], 6. In an attempt to generate group 8 analogues of 2–5, we performed the reaction of arachno-1 with [Fe2(CO)9] and [Ru3(CO)12]. Although, the objective of isolating analogous compounds was not achieved, the reaction with [Fe2(CO)9] led to novel tetrahedral cluster [(Cp*RuCO)\(Fe(CO)3\2S(μ-H)], 7. [Ru3(CO)12], in contrast, yielded known compounds [\Cp*Ru(CO)\2B2H6], 9 and [Cp*Ru(CO)2]2, 10. All the cluster compounds have been characterized by mass spectrometry, IR, and 1H, 11B, and 13C NMR spectroscopy, and the geometric structures were unequivocally established by crystallographic analysis of 2–5 and
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Reactivity of diruthenium and dirhodium analogues of pentaborane(9): agostic versus boratrane complexes
John Wiley & Sons Inc, 2014Co-Authors: Anju R. S., Roy, Dipak Kumar, Mondal Bijan, Yuvaraj K., Arivazhagan C., Saha Koushik, Varghese Babu, Ghosh SundargopalAbstract:A series of novel Cp*-based (Cp*=η5-C5Me5) agostic, bis(σ-borate), and boratrane complexes have been synthesized from diruthenium and dirhodium analogues of pentaborane(9). The synthesis and structural characterization of the first neutral ruthenadiborane(6) analogue are also reported. This new route offers a very efficient method for the isolation of bis(σ-borate) and agostic complexes from diruthenapentaborane(9)
Sunwoo Lee - One of the best experts on this subject based on the ideXlab platform.
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Characterization of boron carbide thin films fabricated by plasma enhanced chemical vapor deposition from boranes
Journal of Applied Physics, 1992Co-Authors: Sunwoo Lee, G. Ramseyer, John Mazurowski, Peter A. DowbenAbstract:We have fabricated boron carbide thin films on Si( 111) and other substrates by plasma-enhanced chemical-vapor deposition (PECVD). The PECVD of boron carbides from nido-cage boranes, specially nido-pentaborane( 9) (B,H,), and methane ( CH4) is demonstrated. The band gap is closely correlated with the boron to carbon ratio and can range from 0.77 to 1.80 eV and is consistent with the thermal activation barrier of 1.25 eV for conductivity. We have made boron carbide by PECVD from pentaborane and methane that is sufficiently isotropic to obtain resistivities as large as 10” n cm at room temperature. This material is also shown to be suitable for photoactive p-n heterojunction diode fabrication in combination with Si( 111).