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Jo, Gunho,Hong, Woong-Ki,Sohn, Jung Inn,Jo, Minseok,Shin, Jiyong,Welland, Mark E.,Hwang, Hyunsang,Geckeler, Kurt E.,Lee, Takhee WILEY-VCH Verlag 2009 Advanced Materials Vol.21 No.21
<B>Graphic Abstract</B> <P>A new layout of complementary logic circuits based on p-channel carbon nanotube and n-channel zinc oxide nanowire transistors is presented, providing a hybrid approach to combine advantageous characteristic functions for the modulation of the current and operating voltage in transistors through proton radiation-generated charges, which allow a simple way to design favorable logic circuits. <img src='wiley_img/09359648-2009-21-21-ADMA200803510-content.gif' alt='wiley_img/09359648-2009-21-21-ADMA200803510-content'> </P>
Nikhil Tiwale,Satyaprasad P. Senanayak,Juan Rubio-Lara,Yury Alaverdyan,Mark E. Welland 대한금속·재료학회 2019 ELECTRONIC MATERIALS LETTERS Vol.15 No.6
Solution processing of metal oxide-based semiconductors is an attractive route for low-cost fabrication of thin flms devices. ZnO thin flms were synthesized from one-step spin coating-pyrolysis technique using zinc neodecanoate precursor. X-raydifraction (XRD), UV–visible optical transmission spectrometry and photoluminescence spectroscopy suggested conversionto polycrystalline ZnO phase for decomposition temperatures higher than 400 °C. A 15 % precursor concentration was foundto produce optimal TFT performance on annealing at 500 °C, due to generation of sufcient charge percolation pathways. Thedevice performance was found to improve upon increasing the annealing temperature and the optimal saturation mobility of0.1 cm2V−1 s−1 with ION/IOFF ratio~107was achieved at 700 °C annealing temperature. The analysis of experimental resultsbased on theoretical models to understand charge transport envisaged that the grain boundary depletion region is major sourceof deep level traps and their efective removal at increased annealing temperature leads to evolution of transistor performance.
Density control of ZnO nanowires grown using Au-PMMA nanoparticles and their growth behavior
Shin, Hyeon Suk,Sohn, Jung Inn,Kim, Dong Chung,Huck, Wilhelm T S,Welland, Mark E,Choi, Hee Cheul,Kang, Dae Joon IOP Pub 2009 Nanotechnology Vol.20 No.8
<P>Au nanoparticles stabilized by poly(methyl methacrylate) (PMMA) were used as a catalyst to grow vertically aligned ZnO nanowires (NWs). The density of ZnO NWs with very uniform diameter was controlled by changing the concentration of Au-PMMA nanoparticles (NPs). The density was in direct proportion to the concentration of Au-PMMA NPs. Furthermore, the growth process of ZnO NWs using Au-PMMA NPs was systematically investigated through comparison with that using Au thin film as a catalyst. Au-PMMA NPs induced polyhedral-shaped bases of ZnO NWs separated from each other, while Au thin film formed a continuous network of bases of ZnO NWs. This approach provides a facile and cost-effective catalyst density control method, allowing us to grow high-quality vertically aligned ZnO NWs suitable for many viable applications. </P>
Sohn, Jung Inn,Hong, Woong-Ki,Lee, Mi Jung,Lee, Takhee,Sirringhaus, Henning,Kang, Dae Joon,Welland, Mark E IOP Pub 2009 Nanotechnology Vol.20 No.50
<P>We demonstrate the effect of surface chemical dynamics on carrier transport and recombination processes of electron–hole pairs in ZnO nanowire field effect transistors. We have found that the electrical conductance decreases and the threshold voltages shift in a positive gate voltage direction, as electrical characteristics are measured repeatedly. We associate this with the enhancement of oxygen adsorption by capturing electrons from the induced current during the probing. This results in an overall depletion of electrons and thus causes the positive shift in threshold voltages associated with the origin and width of characteristic hysteresis loops. In addition, the surface environment dependence of the photo-response related to a recombination process in ZnO nanowires is discussed in terms of the surface chemical reaction and band bending. </P>
Sohn, Jung Inn,Joo, Heung Jin,Ahn, Docheon,Lee, Hyun Hwi,Porter, Alexandra E,Kim, Kinam,Kang, Dae Joon,Welland, Mark E American Chemical Society 2009 NANO LETTERS Vol.9 No.10
<P>We demonstrate that the Mott metal-insulator transition (MIT) in single crystalline VO(2) nanowires is strongly mediated by surface stress as a consequence of the high surface area to volume ratio of individual nanowires. Further, we show that the stress-induced antiferromagnetic Mott insulating phase is critical in controlling the spatial extent and distribution of the insulating monoclinic and metallic rutile phases as well as the electrical characteristics of the Mott transition. This affords an understanding of the relationship between the structural phase transition and the Mott MIT.</P>
Hong, Woong-Ki,Jo, Gunho,Sohn, Jung Inn,Park, Woojin,Choe, Minhyeok,Wang, Gunuk,Kahng, Yung Ho,Welland, Mark E.,Lee, Takhee American Chemical Society 2010 ACS NANO Vol.4 No.2
<P>We demonstrated a controllable tuning of the electronic characteristics of ZnO nanowire field effect transistors (FETs) using a high-energy proton beam. After a short proton irradiation time, the threshold voltage shifted to the negative gate bias direction with an increase in the electrical conductance, whereas the threshold voltage shifted to the positive gate bias direction with a decrease in the electrical conductance after a long proton irradiation time. The electrical characteristics of two different types of ZnO nanowires FET device structures in which the ZnO nanowires are placed on the substrate or suspended above the substrate and photoluminescence (PL) studies of the ZnO nanowires provide substantial evidence that the experimental observations result from the irradiation-induced charges in the bulk SiO<SUB>2</SUB> and at the SiO<SUB>2</SUB>/ZnO nanowire interface, which can be explained by a surface-band-bending model in terms of gate electric field modulation. Our study on the proton-irradiation-mediated functionalization can be potentially interesting not only for understanding the proton irradiation effects on nanoscale devices, but also for creating the property-tailored nanoscale devices.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancac3/2010/ancac3.2010.4.issue-2/nn9014246/production/images/medium/nn-2009-014246_0006.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nn9014246'>ACS Electronic Supporting Info</A></P>
Stress-induced domain dynamics and phase transitions in epitaxially grown VO<sub>2</sub> nanowires
Sohn, Jung Inn,Joo, Heung Jin,Kim, Keun Soo,Yang, Hyoung Woo,Jang, A-Rang,Ahn, Docheon,Lee, Hyun Hwi,Cha, SeungNam,Kang, Dae Joon,Kim, Jong Min,Welland, Mark E IOP Pub 2012 Nanotechnology Vol.23 No.20
<P>We demonstrate that surface stresses in epitaxially grown VO<SUB>2</SUB> nanowires (NWs) have a strong effect on the appearance and stability of intermediate insulating M<SUB>2</SUB> phases, as well as the spatial distribution of insulating and metallic domains during structural phase transitions. During the transition from an insulating M<SUB>1</SUB> phase to a metallic R phase, the coexistence of insulating M<SUB>1</SUB> and M<SUB>2</SUB> phases with the absence of a metallic R phase was observed at atmospheric pressure. In addition, we show that, for a VO<SUB>2</SUB> NW without the presence of an epitaxial interface, surface stresses dominantly lead to spatially inhomogeneous phase transitions between insulating and metallic phases. In contrast, for a VO<SUB>2</SUB> NW with the presence of an epitaxial interface, the strong epitaxial interface interaction leads to additional stresses resulting in uniformly alternating insulating and metallic domains along the NW length.</P>
Nonvolatile Memory Functionality of ZnO Nanowire Transistors Controlled by Mobile Protons
Yoon, Jongwon,Hong, Woong-Ki,Jo, Minseok,Jo, Gunho,Choe, Minhyeok,Park, Woojin,Sohn, Jung Inn,Nedic, Stanko,Hwang, Hyungsang,Welland, Mark E.,Lee, Takhee American Chemical Society 2011 ACS NANO Vol.5 No.1
<P>We demonstrated the nonvolatile memory functionality of ZnO nanowire field effect transistors (FETs) using mobile protons that are generated by high-pressure hydrogen annealing (HPHA) at relatively low temperature (400 °C). These ZnO nanowire devices exhibited reproducible hysteresis, reversible switching, and nonvolatile memory behaviors in comparison with those of the conventional FET devices. We show that the memory characteristics are attributed to the movement of protons between the Si/SiO<SUB>2</SUB> interface and the SiO<SUB>2</SUB>/ZnO nanowire interface by the applied gate electric field. The memory mechanism is explained in terms of the tuning of interface properties, such as effective electric field, surface charge density, and surface barrier potential due to the movement of protons in the SiO<SUB>2</SUB> layer, consistent with the UV photoresponse characteristics of nanowire memory devices. Our study will further provide a useful route of creating memory functionality and incorporating proton-based storage elements onto a modified CMOS platform for FET memory devices using nanomaterials.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancac3/2011/ancac3.2011.5.issue-1/nn102633z/production/images/medium/nn-2010-02633z_0005.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nn102633z'>ACS Electronic Supporting Info</A></P>
Nedelcu, Mihaela,Saifullah, Mohammad S. M.,Hasko, David G.,Jang, Arang,Anderson, David,Huck, Wilhelm T. S.,Jones, Geraint A. C.,Welland, Mark E.,Kang, Dae Joon,Steiner, Ullrich WILEY-VCH Verlag 2010 Advanced Functional Materials Vol.20 No.14
<P>The fabrication of very narrow metal lines by the lift-off technique, especially below sub-10 nm, is challenging due to thinner resist requirements in order to achieve the lithographic resolution. At such small length scales, when the grain size becomes comparable with the line-width, the built-in stress in the metal film can cause a break to occur at a grain boundary. Moreover, the line-width roughness (LWR) from the patterned resist can result in deposited metal lines with a very high LWR, leading to an adverse change in device characteristics. Here a new approach that is not based on the lift-off technique but rather on low temperature hydrogen reduction of electron-beam patterned metal naphthenates is demonstrated. This not only enables the fabrication of sub-10 nm metal lines of good integrity, but also of low LWR, below the limit of 3.2 nm discussed in the International Technology Roadmap for Semiconductors. Using this method, sub-10 nm nickel wires are obtained by reducing patterned nickel naphthenate lines in a hydrogen-rich atmosphere at 500 °C for 1 h. The LWR (i.e., 3 σ<SUB>LWR</SUB>) of these nickel nanolines was found to be 2.9 nm. The technique is general and is likely to be suitable for fabrication of nanostructures of most commonly used metals (and their alloys), such as iron, cobalt, nickel, copper, tungsten, molybdenum, and so on, from their respective metal–organic compounds.</P> <B>Graphic Abstract</B> <P>Sub-10 nm nickel wires of good integrity are obtained by reducing electron-beam-patterned nickel naphthenate lines in a hydrogen-rich atmosphere at 500 °C for 1 h. The line-width roughness (i.e., 3 σ<SUB>LWR</SUB>) of these nickel nanolines is found to be 2.9 nm, which is below the limit of 3.2 nm discussed in the International Technology Roadmap for Semiconductors. <img src='wiley_img_2010/1616301X-2010-20-14-ADFM201000219-content.gif' alt='wiley_img_2010/1616301X-2010-20-14-ADFM201000219-content'> </P>
Nedelcu, Mihaela,Saifullah, Mohammad S. M.,Hasko, David G.,Jang, Arang,Anderson, David,Huck, Wilhelm T. S.,Jones, Geraint A. C.,Welland, Mark E.,Kang, Dae Joon,Steiner, Ullrich WILEY-VCH Verlag 2010 Advanced Functional Materials Vol.20 No.14
<B>Graphic Abstract</B> <P>This computer rendered graphic displays direct writing of sub-10 nm metallic wires of low line-width roughness using an electron beam (shown as a sinusoidal wave), as presented by M. S. M. Saifullah, D. J. Kang, U. Steiner, et al. on page 2317. Sub-10 nm metallic wires of good integrity and low line-width roughness were obtained by reducing electron-beam patterned metal naphthenate lines in a hydrogen-rich atmosphere at 500°C for 1 h. <img src='wiley_img_2010/1616301X-2010-20-14-ADFM201090059-content.gif' alt='wiley_img_2010/1616301X-2010-20-14-ADFM201090059-content'> </P>