Lei, Dangyuan = 表面等離子交叉耦合協助氧化鋅發射的理論和實驗研究 / 雷黨願. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2007. / Includes bibliographical references (leaves 81-85). / Abstracts in English and Chinese. / Lei, Dangyuan = Biao mian deng li zi jiao cha ou he xie zhu yang hua xin fa she de li lun he shi yan yan jiu / Lei Dangyuan. / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Motivations --- p.1 / Chapter 1.2 --- Thesis outline --- p.3 / Chapter 2 --- Background and Proposition --- p.7 / Chapter 2.1 --- Surface plasmon mediated emission from semiconductor --- p.7 / Chapter 2.1.1 --- General mechanism --- p.7 / Chapter 2.1.2 --- Formulation of SP coupling --- p.10 / Chapter 2.1.2.1 --- Derivation of dispersion relation --- p.10 / Chapter 2.1.2.2 --- Plasmonic density of states (DOS) --- p.13 / Chapter 2.1.2.3 --- Field distribution in dielectric/metal/dielectric System --- p.13 / Chapter 2.1.2.4 --- Determination of Purcell factor (Fp) --- p.16 / Chapter 2.1.3 --- Emission enhancement from metal-capped ZnO --- p.17 / Chapter 2.2 --- Proposal for making high efficiency top-emitting LED --- p.22 / Chapter 3 --- Experimental Setup and Measurement System --- p.24 / Chapter 3.1 --- Sample preparation --- p.24 / Chapter 3.1.1 --- Radio frequency magnetron sputtering --- p.24 / Chapter 3.1.2 --- Spin-coating --- p.27 / Chapter 3.1.3 --- Rapid thermal annealing --- p.29 / Chapter 3.2 --- Optical characterizations --- p.29 / Chapter 3.2.1 --- Transmittance measurement --- p.29 / Chapter 3.2.2 --- Photoluminescence (PL) measurement --- p.31 / Chapter 3.2.3 --- EDX for composition measurement --- p.32 / Chapter 4 --- Theoretical Simulations and Experimental Results --- p.36 / Chapter 4.1 --- Tunable surface plasmon resonance by using metal alloys --- p.36 / Chapter 4.1.1 --- Dielectric constants calculation --- p.37 / Chapter 4.1.2 --- Dispersion relation of alloy/Si02 --- p.41 / Chapter 4.1.3 --- Plasmonic density of states and Purcell factor of alloy/semiconductor --- p.43 / Chapter 4.1.3.1 --- Air/AlxAg1-x/ZnO system --- p.43 / Chapter 4.1.3.2 --- Air/AlxAul-x/ZnTe --- p.46 / Chapter 4.1.3.3 --- Air/ AgxAul-x/CdSe system --- p.48 / Chapter 4.1.4 --- Experimental results of AlxAgl-x/ZnO --- p.52 / Chapter 4.1.5 --- Discussion and mini-conclusion --- p.56 / Chapter 4.2 --- Enhanced forward emission from metal-insulator-metal/ZnO by coupled surface plasmon --- p.57 / Chapter 4.2.1 --- Plasmon modes in metal-insulator-metal (MIM) --- p.57 / Chapter 4.2.2 --- Transmittance simulation of MIM and MIMIM --- p.63 / Chapter 4.2.3 --- Transmittance measurement of MIM --- p.68 / Chapter 4.2.4 --- Transmittance and photoluminescence of MIM/ZnO. --- p.73 / Chapter 4.2.5 --- Discussion and mini-conclusion --- p.78 / Chapter 5 --- Conclusions --- p.79 / Chapter 6 --- References --- p.81

Quantum cascade laser (QCL) diodes have potential applications in many areas including emissions analysis and explosives detection, but like many solid-state devices they suer from degraded performance at higher temperatures. To alleviate this drawback, the thermal properties of the QCL diodes must be better understood. Using molecular dynamics (MD) and photothermal radiometry (PTR), the thermal conductivity of a representative QCL diode is computed and measured respectively. The MD results demonstrate that size eects are present in the simulated systems, but if these are accounted for by normalization to experimental results the thermal conductivity of the QCL can be reasonably obtained. The cross-plane conductivity is found to be in the range of 1.8 to 4.3 W=m K, while the in-plane results are in the range of 3.7 to 4.0 W=m K. These values compare well with experimental results from the literature for both QCL materials and for AlInAs and GaInAs, which the QCL is composed of. The cross-plane conductivity results are lower than those of either AlInAs or GaInAs, which demonstrates the phonon scattering at the interfaces. The in-plane results are between AlInAs and GaInAs, which is to be expected. The PTR results are less concrete, as there seem to be heat transfer eects active in the samples which are not included in the models used to t the frequency scans. These effects are not 2D heat transfer artifacts nor are they the result of volumetric absorption. It is possible that they are the results of plasmon induction, but this is only supposition. As the data stand, the PTR and MD results are within an order of magnitude of each other and follow reasonable trends, which suggests that both results are not too far o from reality. While the experimental results are not entirely conclusive, the simulations and experiments corroborate each other suciently to warrant further investigation using these techniques. Additionally, the simulations present sucient internal consistency so as to be useful for thermal property investigation independent of the PTR results.

Quantum Dots (QD) have become a commercial reality for tunable displays and light-emitting diodes. The Department of Energy believes further improvements in efficacy and stability will allow for widespread adoption of solid-state lighting in the United States. QD geometric and compositional architecture, crystal phase and surface chemistry are arguably some of the important aspects governing QD performance in these applications. Chapter I outlines the efforts of QD design, encapsulation and performance for phosphor converted, “on-chip” LEDs. Cadmium chalcogenide QDs with a quantum well geometry and ZnS encapsulation (CdS/CdSxSe1-x/CdS/ZnS) resist photoluminescence bleaching on chip under harsh accelerated ageing tests. Trends in device performance are linked primarily to success of ZnS passivation. Chapter II presents findings regarding crystal structure control (Zinc Blende vs Wurtzite) for CdX (X = S, Se) systems by focusing on crystal phase conversion. The ZB to W transition for CdX is shown to be size, material and surfactant dependent. Chapter III focuses on expanding the precursor compound library for CdSe with aryl substituted cyclic selenones (imidazole and pyrimidine-based compounds). These molecules are shown to react sluggishly at ZB synthetic conditions and that the rate is heavily influenced by compound sterics. Chapter IV presents the findings of a metal carboxylate displacement study on PbS NCs with various L-type ligands. Upon displacement and purification with N,N,N′,N′-tetramethylethylene-1,2-diamine, tri-n-butylamine, and n-octylamine, oriented attachment occurs along the 100 plane and with bis(dimethylphosphino)ethane and tri-n-butylphosphine, attachment is suppressed. This difference allows for the study of ligand density dependent optical properties without the confounding attachment of nanocrystals in solution. A decreasing trend of time resolved photoluminescence lifetime values as a function of ligand density is observed.

The radiation effects in III-V heterojunction devices are investigated in this thesis. Two types of heterojunction devices studied are InGaP/GaAs single heterojunction bipolar transistors (SHBTs) and GaN-based heterojunction light emitting diodes (LEDs). InGaP/GaAS HBTs are investigated for high energy (67 and 105 MeV) proton irradiation effects while GaN heterojunction LEDs are studied for neutron irradiation effects. A compact model and the parameter extraction procedures for HBTs are developed, and hence the I[subscript C]--V[subscript CE] characteristics of pre- and post-irradiation HBTs can be simulated by employing the developed model. HBTs are electrically characterized before and after proton irradiation. Overall, the studied HBT devices are quite robust against high energy proton irradiation. The most pronounced radiation effect shown in SHBTs is gain degradation. Displacement damage in the bulk of base-emitter space-charge region, leading to excess base current, is the responsible mechanism for the proton-induced gain degradation. The performance degradation depends on the operating current and is generally less at higher currents. Compared to the MBE grown devices, the MOVPE grown HBTs show superior characteristics both in initial performance and in proton irradiation hardness. The 67 MeV protons cause more damage than 105 MeV protons due to their higher value of NIEL (non-ionizing energy loss). The HBT I-V characteristics of pre- and post-irradiated samples can be simulated successfully by employing the developed model. GaN heterojunction LEDs are electrically and optically characterized before and after neutron irradiation. Neutron irradiation causes changes in both the I-V characteristic and the light output. Atomic displacement is responsible for both electrical and optical degradation. Both electrical and optical properties degrade steadily with neutron fluence producing severe degradation after the highest fluence neutron irradiation. The light output degrades by more than 99% after 1.6x10����� n/cm�� neutron irradiation, and the radiation damage depends on the operating current and is generally less at higher currents. / Graduation date: 2003

Organic semiconductors have the advantage over traditional inorganic semiconductors, such as Si or GaAs, in that they do not require perfect single crystal films to operate in real devices. Complicated multi-layer structures with nanometer scale thicknesses can thus be easily fabricated from organic materials using low-cost roll-to-roll manufacturing techniques. However, the discrete nature of organic semiconductors also implies that they typically contain almost no intrinsic charge carriers (i.e., electrons or holes), and thus act as insulators until electrical charges are injected into them. In electrical device applications this means that all of the holes and electrons within a device must be injected from the anode and cathode respectively. As a result, device stability, performance, and lifetime are greatly influenced by the interface between the organic materials and the electrode contacts. Despite the fundamental importance of the electrode/organic contacts, much of the basic physical understanding of these interfaces remains unclear. As a result, the current design of state-of-the-art organic optoelectronic devices tends to be based on trial and error experimentation, resulting in overly complicated structures that are less than optimal. In the present thesis, various electrode/organic interfaces relevant to device applications are studied using a variety of different techniques, including photoelectron spectroscopy and the iii temperature dependent current-voltage characteristics of single carrier devices. The fundamental understanding gleaned from these studies has been used to develop new strategies for controlling the energy-level alignment at electrode/organic interfaces. A universal method for tuning the work function of electrode materials using a halogenated organic solvent and UV light has been developed. Application of this technique in organic light emitting diodes enabled the first highly simplified two-layer device with a state-of-the-art record breaking efficiency.

This dissertation presents a wide-band lumped element equivalent circuit model and a building block-based scalable circuit model for multiple quantum well laser diodes. The wide-band multiple-resonance model expresses two important laser diode characteristics such as input reflection and electrical-to-optical transmission together. Additionally, it demonstrates good agreements with the measurement results of the selected commercial discrete laser diodes. The proposed building block-based modeling approach proves its validity using a numerically derived scalable rate equation. Since success in a circuit design depends largely on the availability of accurate device models, the practical application of the proposed models provides improved accuracy, simple implementation and a short design time.

The pre-Botzinger complex (pBC) is a sub-circuit of the respiratory central pattern generator. The pBC is required for eupnea and is contained in a transverse slice of the ventrolateral medulla. In the slice, pBC cells are responsible for generating the respiratory rhythm, and hypoglossal motoneurons (HMs) are responsible for transmitting the rhythm out of the brainstem to the muscles. Understanding how the transverse slice rhythm is generated and transmitted is a first step in understanding how this process occurs in vivo. To understand this network, we developed ionic current models of the individual network components and explored how the various ion channels affect single-cell firing characteristics and network dynamics. First, we used the considerable amounts of experimental data from neonatal HMs to develop an HM model. The model was used to explore the roles of ion channels in shaping the complex dynamics of the neonatal HM action potential (AP) and to investigate the age-dependent changes in HMs. We used a genetic algorithm to optimize the HM model to more closely fit experimental measures of AP shape. A comparison of feature-based and template-based fitness functions revealed that a feature-based fitness function performs best when optimizing the HM model to fit characteristics of the neonatal HM AP. Next, we used our existing pBC models to understand how different ionic currents affect rhythmogenesis in the pBC. Our results indicate that intrinsic bursters increase the robustness of rhythm generation in the pBC. Finally, we developed an improved pBC neuron model and explored how various ion channels affect bursting dynamics at the single-cell level. The HM and pBC models developed in this study will be used in future network models of the transverse slice.

We have developed high-efficiency blue organic light-emitting devices incorporate 1,3,5-Tri(1-pyrenyl)benzene(TPB3) as emitting layer and 4,7-diphenyl-1,10-phenanthroline(BPhen) as the electron transporting layer, which has a large Highest Occupied Molecular Orbital energy level and has good electron mobility. A device having the configuration : ITO(140 nm)/NPB(65 nm)/(TPB3 40nm)/BPhen(30 nm)/LiF(0.8 nm)/Al(200 nm) exhibited a maximum luminance at 9.5V of 29940 cd/m2, The maximum current and power efficiencies were 3.85 cd/A and 2.38 lm/W, respectively. The current and power efficiencies were greater than 3cd/A and 1.1 lm/W respectively, Over a large range of potentials (3.5~10.0V) with good Commission Internationale de l¡¦Eclairage (CIE) coordinates of (0.17, 0.22). These results indicate that TPB3 is good blue-emitting material for OLED applications. The photophysical and chemical properties of TPB3 have also been studied in this research.

The high performance organic light-emitting diodes (OLEDs) have been studied. First, we have fabricated a WOLED with AlF3 and m-MTDATA as a hybrid buffer layer. Results indicate that the turn-on voltage can be reduced to 3.1V, and the luminous efficiency can be improved to 14.7 cd/A when a hybrid buffer layer was used. Since the turn-on voltage decreases and the efficiency increases, the power consumption as well as lifespan are then improved. Moreover, the luminous efficiency of the hybrid buffer layer devices also immunes to drive voltage variations. Second, we studied the properties of transportation in OLEDs. The study presented the device of a WOLED with a combination of a graded hole transport layer (GH) structure and a gradually doped emissive layer (GE) structure as a double graded (DG) structure. The DG structure: ITO/MTDATA(15 nm/NPB(15 nm)/NPB:25% BAlq (15 nm)/NPB : 50% BAlq (15 nm)/BAlq:0.5% Rubrene (10 nm)/ BAlq : 1% Rubrene (10nm) /BAlq:1.5%Rubrene (10 nm) / Alq3 (20 nm)/ LiF (0.5 nm)/Al (200 nm) is beneficial for improving both electrical and optical performances. The luminous efficiency of the DG device is 11.8cd/A, which is larger than that of 7.9cd/A with the HJ device. This improvement is attributed to the discrete interface between hole transport layer and emissive layer can be eliminated, surplus holes can be suppressed, electron-hole pairs can obtain optimal transportation and recombination in the emissive layer, and quenching effects can be significantly suppressed. Moreover, the spectra were almost not changed with an increasing drive current. As the efficiency was improved, it is expected that the power consumption can be reduced as well. Third, high efficiency and brightness p-i-n OLEDs with a CsI-doped Alq3 layer as a n-ETL has been studied. The p-i-n WOLED with a 15 % CsI-doped Alq3 layer exhibits a luminous efficiency of 5.75 cd/A at a driving current of 20mA/cm2 as well as a maximum power efficiency of 4.67lm/W. This improved performance is attributed to the increased electron carriers of the n-ETL and the balance of electrons and holes in the recombination zone. The X-ray photoelectron spectroscopy (XPS) have shown that doping of CsI caused chemical reaction, attributing to the increase of carriers. Finally, we focus on the improvement of contrast ration (CR) of OLEDs. We successfully fabricated a conductive organic-metal light-absorbing layer with a high CR and low reflectance for use as a black cathode in an OLED. The black cathode that was fabricated using vacuum deposition has the advantages of low cost and simple fabrication. Moreover, the J-V characteristic of the black cathode device is almost identical to that of a conventional device. Additionally, the reflectance can be reduced from 66.2% to 11.3% and a small reflectance variation around 3.3% over the visible spectrum is appealed. At an ambient illumination of 250 lx, the CR can be increased from 4.2 to 10.8 at a brightness of 250 cd/m2.

Pure m-plane p-GaN/InGaN/n-GaN on the m-sapphire grown by plasma assisted molecular beam epitaxy (PAMBE) had been achieved. V/III ratio of the first layer m-plane GaN is 20 and growth temperature is 665 ¢XC. ¢½/¢» ratio and the growth temperature are the most important factors in the growth sequence. M-InGaN film with better crystal quality was grown successfully by tuning these two factors. We have obtained a narrow window for epitaxial growth of m-plane InGaN/GaN on m-sapphire at 450 ¢XC. The striated surface is along (1120) a-axis direction of m-InGaN epilayer. As the growth temperature is increased further to 550 ¢XC, there is no InGaN signal from x-ray diffraction (XRD). We study the effect of growth condition on the structural properties and morphology of these films using high-resolution x-ray diffractometer (XRD) and scanning electron microscopy (SEM)