Ion-conducting, sub-100 nm-thick film of amorphous hafnium silicate

Finite Size Effect of Proton-Conductivity of Amorphous Silicate Thin Films Based on Mesoscopic Fluctuation of Glass Network

“…In addition, the σ H2O becomes almost constant, and σ H2O is larger than that of σ in dry air by a factor of more than 10 at T < 200 °C. The enhancement of the conductivity at relatively low temperatures by moisture is due to the additional protonic carriers on Lewis acid sites, which are given by the water adsorption onto an oxygen vacancy site. , Both films show the clear H/D effect on proton conductivity in the measured temperature ranges, and σ D2O is lower than σ H2O by a factor of 1.1−1.4 even though the temperature dependency of σ D2O is very similar to that of σ H2O in every thickness. Other M 0.1 Si 0.9 O x films also show the similar isotope effect in conductivity.…”

“…The amount of desorbed CH 4 ( m / z = 16), CO ( m / z = 28), and CO 2 ( m / z = 44) was very small in the measured temperature range, suggesting that the desorbed waters are not a product by combustion of contaminant organic species. There is an intensive desorption of water gas in all films at a relatively low temperature below 250 °C owing to desorption of the adsorbed water. , Such water is not concerned with the proton conductivity discussed later since the measurements were performed by cooling a sample from 400 °C to given temperatures of measurement with nonhumidified atmosphere. The films show a single desorption peak at temperatures above 400 °C, which is assigned to the decomposition of the Brønsted acid site .…”

“…Thin films of various metal silicates, M 0.1 Si 0.9 O x (M = Al, Ti, Hf, La, Ta, and Ga), were prepared from mixed precursor solutions of tetraethoxysilane (TEOS) and individual metal alkoxides (M(OR) n ) with the fixed M/Si atomic ratio of 5/95, as reported elsewhere. , TEOS (99.99%) and titanium tetra- n -butoxide (Ti(O n Bu) 4 , 98%) and tantalum penta- n -butoxide (Ta(O n Bu) 4 , 99.9%) were obtained from Kanto Chemical. Lanthanum trimethoxyethoxide (La(OEtOMe) 3 , 10 wt % in 1-methoxyethanol) and gallium triethoxide (Ga(OEt) 3 , 99%) were obtained from Gelest.…”

“…In fact, the various amorphous silicate thin films, a -M 0.1 Si 0.9 O x (M = Al, Zr, Hf, etc. ), exhibit the efficient proton conductivity in nonfumidified, dry atmosphere owing to the Brønsted acidity. , Therefore, it is of fundamental and technological interest to study the thickness dependency of proton conductivity of these films. Herein, we report on the thickness dependency of the proton conductivity in amorphous films of various metal silicates, a -M 0.1 Si 0.9 O x (M = Al, Hf, Ta, Ga, La, and Ti), in the nanoscale thickness region.…”