Chien-Yuan Lu

Ultraviolet photodetectors with ZnO nanowires prepared on ZnO:Ga/glass templates

Vertically well-aligned ZnO nanowire ultraviolet (UV) photodetectors were fabricated by spin-on-glass technology on ZnO:Ga/glass templates. With 2V applied bias, it was found that dark current density of the fabricated device was only 2.0×10−7A∕cm2. It was also found that UV-to-visible rejection ratio and quantum efficiency of the fabricated ZnO nanowire photodetectors were more than 1000 and 12.6%, respectively.

ZnO Nanowire-Based Oxygen Gas Sensor

We report growth of vertically well-aligned ZnO nanowires on ZnO:Ga/glass templates and the fabrication of resistive ZnO nanowire-based oxygen gas sensor. It was found that the ZnO nanowires are grown preferred oriented in the (002) direction with a small X-ray diffraction full-width-half-maximum. From high resolution transmission electron microscopy, scanning electron microscopy and micro-Raman measurements, it was found that the ZnO nanowires prepared in this study are single crystalline with good crystal quality. It was also found that measured sample resistance increased logarithmically as the oxygen gas pressure in the chamber was increased. Such a relationship suggests that the device is potentially useful for resistive oxygen gas sensing at room temperature.

Electrical and Optical Characteristics of UV Photodetector With Interlaced ZnO Nanowires

A zinc oxide (ZnO) nanowire (NW) photodetector was fabricated with a simple method by bridging the gap of interdigitated gallium-doped ZnO pattern deposited on a silicon oxide (SiO₂) thin film with interlaced ZnO NWs. With an incident wavelength of 375 nm, it was found that measured responsivity was 0.055 A/W for the interlaced ZnO NWs photodetector with a 1 V applied bias. The transient time constants measured during the turn-on and turn- off states were τ_ON = 12.72 ms and τ_OFF = 447.66 ms , respectively. Furthermore, the low-frequency noise spectra obtained from the ultraviolet photodetector were purely due to the 1/<i>f</i> noise. Besides, the noise equivalent power and normalized detectivity (<i>D</i>^*) of the ZnO NW photodetector were 2.32 ×10^-9 W and 7.43 ×10⁹ cm·Hz^0.5·W^-1, respectively.

Noise Characteristics of ZnO-Nanowire Photodetectors Prepared on ZnO:Ga/Glass Templates

In this paper, we report the fabrication of vertically well-aligned ZnO nanowire ultraviolet (UV) photodetectors on ZnO:Ga/glass templates. With 1 V applied bias, it was found that dark current density of the device was only 1.37times10^-7 A/cm². It was also found that UV-to-visible rejection ratio of the fabricated photodetector was around 1000 with a maximum quantum efficiency of 12.6%. It was also found that noise equivalent power and normalized detectivity of the ZnO nanowire photodetector were 5.73times10^-11 W and 6.17times10⁹ cmHz^0.5W^-1, respectively.

A lateral ZnO nanowire UV photodetector prepared on a ZnO:Ga/glass template

We report the lateral growth of ZnO nanowires on a ZnO:Ga/glass template. By reducing the oxygen flow ratio, it was found that we could change the growth direction of ZnO nanowires from vertical to lateral. ZnO nanowire-based photodetectors were also fabricated using the laterally grown ZnO nanowires. It was found that the detector current increased by more than 12 times upon ultraviolet illumination. It was also found that the corresponding time constant of our lateral ZnO nanowire photodetector was around 452 ms.

Comparison of Thermal Stability and Chemical Bonding Configurations of Plasma Oxynitrided Hf and Zr Thin Films

Achieving high-performance complementary metal-oxidesemiconductor field-effect transistors drives the downscaling of silicon technology forward. High dielectric constant materials are becoming increasingly favorable due to the exponential increase in tunneling currents with decreasing SiO2 thickness in the ultrathin regime. Of these, ZrO2 and HfO2 are the most promising candidates for their high relative dielectric constant = 20-25 and good thermal stability. Applying high- materials can maintain the same gate capacitance in terms of the equivalent oxide thickness EOT of SiO2 while decreasing the tunneling current with a thicker physical thickness.

A novel fabrication of p-n diode based on ZnO nanowire/p-NiO heterojunction

We report the deposition of NiO onto ZnO nanowires prepared on ZnO:Ga/glass templates. With the sputtered NiO, the nanowires became mushroom-like. Experimental results point out that sputtered NiO also formed nanoshells surrounding ZnO nanowires. The p-NiO/n-ZnO heterostructure exhibits rectifying behavior with a sharp turn on at ~1 V. Furthermore, the current vs voltage characteristic is dominated by space-charge-limited current (SCLC) at high (1.1 V) forward bias.

Luminescence Enhancement Mechanism of ZnGa2O4 Phosphor Screen with an In2O3 Buffer Layer

The luminescence enhancement mechanism of a white ZnGa 2 O 4 phosphor screen with an In 2 O 3 buffer layer was studied by growing ZnGa 2 O 4 with optimal sputtering parameters and varying the deposition conditions of In 2 O 3 . A ZnGa 2 O 4 film with better crystallization and smaller grains was obtained when it was deposited on In 2 O 3 . These qualities revealed that the resistivity of the phosphor screen was correlated with the surface roughness and resistivity of the In 2 O 3 buffer layer. The photoluminescence spectra of the phosphor screen revealed that the ligand field of the Ga luminescence center was not modified when the In 2 O 3 deposition parameters were varied; however, the emission intensities were altered due to the electron-transition probability in the Ga energy levels changing with the crystallization of phosphor. A significantly enhanced emission from the phosphor screen was observed by improving the crystallization, surface morphology, and resistivity of the prepared ZnGa 2 O 4 phosphor film with the In 2 O 3 buffer layer.