A new solution for mirror coating in γ\gamma-ray Cherenkov Astronomy

In the $\gamma$-ray Cherenkov Astronomy framework mirror coating plays a crucial role in defining the light response of the telescope. We carried out a study for new mirror coating solutions with both a numerical simulation software and a vacuum chamber for small sample production. In this article, we present a new mirror coating solution consisting of a 28-layer interferometric SiO$_{2}$-TiO$_{2}$-HfO$_{2}$ design deposited on a glass substrate, whose average reflectance is above $90\%$ for normally incident light in the wavelength range between 300 and 550 nm.Comment: 6 pages, 5 figures. Article submitted to Experimental Astronomy, the final publication is available at link.springer.co

Phase stability of hafnium oxide and zirconium oxide on silicon substrate

Phase stabilities of Hf-Si-O and Zr-Si-O have been studied with first-principles and thermodynamic modeling. From the obtained thermodynamic descriptions, phase diagrams pertinent to thin film processing were calculated. We found that the relative stability of the metal silicates with respect to their binary oxides plays a critical role in silicide formation. It was observed that both the HfO$_2$/Si and ZrO$_2$/Si interfaces are stable in a wide temperature range and silicide may form at low temperatures, partially at the HfO$_2$/Si interface.Comment: 5 pages, 3 figure

Temperature (5.6-300K) Dependence Comparison of Carrier Transport Mechanisms in HfO2/SiO2 and SiO2 MOS Gate Stacks

Temperature dependent measurements have been used to examine transport mechanisms and energy band structure in MOS devices. In this study, a comparison between high-k HfO2 dielectrics and conventional SiO2 dielectrics is made to investigate dielectric specific thermally activated mechanisms. Temperature dependent measurements on large area n/pMOSFETs composed of SiO2 and HfO2/SiO2 gate dielectrics were performed from 5.6 K to 300 K. A large increase in the gate leakage current is observed at the formation of the minority carrier channel. The data indicate that gate leakage current prior to the formation of the minority channel is carrier rate limited while gate leakage current is tunneling rate limited above the threshold voltage. Gate leakage current measurements show two distinct Arrhenius transport regimes for both SiO2 and HfO2 gate dielectrics. The Arrhenius behavior of the gate leakage current is characterized by a strong temperature dependent regime and a weak temperature dependent regime. The activation energy of the strong temperature regime is found to vary with the applied gate voltage. Frenkel-Poole or other electric field models are able to explain the gate voltage dependence of the gate leakage current for the low-temperature/voltage regime investigated. The data suggest that the variation of the activation energy for the Arrhenius behavior is weakly electric-field driven and strongly voltage, or Fermi energy level, driven

Design, fabrication and measurements with a UV Linear-Variable Optical Filter microspectrometer

An IC-Compatible Linear-Variable Optical Filter (LVOF) for application in the UV spectral range between 310 nm and 400 nm has been fabricated using resist reflow and an optimized dry-etching. The LVOF is mounted on the top of a commercially available CMOS camera to result in a UV microspectrometer. A special calibration technique has been employed that is based on an initial spectral measurement on a Xenon lamp. The image recorded on the camera during calibration is used in a signal processing algorithm to reconstruct the spectrum of the Mercury lamp and the calibration data is subsequently used in UV spectral measurements. Experiments on fabricated LVOF-based microspectrometer with this calibration approach implemented reveal a spectral resolution of 0.5 nm