The dielectric properties and phase transformation of poled <001>-oriented Pb(Mg1/3Nb2/3)O3-x%PbTiO3(PMN-x%PT) single crystals with compositions of x=20, 30, and 35mole% are investigated for orientations both parallel andperpendicular to the [001] poling direction. An electric-field-induced monoclinic phase was observed for the initial poled PMN-30PT and PMN-35PT samples by means of high-resolution synchrotron x-ray diffraction. The monoclinic phase appears from−25oC to 100oC and from −25oC to 80oC for the PMN-30PT and PMN-35PT samples, respectively. The dielectric constant (ε)-temperature (T) characteristics above the Curie temperature were found to be described by the equation(1/ε−1/εm)1/n=(T−Tm)/C, where εm is the maximum dielectric constant and Tm is the temperature giving εm, and n and C are constants that changewith the composition. The value of n was found to be 1.82 and 1.38 for 20PT and 35PT, respectively. The results of meshscans and the temperature-dependence of the dielectric constant demonstrate that the initial monoclinic phase changes to a singledomain tetragonal phase and a to paraelectric cubic phase. In the ferroelectric tetragonal phase with a single domain state, thedielectric constant measured perpendicular to the poling direction was dramatically higher than that measured in the paralleldirection. A large dielectric constant implies easier polarization rotation away from the polar axis. This enhancement is believedto be related to dielectric softening close to the morphotropic phase boundary.

The structure and dielectric properties of poled<001>-oriented 0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 (PMN-0.3PT) crystals have been investigated for orientations both parallel and perpendicular to the [001] poling direction. An electric field induced monoclinic phase was observed for the initial poled sample. The phase remained stable after the field was removed. A quite different temperature dependence of dielectric constant has been observed between heating and cooling due to an irreversible phase transformation. The results of mesh scans and temperature dependence of the dielectric constant demonstrate that the initial monoclinic phase changes to a single domain tetragonal phase at 370K and to a paraelectric cubic phase at 405K upon heating. However, upon subsequent cooling from the unpoled state, the cubic phase changes to a poly domain tetragonal phase and to a rhombohedral phase. In the ferroelectric tetragonal phase with a single domain state, the dielectric constant measured perpendicular to the poling direction was dramatically higher than that of the parallel direction. A large dielectric constant implies easier polarization rotation away from the polar axis. This enhancement is believed to be related to dielectric softening close to the morphotropic phase boundary and at the phase transition temperature.

The domain structures of annealed (001)-oriented Pb(Mg1/3Nb2/3)O3-x%PbTiO3 (PMN-x%PT) crystals for x = 10, 20, 30, 35, and 40 at% were investigated by Polarized Optical Microscopy (POM) and Scanning Force Microscopy (SFM) in the piezoresponse mode. Both Polar Nano-Domains (PND) and long strip-like domains were clearly observed. The results also showed how the domain structure changed between phases with an increasing x in the PMN-x%PT crystals and the domain hierarchy on various length scales ranging from 40 nm to 0.1 mm. Distorted pseudo-cubic phase (x< 20%) consisted of PNDs that did not self-assemble into macro-domain plates. The rhombohedral phase (x = 30%) consisted of PNDs that began to self-assemble into colonies along preferred 110 planes. The monoclinic phase (x = 35%) consisted of miniature polar domains on the nm scale, whereas, the tetragonal phase (x = 40%) consisted of 001 oriented lamella domains on the mm scale that had internal nano-scale heterogeneities, which self-assembled into macro-domain plates oriented along 001 the mm scale.

Vapor phase polymerization of a conductive polymer on a SiO2 surface can offer an easy and convenient means to depositing pure and conductive polymer thin films. However, the vapor phase deposition is generally associated with very poor adhesion as well as difficulty when patterning the polymer thin film onto an oxide dielectric substrate. For a significant improvement of the patternability and adhesion of Poly(3-hexylthiophene) (P3HT) thin film to a SiO2 surface, the substrate was pre-patterned with n-octadecyltrichlorosilane (OTS) molecules using a μ-contact printing method. The negative patterns were then backfilled with each of three amino-functionalized silane self-assembled monolayers (SAMs) of (3-aminopropyl) trimethoxysilane (APS), N-(2-aminoethyl)-aminopropyltrimethoxysilane (EDA), and (3- trimethoxysilylpropyl)diethylenetriamine (DET). The quality and electrical properties of the patterned P3HT thin films were investigated with optical and atomic force microscopy and a four-point probe. The results exhibited excellent selective deposition and significantly improved adhesion of P3HT films to a SiO2 surface. In addition, the conductivity of polymeric thin films was relatively high (~13.51 S/cm).

Ti과 Si의 비가 서로 다른 종류의 타 을 Ar/N2의 혼합기체를 사용하여 rf magnetron sputtering방법으로 증착된 Ti-Si-N박막의 증착특성에 대해 연구하였다. Ti-Si-N박막의 조성과 증착률은 각 타 Ti/Si의 비율과 증착시의 질소기체의 유량에 따라 크게 변하였다. 이것은 Ti과 Si의 nitriding 정도의 차이로 인한 서로 다른 sputter yield에 의한 것으로 나타났다. Si이 비교적 적게 포함된 Ti-Si-N박막은 증착시부터 박막내 TiN의 결정화가 일어났으며, 낮은 비저항을 나타내었다. N의 함량의 증가는 박막의 밀도와 압축응력을 증가시켜 Ti-Si-N박막의 확산방지 능력에 큰 영향을 미치는 인자로 나타났다. 본 연구에서 N2의 유략과 타 의 Ti/Si비율을 조절함으로써 효율적인 확산방지막인 Ti-Si-N 박막의 공정조건을 확립할 수 있었다. 박막의 공정조건을 확립할 수 있었다.

O2plasma와 H(hfac)을 이용한 Cu 박막의 건식 식각을 조사하였다. 휘발성이 큰 Cu(hfac)2와 H2O를 탈착시키기 위하여 O2 Plasma를 이용한 Cu 박막의 산화와 생성된 Cu 산화막을 H(hfac)과의 반응으로 제거하는 공정으로 식각을 수행하였다. Cu 박막의 식각율은 50-700 /min의 범위를 보였으며, 기판온도, H(hfac)/O2 유량비, plasma power에 따라 변하였다. Cu 박막의 식각율은 기판온도 215˚C보다 높은 온도구간에서 RF power가 증가함에 따라 증가하였고, 산화 공정과 H (hfac)과의 반응이 균형을 이루는 최적의 H (hfac)/O2 유량비는 1:1임을 확인하였다. Ti mask를 사용한 Cu Patterning은 유량비 1 : 1, 기판온도 250˚C에서 실시하였고, 30˚외 taper slope를 갖는 등방성 etching profile을 얻을 수 있었다. Taper angle을 갖는 Cu 건식 patterning은 고해상도의 대면적 thin film transistor liquid-crystal(TFT-LCDs)를 위래 필요한 것으로써 기판온도, RF power, 유량비를 조절한 one-step 공정으로부터 성공적으로 얻을 수 있었다.

열CVD법에 의하여 아세틸렌 가스를 탄소 원으로 사용한 탄소 나노튜브의 성장거동을 조사하였다. 닉켈 분말의 직경을 15nm 내지 90nm 범위로 조정하여 기판 에 촉매로 배열하였다. 탄소 나노튜브는 질소, 수소, 알곤, 암모니아 등 여러가지의 가스 분위기에서 증착되었으며 이들 가스의 혼합 분위기가 탄소나 노튜브의 성장에 미치는 영향을 조사하였다. 증착은 대기압 압력하에서 85 의 온도에서 이루어졌다. 순수한 질소 분위기에서는 탄소 나노튜브의 성장이 이루