Optical colorimetric LiTaO_(3)wafers for highprecision lithography on frequency control of SAW devices

Surface acoustic wave(SAW)resonators based on lithium tantalate(LT,LiTaO_(3))wafers are crucial elements of mobile communication filters.The use of intrinsic LT wafers typically brings about low fabrication accuracy of SAW resonators due to strong UV reflection in the lithography process.This hinders their resonance frequency control seriously in industrial manufacture.LT doping and chemical reduction could be applied to decrease the UV reflection of LT wafers for high lithographic precision.However,conventional methods fail to provide a fast and nondestructive approach to identify the UV performance of standard single-side polished LT wafers for highprecision frequency control.Here,we propose a convenient on-line sensing scheme based on the colorimetry of reduced Fe-doped LT wafers and build up an automatic testing system for industrial applications.The levels of Fe doping and chemical reduction are evaluated by the lightness and color difference of LT-based wafers.The correlation between the wafer visible colorimetry and UV reflection is established to refine the lithography process and specifically manipulate the frequency performance of SAW resonators.Our study provides a powerful tool for the fabrication control of SAW resonators and will inspire more applications on sophisticated devices of mobile communication.

In situ growth of NiSe_(2) nanocrystalline array on graphene for efficient hydrogen evolution reaction

Nickel selenide electrocatalysts for hydrogen evolution reaction(HER)with a high efficiency and a lowcost have a significant potential in the development of water splitting.However,the inferiority of the high overpotential and poor stability restricts their practical applications.Herein,a composite nanostructure consists of ultrasmall NiSe_(2) nanocrystals embedded on graphene by microwave reaction is reported.The prepared NiSe_(2)/reduced graphite oxide(rGO)electrocatalyst exhibited a high HER activity with an overpotential of 158 mV at a current density of 10 mA/cm^(2) and a corresponding moderate Tafel slope of 56 mV/dec in alkaline electrolyte.In addition,a high retention of electrochemical properties(approximately 100%)was demonstrated with an unchangeable microstructure after 100 h of continuous operation.

Development of superconducting microcalorimeters for the HUBS mission

Hot Universe Baryon Surveyor(HUBS)is a proposed space‐borne observatory for X‐ray astronomy.The primary scientific objectives of the mission are to fill a void in probing the ecosystem of galaxies and thus to advance our understanding of galaxy formation and evolution,which is of fundamental importance in cosmology.More specifically,HUBS aims at directly detecting soft X‐ray emission from diffuse gas of temperature exceeding 106 K,which is theoretically postulated to permeate the large structures in the cosmic web and also fill the extended halo of galaxies.However,although some indirect evidence exists,the presence of such hot gas has yet to be well established observationally,due to the lack of effective tools to probe it.In this paper,we describe the design of HUBS,focusing on its scientific payload,which employs superconducting technologies in the detector system,and particularly on progress in the development of superconducting microcalorimeters.