Control of Semiconducting and Metallic Indium Oxide Nanowires

Lim, Taekyung,Lee, Sumi,Meyyappan, M.,Ju, Sanghyun American Chemical Society 2011 ACS NANO Vol.5 No.5

<P>Oxide semiconductors are candidates for chemical sensors, transparent electrodes, and electronic devices. Here, we have investigated metal-to-semiconductor transitions during In<SUB>2</SUB>O<SUB>3</SUB> nanowire growth with variations in the O<SUB>2</SUB> gas rate. Photoluminescence and current–voltage characteristics of In<SUB>2</SUB>O<SUB>3</SUB> nanowire transistors have been used to understand the transition behavior. The proportion of metallic nanowires to semiconducting nanowires significantly changes from 80:20 to 25:75 when the O<SUB>2</SUB> fraction in argon increases from 0.005% to 0.2%. We believe that excessive oxygen vacancies at low O<SUB>2</SUB> gas rates increase the conductivity and thereby the number of nanowires with metallic characteristics. With an increase in oxygen flow, the oxygen vacancies in the nanowires are substituted with oxygen and the subsequent reduction in oxygen vacancies increases the number of semiconducting nanowires. The threshold voltage of transistors fabricated with semiconducting nanowires shifts in a positive direction by about +3.3 eV between nanowires grown with 0.005% and 0.2% oxygen. The results here indicate that electrical and optical characteristics of oxide nanowires can be controlled by the amount of oxygen during growth instead of relying on conventional postgrowth high-temperature annealing or other postprocessing techniques.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancac3/2011/ancac3.2011.5.issue-5/nn200390d/production/images/medium/nn-2011-00390d_0004.gif'></P>

A-site Doping Effect of Multiferroic BiFeO3 Ceramics

Lim Taekyung,Jeon Ok Sung,La Yunju,Park Sang Yoon,Yoo Young Joon,Yang Keun-Hyeok 한국물리학회 2020 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.77 No.11

The structural, magnetic and ferroelectric properties of polycrystalline A-site ($A$ = Ho, Pr and Ce of 10%) doped BiFeO3, which were prepared by the solid-state and rapid sintering methods, have been investigated. The powder X-ray diffraction pattern reveals that all the samples show rhombohedral perovskite structure R3c. The Ho-doped BiFeO3 shows that the magnetic property is slightly increased due to compressive lattice distortion and Ho3+ ion doping effect. For the Pr and Ce doped BiFeO3, the remnant polarization and coercive field increased because Pr3+ and Ce3+ ions substitution suppressed oxygen vacancies.

Pore Structure Analysis to Adsorb NOx Gas based on Porous Materials

Lim Taekyung,La Yunju,Jeon Ok Sung,Park Sang Yoon,Yoo Young Joon,Yang Keun-Hyeok 한국물리학회 2020 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.77 No.9

We studied the adsorption of nitrogen oxides according to various porous materials room temperature, which can effectively to adsorb the nitrogen oxides. Based on results of measuring NOx concentration, the activated carbon materials have been shown to adsorb NOx well, and they have been shown to more efficiently removing NO2, which is very harmful to the environment. In particular, in the case of the coconut activated carbon, the removal efficiency of NO and NO2 was very excellent, and the removal rate of was 30% for 100 minutes and 19.5% for 840 minutes. Our measurement results confirmed that the activated carbon materials have a very large specific surface area and pore volume. In addition, the coconut activated carbon appears to have a large specific surface area and pore volume to remove NOx over a long period of time. Based on the experimental results, it is expected to be used as a material that efficiently removes nitrogen oxides at room temperature.

Highly Stable Operation of Metal Oxide Nanowire Transistors in Ambient Humidity, Water, Blood, and Oxygen

Lim, Taekyung,Bong, Jihye,Mills, Edmund M.,Kim, Sangtae,Ju, Sanghyun American Chemical Society 2015 ACS APPLIED MATERIALS & INTERFACES Vol.7 No.30

<P>The capability for robust operation of nanoscale transistors under harsh environments is equally important as their operating parameters such as high on-currents, high mobility, and high sensing selectivity. For electronic/biomedical applications, in particular, transistor operation must be stable under diverse conditions including ambient humidity, water, blood, and oxygen. Here we demonstrate the use of a self-assembled monolayer of octadecylphosphonic acid (OD-PA) to passivate a functionalized nanowire transistor, allowing the device to operate consistently in such environments. In contrast, without passivation, the characteristics (especially the threshold voltage) of identical nanowire transistors were dramatically altered under these conditions. Furthermore, the OD-PA-passivated transistor shows no signs of long-term stability deterioration and maintains equally high sensing selectivity to light under the harsh environments because of OD-PA’s optical transparency. These results demonstrate the suitability of OD-PA passivation methods for fabricating commercial nanoelectronics.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2015/aamick.2015.7.issue-30/acsami.5b03038/production/images/medium/am-2015-030386_0006.gif'></P>

Fully stretchable and highly durable triboelectric nanogenerators based on gold-nanosheet electrodes for self-powered human-motion detection

Lim, Guh-Hwan,Kwak, Sung Soo,Kwon, Nayoung,Kim, Taekyung,Kim, Han,Kim, Seong Min,Kim, Sang-Woo,Lim, Byungkwon Elsevier 2017 Nano energy Vol.42 No.-

<P><B>Abstract</B></P> <P>A patchable triboelectric nanogenerator (TENG) is highly promising for self-powered human-motion detection, but it may undergo repeated stretching/releasing cycles during daily activities of a human, which may lead to mechanical fracture of each component and degradation in electrical output performance of the TENG device. Here, we report a fully stretchable and durable triboelectric nanogenerator (TENG) with gold (Au) nanosheets (NSs) embedded into both PDMS matrix and micropyramid-patterned PDMS. It was found that a new design of the Au NS electrodes dramatically improves the mechanical flexibility and stretchability, enabling to achieve the outstanding output stability of the Au NS electrode-based TENG (Au NS-TENG) during 10,000 cycles of repeated pushing and stretching tests. Our fully stretchable and durable Au NS-TENGs were successfully applied to the hand joints that can be used in the self-powered human-motion detection processes for wearable applications.</P> <P><B>Highlights</B></P> <P> <UL> <LI> We report a fully stretchable and durable triboelectric nanogenerator (TENG). </LI> <LI> The TENG consisted of gold nanosheet (Au NS)-embedded elastomer electrodes. </LI> <LI> Au NS-TENG showed excellent output stability during pushing and stretching tests. </LI> <LI> Au NS-TENGs were successfully applied for self-powered human-motion detection. </LI> </UL> </P> <P><B>Graphic abstract</B></P> <P>Fully stretchable and durable triboelectric nanogenerator with gold nanosheet embedded into both PDMS matrix and micro pyramid patterned PDMS has been successfully demonstrated in both pushing and stretching modes, then the durability test with 10,000 cycles. As our device is applied to hand joints, the possibility of self-powered systems as power source for wearable applications has been shown.</P> <P>[DISPLAY OMISSION]</P>

Detection of chlorobenzene in water using a wettability-controlled three-dimensional graphene selective filter

Lim, Taekyung,Lee, Jaejun,Kim, Jihyoung,Seo, Sungwon,Ju, Sanghyun Japan Society of Applied Physics 2017 Applied physics express Vol.10 No.1

Surface Modification of Oxide Nanowires by Nitrogen Plasma

Lim, Taekyung,Lee, Sumi,Suh, Misook,Ju, Sanghyun The Electrochemical Society 2011 Electrochemical and solid-state letters Vol.14 No.5

Direct growth of SnO₂ nanowires on WO_x thin films

Lim, Taekyung,Ryu, Seung Yoon,Ju, Sanghyun IOP Pub 2012 Nanotechnology Vol.23 No.48

<P>Single-crystalline SnO<SUB>2</SUB> nanowires were directly grown on an amorphous WO<SUB>x</SUB> thin film, leading to the formation of nano-scale contacts with a near-Ohmic conductance. The WO<SUB>x</SUB> facilitated the diffusion of SnO<SUB>2</SUB> on the surface of the WO<SUB>x</SUB> thin film, and SnO<SUB>2</SUB> nanowires could be uniformly grown from the diffused SnO<SUB>2</SUB>. The contact properties between the metallic WO<SUB>x</SUB> and a semiconducting SnO<SUB>2</SUB> nanowire were examined. The resistivity of the WO<SUB>x</SUB>–SnO<SUB>2</SUB> nanowire contact was found to be approximately 2.6 × 10<SUP>−5</SUP> Ω cm<SUP>2</SUP>. This was comparable to the resistivity of a contact between an Al electrode and a SnO<SUB>2</SUB> nanowire with a contact area. A fabricated SnO<SUB>2</SUB> nanowire transistor exhibited an on-current of approximately 386 nA, a threshold voltage of approximately 3.8 V, a subthreshold slope of approximately 0.26 V/dec and a field-effect mobility of approximately 43 cm<SUP>2</SUP> V<SUP>−1</SUP> s<SUP>−1</SUP>. </P>

Photostable Zn₂SnO₄ Nanowire Transistors for Transparent Displays

Lim, Taekyung,Kim, Hwansoo,Meyyappan, M.,Ju, Sanghyun American Chemical Society 2012 ACS NANO Vol.6 No.6

<P>Although oxide nanowires offer advantages for next-generation transparent display applications, they are also one of the most challenging materials for this purpose. Exposure of semiconducting channel areas of oxide nanowire transistors produces an undesirable increase in the photocurrent, which may result in unstable device operation. In this study, we have developed a Zn<SUB>2</SUB>SnO<SUB>4</SUB> nanowire transistor that operates stably regardless of changes in the external illumination. In particular, after exposure to a light source of 2100 lx, the threshold voltage (<I>V</I><SUB>th</SUB>) showed a negative shift of less than 0.4 V, and the subthreshold slope (SS) changed by ∼0.1 V/dec. ZnO or SnO<SUB>2</SUB> nanowire transistors, in contrast, showed 1.5–2.0 V negative shift in <I>V</I><SUB>th</SUB> and an SS change of ∼0.3 V/dec under the same conditions. Furthermore, the Zn<SUB>2</SUB>SnO<SUB>4</SUB> nanowire transistors returned to their initial state immediately after the light source was turned off, unlike those using the other two nanowires. Thus, Zn<SUB>2</SUB>SnO<SUB>4</SUB> nanowires achieve photostability without the application of a black material or additional processing, minimizing the photocurrent effect for display devices.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancac3/2012/ancac3.2012.6.issue-6/nn300401w/production/images/medium/nn-2012-00401w_0008.gif'></P>

Efficient catalyst recovery systems based on Pd-coated γ-alumina particles

Lim, Jin Hyun,Im, Kyungmin,Jung, Euiyoung,Yu, Taekyung,Kim, Jinsoo,Park, Bum Jun THE KOREAN SOCIETY OF INDUSTRIAL AND ENGINEERING 2018 JOURNAL OF INDUSTRIAL AND ENGINEERING CHEMISTRY -S Vol.62 No.-

<P><B>Abstract</B></P> <P>Spherical mesoporous γ-Al<SUB>2</SUB>O<SUB>3</SUB> (γ-Al) particles, embedded with magnetite nanoparticles (MNPs), were successfully prepared using a novel approach combining sol-gel and spray pyrolysis methods. Due to the magnetism of the embedded MNPs, the MNP/γ-Al particles can be utilized as recyclable catalyst supports. To demonstrate their recovery efficacy, Pd nanoparticles were impregnated on the surface of the MNP/γ-Al particles using the wetness impregnation method, and the resulting Pd/MNP/γ-Al catalysts were used to catalyze hydrogenation reactions of 4-nitrophenol. We demonstrated that when the magnetic nanoparticles were embedded in the catalysts, the recovery efficiency of the catalysts was further improved under the magnetic field.</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>