Effective passivation of defects in Ge-rich SiGe-on-insulator substrates by Al2O3 deposition and subsequent post-annealing

A method of Al₂O₃ deposition and subsequent post-deposition annealing (Al₂O₃-PDA) was proposed to passivate electrically active defects in Ge-rich SiGe-on-insulator (SGOI) substrates, which were fabricated using Ge condensation by dry oxidation. The effect of Al₂O₃-PDA on defect passivation was clarified by surface analysis and electrical evaluation. It was found that Al₂O₃-PDA could not only suppress the surface reaction during Al-PDA in our previous work [Yang H, Wang D, Nakashima H, Hirayama K, Kojima S, Ikeura S. Defect control by Al-deposition and the subsequent post-annealing for SiGe-on-insulator substrates with different Ge fractions. Thin Solid Films 2010; 518: 2342-5.], but could also effectively passivate p-type defects generated during Ge condensation. The concentration in the range of 10¹⁶-10¹⁸ cm⁻³ for defect-induced acceptors and holes in Ge-rich SGOI drastically decreased after Al₂O₃-PDA. As a result of defect passivation, the electrical characteristics of both back-gate p-channel and n-channel metal-oxide-semiconductor field-effect transistors fabricated on Ge-rich SGOI were greatly improved after Al₂O₃-PDA.     

Structural tuning of wide‐gap chalcopyrite CuGaSe2 thin films and highly efficient solar cells: differences from narrow‐gap Cu(In,Ga)Se2

Simultaneous realization of high values of open circuit voltage (V_oc), fill factor (FF), and energy conversion efficiency (η) in wide‐gap CuGaSe₂ (CGS) solar cells has long been one of the most challenging issues in the realm of chalcopyrite photovoltaics. In this communication, structural tuning of CGS thin films by means of controlling the amount of Se flux used during CGS film growth and improvements in solar cell performance (V_oc > 0.9 V, FF > 0.7, and η > 10%) are demonstrated. Systematic variations in CGS film properties with the Se flux and correlation with device properties are shown. The unique CGS thin‐film growth kinetics, which are different from narrow‐gap Cu(In,Ga)Se₂, are also presented and discussed. This development of double digit efficiency for CGS solar cells opens a new frontier for the broad application of a new class of chalcopyrite‐based devices. Copyright © 2014 John Wiley & Sons, Ltd.     

Application of magnetic nanoparticles to gene delivery

Nanoparticle technology is being incorporated into many areas of molecular science and biomedicine. Because nanoparticles are small enough to enter almost all areas of the body, including the circulatory system and cells, they have been and continue to be exploited for basic biomedical research as well as clinical diagnostic and therapeutic applications. For example, nanoparticles hold great promise for enabling gene therapy to reach its full potential by facilitating targeted delivery of DNA into tissues and cells. Substantial progress has been made in binding DNA to nanoparticles and controlling the behavior of these complexes. In this article, we review research on binding DNAs to nanoparticles as well as our latest study on non-viral gene delivery using polyethylenimine-coated magnetic nanoparticles.     

Block copolymers combining semi-fluorinated poly(arylene ether) and sulfonated poly(arylene ether sulfone) segments for proton exchange membranes

A series of aromatic multiblock copolymers based on alternating segments of hydrophilic sulfonated polysulfone (PSU) and hydrophobic polyfluoroether (PFE) were prepared and characterized as proton exchange membranes. PSU precursor blocks were synthesized by polycondensation of dichlorodiphenylsulfone and resorcinol, and PFE precursor blocks were prepared by combining decafluorobiphenyl and isopropylidenediphenol. After preparation of the multiblock copolymers via a mild coupling reaction of the precursor blocks, the resorcinol units of the PSU blocks were selectively and almost completely sulfonated under mild reaction conditions using trimethylsilylchlorosulfonate. Transparent and robust membranes with different PSU-PFE copolymer compositions and ion-exchange capacities were cast from solution. Atomic force microscopy of the membranes revealed a distinct nanophase separated morphology. At 80 °C, the proton conductivity reached 10 mS cm⁻¹ under 65% relative humidity and 100 mS cm⁻¹ under fully hydrated conditions.     

Impact of Oncogenic Targets by Tumor-Suppressive miR-139-5p and miR-139-3p Regulation in Head and Neck Squamous Cell Carcinoma

We newly generated an RNA-sequencing-based microRNA (miRNA) expression signature of head and neck squamous cell carcinoma (HNSCC). Analysis of the signature revealed that both strands of some miRNAs, including miR-139-5p (the guide strand) and miR-139-3p (the passenger strand) of miR-139, were downregulated in HNSCC tissues. Analysis of The Cancer Genome Atlas confirmed the low expression levels of miR-139 in HNSCC. Ectopic expression of these miRNAs attenuated the characteristics of cancer cell aggressiveness (e.g., cell proliferation, migration, and invasion). Our in silico analyses revealed a total of 28 putative targets regulated by pre-miR-139 (miR-139-5p and miR-139-3p) in HNSCC cells. Of these, the GNA12 (guanine nucleotide-binding protein subunit alpha-12) and OLR1 (oxidized low-density lipoprotein receptor 1) expression levels were identified as independent factors that predicted patient survival according to multivariate Cox regression analyses (p = 0.0018 and p = 0.0104, respectively). Direct regulation of GNA12 and OLR1 by miR-139-3p in HNSCC cells was confirmed through luciferase reporter assays. Moreover, overexpression of GNA12 and OLR1 was detected in clinical specimens of HNSCC through immunostaining. The involvement of miR-139-3p (the passenger strand) in the oncogenesis of HNSCC is a new concept in cancer biology. Our miRNA-based strategy will increase knowledge on the molecular pathogenesis of HNSCC.     

In situ formation of TiC particulate composite layer on cast iron by laser alloying of thermal sprayed titanium coating

Commercial flake graphite cast iron substrate was coated with titanium powder by low pressure plasma spraying and was irradiated with a CO₂ laser to produce the wear resistant composite layer. The macro and microstructural changes of an alloyed layer with the traveling speeds of laser beam, the precipitate morphology of TiC particulate and the hardness profile of the alloyed layer was examined. From the results, it was possible to composite TiC particulate on the surface layer by direct reaction between carbon existed in the cast iron matrix and titanium with thermal sprayed coating by remelting and alloying them using laser irradiation. The cooling rate of the laser remelted cast iron substrate without a titanium coating was about 1 × 10⁴ K/s to 1 × 10⁵ K/s in the order under the condition of this study. The microstructure of the alloyed layer consisted of three zones; the TiC particulate precipitate zone (MHV 400–500), the mixed zone of TiC particulate + ledeburite (MHV 650–900) and the ledeburite zone (MHV 500–700). TiC particulates were precipitated as a typical dendritic morphology. The secondary TiC dendrite arms were grown to a polygonized shape and were necking. Then the separated arms became cubic crystal of TiC at the slowly solidified zone. In the rapidly solidified zone near the fusion boundary, however the fine granular TiC particulates were grouped like grapes.     

Precursor Cat-CVD a-Si films for the formation of high-quality poly-Si films on glass substrates by flash lamp annealing

Amorphous Si (a-Si) films with lower hydrogen contents show better adhesion to glass during flash lamp annealing (FLA). The 2.0 µm-thick a-Si films deposited by plasma-enhanced chemical vapor deposition (PECVD), containing 10% hydrogen, start to peel off even at a lamp irradiance lower than that required for crystallization, whereas a-Si films deposited by catalytic CVD (Cat-CVD) partially adhere even after crystallization. Dehydrogenated Cat-CVD a-Si films show much better adhesion to glass, and are converted to polycrystalline Si (poly-Si) without serious peeling, but are accompanied by the generation of crack-like structures. These facts demonstrate the superiority of as-deposited Cat-CVD a-Si films as a precursor material for micrometer-thick poly-Si formed by FLA.     

Theranostic Agent Combining Fullerene Nanocrystals and Gold Nanoparticles for Photoacoustic Imaging and Photothermal Therapy

Developing photoactivatable theranostic platforms with integrated functionalities of biocompatibility, targeting, imaging contrast, and therapy is a promising approach for cancer diagnosis and therapy. Here, we report a theranostic agent based on a hybrid nanoparticle comprising fullerene nanocrystals and gold nanoparticles (FGNPs) for photoacoustic imaging and photothermal therapy. Compared to gold nanoparticles and fullerene crystals, FGNPs exhibited stronger photoacoustic signals and photothermal heating characteristics by irradiating light with an optimal wavelength. Our studies demonstrated that FGNPs could kill cancer cells due to their photothermal heating characteristics in vitro. Moreover, FGNPs that are accumulated in tumor tissue via the enhanced permeation and retention effect can visualize tumor tissue due to their photoacoustic signal in tumor xenograft model mice. The theranostic agent with FGNPs shows promise for cancer therapy.