Young Rae Jang

Synthesis and characterization of the first adamantane-based poly(p-phenylenevinylene) derivative: an intelligent plastic for smart electronic displays

Abstract A novel poly( p -phenylenevinylene) (PPV) derivative containing adamantane substituent—poly(2-methoxy-5-adamantaneethyloxy- p -phenylenevinylene) (MAE-PPV) is synthesized through the Gilch route. Adamantane was incorporated into this polymer because of its rigid and spherical structure, which results in reduction of interchain interaction. MAE-PPV is solution processable and shows high photoluminescence intensity. This polymer also demonstrates good electroluminescene properties.

Er3+ photoluminescence from Er-doped amorphous SiOx films prepared by pulsed laser deposition at room temperature: The effects of oxygen concentration

We have fabricated Er-doped amorphous SiOx films by laser ablation of a Si:Er2O3 target in He atmosphere. The photoluminescence intensity at 1.54 μm was highly dependent on the oxygen content in the film, which turned out to be changed significantly by the ambient He pressure. Also, we have adopted time-of-flight quadrupole mass spectroscopy to obtain kinetic energies of ionic species in a plume produced by laser ablation. Si and Er ions do not overlap spatially as they expand toward the Si substrate and Er ions impinge on the preformed SiOx layer.

Rapid thermal annealing of ZnO thin films grown at room temperature

The authors successfully obtained high quality ZnO thin films by growing them at room temperature (RT) and postannealing by rapid thermal annealing (RTA). The thin films were grown by pulsed laser deposition on Si (100) substrates at RT, and RTA was performed under various temperatures and ambient conditions. Based on the UV emission to visible emission ratio in RT photoluminescence (PL) spectra, the optimum film was obtained at annealing temperature ∼700 °C in an ambient of Ar, N2, or O2 at 0.1 Torr, while the optimum annealing temperature was above 1100 °C in the air ambient at atmospheric pressure. The morphology and structure of the films in different RTA conditions were investigated by using field emission scanning electron microscopy and grazing incidence x-ray diffraction, and were discussed in conjunction with the PL data.

Dependence of Optical Matrix Elements on the Boundary Conditions of the Continuum States in Quantum Wells

Unlike for the bound states, several different boundary conditions are used for the continuum states above the barrier in semiconductor quantum wells. We employed three boundary conditions, infinite potential barrier boundary condition, periodic boundary condition and scattering boundary condition, and calculated the local number of states, wavefunctions and optical matrix elements for the symmetric and asymmetric quantum wells. We discussed how these quantities are related in the three boundary conditions. We argue that the scattering boundary condition has several advantages over the other two cases. These results would be useful in understanding quantum well lasers and detectors involving continuum states.

Synthesis of new PPV based polymer and its application to display

Abstract We have synthesized PPV derivative containing an adamantane side group, poly(1-(2-ethylhexyloxy)-4-(1-adamantaneethyloxy)-2,5-phenylenevinylene, EHAE-PPV) and fabricated the segment device using this polymeric electroluminescent material. EHAE-PPV is solution processable and shows high photoluminescence intensity, probably due to the steric effect of the adamantyl group. This polymer also has exhibited good electroluminescent properties.

Er3+ Photoluminescence from Er-doped Silicon-Rich Silicon Oxide Films Deposited by Laser Ablation of a Si:Er Target in an Oxygen Atmosphere

We have developed a new pulsed laser deposition method for fabricating Er-doped silicon-rich silicon oxide (SRSO:Er) films. A target composed of a pure Si disk and an Er metal strip was ablated by a line-focused laser beam in oxygen atmosphere. The oxygen concentration that determines the relative concentrations of the three phases (Si–Si, SiOx, and SiO2) in the film was easily controlled by varying the ambient oxygen pressure. The photoluminescence intensity at 1.54 µm from Er3+ ions was strongly dependent on the amount of the Si–Si phase in the SRSO:Er films.

Properties of ZnO Thin Films Grown on Si (100) Substrates by Pulsed Laser Deposition

ZnO thin films were grown on Si (100) substrates by pulsed laser deposition using a ZnO target. The substrate temperature was varied in the range of room temperature to 800°C, and the oxygen partial pressure of 0.1333 Pa (1 mTorr) to 1333 Pa (10 Torr). The properties of the resulting films were investigated by photoluminescence (PL), grazing incidence X-ray diffraction (GIXRD), X-ray photoelectron spectroscopy (XPS), and field emission scanning electron microscopy (FESEM). Based on the ultraviolet (UV, ∼380 nm) to visible emission ratio in the PL spectrum, the optimum growth conditions were determined to be 600°C and 133.3 Pa (1 Torr), respectively. The oxygen 1 s peak in the XPS spectrum was decomposed into two peaks. The peak at lower binding energy increased in intensity with the oxygen partial pressure from 0.1333 Pa (1 mTorr) to 133.3 Pa (1 Torr) while the other peak decreased. The GIXRD curve at the optimum condition showed strong two peaks (002 and (103). A strong correlation between the (103) peak intensity and the UV emission intensity was found.

Accurate measurement of thickness of large-area graphene layers by neutron reflectometry

Neutron reflectometry was used to determine the thickness of large-area graphene layers on SiO2/Si substrates. Preliminary simulations showed that the optimum thickness of the SiO2 layer for neutron reflection is about a few hundred angstroms. The thicknesses of the graphene and the SiO2 layers were obtained by fitting the experimental reflectivity spectra. Transmission electron microscopy and Raman experiments were performed on the same samples, and verified that the neutron reflection results are reliable and accurate at the subangstrom level. This neutron reflectometry is nondestructive and applicable to wafer-size layers to yield the mean thickness. This accurate determination of the thickness will be helpful for managing quality of large-area graphene films.

1.54 μm emission mechanism in Er-doped silicon-rich silicon oxides

Silicon-rich silicon oxide (SRSO) and Er-doped SRSO (SRSO:Er) thin films were formed by pulsed laser deposition, and characterized by photoluminescence (PL), x-ray photoelectron spectroscopy (XPS), x-ray diffraction (XRD), and UV-visible transmission in order to clarify the 1.54 μm emission mechanism in the SRSO:Er films. The oxygen content of the films was varied by the adjustment of oxygen partial pressure. The behavior of the 1.54 μm PL with oxygen partial pressure combined with XPS and XRD data show that the 1.54 μm emission intensity is related to the amount of SiOx phase. This conclusion is well supported by the measurements of UV-visible transmission. In many previous papers, the 1.54 μm emission is associated with Si nanocrystals, but in our study the correlation between 1.54 μm emission intensity and the amount of SiOx phase is much clearer.

Strong visible PL from the nc-Si thin film by Ni silicide mediated crystallization

Abstract We studied the growth of nanocrystalline silicon (nc-Si) thin film exhibiting a strong room temperature photoluminescence (PL) at 1.81– 2.003 eV . The amorphous silicon was crystallized by Ni silicide mediated crystallization (Ni SMC) and then Secco-etched to exhibit the PL. The PL peak energy and intensity increase with increasing the metal density on the a-Si because of the reduction in the grain size down to 2 nm . The photoluminescence energy and peak intensity depend strongly on the Secco etch time because the grain size is reduced by etching the grain boundaries.