| LINK | Xiao, Xingcheng; Lu, Peng; Ahn, Dongjoon |
| Ultrathin Multifunctional Oxide Coatings for Lithium Ion Batteries |
| Advanced Materials, 2011, n/a-n/a |
| LINK | Kim, J. B.; Fuentes-Hernandez, C.; Hwang, D. K.; Tiwari, S. P.; Potscavage Jr, W. J.; Kippelen, B. |
| Vertically stacked complementary inverters with solution-processed organic semiconductors |
| Organic Electronics, 2011, 12, 1132-1136 |
| Abstract: | We report on vertically stacked complementary inverters implemented with a solution-processed [6,6]-phenyl c61 butyric acid methyl ester (PCBM) n-channel thin-film transistor (TFT) fabricated on top of a 6,13-bis(triisopropylsilylethynyl) pentacene (TIPS-pentacene) and poly(triarylamine) (PTAA) blend p-channel TFT. With a shared common gate electrode positioned between two dielectric layers, bottom-contact p- and top-contact n-channel TFTs showed saturation mobility values of 0.25 and 0.004 cm2/V s and threshold voltages of -3.9, and 0.3 V, respectively. The inverter yielded a gain value of -24 V/V with a switching threshold voltage value of 3.3 V at a supply voltage of 7 V. This demonstration of the use of solution-processed semiconductors in a vertically stacked complementary inverter geometry is a step forward towards the development of low-cost complementary electronics. |
| LINK | Guan, Dongsheng; Jeevarajan, Judith A.; Wang, Ying |
| Enhanced cycleability of LiMn2O4 cathodes by atomic layer deposition of nanosized-thin Al2O3 coatings |
| Nanoscale, 2011, 3, 1465-1469 |
| Abstract: | This report is the first effort to use atomic layer deposition method for deposition of nanosized-thin and highly conformal Al2O3 coatings onto LiMn2O4 cathodes with precise thickness-control at atomic scale. The coated cathodes exhibit significantly enhanced cycleability than bare cathodes, as the dense ALD coating protects the cathode material from severe dissolution. |
| LINK | Dafinone, Majemite I.; Feng, Gang; Brugarolas, Teresa; Tettey, Kwadwo E.; Lee, Daeyeon |
| Mechanical Reinforcement of Nanoparticle Thin Films Using Atomic Layer Deposition |
| ACS Nano, 2011, 5, 5078-5087 |
| Abstract: | Thin films composed of nanoparticles exhibit synergistic properties, making them useful for numerous advanced applications. Nanoparticle thin films (NTFs), however, have a very low resistance to mechanical loading and abrasion, presenting a major bottleneck to their widespread use and commercialization. High-temperature sintering has been shown to improve the mechanical durability of NTFs on inorganic substrates; however, these high-temperature processes are not amenable to organic substrates. In this study, we demonstrate that the mechanical durability of TiO2/SiO2 nanoparticle layer-by-layer (LbL) films on glass and polycarbonate substrates can be drastically improved using atomic layer deposition (ALD) at a relatively low temperature. The structure and physical properties of ALD-treated TiO2/SiO2 nanoparticle LbL films are studied using spectroscopic ellipsometry, UV–vis spectroscopy, contact angle measurements, and nanoindentation. The composition of TiO2/SiO2 LbL films as a function of ALD-cycle number is determined through solution ellipsometry, enabling the determination of the characteristic pore size of nanoparticle thin films. Mechanical durability is also investigated by abrasion tests, showing that the robustness of ALD-treated nanoparticle films is comparable to that of thermally calcined films. More importantly, ALD-treated nanoparticle films retain the original functionality of the TiO2/SiO2 LbL films, such as superhydrophilicity and antireflection properties, demonstrating the utility of ALD as a reinforcement method for nanoparticle thin films. |
| LINK | Chung, K. J.; Park, T. J.; Sivasubramani, P.; Kim, J.; Ahn, J. |
| Impact of ozone concentration on atomic layer deposited HfO2 on GaAs |
| Microelectronic Engineering |
| Abstract: | Effect of ozone (O3) concentration (90, 300 g/Nm3) on atomic layer deposition of HfO2 thin films on GaAs wafers using tetrakis (dimethylamino)hafnium (TDMAHf) as Hf precursor was systematically studied including MISCAP performance and related microstructure. High-resolution transmission electron microscopy analyses show that oxidation of the GaAs substrate enhances with O3 concentration which leads to an increase in interfacial layer (IL) thickness between the high-k dielectric and the substrate. The thin IL was maintained after PDA, while the high-k (HfO2) layer experienced shrinkage of ~12% due to densification. However HfO2 film deposited using O3 concentration of 300 g/Nm3 produced relatively thicker IL and thinner high-k layer which both did not show a noticeable change after PDA. This led to Cmax variations depending on the different O3 concentration. In the case of O3 concentration of 90 g/Nm3, increase of leakage current density by an order was observed and corresponding micro-structural change is discussed. |
| LINK | K.D. Chabak, D.E. Walker Jr., M. Trejo, A. Crespo, M. Kossler, J.K. Gillespie, R. Gilbert, B. Poling, S. Tetlak, R.C. Fitch, G.D. Via |
| Performance of Strained AlInN/AlN/GaN HEMTs with Si3N4 and Ultra-Thin Al2O3 Passivation |
| 2011 |
| LINK | Nagpal, Prashant; Josephson, David P.; Denny, Nicholas R.; DeWilde, Joseph; Norris, David J.; Stein, Andreas |
| Fabrication of carbon/refractory metal nanocomposites as thermally stable metallic photonic crystals |
| Journal of Materials Chemistry, 2011, 21, 10836-10843 |
| Abstract: | Metallic photonic crystals (MPhCs), three-dimensionally nanostructured metals, have been previously investigated as efficient emitters for thermophotovoltaic conversion of solar energy and waste heat into electricity. However, the thermal stability of these nanoscaled structures is limited at high temperatures. Here we present a fabrication scheme for preparing metal-coated carbon inverse opal photonic crystal structures that may be useful for thermal emission modification. Three-dimensionally ordered macroporous (3DOM) carbon films and monoliths, which can maintain their structure up to at least 2200 [degree]C in argon, were used as thermally stable scaffolds for chemical vapor deposition (CVD) of the refractory metals tungsten, molybdenum, or tantalum, all with a thin hafnia interlayer. The tungsten-coated photonic crystals were found to be stable after heat treatment at 1000 [degree]C for at least five hours, under high vacuum (10-6 torr). The thermal stability of these nanocomposite materials is mainly limited by the adhesion of the refractory metals on the 3DOM carbon scaffold. The hafnia interlayer serves as an adhesion promoter for this material, and structures without a hafnia coating show metal agglomeration after heat treatment at 1000 [degree]C, as demonstrated with millimetre-sized 3DOM carbon monoliths that were only partially coated with hafnia. These results can have important implications not only for the development of efficient thermophotovoltaic emitters, but also for fabrication of other thermally stable, functional nanocomposite materials. |
| LINK | Borgese, L.; Bontempi, E.; Gelfi, M.; Depero, L. E.; Goudeau, P.; Geandier, G.; Thiaudière, D. |
| Microstructure and elastic properties of atomic layer deposited TiO2 anatase thin films |
| Acta Materialia, 2011, 59, 2891-2900 |
| Abstract: | Amorphous TiO2 thin films were deposited by means of atomic layer deposition on Kapton substrates and then crystallized ex situ by annealing at 300 °C to obtain the anatase phase. The morphology, structure and microstructure of films treated for 12, 24, 72 and 90 h were investigated. The local Ti coordination changes were studied by X-ray near-edge structure (XANES). On the basis of X-ray diffraction residual stress calculations, the elastic anisotropy of the films is experimentally determined for the first time (, ). The film macro-strains increased with the time of treatment, while the micro-strains decreased. This effect may be correlated with the incipient anatase-to-rutile transformation as suggested by the changes observed in the XANES pattern of the film treated for 90 h. However, the contribution of the substrate cannot be excluded. |
| LINK | Sinha, Godhuli; Depero, Laura E.; Alessandri, Ivano |
| Recyclable SERS Substrates Based on Au-Coated ZnO Nanorods |
| ACS Applied Materials & Interfaces, 2011, 3, 2557-2563 |
| Abstract: | Vertically aligned Au-coated ZnO nanorods (Au-ZnO NRs) were investigated as cheap, efficient and recyclable SERS-active substrates. The ZnO NRs were prepared through a simple, low-temperature hydrothermal route and made SERS-active through deposition of gold nanoislands by sputtering at room temperature. Optimized samples were able to detect methylene blue over a wide range of low concentrations (from 1 × 10–4 to 1 × 10–12 M), with good reproducibility. The photocatalytic properties of Au-ZnO NRs were exploited to recycle these substrates through UV-assisted cleaning. The experimental results showed that these substrates are characterized by high reproducibility and long shelf life, which make them promising as SERS platforms for multiple detection of different molecular species. |
| LINK | Yongjin Kim, Namsu Kim, Hyungchul Kim, Samuel Graham |
| The Development of Thin Film Barriers for Encapsulating Organic Electronics |
| 2011 |