Vacuum ultraviolet radiation (VUV, from 100 nm to 200 nm wavelength) is indispensable in many applications, but its detection is still challenging. We report the development of a VUV photoconductive detector, based on titanium dioxide (TiO2) nanoparticle thin films. The effect of crystallinity, optical quality, and crystallite size due to film thickness (80 nm, 500 nm, 1000 nm) and type of substrate (silicon Si, quartz SiO2, soda lime glass SLG) was investigated to explore ways of enhancing the photoconductivity of the detector. The TiO2 film deposited on SiO2 substrate with a film thickness of 80 nm exhibited the best photoconductivity, with a photocurrent of 5.35 milli-Amperes and a photosensitivity of 99.99% for a bias voltage of 70 V. The wavelength response of the detector can be adjusted by changing the thickness of the film as the cut-off shifts to a longer wavelength, as the film becomes thicker. The response time of the TiO2 detector is about 5.8 μs and is comparable to the 5.4 μs response time of a diamond UV sensor. The development of the TiO2 nanoparticle thin film detector is expected to contribute to the enhancement of the use of VUV radiation in an increasing number of important technological and scientific applications.

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The effect of Si surface atomically flattening (SAF) on the Hf-based metal/oxide/nitride/oxide/Si (MONOS) nonvolatile memory (NVM) characteristics was investigated. The memory window (MW) obtained in the C–Vcharacteristics for the Hf-based MONOS diode was increased from 4.5 to 4.8 V by the Si SAF. The charge centroid (Z eff) was found to be shifted from the center of the HfN1.1 charge trapping layer (CTL) to the interface at block layer and CTL for the Hf-based MONOS diode with the Si SAF. Furthermore, the MW of 3.2 V was realized for the Hf-based MONOS NVM with improvement of device characteristics by Si SAF.

The effect of HfN multi charge trapping layers (CTLs) on the Hf-based metal/oxide/nitride/oxide/Si (MONOS) nonvolatile memory characteristics was investigated to improve the threshold voltage (V TH) controllability. The Hf-based MONOS structure with HfN1.3/HfN1.1/HfN1.3/HfN1.1 4-layer CTL realized precise control of flat-band voltage (V FB) and V TH compared to the Hf-based MONOS with HfN1.1 1-layer CTL. The hysteresis width after the program operation was markedly decreased which was originated from the stable trap site formation at the interface of the multi CTL. The retention and fatigue characteristics were found to be remarkably improved for the Hf-based MONOS structure with HfN multi CTL.

We have investigated the reduction of the process temperature for the Si surface flattening process by annealing in Ar/H2 ambient and its application to Si-on-insulator (SOI) metal-insulator-semiconductor field-effect transistors (MISFETs) with bilayer HfN high-k gate insulator. The surface rms roughness of 0.057 nm was realized for the p-Si(100) substrates by the annealing at 925 °C/10 min in Ar/1.0%H2 ambient. Although slip-line defects were observed in the isolated SOI region after the optimized flattening process, the device characteristics of the fabricated SOI-MISFETs with HfN1.3/HfN1.1/Si(100) bilayer gate insulator were found to have been improved by the surface flattening utilizing Ar/1.0%H2 annealing.