Chen-Chan Wang

Flexible field emitter made of carbon nanotubes microwave welded onto polymer substrates

The drastic temperature rise of multiwall carbon nanotubes (MWCNTs) in response to microwave irradiation was applied to weld a MWCNT paste on a polymer substrate within a few seconds. It provides a strong bonding between the MWCNT and polymer without thermal damage to the substrate. A flexible field emitter was made from MWCNT microwave welded on polycarbonate, showing excellent electrical conduction and field-emission properties even under bending. The field emitter works with a turn-on voltage of 0.8V∕μm due to the direct electron transfer. By this method, printed circuits and field-emission devices can be processed simultaneously within seconds leading to important applications in flexible electronic devices.

Memory characteristics of au nanocrystals embedded in metal-oxide-semiconductor structure by using atomic-layer-deposited Al2O3 as control oxide

The nonvolatile memory characteristics of metal?oxide?semiconductor (MOS) structures containing Au nanocrystals in the Al2O3/SiO2 matrix were studied. In this work, we have demonstrated that the use of Al2O3 as control oxide prepared by atomic-layer-deposition enhances the erase speed of the MOS capacitors. A giant capacitance?voltage hysteresis loop and a very short erase time which is lower than 1?ms can be obtained. Compared with the conventional floating-gate electrically erasable programmable read-only memories, the erase speed was promoted drastically. In addition, very low leakage current and large turn-around voltage resulting from electrons or holes stored in the Au nanocrystals were found in the current?voltage relation of the MOS capacitors.

Charge storage characteristics of Au nanocrystals embedded in high-k gate dielectrics on Si

The charge storage characteristics of metal-oxide-semiconductor structures containing Au nanocrystals in atomic-layer-deposited high-k gate dielectrics were studied. Cross-sectional high-resolution transmission electron microscopy reveals that the Au nanocrystals are self-assembled in the high-k dielectric matrix after high temperature annealing in N2 ambient. The memory effect was observed from capacitance-voltage (C-V) relations and a satisfactory charge retention characteristic was obtained in the sample using Al2O3 as the gate dielectric than in the one using Hf2AlOx. Moreover, a saturation of electron storage in the metal-oxide-semiconductor capacitors was also observed.

Effect of Al Incorporation in the Thermal Stability of Atomic-Layer-Deposited HfO2 for Gate Dielectric Applications

The thermal stability in structural and electrical properties of HfO 2 , HfAlO x alloy, and Al 2 O 3 /HfO 2 stack thin films prepared by atomic layer deposition were comparatively investigated. Both HfAlO x and Al 2 O 3 /HfO 2 exhibit improved property against thermal degradation compared to the HfO 2 film. However, the incorporation of Al in alloy form provides characteristics superior to that in stack structure by retaining an amorphous structure up to 1000°C, which suppresses the leakage current and retards the growth of interfacial layer giving rise to lower increment of equivalent-oxide-thickness and interface trap density.

Improvement in charge retention in Au-nanocrystal-based memory structures by employing (Ba0.5Sr0.5)TiO3 as control oxide

The use of (Ba0.5Sr0.5)TiO3 (BST) as the control oxide in a Au-nanocrystal-based memory structure was investigated. The Au nanocrystals, surrounded with a core shell of Au-doped BST, were self-assembled in a BST∕SiO2 stack. The leakage of the gate dielectric is reduced by a partial dissolution of Au into the BST matrix, which enlarges the energy band gap of BST. Moreover, direct tunneling through the tunnel oxide is suppressed because the internal field induced by the charges in the Au nanocrystals can be screened by the ultrahigh-k shell of BST. Therefore, the retention property of the Au-nanocrystal-based memory structure is improved.

The memory characteristics of submicron feature-size PZT capacitors with PtOx top electrode by using dry-etching

Dry etching and its effect on the characteristics of submicron feature-size PbZr1−xTixO3 (PZT) capacitors with PtOx top electrode were investigated. The photoresist (PR)-masked PtOx films were etched by an Ar/(20%)Cl2/O2 helicon wave plasma. A fence-free pattern with a significantly high etch rate and sidewall slope was obtained by the addition of O2 into the etching gas mixture, due to the chemical instability of PtOx and the formation of a PtO2 passivation layer to suppress redeposition of the etch by-products on the etched surface. The patterned PtOx electrode can be further used as a hard mask for etching the PZT film, subsequently, with the gas mixture of Ar, CF4 and O2. A high etching rate of PZT and a good etching selectivity to PtOx can be obtained at 30% O2 addition into the Ar/(50%)CF4 plasma. The etched capacitors have a steep, 72°, sidewall angle with a clean surface. Moreover, the addition of O2 into the etching gas can well preserve the properties and the fatigue endurance of PtOx/PZT capacitors.