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Daejeon, South Korea

Park J.H.,Korea National NanoFab Center | Lee D.-Y.,Yeungnam University
Journal of the Korean Physical Society | Year: 2012

A two-axes nano-scanner for a scanning probe microscope (SPMs) was developed. The flexure-guided nano-scanner can move SPM samples or the probe itself along the x and y axes. The theoretical stiffness and resonant frequency of the flexure guide were obtained by using Castigliano's theorem. An optimal nano-scanner that maximize the scanning speed under appropriate constraints was designed. The optimal results were compared with the results of a finite element analysis. The scanner performance was evaluated by using various experiments and was compared with the optimal design results. Finally, atomic force microscope images obtained by using the proposed nano-scanner are presented. © 2012 The Korean Physical Society.

Park J.H.,Korea National NanoFab Center | Park H.-H.,Yonsei University
Micro and Nano Letters | Year: 2011

Piezoelectric (PZT) (Pb(Zr 0.52Ti 0.48)O 3) thick film-based microtransducers demonstrate excellent piezoelectric performances. PZT thick films on Si-based substrate can be used as piezoelectric actuators and sensors with the introduction of microelectromechanical system technology and the screen printing method. However, the thick films made just by the screen printing method have high porosity compared with bulk product, and the PZT thick films on Si-based substrate have problems regarding degradation of active materials and interface properties owing to inter-diffusion or reaction between Si substrate and PZT materials at high temperature for sintering. Thus, the authors have fabricated screen printed PZT thick films on Si substrate using the screen printing method and sol infiltration for enhancing densification. Ethanol-based photo-cross-linkable sol and conventional diol-based sol were used to compare influence of patterning process. Thick films with relative high densities at low temperature, 800°C and without inter-diffusion and reaction between the layers and thick film were accomplished. Also, it was revealed that the PZT thick film treated by ethanol-based photo-cross-linkable sol showed better electrical properties as well as excellent patternability. © 2011 The Institution of Engineering and Technology.

Cho S.-Y.,Korea Advanced Institute of Science and Technology | Cho S.-Y.,KAIST | Yoo H.-W.,Agency for Defense Development | Kim J.Y.,Korea Advanced Institute of Science and Technology | And 10 more authors.
Nano Letters | Year: 2016

The development of high-performance volatile organic compound (VOC) sensor based on a p-type metal oxide semiconductor (MOS) is one of the important topics in gas sensor research because of its unique sensing characteristics, namely, rapid recovery kinetics, low temperature dependence, high humidity or thermal stability, and high potential for p-n junction applications. Despite intensive efforts made in this area, the applications of such sensors are hindered because of drawbacks related to the low sensitivity and slow response or long recovery time of p-type MOSs. In this study, the VOC sensing performance of a p-type MOS was significantly enhanced by forming a patterned p-type polycrystalline MOS with an ultrathin, high-aspect-ratio (∼25) structure (∼14 nm thickness) composed of ultrasmall grains (∼5 nm size). A high-resolution polycrystalline p-type MOS nanowire array with a grain size of ∼5 nm was fabricated by secondary sputtering via Ar+ bombardment. Various p-type nanowire arrays of CuO, NiO, and Cr2O3 were easily fabricated by simply changing the sputtering material. The VOC sensor thus fabricated exhibited higher sensitivity (ΔR/Ra = 30 at 1 ppm hexane using NiO channels), as well as faster response or shorter recovery time (∼30 s) than that of previously reported p-type MOS sensors. This result is attributed to the high resolution and small grain size of p-type MOSs, which lead to overlap of fully charged zones; as a result, electrical properties are predominantly determined by surface states. Our new approach may be used as a route for producing high-resolution MOSs with particle sizes of ∼5 nm within a highly ordered, tall nanowire array structure. © 2016 American Chemical Society.

Cho S.-Y.,Korea Advanced Institute of Science and Technology | Jeon H.-J.,Korea National NanoFab Center | Yoo H.-W.,Agency for Defense Development | Cho K.M.,Korea Advanced Institute of Science and Technology | And 3 more authors.
Nano Letters | Year: 2015

Enhancement of the fluorescence intensity of quantum dot (QD)-polymer nanocomposite arrays is an important issue in QD studies because of the significant reduction of fluorescence signals of such arrays due to nonradiative processes in densely packed polymer chains in solid films. In this study, we enhance the fluorescence intensity of such arrays without significantly reducing their optical transparency. Enhanced fluorescence is achieved by hybridizing ultrathin plasmonic Au nanowalls onto the sidewalls of the arrays via single-step patterning and hybridization. The plasmonic Au nanowall induces metal-enhanced fluorescence, resulting in a maximum 7-fold enhancement of the fluorescence signals. We also prepare QD nanostructures of various shapes and sizes by controlling the dry etching time. In the near future, this facile approach can be used for fluorescence enhancement of colloidal QDs with plasmonic hybrid structures. Such structures can be used as optical substrates for imaging applications and for fabrication of QD-LED devices. © 2015 American Chemical Society.

Jang H.-I.,Korea National NanoFab Center | Jang H.-I.,University of Seoul | Ko S.,Korea University | Park J.,Korea Advanced Institute of Science and Technology | And 5 more authors.
Applied Physics A: Materials Science and Processing | Year: 2012

In this study, accurate nanostructures with various aspect ratios are created on several types of material. This work is highly applicable to the energy, optical, and nano-bio fields, for example. A silicon (Si) nano-mold is preserved using the method described, and target nanostructures are replicated reversibly and unlimitedly to or from various hard and soft materials. It is also verified that various materials can be applied to the substrates. The results confirm that the target nanostructures are successfully created in precise straight line structures and circle structures with various aspect ratios, including extremely high aspect ratios of 1 : 18. It is suggested that the optimal replicating and demolding process of nanostructures with high aspect ratios, which are the most problematic, could be controlled by means of the surface energy between the functional materials. Relevant numerical and analytical studies are also performed. It is possible to expand the applicability of the nanostructured mold by adopting various backing materials, including rounded substrates. The scope of the applications is extended further by transferring the nanostructures between different species of materials including metallic materials as well as identical species. © Springer-Verlag 2012.

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