A new
deposition technique is required to grow the active oxide
semiconductor layer for emerging oxide electronics beyond the conventional
sputtering technique. Atomic layer deposition (ALD) has the benefits
of versatile composition control, low defect density in films, and
conformal growth over a complex structure, which can hardly be obtained
with sputtering. This study demonstrates the feasibility of growing
amorphous In–Zn–Sn–O (a-IZTO) through ALD for
oxide thin-film transistor (TFT) applications. In the ALD of the a-IZTO
film, the growth behavior indicates that there exists a growth correlation
between the precursor molecules and the film surface where the ALD
reaction occurs. This provides a detailed understanding of the ALD
process that is required for precise composition control. The a-IZTO
film with In/Zn/Sn = 10:70:20 was chosen for high-performance TFTs,
among other compositions, regarding the field-effect mobility (μFE), turn-on voltage (V
on), and
subthreshold swing (SS) voltage. The optimized TFT device with the
a-IZTO film thickness of 8 nm revealed a high performance with a μFE of 22 cm2 V–1 s–1, V
on of 0.8 V, and SS of 0.15 V dec–1 after annealing at 400 °C for 30 min. Furthermore,
an emerging device such as a vertical channel TFT was demonstrated.
Thus, the a-IZTO ALD process could offer promising opportunities for
a variety of emerging oxide electronics beyond planar TFTs.
Research on two-dimensional (2D) metal dichalcogenides is rapidly expanding owing to their unique characteristics that do not exist in bulk materials. The industrially compatible development of these emerging materials is indispensable to facilitate the transition of 2D metal dichalcogenides from the research stage to the practical industrial application stage. However, an industrially relevant method, i.e., the low-temperature synthesis of wafer-scale, continuous, and orientation-controlled 2D metal dichalcogenides, still remains a significant challenge. Here, we report the low-temperature (≤350 °C) synthesis of uniform and continuous n-type SnS2 thin films via the combination of atomic layer deposition (ALD) of tin oxides and subsequent sulfurization. Well-crystallized and aligned SnS2 layers parallel to the substrate are demonstrated through the phase engineering of the ALD-grown tin oxide and the substrate surface. The additional H2S plasma treatment at 300 °C leads to the formation of stoichiometric SnS2. The formation of conformal SnS2 layers over a three-dimensional undulating hole structure is confirmed, which reveals the potential for applications beyond the planar structured architecture. The present results could be a step toward the realization of 2D metal dichalcogenides in industry.
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