Chung-Chun Hsu

High birefringence and wide nematic range bis-tolane liquid crystals

Several dialkyl and fluoro bis-tolane liquid crystals were synthesized and their physical properties evaluated. These highly conjugated liquid crystals exhibit a wide nematic range, small heat fusion enthalpy, high birefringence, and relatively low viscosity. Their excellent compatibility with commercial cyano mixtures makes these liquid crystals attractive for many electro-optic applications.

Synthesis of laterally substituted bistolane liquid crystals

Methods for synthesizing bistolane liquid crystal materials with lateral methyl and ethyl substituents are presented. Some of the bistolanes are nematic at room temperature. These highly conjugated mesogens exhibit wide nematic ranges, small enthalpies of fusion, high birefringence and modest viscosity. Their potential applications for flat panel displays employing light scattering or Bragg reflection and for infrared optically phased arrays are foreseeable.

High birefringent liquid crystals

Abstract Several liquid crystal dyes and fluorinated compounds with high birefringence are synthesized and their properties evaluated. These polar compounds are useful dopants for enhancing the dielectric anisotropy of the dialkyl diphenyl-diacetylene host.

Room Temperature Difluoro-Tolane and Diphenyl-Diacetylene Liquid Crystals with Negative Dielectric Anisotropy

Abstract Several laterally difluorinated tolane and diphenyl-diacetylene liquid crystals were synthesized and their physical properties evaluated. These compounds exhibit low melting temperature, small heat fusion enthalpy and large negative dielectric anisotropy. Their potential applications are in the high contrast displays using a homeotropic cell and for infrared spatial light modulators.

High-Performance Schottky Contact Quantum-Well Germanium Channel pMOSFET With Low Thermal Budget Process

We present a high-performance Si/Ge/Si p-channel metal-oxide-semiconductor field-effect transistor (pMOSFET) with a NiSiGe Schottky junction source/drain (S/D) formed through microwave-activated annealing. A Schottky contact S/D is preferable, because the lower process temperature is beneficial for eliminating Ge diffusion. The fabricated NiSiGe Schottky junction exhibited a high effective barrier height (ΦBn) of 0.69 eV for electrons, resulting in a high junction current ratio of more than 105 at the applied voltage of |Va| = 1 V. Our quantum-well pMOSFET exhibited a high ION/IOFF ratio of ~107 (IS) and a moderate subthreshold swing of 166 mV/decade.

Low-Leakage Tetragonal ZrO 2 (EOT In Situ Plasma Interfacial Passivation on Germanium

We successfully fabricated gate stacks (ZrO2/GeOx/Ge) with a subnanometer equivalent oxide thickness (EOT) and low-leakage current on n-/p-Ge through plasma-enhanced atomic layer deposition (ALD). A 0.78-nmthick GeOx was formed through plasma oxidation (i.e., in situ plasma interfacial passivation, followed by 3.48-nm-thick ZrO2 growth in the same ALD reactor). A subnanometer EOT of N0.9 nm was achieved with a relatively high dielectric constant (roughly 30) of tetragonal-phase ZrO2. The gate leakage was N1 x 10-4 A/cm2 at VFB - 1 V, and roughly 5 x 10-5 A/cm2 at VFB t 1 V on pand n-type Ge, respectively. Our ZrO2 stabilized in the tetragonal phase, when the post-deposition annealing temperature, was higher than 500 °C. Therefore, the proposed scheme is simple and effective for use in pursuing an ultralow EOT gate dielectric on Ge.

Experimental Realization of a Ternary-Phase Alloy Through Microwave-Activated Annealing for Ge Schottky pMOSFETs

This paper presents a high-performance Ge p-channel MOSFET (pMOSFET) with NiGePt as a ternary-phase alloy of Schottky source/drain (S/D) formed through low-temperature microwave-activated annealing (MWA). We fabricated a NiGePt alloy contact with uniform crystallinity through structural engineering and MWA. We clarified the phenomena of thermal reaction and diffusion for forming ternary-phase alloys using MWA properties such as thermal dynamics and ionic transportation. The ternary-phase NiGePt alloy is crucial for improving the off-leakage current of the junction. A lower process temperature is beneficial for eliminating surface roughness and reducing alloy agglomeration of the Schottky contact S/D. Consequently, the fabricated NiGePt/n-Ge Schottky junction exhibited a high effective barrier height (ΦBn) of 0.59 eV, resulting in a high junction current ratio of more than 105 at an applied voltage of |Va| = 1 V. In addition, we exploited the advantages of low-temperature microwave annealing to fabricate the pMOSFET, which includes a GeO2 passivation layer and a Schottky S/D. Our ternary Schottky Ge pMOSFET (L = 4μm) exhibited high ION/IOFF ratios of approximately 3.7 × 103 (ID) and 1.3 × 105 (IS) and a moderate subthreshold swing of 126 mV/dec.

SYNTHESIS AND CHARACTERIZATION OF SIDE-CHAIN LIQUID-CRYSTALLINE POLYMETHACRYLATES CONTAINING FLUORINATED DIPHENYLDIACETYLENE SIDE-GROUPS

Abstract The synthesis of four side-chain liquid crystalline polymethacrylates containing either 4-alkanyloxy-4′-flourodiphenyldiacetylenes or 4-alkanyloxy-3′,4′-difluorodiphenyldiacetylenes side groups is presented. The phase behavior of both monomeric and polymeric liquid crystals was characterized by differential scanning calorimetry and optical polarizing miocroscopy. All synthesized polymethacrylates present nematic mesomorphism. The glass transition temperature of the obtained polymers decreases as the spacer length increases. The mesomorphic behavior of the prepared polymers depends very much on the degree of substitution of the mesogenic side groups on the polymer backbones.

3D-TCAD simulation study of the contact all around T-FinFET structure for 10nm metal-oxide-semiconductor field-effect transistor

We propose a new device structure, namely CAA T-FinFET, for 10nm MOSFETs with using contact all around (CAA) structure. According to 3D simulation study, the CAA T-FinFET possess many advantages over the conventional FinFET structure, such as short channel effect (SCE) suppression by self-aligned oxide (SA oxide), parasitic leakage path isolation with body-tied bulk, source/drain series resistance reducing and fin to fin pitch scaling by contact all around process. Base on heterogeneous bulk for strain application, CAA T-FinFET has better electrical performance and easy process control. All these advantages are achieved by depositing a self-aligned oxide after isotropic etching in S/D region. Contact all around can efficiently solve the series resistance degradation and pitch scaling by replacing diamond-shape S/D stressor with the full contact metal. CAA T-FinFET has high potential to be applied to the varied heterogeneous substrate and high mobility channel (Ge and III-V) MOSFETs by SA oxide.

Microwave Annealing for NiSiGe Schottky Junction on SiGe P-Channel

In this paper, we demonstrated the shallow NiSiGe Schottky junction on the SiGe P-channel by using low-temperature microwave annealing. The NiSiGe/n-Si Schottky junction was formed for the Si-capped/SiGe multi-layer structure on an n-Si substrate (Si/Si0.57Ge0.43/Si) through microwave annealing (MWA) ranging from 200 to 470 °C for 150 s in N2 ambient. MWA has the advantage of being diffusion-less during activation, having a low-temperature process, have a lower junction leakage current, and having low sheet resistance (Rs) and contact resistivity. In our study, a 20 nm NiSiGe Schottky junction was formed by TEM and XRD analysis at MWA 390 °C. The NiSiGe/n-Si Schottky junction exhibits the highest forward/reverse current (ION/IOFF) ratio of ~3 × 105. The low temperature MWA is a very promising thermal process technology for NiSiGe Schottky junction manufacturing.