The preparation of high‐quality In2O3:H, as transparent conductive oxide (TCO), is demonstrated at low temperatures. Amorphous In2O3:H films were deposited by atomic layer deposition at 100 °C, after which they underwent solid phase crystallization by a short anneal at 200 °C. TEM analysis has shown that this approach can yield films with a lateral grain size of a few hundred nm, resulting in electron mobility values as high as 138 cm2/V s at a device‐relevant carrier density of 1.8 × 1020 cm–3. Due to the extremely high electron mobility, the crystallized films simultaneously exhibit a very low resistivity (0.27 mΩ cm) and a negligible free carrier absorption. In conjunction with the low temperature processing, this renders these films ideal candidates for front TCO layers in for example silicon heterojunction solar cells and other sensitive optoelectronic applications. (© 2014 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)

The atomic layer deposition (ALD) process of hydrogen-doped indium oxide (InO:H) using indium cyclopentadienyl (InCp) and both O and HO as precursors is highly promising for the preparation of transparent conductive oxides. It yields a high growth per cycle (>0.1 nm), is viable at temperatures as low as 100 °C, and provides a record optoelectronic quality after postdeposition crystallization of the films ( ACS Appl. Mat. Interfaces , 2015 , 7 , 16723 - 16729 , DOI: 10.1021/acsami.5b04420 ) . Since both the dopant incorporation and the film microstructure play a key role in determining the optoelectronic properties, both the crystal growth and the incorporation of the hydrogen dopant during this ALD process are studied in this work. This has been done using transmission electron microscopy (TEM) and atom probe tomography (APT) in combination with deuterium isotope labeling. TEM studies show that an amorphous-to-crystalline phase transition occurs in the low-temperature regime (100-150 °C), which is accompanied by a strong decrease in carrier density and an increase in carrier mobility. At higher deposition temperatures (>200 °C), enhanced nucleation of crystals and the incorporation of carbon impurities lead to a reduced grain size and even an amorphous phase, respectively, resulting in a strong reduction in carrier mobility. APT studies on films grown with deuterated water show that the incorporated hydrogen mainly originates from the coreactant and not from the InCp precursor. In addition, it was established that the incorporation of hydrogen decreased from ∼4 atom % for amorphous growth to ∼2 atom % after the transition to crystalline film growth.

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