We demonstrated the ion-sensitive field-effect transistors (IS-FETs) based on nanowires (NWs) with different diameters and doping concentrations to obtain the high sensitivity and various applications. The growth of the catalyst-free InAs NWs was carried out using a horizontal reactor MOCVD system (AIXTRON Inc.). A p-type Si (111) wafer (ρ = 1 -10 Ω-cm) was prepared for the NW growth. Here, NWs with diameters of around 50 ~ 150 nm were grown and the doping concentration also was changed around x±1016~18 /cm2. IS-FETs with the grown InAs NWs were fabricated using the photolithography and the lift-off process. The gas sensing characteristics have been investigated through studying the gate response of the NW conductance in different ambient conditions.
We analyzed and demonstrated the double layered metallic nano-structures using polystyrene lift-off process on the
conventional surface plasmon resonance (SPR) sensor to enhance the sensitivity of an SPR surface. The double layered
plasmonic structures are optimized using the three-dimensional finite-difference time-domain method for the width,
thickness, and period of the polystyrene beads. The thickness of the metal film and the metallic nano-hole is 20 and 20
nm in the 305 nm wide nano-hole size, respectively. The double layered metallic nano-structures are fabricated with
monolayer polystyrene beads of chloromethyl latex 4% w/v 0.4 μm. The sensitivities of the conventional SPR sensor
and the double layered plasmonic sensor are obtained to 42.2 and 60 degree/RIU, respectively. The SPR devices are also
applied to the lead ion sensor. The resonance shifts of SPR sensors with and without a poly(vinyl chloride) membrane
are 1328 RU and 788 RU from 10-5 M to 10-2 M concentration, respectively.
Dye-Sensitized solar cell (DSSC) is expected to be one of the next-generation photovoltaics because of its environment-friendly and low-cost properties. However, commercialization of DSSC is difficult because of the electrolyte leakage. We propose a new thermal curable base on silicon resin. The resin aimed at sealing of DSSC and gives a promising resolution for sealing of practical DSSC. Furthermore, the optimized resin was fabricated into solar cells, which exhibited best durability by retaining 97% of the initial photoelectric conversion efficiency after 1,000 hours tracking test at 80℃.
We proposed and demonstrated the metallic nano-ring structure using polystyrene lift-off process to enhance the
sensitivity of an SPR surface. The double layered SPR structures are optimized using the finite-difference time-domain
method for the width, thickness, and period of the polystyrene beads. The optimum thickness of the metal film and the
metallic nano-ring is 30 and 20 nm in the 214 nm wide nano-hole size, respectively. The metallic nano-ring structures
are fabricated with monolayer polystyrene beads of 400 nm wide. The various metallic nano-ring structures have been
obtained by transferring method. The sensitivities of the conventional SPR sensor and the metallic nano-ring structures
are obtained to 42.2 and 52.1 degree/RIU, respectively.
In this works, we have demonstrated a VOA integrated with mPDs, based on silica-on-silicon PLC and flip-chip bonding technologies. The suspended ridge structure was applied to reduce the power consumption. It achieves the attenuation of 30dB in open loop operation with the power consumption of below 30W. We have applied two-step flipchip bonding method using passive alignment to perform high density multi-chip integration on a VOA with eutectic AuSn solder bumps. The average bonding strength of the two-step flip-chip bonding method was about 90gf.
Typical Dye-sensitized solar cells (DSSC) are composed of mesoporous TiO2 nanocrystals electrode on transparent fluorine-doped tin oxide (FTO) substrate, sensitizers on the TiO2 nanocrystals, platinum (Pt) on the FTO substrate as a counter-electrode, and iodine/iodide electrolytes between the two transparent conducting oxide (TCO) substrate. But two transparent conductive oxide(TCO) substrates are estimated to be about 60[%] of the total cost of the DSSCs. Currently novel TCO-less structures have been investigated in order to reduce the cost. We suggested a TCO-less DSSCs which has titanium layer electrodes. Titanium layer electrodes are formed by electron-beam evaporation method. And we proposed the formation of hole for injecting the electrolyte of DSSC by using lithographic method. The sizes of holes are 4um and the intervals of holes are 2um. Finally, we prepared the 0.45 cm2 DSSC device and analytical instruments such as electrochemical impedance spectroscopy, scanning electron microscope were used to evaluate the TCO-less DSSCs.
In this works, the piezoelectric devices of ZnO nano-rods were fabricated for piezoelectric sensor. The ZnO nano-rods were grown by hydrothermal synthesis through two-dimensional nano-patterns using a laser interference lithography. ZnO nano-rods were preferred orientation with c-axis and wurtzite structure. It was found that the electricity of nano-rod piezoelectric device was 8x10-7 Wh under the load of 0.8kgf. The piezoelectric behaviors are attributed to the direct compression of ZnO nano-rods by an external force. Therefore, the piezoelectric devices of ZnO nano-rods fabricated by hydrothermal methods were applicable to the pressure sensors.
We introduce an ultra-sensitive integrated photonic sensor structure using silicon on insulator based triangular resonator, in which a surface plasmon resonance (SPR) gold film is applied on a total internal reflection mirror. We have analyzed and optimized the triangular resonator sensor structure with an extremely small SPR mirror sensing area. Due to the large phase shift in the SPR mirror, a significantly enhanced sensitivity of 800 nm/RIU (refractive index unit) and the maximum peak shift of half free spectral range have been obtained at the SPR angle of 22.65° with Au thickness of 35 nm for the change of the refractive index Δn = 1x10-3.
Two different shaped ZnO nanorods were grown on ZnO buffered Al2O3 substrate by laser interference lithography and hydrothermal method. The light waveguide within ZnO nano rod and photonic crystal effects in arrayed ZnO nanorods was calculated by 3D-finite dimension time domain(3D-FDTD) programs. The ZnO photonic crystal effect and number of modes of ZnO nanorod was governed by arrangement and shape of ZnO nanorod, respectively.
Organic Light Emitting Device (OLED) has a characteristic to change the electric energy into the light when the electric field is applied to the organic material. OLED is currently employed as a light source for the lighting tools because research has extensively progressed in the improvement of luminance, efficiency, and life time. OLED is widely used in the plate display device because of a simple manufacture process and high emitting efficiency. But most of OLED lighting projects were used the vacuum evaporator (thermal evaporator) with low molecular. Although printing method has lower efficiency and life time of OLED than vacuum evaporator method, projects of printing OLED actively
are progressed because was possible to combine with flexible substrate and printing technology. Printing technology is ink-jet, screen printing and slot coating. This printing method allows for low cost and mass production techniques and large substrates. In this research, we have proposed inkjet printing for organic light-emitting devices has the dominant method of thick film deposition because of its low cost and simple processing. In this research, the fabrication of the passive matrix OLED is achieved by inkjet printing, using a polymer phosphorescent ink. We are measured optical and electrical characteristics of OLED.
We investigated the properties of a triangular microresonator using the total internal reflection (TIR) mirrors with a
long evanescent field around the critical angle. For the sensitivity analysis, we have calculated the mirror offset due to
the Goos-Hänchen effect and the resonance shift of the triangular resonator with the refractive index change of the outer
region in the TIR mirror. The mirror offset is increased up to 0.8 μm for the transverse electric (TE) polarization and
2.0 μm for the transverse magnetic (TM) polarization to the incident angle of 18°. Then, the resonance shift of 417 pm
for the TM polarized light and 34 pm for the TE polarized light were observed, respectively, by changing the refractive
index of 4×10-5. The measured extinction ratio of triangular ring resonator was about 6 dB near 1550 nm, in where the
incidence angle of the TIR mirror inside the resonator was 18°.
We proposed the photonic crystal coupled surface plasmon resonance sensors using gold nano-structure to enhance the
sensitivity of an SPR sensor. The proposed configuration with the photonic crystal structure is Au(Photonic
crystal)/Au/Ag/Cr/Glass. The 20 nm silver film and the 20 nm gold film are layered on the glass substrate. Then, the
dot-like gold photonic crystal structures with a period pitch are patterned on the Au/Ag/Cr/Glass structure. The
reflectance and the optical-mode propagations as a function of incident angle are calculated using the three-dimensional
finite-difference time-domain method. Under this resonance condition, the incident light is highly absorbed and loses a
fair amount of its energy, which results in a dip in the intensity profile of the reflected light. The optimum resonance
angle of 44.5 degrees is obtained in the 75-nm-radius Au photonics crystal structure with a period of 300 nm.
Titanium dioxide (TiO2) thin films were prepared by ion-assisted electron-beam deposition on glass at room
temperature and were annealed by rapid thermal annealing in O2 and N2 gas flow. TiO2 thin films annealed in N2 gas
flow are (110) rutile phase and (101) anatase phase, but in O2 gas flow are (110) rutile phase. The optical band gaps of
the TiO2 thin films are increased to 3.281 eV with annealing treatment of 300 ~ 500 °C in O2 gas flow and to 3.271 eV in
N2 gas flow. However, the band gap begins to decrease to 3.277 eV at the annealing temperature of 600 °C in O2 gas
flow and to 3.257 eV in N2 gas flow, respectively.
We proposed the grating coupled surface plasmon resonance (GC-SPR) sensors using ZnO and metallic nanograting
structures to enhance the sensitivity of an SPR sensor. The GC-SPR sensors were analyzed using the finitedifference
time-domain method. The optimum resonance angles of 49 and 55.5 degrees are obtained in the 150 nm wide
grating structure with a period of 300 nm for the ZnO thickness of 30 and 50 nm, respectively. Here, an enhanced
evanescent field is obtained due to the surface plasmon on the edge of the bandgap when the ZnO and metallic grating
structures are used to excite the surface plasmon.
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