1

Nature Materials 5, 102 (2006)

Photosensitive gold-nanoparticle-embedded dielectric nanowires MING-SHIEN HU1,2, HSIN-LI CHEN3,4, CHING-HSING SHEN4, LU-SHENG HONG1, BOHR-RAN HUANG3, KUEI-HSIEN CHEN2,4 AND LI-CHYONG CHEN4 1Department of Chemical Engineering, National Taiwan University of Science and Technology, Taipei 106, Taiwan 2Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 106, Taiwan 3Department and Institute of Electronic Engineering, National Yunlin University of Science and Technology, Yunlin 640, Taiwan 4Center for Condensed Matter Sciences, National Taiwan University, Taipei 106, Taiwan

Noble-metal nanoparticles embedded in dielectric matrices are considered to have practical applications in ultrafast all-optical switching devices owing to their enhanced third-order nonlinear susceptibility, especially near the surface-plasmon-resonance (SPR) frequency1,2. Here we present the use of a microreactor approach to the fabrication of a self-organized photosensitive gold nanoparticle chain encapsulated in a dielectric nanowire. Such a hybrid nanowire shows pronounced SPR absorption. More remarkably, a strong wavelength-dependent and reversible photoresponse has been demonstrated in a two-terminal device using an ensemble of gold nanopeapodded silica nanowires under light illumination, whereas no photoresponse was observed for the plain silica nanowires. These results show the potential of using gold nanopeapodded silica nanowires as wavelength-controlled optical nanoswitches. The microreactor approach can be applied to the preparation of a range of hybrid metal–dielectric one-dimensional nanostructures that can be used as functional building blocks for nanoscale waveguiding devices, sensors and optoelectronics.

Fig 1. TEM images and EDX spectra of the gold nanopeapodded silica nanowire. a–e, TEM images showing structural evolution with growth times of a, 0min,b, 2min, c, 5min, d, 10min, and e, 20min. The inset in e shows an electron-diffraction pattern recorded along the [120] zone axis. f, HRTEM image of the gold core in a silica nanowire, showing an ellipsoidal shape with an aspect ratio of ~1.18. g–h, EDX spectra of a composite nanowire taken at the shell and gold region, respectively.

Fig 2. Photoresponse measurements. The room-temperature resistance response as a function of time to light illumination for plain silica nanowires (upper part) and gold nanopeapodded silica nanowires (lower part). Shaded (pink, excitation wavelength λex =635 nm; green, λex =532 nm; purple, λex =405 nm) and unshaded regions mark the light-on and light-off periods, respectively.

2

Phys. Rev. Lett. 97, 097204 (2006) Lattice Disorder and Size-Induced Kondo Behavior in CeAl2 and CePt2+x S.-W. Han,1,2 C. H. Booth,1 E. D. Bauer,3 P. H. Huang,4 Y.Y. Chen,4 and J. M. Lawrence5 1Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA 2Chonbuk National University, Jeonju, 561-756, Korea 3Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA 4Institute of Physics, Academia Sinica, Taipei, Taiwan, Republic of China 5Department of Physics, University of California, Irvine, California 92697, USA When the size of CeAl2 and CePt2+x particles is reduced to the nanometer scale, antiferromagnetism is suppressed and Kondo behavior predominates, with the Kondo temperature TK either decreasing (CeAl2) or increasing (CePt2+x) relative to the bulk. Local structure measurements show that these nanoparticles are significantly distorted. While such distortions should strongly affect magnetic and electronic properties, we find they cannot explain the observed changes in TK. Other size-induced changes to the electronic structure must, therefore, play a significant role.

FIG. 1. Ce LIII-edge XANES at 20 K on (a) CeAl2, (b) CePt2, and (c) CePt2.5, together with estimates of nf. These nf estimates include the contribution of any cerium impurities. Energy is calibrated by setting the first inflection point of the CeO2 Ce LIII edge to 5724.0 eV.

FIG. 2. EXAFS (kχ) as a function of k measured at 20 K. From top, Ce LIII edge on CeAl2, CePt2 and CePt2.5, and Pt LIII edge on CePt2 and CePt2.5. The Ce LIII-edge EXAFS data are limited to k = 10Å−1 by the Ce LII edge.

3

Advanced Materials, 18, 1517 (2006) DNA as an Electron-Beam Sensitive Reagent for Nano-Patterning Hung-Yi Lin, Department of Material Science, National University of Tainan, Tainan 70005, Taiwan Li-Chu Tsai, Department of Molecular Science and Engineering, National Taipei University of Technology Pei-Yin Chi, Institute of Physics, Academia Sinica, Nankang 11529, Taipei, Taiwan Chii-Dong Chen, Institute of Physics, Academia Sinica, Nankang 11529, Taipei, Taiwan In this study, we propose and demonstrate a new application using DNA as an e-beam sensitive reagent for patterning. The technique allows direct electron-beam patterning of oligonucleotides. To this end, thiolated single-strand DNA was bombarded using a focused electron beam, resulting in the inhibition of hybridization to complementary strands. The degree of inhibition as a function of the exposure dose was studied using both fluorescence-probe and Au-nano-particle labeling. Finally, for demonstration purposes gold nano-particles were used as markers to produce nano-scaled patterns. The results of which are presented in this paper. This technique has potential applications in the fabrication of DNA-based nano-structures.

Fig. 2 Gold nano-particle pattern produced by utilizing DNA molecular layer as an e-beam sensitive reagent. In this approach, thiolated single-strand DNA was bombarded using a focused electron beam, resulting in the inhibition of hybridization to complementary strands, and then gold nano-particles were used as markers to reveal nano-scaled patterns. This technique has potential applications in the fabrication of DNA-based nano-structures.

1 µm 1 µm

Fig.1 Sample preparation procedures. a) Application of HS-20T solution to a gold surface. b) Immobilization of HS-20T oligonucleotides through sulfur–gold interaction. c) Electron-beam patterning on the oligonucleotide thin film. d) Hybridization of Hex-20A with HS-20T.

4

Chem. Commun., (2006) 3435 Controlled synthesis of highly dispersed platinum nanoparticles in ordered mesoporous carbons Shou-Heng Liu,a Rong-Feng Lu,b Shing-Jong Huang,a An-Ya Lo,a Shu-Hua Chienb,c and Shang-Bin Liua

aInstitute of Atomic and Molecular Sciences, Academia Sinica, Taipei, 10617, Taiwan. bInstitute of Chemistry, Academia Sinica, Taipei 11529, Taiwan cDept. of Chemistry, National Taiwan University, Taipei 10617, Taiwan A novel route has been developed to fabricate ordered carbon mesoporous materials with well-dispersed, highly stable Pt nanoparticles of ca. 2–3 nm on the pore walls using platinum acetylacetonate as the co-feeding carbon and Pt precursor.

Fig. 2 (a) and (b) TEM images of tubular Pt-CMM-0.6 sample. Insert: image along the [100] direction.

Fig. 3 Schematic drawings of synthesis routes for (a) →(e) Pt-CMMs, and (a) → (f) CMK-5.

Fig. 1 (a) Powder XRD patterns of SBA-15, CMM, and various Pt-CMMs samples; (b) platinum XPS spectrum of Pt-CMM-0.6; (c) carbon XPS spectrum of Pt-CMM-0.6.

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Solid State Commun. 138 (2006) 516

Low-temperature specific heat of double wall carbon nanotubes B. Xianga, C.B. Tsaib, C.J. Leec, D.P. Yua, Y.Y. Chenb a State Key Laboratory for Mesoscopic Physics, and Electron Microscopy Laboratory, School of Physics, Peking University, Beijing 100871, People’s Republic of China b Institute of Physics, Academia Sinica, Taipei, Taiwan c Department of Nanotechnology, Hanyang University, Seoul 133-791, South Korea We report the analysis on the low-temperature specific heat of the double-walled carbon nanotubes (DWNTs) in the temperature range between 0.3 and 30 K, in comparison with that of the single-walled carbon nanotubes (SWNTs). The low-temperature specific heat of the SWNTs can be analyzed in terms of the acoustic phonon modes and the neighboring-tube interactions (αT3), which are in good agreement with earlier reports. The low-temperature specific heat of the DWNTs is smaller than that of the SWNTs. Taking account of the theoretical framework of the DWNT proposed by Damnjanovic et al. and the neighboring-tube interactions (CT3), the measured low-temperature specific heat of the DWNTs is well consistent with the theoretical predication. Our experimental results indicate that the neighboring-tube and intralayer interactions are not negligible in the low-temperature specific heat of the DWNTs.

Fig. 2. The CDWNTs–T curve of the DWNTs. The dotted line is the calculated data of specific heat of the DWNTs with considering the intralayer interaction. The open circle is the experiment data of our DWNTs sample. The solid circle is the net specific heat in which the interaction CT

3 term was subtracted from the open circle curve

(CT3+DT

x).

Fig. 1. (a) Low-magnified TEM image revealing the typical morphology of the bundles of DWNTs. (b) HRTEM image shows the abundance of the doublewalled CNTs.

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Thin Solid Films 498 (2006) 193 – 197 Template-assisted synthesis of mesoporous tubular carbon nanostructure by chemical vapor infiltration method A.Y. Loa, S.J. Huangb, W.H. Chenb, Y.R. Penga, C.T. Kuoa, S.B. Liub a Departement of Material Science and Engineering, National Chiao Tung University, Hsinchu 300, Taiwan b Institute of Atomic and Molecular Sciences, Academia Sinica, P. O. Box 23-166, Taipei 106, Taiwan A novel synthesis route for fabrication of tubule mesoporous carbon by chemical vapor infiltration method using a mesoporous silica template is reported. Powder X-ray diffraction and pore size analysis revealed that the nano-sized carbon material consists of threedimensional framework structure and possesses a bimodal pore distribution with average pore diameters of 1.5 and 3.3 nm. The formation of the former pore is ascribed due to removal of the silica template, whereas the latter represents pore size of tubule carbon with ordered structure having an average wall thickness corresponding to about 1.3 layers of graphitic sheets, as verified by Raman spectroscopy and electron microscopy.

Fig. 1. TEM images of (a) MCM-48 template and (b) CMT-1 carbon along the [110] plane. (c) A close-up view near the edge of CMT-1 sample particle.

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Appl. Phys. Lett. 88, 222509 (2006)

Interfacial effects on magnetostriction of CoFeB/AlOx/Co junction Yuan-Tsung Chen Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu, Taiwan 30043, Republic of China S. U. Jen and Y. D. Yao Institute of Physics, Academia Sinica, Nankang, Taipei, Taiwan 11529, Republic of China Jenn-Ming Wu Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu, Taiwan 30043, Republic of China An-Cheng Sun Department of Physics and Center for Nanostorage Research, National Taiwan University, Taipei 106, Taiwan, Republic of China

Saturation magnetostriction (λs) of CoFeB/AlOx/Co magnetic tunnel junctions (MTJs) has been measured. There are three kinds of MTJs in this study, i.e., glass/CoFeB(tA)/AlOx(δto)/Co(tB) with tA+tB=150 Å; tA=100, 75, and 50 Å; and δto=0–30 Å. When plotting λs as a function of δto, the curve is concave up. We also investigated the compositional distribution of Fe, Al, and O across the tunneling part of the

CoFeB(75 Å)/AlOx/Co(75 Å) junction. Based on these results, we propose a model to describe how the total λs is affected by the CoFeB/AlOx and AlOx/Co interfaces.

FIG. 1. (a) The stacking sequence of the laminated CoFeB/AlOx /Co junction. (b) The ∆λ curve represents the theoretical net interfacial effect. δto is the thickness of AlOx.

FIG. 2. A typical high-resolution cross-sectional TEM image of the glass/CoFeB(75 Å)/AlOx(17 Å)/Co(75 Å) tunnel junction.

2 nm

AlOx

8

New Journal of Physics, 8, 300, (2006)

Coupled single electron transistors as a differential voltage amplifier C. S. Wu and C.F. Lin Graduate Institute of Electro-Optical Engineering and Department of Electrical Engineering, National Taiwan University, Taipei, Taiwan Watson Kuo Department of Physics, National Chung Hsing University C. D. Chen* Institute of Physics, Academia Sinica, Nankang 11529, Taipei, Taiwan We have investigated a possible application of single electron transistor (SET) devices for use as a differential voltage amplifier. The device consists of a pair of box-SET and probe-SET coupled with each other through a tunnel junction, with the gate electrodes of the two SETs acting as differential signal inputs. The voltage across the probe-SET at a fixed bias current provides information about the charge states of both the probe-SET and the box-SET, which was confirmed by simulations based on the orthodox theory of single-electron tunneling. When operated as a differential amplifier, the output probe-SET voltage signal was measured as a function of the two gate input signals. While the output signal was found to be proportional to the difference in the two input signals, it remained unchanged for input signals of the same amplitude (referred to as the common mode signal), and the common mode rejection ratio was found to be 27.5dB.

Fig. 2. (left) Intensity plot of VP as a function of gate voltages Vbg and Vpg measured at Ip=0.43nA. Bright regions indicate high VP values. (right) The same plot as in (left) but made by simulation. The dashed line and dotted line indicate the applied gate voltages for common-mode and differential-mode input signals, respectively.

Fig. 1. SEM image of a measured sample. The junctions areas are marked by white parallelograms and the two control gates are located outside the image.

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J. Magn. Magn. Mater. 304 e231 (2006) Effects of SiO2 inserted layers on the Structure and magnetic properties of FePt (0 0 1) films D.H. Weia, K.L. Youa, Y.D. Yaoa, Y. Lioua, T.S. Chinb, C.C. Yuc aInstitute of Physics, Academia Sinica, Taipei 115, Taiwan bDepartment of Materials Science and Engineering, National Tsing Hua University, Hsinchu 300, Taiwan cDepartment of Applied Physics, National Kaohsiung University, Kaohsiung 811, Taiwan SiO2 (0.8–3.2 nm) ultrathin layers were inserted into Fe/Pt multilayers to introduce controllable defects on the interfaces between SiO2 and Fe/Pt multilayers. The insertion of SiO2 layers effectively reduced the average grain size and the size of magnetic domains. Out-of plane coercivity of the FePt films decreased with increasing thickness of the SiO2 insert layer. Studies on the angle-dependent coercivity of Fe/Pt multilayers without and with SiO2 insert layer, the magnetization reversal behavior changed from near domain-wall motion type to close to the a Stoner–Wohlfarth type of rotation mode.

Fig. 1. Out-of-plane coercivity Hc (a), saturation magnetization Ms (b), and average grain size Dg (c) values for FePt films versus the thickness of SiO2 insert layer.

Fig. 2. Angular dependence of coercivity for the FePt films without and with the SiO2 insert layer of 3.2 nm. The angle refers to that between the easy axis (film normal) and the field direction.

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Presented at The 9th International Conference on Synchrotron Radiation Instrumentation (SRI 2006)

Using E-Beam and X-Ray Lithography Techniques to Fabricate Zone Plate T. N. Loa, Y. T. Chena,c, W. D. Changa,b, T. Y. Laia,b, H. J. Wua,b, I. K. Lina, C. I. Sua,b, B. Y. Shewd, and Y. Hwua,b,d

aInstitute of Physics, Academia Sinica, Taipei 11529, Taiwan bInstitute of Optoelectronic Sciences, National Taiwan Ocean University, Keelung 20224, Taiwan cDepartment of Materials Engineering, Tatung University, Taipei 10452, Taiwan dNational Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan High-resolution zone plate for focusing and magnifying hard-x-rays post perhaps the most challenging task to the nanofabrication for the required very high fabrication precision and high aspect ratio metal structures. In this work, we present a nanofabrication strategy to fabricate a high-resolution zone plate for x-ray applications which takes advantage of the X-Ray lithography and electroplating processes. The substrate used to fabricate the x-ray mask is first prepared by depositing Si3N4 film and W film on a wafer. Electron beam lithography is then used to create designed zone plate pattern on the W film. A lift-off process exposed the fabricated Cr pattern. Finally, KOH is used to etch the Si wafer and to produce the desired X-Ray hard mask. This hard mask defines the zone plate pattern with the x-ray lithography method and produced the Au structures by electroplating.

Fig. 2. SEM image of Au electroplating on etched zone plate pattern.

Fig. 1. The zone plate pattern after e-beam lithography.

200 nm

100 nm

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Presented at The 9th International Conference on Synchrotron Radiation Instrumentation (SRI 2006) Fabrication of High Resolution Hard X-Ray Zone Plates by Electron Beam Lithography and Inductive Coupled Plasma Etching Y. T. Chena, b, I. K. Lina, T. N Loa, C. I. Sua,c, C. J. Liua , J. H. Jed, G. Margaritondoe , and Y. Hwua,c aInstitute of Physics, Academia Sinica, Taipei 115, Taiwan. b Department of Materials Engineering, Tatung University, Taipei 104, Taiwan.

c Institute of Optoelectronic Science at National Taiwan Ocean University, Keelung 202, Taiwan dDepartment of Materials Science and Engineering, Pohang University of Science and Technology, Pohang, Korea eEcole Polytechnique Fédérale, CH-1015 Lausanne, Switzerland

We used an approach combining Inductively Coupled Plasma (ICP) etching process and high resolution electron beam lithography and successfully fabricate high aspect ratio zone plate for hard-x-ray applications. The electron beam lithography defines the pattern with outmost zone dimension smaller than 100nm while the consequently ICP produced high aspect ratio structures. Both characteristics, high resolution patterning and high aspect ratio are required to produce zone plate devices for multi-keV x-rays. We demonstrated that a zone plate with a 60nm outmost zone and a thickness of 500nm is achievable by this approach.

Fig. 1. Etching profile of LOR5B at ICP power of 250 W and DC bias of 50V for 120s.

Fig.2. Etching profiles of LOR5B at ICP power of 300 W and DC bias of 50V for 240s.

503 nm

60 nm

1 µm