Transparent conductive CuCrO₂thin films deposited by pulsed injection metal organic chemical vapor deposition: up-scalable process technology for an improved transparency/conductivity trade-off

Abstract

aMetal organic chemical vapor deposition is carefully optimized for the growth of pure CuCrO 2 delafossite coatings on glass substrates. The pulsed direct liquid delivery is demonstrated to be an efficient process technology for the controlled supply of the precursor solution in the evaporation chamber, which is shown to be one of the main process parameters to tailor the thin-film properties.We investigated the influence of the precursor concentration ratio Cu(thd) 2 (bis[2,2,6,6-tetramethyl-3,5-heptanedionato]copper(II)) and Cr(thd) 3 (tris[2,2,6,6-tetramethyl-3,5-heptanedionato]chromium(III)) on the crystal structure, morphology and electrical conductivity, at a reduced temperature of 370 1C. We observe for a low ratio, a pure delafossite phase with a constant Cu-poor/Cr-rich chemical composition, while at a high ratio a mixture of copper oxides and CuCrO 2 was found. The as-grown 140 nm-thick pure delafossite films exhibit an exceptional high electrical conductivity for a non-intentionally doped CuCrO 2 , S cm À1, and a near 50% transparency in the visible spectral range.

Tuning the electrical properties of the p-type transparent conducting oxide Cu1−xCr1+xO2 by controlled annealing

“…Values around 100–130 µV −1 are measured for as-deposited high conductive samples. Similar values are usually reported for off-stoichiometric or doped delafossite thin-films with electrical conductivities around 10 S cm −1 or higher 2,10–14,24 . After short annealing times (up to 60 s) the coefficient increases up to values around 360 µV K −1 .…”

“…Electrical conductivity values of tens of S cm −1 are obtained using the set of deposition’s parameters described within the experimental methods section. This level of conductivities is usually reported for off-stoichiometric delafossites thin- films fabricated using non-equilibrium chemical methods as dynamic liquid injection chemical vapour deposition 10,11,14 or chemical spray deposition 12,13 . These values are significantly higher than those reported for intrinsic 20,21 or some doped 22,23 CuCrO 2 delafossites thin-films.…”

“…Moreover, recent reports had shown large conductivity (larger than 10 S cm −1 ) and adequate transparency for highly off-stoichiometric copper chromium delafossites. 10–13 In these particular compounds the crystalline phase of delafossite is preserved although a copper deficiency up to 33% is observed.…”

Hall measurements on low-mobility thin films

“…(11), Fig. 3 shows the reduced Hall resistances for a Hall measurement of a non-intentionally-doped CuCrO 2 transparent conductive thin film 19 at a sample temperature of 270 K. Despite large scatter in the data, the p-type conductivity at a mobility of the order of 10 À2 cm 2 /(V s) is still resolved.…”

Temperature‐dependent electrical transport behavior and structural evolution in hollandite‐type titanium‐based oxide

“…Hence, two maxima are observed at temperatures of approximately 400 and 800°C in K 1.36 Ti 8 O 16 , which are different from other titanium-based oxides with diverse structures. 55 According to the results of TG and TEC measurements, Ti 3+ is barely oxidized in the temperature range below 400°C, and thus, the electron carrier concentration is almost unchanged. 50,51 For doped titanium dioxide, electronic conduction follows a thermally activated mechanism of SPH between Ti 4+ and Ti 3+ ions when the temperature is higher than D ∕2 is the Debye temperature).…”