Abstract: ZnS:Mn quantum dots were prepared in the aqueous medium from readily available
precursors. The construction, morphology and luminescence properties of the ZnS:Mn quantum
dots were evaluated by XRD,TEM and photoluminescence spectra. The blue and orange emission
of the ZnS:Mn quantum dots excited by a 532nm picosecond laser were discussed.
Abstract: The porous silicon (PS) layers were fabricated on n(100) and n(111) silicon by applying
the constant and repeated currents in different HF solutions. The electrochemical impedance
spectroscopy (EIS) was used to in-situ characterize the Si/electrolyte interface before and after the
PS formations. The surface and structure of PS layers were examined in terms of
Abstract: We report on the development of wide gain InAs/InGaAlAs/InP quantum-dash structure
for broadband diode laser and amplifier. Characterizations of this material system have been
performed using spectroscopy and microscopy techniques. Gain-guided broad area laser fabricated
using this material system exhibits lasing wavelength coverage of up to 76 nm at ~1.64 (m center
wavelength from simultaneous multiple confined states lasing at room temperature.
Abstract: We fabricated improved carbon counter electrodes to improve conversion efficiency of dye
sensitized solar cells (DSSCs). Unlike conventional carbon counter electrodes, we added small
quantity of TiO2 nano powder and used chemical sintering methodology developed by Park’s group
to make surface morphology of the electrodes to change. Through these methods, we could observe
change of surface morphology of carbon electrodes and influences on short circuit current density
(JSC) and conversion efficiency.
Abstract: Nano-scale spatial wavelength engineering of quantum nanostructures using nitrogen
ion-implantation induced intermixing has been developed for tuning the bandgap of quantum-well,
quantum-dash-in-well, and quantum-dot nanostructures. High performance bandgap-tuned
quantum-well and quantum-dash lasers fabricated using this technique has been demonstrated.
Abstract: Excimer lasers have been utilized for the crystallization of hydrogenated amorphous
silicon for electronic applications. These lasers typically operate in the ultraviolet and hence photons
are absorbed by the silicon thin films within a few nanometres of the surface, melting and
solidifying the silicon on a nanosecond timescale, often without affecting the underlying substrate.
This technique enables the use of inexpensive substrates, such as glass, which are highly preferable
for low cost, large-area electronic devices. The depth of crystallization becomes important for
applications such as photovoltaics, which depends on a number of factors; with laser beam shape
one of the most significant. A Gaussian beam profile has been reported to be best suited for
controlled evolution of hydrogen during crystallization with minimum surface damage. Previous
reports show the typical energy densities of crystallization, comparing the crystalline volume and
surface roughness of the resultant films for different film thicknesses. We report significant
reductions of laser energy densities for crystallization by modifying the Gaussian pulse profile,
while retaining the controlled evolution of hydrogen from hydrogenated amorphous silicon films.
An asymmetrical, shorter pulse profile retains the desirable gradual leading edge of the Gaussian
pulse for controlled evaporation of hydrogen, while increasing the peak energy. The resultant films
show increased surface roughness along with higher crystalline volumes, which may be beneficial
Abstract: In this paper, we report a DFB laser diode with a buried SiO2 grating. Epitaxy lateral
overgrowth by metalorganic chemical vapour deposition (MOCVD) is conducted to grow the p-type
InP cladding layers in the nano-patterned dielectric grating template. The large refractive index
difference between SiO2 and InP results an index coupling coefficient κ of about 250 cm-1. The
fabricated DFB laser showed a side mode suppression ratio larger than 45 dB measured. The
technology developed can also be used for other applications that require high efficiency grating
Abstract: Single ZnO nanorods with diameters of 100nm were directly grown on GaN surface by
using low-temperature hydrothermal synthesis. Individual nanorods were removed from the
substrate and placed between the Au contact pads and the current voltage measurement was
proceeded to characterize the electrical properties of the ZnO nanorods. By using thermionic field
emission model of Padovani and Stratton , the resistivity, carrier concentration, electron mobility can
be extracted with the values of 0.14 Ωcm, 9.2x1016/cm3,33.82cm2V-1s-1, respectively. The single
ZnO nanorods also showed high sensitivity to the UV light (325nm). Under the UV illumination, the
UV induced current increase nearly 10 times than the dark current. In addition, the nanorods also
exhibited a slow UV response due to the effects of the oxygen ions on the surface of the nanorods.
Abstract: We report on the experimental and theoretical studies of population/depopulation
dynamics of excitons in the structures with Si nanocrystals in SiO2 matrix (nc-Si/SiO2) under strong
optical excitation. The experimental results are explained using a phenomenological model based
on rate equations for coupled system of energy donors (excitons) and energy acceptors (erbium
ions). Exciton luminescence is found to exhibit superlinear dependence for Er-doped samples. At
the same time the Er-related luminescence at 1.5 μm shows a saturation of the intensity and
shortening of the lifetime, which are attributed to the population inversion of the Er ions states. The
obtained results demonstrate that nc-Si/SiO2:Er systems can be used for applications in Si-based
optical amplifiers and lasers, compatible with planar Si-technology.