High ultraviolet transparent conducting electrodes formed using tantalum oxide/Ag multilayer

Abstract

We investigated the optical and electrical properties of Ta 2 O 5 /Ag/Ta 2 O 5 films as functions of the thicknesses of the Ta 2 O 5 and Ag layers. It was found that with an increase in the thicknesses of the Ta 2 O 5 and Ag layers from 10 to 40 nm and from 12 to 24 nm, respectively, the sheet resistance, carrier concentration, electron mobility, and resistivity of the Ta 2 O 5 /Ag/Ta 2 O 5 film varied from 2.02 to 8.95 Ω/sq, 5.74 × 10 21 to 2.92 × 10 22 cm –3 , from 13.21 to 24.07 cm 2 /V·s, and from 8.89 × 10 -6 to 8.24 × 10 -5 Ω cm, respectively. The average transmittance ( T av ) of the multilayer samples ranged from 57.18% to 93.99%, and it depended on the Ta 2 O 5 and Ag layer thicknesses. The highest T av of 93.99% was observed for the film with 35 nm thick Ta 2 O 5 and 18 nm thick Ag layers, and the peak Haacke's figure of merit (157.04 × 10 –3 Ω –1 ) was obtained for 20 nm thick Ta 2 O 5 and 21 nm thick Ag layers. Ta 2 O 5 (100 nm) and Ta 2 O 5 /Ag/Ta 2 O 5 (20 nm/21 nm/20 nm) samples had optical bandgaps of 4.70 and 4.45 eV, respectively. Film Wizard simulations were conducted to understand the dependence of the transmittance of the multilayer on the thicknesses of the Ta 2 O 5 and Ag layers, and phasor analyses were performed to determine how the transmittance of the Ta 2 O 5 /Ag/Ta 2 O 5 (20 nm/21 nm/20 nm) film depended on the Ta 2 O 5 layer's thickness.