Francesca Monforte

Isoniazid-related copper(II) and nickel(II) complexes with antimycobacterial in vitro activity. Part 9

Isonicotinoylhydrazones 1, obtained by the primary antituberculous agent Isoniazid, have been used as monoanionic ligands (L) to prepare copper(II) 2 and nickel(II) 3 octahedral complexes of stoichiometry [MeL2(H2O)2]. Their antimycobacterial in vitro activity was evaluated against Mycobacterium tuberculosis H37Rv in comparison with the ligands. Complexes 2a, 2b, 2f, 3b, 3d and 3g displayed MIC values < or = 0.2 microg/mL.

In Vitro Antimycobacterial Activities of 2′-Monosubstituted Isonicotinohydrazides and Their Cyanoborane Adducts

ABSTRACT As a result of our search for new isoniazid derivatives with extended spectra of activity, we evaluated the in vitro antimycobacterial activities of isonicotinohydrazides (compounds 2) and their cyanoborane adducts (compounds 3), both obtained by the reaction of isonicotinoylhydrazones (compounds 1) with sodium cyanoborohydride. Most of the tested compounds displayed moderate to high activity against Mycobacterium tuberculosis H37Rv, with MICs ranging from 0.2 to 12.5 μg/ml. In particular, some hydrazides showed activity similar to that of rifampin (MIC = 0.2 μg/ml) and rather low cytotoxicity, so that they were generally shown to possess high safety indices. In contrast, the coordination to a cyanoborane (BH2CN) group (compounds 3) in general brought about a decrease in antimycobacterial activity, while cytotoxicity increased. Interestingly, selected compounds 1 to 3, mostly hydrazides (compounds 2), were effective in killing M. tuberculosis growing within macrophages at concentrations in culture medium which were much lower than the corresponding MICs. These compounds also displayed good activity against drug-resistant M. tuberculosis strains.

Nickel(II) 2,6-diacetylpyridine bis(isonicotinoylhydrazonate) and bis(benzoylhydrazonate) complexes : Structure and antimycobacterial evaluation. Part XI

The reaction of 2,6-diacetylpyridine (dap) and isonicotinoyl- or benzoylhydrazide leads to bishydrazones H(2)dapin (1a) and H(2)dapb (1b), respectively. The condensation can either take place as a bimolecular kinetic process between the two reactants or as a monomolecular metal-templated synthesis in the presence of nickel(II) ions. In the latter case the reaction products are charged 2,6-diacetylpyridine bis(hydrazone) nickel(II) complexes, which can be easily deprotonated to neutral hydrazonates. Diffractometric analysis of one of these [Ni(dapb)](2) (8b) has shown a binuclear structure with two octahedral nickel(II) ions bridged by two helicoidal dap (bishydrazonates) in a spheroidal structure of C(2V) symmetry. The synthesized complexes 8 are promising as antimycobacterial agents against M. tuberculosis H37Rv. In particular, 8b displays significant activity (MIC=0.025 microg/mL) 10-fold higher than rifampin and equal to isoniazid, while its ligand is ineffective. Compound 8b is also capable of reducing HIV-induced cytopathogenic effect in human T(4 )lymphocytes.

Antimycobacterial in vitro activity of cobalt(ii) isonicotinoylhydrazone complexes. Part 10

Octahedral cobalt(II) complexes of isonicotinoylhydrazones, which were obtained from the primary antituberculous agent isoniazid, have been synthesised and characterised. Their antimycobacterial in vitro activity has been evaluated against Mycobacterium tuberculosis H37Rv: they exhibit MIC values ranging from < 0.1 to 0.39 microg/mL, showing them to be generally more active than previously reported analogous Cu(II) and Ni(II) complexes.

Nitrogen Bonding Configurations of SiO x N y Thin Films in Power MOSFET Gate Interfaces

bSTMicroelectronics, 95121 Catania, Italy The structural properties of silicon oxynitride films grown in a N2O environment at temperatures higher than 900°C and for use as gate dielectrics in vertically diffused power metal oxide semiconductor field effect transistor PowerVDMOS technologies have been studied by means of X-ray photoelectron spectroscopy. The progressive modifications of the bonding environments upon reaching the oxynitride‐silicon interface have been analyzed as well as of the relation between these modifications and the selected oxynitridation process. The results show that the chemistry of the oxynitride layer is a rather complex one, and it significantly and progressively changes by moving toward the silicon interface, in a way strongly affected by the growth process. In particular, the medium thermal budget processes 950°C, 20‐60 min favor the formation of a relatively uniform distribution of the single oxidized O‐N‐Si2 bonds both at the interface and throughout its immediate backstage. Such findings can help in assessing the role played by the nitridation process in the quality and reliability performances of the final device. In the last few years, silicon oxynitride thin films have been proposed as an alternative to SiO2 as a thin gate dielectric for microelectronics applications. As the scale of integration increases and the thickness of the dielectric is reduced, the SiO2 dielectric layer properties get less and less sufficient to reliably withstand the increasing electric field. As a consequence, the device degradation due to the high leakage currents and even gate rupture shows up at a higher rate. Silicon oxynitrides SiOxNy are materials with a higher dielectric constant and, in thin layer form, exhibit reduced susceptibility to interface state generation with respect to SiO2, higher timeto-breakdown values and reliability, improved I-V and C-V characteristics. 1-3 Therefore, silicon oxynitride could eventually replace thin gate dielectrics characterized by a smaller thickness but an equal capacitance, thus assuring an improved robustness of the device. In this context, several analyses have been performed to characterize SiOxNy film quality in terms of both device performance and processing. 4,5 A clear understanding of the structure and chemical composition of the oxynitride film could be valuable help in assessing its quality as a gate layer in power devices. Nevertheless, in many works found in the literature, the only relevant parameter taken into account is the overall nitrogen content. In the attempt to disclose the role of the oxynitride structure in the electrical defectivity and reliability, it is of fundamental importance to know the nitrogen bonding configurations present at the silicon substrate interface and their relation with the selected oxynitridation process. In this respect, X-ray photoemission spectroscopy XPS is a powerful tool to perform a compositional analysis and also to investigate the relative bonding arrangements of silicon, oxygen, and nitrogen atoms. The aim of the present work is to investigate the progressive modifications of the nitrogen bonding arrangements upon reaching the interface for a set of oxynitride layers grown by means of furnace N2O-based dry processes at different temperatures and times to be used as gate dielectrics in vertically diffused power metal oxide semiconductor field effect transistor PowerVDMOS technologies. Changes of the main bonding configurations, moving toward the Si interface, were found to significantly depend on nitridation process parameters, such as the process duration and the furnace temperature at which the oxynitridation processes were performed. The overall picture of the atomic concentrations evolution was checked carrying out a deconvolution of the XPS photoelectron spectra using a fourband model according to existing literature data. 3,6-9

Carrier trapping in thin N2O-grown oxynitride/oxide di-layer for powerMOSFET devices

Abstract A detailed study of the carrier trapping properties shown by the silicon/oxynitride/oxide gate layers in PowerVDMOS technologies is reported. A quantitative analysis of hole and electron trap densities versus the specific N 2 O based nitridation process, extracted from Fowler–Nordheim constant current stress kinetics, allows a deep understanding of the role played by those defects in the susceptibility of every nitrided layer.

Reoxidization Process Effects on the Nitrogen Bonding Configurations in SiO x N y Power MOSFET Dielectric Gate

The structural properties of silicon oxynitride films used at the gate dielectrics interface in Power vertically diffused metal oxide semiconductor technologies have been studied by means of X-ray photoelectron spectroscopy. An overall picture of the interface chemistry evolution as a function of the growth parameters in relation to the effects of the postgrowth reoxidation process is reported. The films were grown in an N 2 O environment at temperatures higher than 900°C and subsequently reoxidized at 1000°C in a dry oxygen environment. The results show that the chemistry of the oxynitride layer progressively changes by moving toward the silicon interface and, after the reoxidation process, the interface chemical configurations are strongly affected by the initial specific oxynitridation process. In particular, the application of the final reoxidation plays a significative role in determining the distribution of the oxidized O-N-Si 2 bonds near the interface.

Nitrogen bonding configurations near the oxynitride/silicon interface after oxynitridation in N2O ambient of a thin SiO2 gate.

The identification of the bonding environments and their progressive modifications upon reaching the oxynitride/silicon interface, in a SiO 2 /SiO x N y /Si structure, have been investigated by means of X-ray photoemission spectroscopy (XPS). The SiO 2 film was grown at 850 °C by means of a mixed dry-steam process, followed by a 60 min, 950 °C furnace oxynitridation in N 2 O gas. A depth profile analysis was carried out by a progressive chemical etching procedure, reaching a residual oxide thickness of about 1.2 nm. XPS analysis of the Si 2p and N Is photoelectron peaks pointed out that the chemistry of the oxynitride layer is a rather complex one. Four different nitrogen bonding environments were envisaged. Both the overall nitrogen content, which rises up to 2.5%, and its bonding configurations are progressively changing while moving towards the silicon interface.

Interface states and traps in thin N2O-grown oxynitride/oxide di-layer for PowerMOSFET devices

Abstract A detailed study of the interface state properties shown by the silicon/oxynitride/oxide gate layers used in Vertically Diffused PowerMOSFET (PowerVDMOS) technologies is reported. A quantitative analysis of interface states versus the specific N 2 O based nitridation process, extracted from current–voltage characteristics in depletion regime, provided a clear trend and turns to be of great importance for reliability performances of the final device.