Abstract
We report here the fabrication of freestanding HfO2 grating by combining fast atom beam etching (FAB) of HfO2 film with dry etching of silicon substrate. HfO2 film is deposited onto silicon substrate by electron beam evaporator. The grating patterns are then defined by electron beam lithography and transferred to HfO2 film by FAB etching. The silicon substrate beneath the HfO2 grating region is removed to make the HfO2 grating suspend in space. Period- and polarization-dependent optical responses of fabricated HfO2 gratings are experimentally characterized in the reflectance measurements. The simple process is feasible for fabricating freestanding HfO2 grating that is a potential candidate for single layer dielectric reflector.PACS: 73.40.Ty; 42.70.Qs; 81.65.Cf.
Highlights
As an excellent optical material, hafnium oxide (HfO2) film presents high laser damage threshold, thermal and chemical stability [1,2,3]
There is no special requirement of etching mask, and electron beam (EB) resist can serve as an etching mask
Since the thickness of EB resist varies due to the proximity effect in EB lithography, the HfO2 gratings generated in reality are trapezoidal profiles and deviate from the designed rectangular elements
Summary
As an excellent optical material, hafnium oxide (HfO2) film presents high laser damage threshold, thermal and chemical stability [1,2,3]. Since HfO2 film is transparent from visible to infrared range, it often servers as the high refractive index material for fabricating multilayer reflection mirror [4,5], or acts as the waveguiding layer for the realization of guide mode resonant optical filter [6]. The high refractive index contrast between HfO2/air endows the freestanding HfO2 micro/nano structures with the capacity to function as single layer dielectric reflector or guide mode resonant filter.
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