Schematic diagram of rotational sequential sputtering system, including four bottom-mounted parallel-gun targets with 4 in. diameters and a rotating sample-holder-plate for eight samples. Film deposition rate is controlled by the rotation speed of the sample holder and the shutter windows.
(Color online) (a) TEM image of ITO/AlON NML films with periodic thickness of 3.6 nm. (b) FE-SEM image of ITO/AlON NML films with periodic thickness of 6.263 nm, in which an individual period comprises one brighter and one darker layer.
(Color online) XRD patterns of ITO films with In2O3 phase and film thicknesses of 5.6, 24, and 213 nm. Inset illustrates the relationship between resistivity and film thickness at RTA 500 °C (▪) and 400 °C (◆).
(Color online) (a) Transmittance and reflectance spectra of flexible ITO sample-a and sample-b, with resistivity values of 5.08 × 10−4 and 4.6 × 10−4 Ω·cm, respectively. (b) In the photograph of the flexible ITO substrates, cylindrical and flat ITO samples are placed on a compact disc to illustrate the transparency.
(Color online) Ultrathin ITO films of various thicknesses are obtained by altering the rotation speed of the sample holder: (a) 57 s (3.29 nm), (b) 50 s (3.04 nm), (c) 42 s (2.66 nm), (d) 35 s (2.36 nm), (e) 31 s (2.07 nm), (f) 27 s (1.86 nm), (g) 20 s (1.66 nm), (h) 12 s (1.38 nm), and (i) 114 s (5.6 nm). XRR characterization is used to simulate the thicknesses of films [(a)–(e)] and then fitted using a two-layer model, as shown in the inset. The thicknesses of the films [(f)–(h)] are fitted using a single-layer model. The relationship between the thickness and resistivity of the films [(a)–(c) and (i)] is presented in the inset.
(Color online) Measurement (○, circles) and simulation results (—, solid lines) obtained by XRR characterization. The thicknesses of the ultrathin ITO films are (a) 3.29 nm, (b) 3.04 nm, (c) 2.66 nm, (d) 2.36 nm, (e) 2.07 nm, (f) 1.86 nm, (g) 1.66 nm, and (h) 1.38 nm.
(Color online) XRR characterization results: Sample (a) is an 8-period (16 layers) TiO2/ITO NML structure with TiO2 single-layer thickness of 1.78 nm and ITO of 1.2 nm; samples (b) and (c) are 10-period (20 layers) and 12-period (24 layers) SiOx/ITO NML structures with ITO single-layer thicknesses of 4.8 nm and 5.75 nm, resulting in SiOx/ITO thickness ratios of 0.5 and 0.9565, respectively.
(Color online) Measurement results of reflectance and transmittance: samples include (a) TiO2/ITO NML marked as (●, ○); (b) ITO marked as (▲, △,); (c) SiOx/ITO NML marked as (▪, ◻), with total film thicknesses of 93 nm, 164 nm, 121.5 nm, respectively.
(Color online) Relationship between resistivity and volume fractions of NML films: TiO2/(TiO2+ITO) and SiOx/(SiOx+ITO) films are marked with (●) and (♦), respectively; ITO film is marked with (▲). The two dashed lines indicate the margins of the transparent conductive NML films with resistivities lower than 10−3 Ω·cm.
(Color online) Optical refractive index curves of TiO2, ITO, and SiOx are marked with solid lines. Optical refractive index curves of TiO2/ITO and SiOx/ITO NML films are marked with dashed curves (a) and (b), with thickness ratios of 2.5:1 (TiO2:ITO) and 1.3:1 (SiOx:ITO), and resistivities of 1.18 × 10−3 and 1.41 × 10−3 Ω·cm, respectively.
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