Over the past several decades, tin monoxide (SnO) has been studied extensively as a p-type thin film transistor (TFT). However, its TFT performance is still insufficient for practical use. Many studies suggested that the instability of the valence state of Sn (Sn2+/Sn4+) is a critical reason for the poor performance such as limited mobility and low on/off ratio. For SnO, the Sn 5s–O 2p hybridized state is a key component for obtaining p-type conduction. Thus, a strategy for stabilizing the SnO phase is essential. In this study, we employ a variety of analytical methods such as X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS), and Hall measurement to identify the main contributors to the physical properties of SnO. It is revealed that precision control of the process temperature is needed to achieve both the crystallinity and thermal stability of SnO. In other words, it would be ideal to obtain high-quality SnO thin films at low temperature. We find that atomic layer deposition (ALD) is a quite advantageous process for obtaining high-quality SnO thin films by the following two-step process: (i) growth of highly c-axis oriented SnO at the initial stage and (ii) further crystallization along the in-plane direction by a postannealing process. Consequently, we obtained a highly dense SnO thin film (film density: 6.4 g/cm3) with a high Hall mobility of ∼5 cm2/(V·s). The fabricated SnO TFTs exhibit a field-effect mobility of ∼6.0 cm2/(V·s), which is a quite high value among the SnO TFTs reported to date, with long-term stability. We believe that this study demonstrates the validity of the ALD process for SnO TFTs.

Ruthenium (Ru) has drawn attention in the field of future semiconductor processing as a diffusion barrier layer and an electrode material. Here, ruthenium films are deposited by atomic layer deposition (ALD) using a novel precursor, Ru2{μ2-η3-N­(tBu)–C­(H)–C­(iPr)}­(CO)6 (T-Rudic), and two different co-reagents, that is, H2O and O2. Ru films are deposited at 0.1 Å/cycle at 150 °C with H2O and 0.8 Å/cycle at 200 °C with O2. The H2O reactant set exhibits ALD saturation between 150 and 200 °C. However, the O2 reactant set shows a linear incremental growth rate over 200 °C and nongrowth under 175 °C. Film growth preference is observed on various substrates (e.g., Si, SiO2, Al2O3, and graphitic carbon) when the H2O reactant is applied at 150 °C. Both experimental data and density functional theory calculations indicate that preferential growth occurs on a hydrogen-terminated surface (Si) rather than a hydroxyl-terminated surface (SiO2). The Auger electron spectroscopy mapping image of a selectively deposited Ru film on a patterned Si and SiO2 substrate supports that this selective deposition mechanism also occurs in a square-patterned substrate.

Metalcone films can be rearranged from amorphous structures to 2D-like carbon by electron beam irradiation. The irradiated indicone (HQ) film can be used as an inhibitor for selective deposition delaying 20 cycles of ALD of ZnO.