New approaches for area-selective deposition (ASD) are becoming critical for advanced semiconductor patterning. Atomic layer deposition (ALD) and atomic layer etching (ALE), that is, "inverse ALD", are considered important for ASD, but to date, direct integration of ALD and ALE for ASD has not been reported. This work demonstrates that self-limiting thermally driven ALE, using WF 6 and BCl 3 , can be directly coupled with selflimiting thermal ALD, using TiCl 4 and H 2 O, in a single isothermal reactor at temperature <200 °C to achieve ASD of TiO 2 thin films on common Si/SiO 2patterned surfaces without the use of organic nucleation inhibitors. We show that ALD/ALE "supercycles" (where one supercycle comprises, e.g., 30 ALD cycles followed by 5 ALE cycles) can be reliably repeated to yield more than 12 nm of TiO 2 while maintaining a selectivity fraction S > 0.9, nearly a 10× improvement over previous reports of inherent TiO 2 ASD. After ALD/ALE (=30/5) 14 supercycles at 170 °C, X-ray photoelectron spectroscopy data show a small Ti 2p signal on Si−H (hydrogen fluoride-cleaned Si), with no Ti 2p signal detected after additional "postetch" ALE cycles. At 150 °C, extended supercycles lead to unwanted particles visible by electron microscopy, which is ascribed to the formation of unreactive mixed silicon/titanium oxide nuclei. The number density of visible particles is consistent with modeled film growth trends. Overall, this work provides new insights into the capabilities for ASD of dielectric materials and a starting point to realize more complex atomic-scale processes using ALD, ALE, and other self-limiting reaction schemes.

In this work, a whole manufacturing process of the curved copper nanowires (CCNs) based flexible transparent conductive electrode (FTCE) is reported with all solution processes, including synthesis, coating, and networking. The CCNs with high purity and good quality are designed and synthesized by a binary polyol coreduction method. In this reaction, volume ratio and reaction time are the significant factors for the successful synthesis. These nanowires have an average 50 nm in width and 25-40 μm range in length with curved structure and high softness. Furthermore, a meniscus-dragging deposition (MDD) method is used to uniformly coat the well-dispersed CCNs on the glass or polyethylene terephthalate substrate with a simple process. The optoelectrical property of the CCNs thin films is precisely controlled by applying the MDD method. The FTCE is fabricated by networking of CCNs using solvent-dipped annealing method with vacuum-free, transfer-free, and low-temperature conditions. To remove the natural oxide layer, the CCNs thin films are reduced by glycerol or NaBH4 solution at low temperature. As a highly robust FTCE, the CCNs thin film exhibits excellent optoelectrical performance (T = 86.62%, R(s) = 99.14 Ω ◻(-1)), flexibility, and durability (R/R(0) < 1.05 at 2000 bending, 5 mm of bending radius).

We report an effective method for fabricating highly transparent and stretchable large-area conducting films based on a directional arrangement of silver nanowires (AgNWs) driven by a shear force in a microliter-scale solution process. The thin conducting films with parallel AgNWs or cross-junctions of AgNWs are deposited on the coating substrate by dragging a microliter drop of the coating solution trapped between two plates. The optical and electrical properties of the AgNW thin films are finely tuned by varying the simple systematic parameters in the coating process. The transparent thin films with AgNW cross-junctions exhibit the superior electrical conductivity with a sheet resistance of 10 Ω sq(-1) at a transmittance of 85% (λ = 550 nm), which is well described by the high ratio of DC to optical conductivity of 276 and percolation theory in a two-dimensional matrix model. This simple coating method enables the deposition of AgNW thin films with high optical transparency, flexibility, and stretchability directly on plastic substrates.

During TiO2 atomic layer deposition (ALD) using TiCl4 and H2O at ∼150 °C, nucleation proceeds rapidly on hydroxylated SiO2 but is inherently delayed on passivated surfaces such as H-terminated silicon (Si-H) and trimethylsilyl-passivated SiO2 (SiO2-TMS) formed using dimethylamino-trimethylsilane (DMA-TMS) as a small molecule inhibitor. In this work, we explore details of TiO2 nucleation on both Si-H and SiO2-TMS and show that the mechanisms leading to unwanted nuclei depend strongly on the passivation mechanism. Initial growth is observed as a function of ALD cycles using scanning electron microscopy to obtain average particle size, density, and overall surface coverage fraction. Also, average film thickness vs cycle is estimated using ellipsometry or Rutherford backscattering spectrometry. Data are compared to an analytical model that considers that either nucleation sites are present on the starting non-growth surface or sites are generated during the ALD process. On the Si-H surface, data and modeling indicate that nucleation occurs predominantly from a fixed number of nucleation sites present on the starting growth surface that start to immediately grow. However, on TMS-passivated SiO2, nucleation sites are predominantly generated during the growth process so that the density of nucleation sites increases as growth proceeds. Results indicate that nucleation sites are created when adsorbed ALD reactants become kinetically trapped on the SiO2-TMS surface. This demonstrates that mechanisms associated with unwanted nucleation during area-selective deposition (ASD) can depend on details of the surface passivation scheme, thereby providing insight to help to improve ASD strategies for advanced applications.

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