| Application of Silica Aerogel Films to the Fabrication of
Surface Acoustic Wave Filters |
Wei Zheng,1,* Xun Xiang,1 Yao Wang,1 Yinhua Cui,1 Yuan Bao,1 Siliang He,1, 2 Pengfei Li1 and
Chuan Hu1
Pages : 183-189
DOI : 10.1080/0371750X.2022.2149627 |
| Abstract |
| Herein, silica aerogel films were used in the fabrication of surface acoustic wave
(SAW) filters for the first time. Firstly, silica aerogel films with various silica sol drip
times were prepared and characterized. According to spectroscopic ellipsometry, the
refractive index of an aerogel film with a silica sol drip time of 9 min decreased by
5.9% compared with a film with sol drip time of 18 min in the intermediate region of
the sample. The increase in sol drip time led to an increase in particle size and
thickness, and a decrease in pore size. Secondly, four different types of SAW filters
were designed, i.e. covered with either air, poly(dimethylsiloxane) (PDMS), PDMS
filled with silica aerogel powder, or a silica aerogel film. Addition of silica aerogel
powder to PDMS increased the bandwidth of the resulting SAW filter to 2.362 MHz,
increased its central frequency to 0.001 GHz and decreased its insertion loss to 1.545
dB. Although they had low porosity, the SAW filters covered with silica aerogel films
had a bandwidth of 60.586 MHz, a central frequency of 2.447 GHz, a Q value of 40.073,
and the largest insertion loss of –15.397 dB. SAW filters with silica aerogel films with
various sol drip times were also tested. The results indicated that more porous the
silica aerogel films, stronger is the signal strength and smaller is the insertion loss
of the SAW filter.
[Keywords: Silica aerogel film, Sol drip time, SAW filter chip, Insertion loss] |
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