Atomic layer deposition

About: Atomic layer deposition is a research topic. Over the lifetime, 19821 publications have been published within this topic receiving 477332 citations. The topic is also known as: ALD.

Atomic layer deposited Pt-Ru dual-metal dimers and identifying their active sites for hydrogen evolution reaction

Abstract: Single atom catalysts exhibit particularly high catalytic activities in contrast to regular nanomaterial-based catalysts. Until recently, research has been mostly focused on single atom catalysts, and it remains a great challenge to synthesize bimetallic dimer structures. Herein, we successfully prepare high-quality one-to-one A-B bimetallic dimer structures (Pt-Ru dimers) through an atomic layer deposition (ALD) process. The Pt-Ru dimers show much higher hydrogen evolution activity (more than 50 times) and excellent stability compared to commercial Pt/C catalysts. X-ray absorption spectroscopy indicates that the Pt-Ru dimers structure model contains one Pt-Ru bonding configuration. First principle calculations reveal that the Pt-Ru dimer generates a synergy effect by modulating the electronic structure, which results in the enhanced hydrogen evolution activity. This work paves the way for the rational design of bimetallic dimers with good activity and stability, which have a great potential to be applied in various catalytic reactions. Atomically precise control over elemental distributions presents a challenge in the preparation of catalytic nanomaterials. Here the authors report Pt-Ru bimetallic dimer structures through atomic layer deposition process and identify the roles of Pt and Ru in hydrogen evolution reaction.

Copper interconnect barrier layer structure and formation method

Abstract: A method for forming a tungsten-containing copper interconnect barrier layer (e.g., a tungsten [W] or tungsten-nitride [WxN] copper interconnect barrier layer) on a substrate with a high (e.g., greater than 30%) sidewall step coverage and ample adhesion to underlying dielectric layers. The method includes first depositing a thin titanium-nitride (TiN) or tantalum nitride (TaN) nucleation layer (12) on the substrate, followed by the formation of a tungsten-containing copper interconnect barrier layer (20) (e.g., a W orWxN copper interconnect barrier layer) overlying the substrate. The tungsten-containing copper interconnect barrier layer can, for example, be formed using a Chemical Vapor Deposition (CVD) technique that employs a fluorine-free tungsten-containing gas (e.g., tungsten hexacarbonyl [W(CO)6]) or a WF6-based Atomic Layer Deposition (ALD) technique. The presence of a thin TiN (or TaN) nucleation layer facilitates the formation of a tungsten-­containing copper interconnect barrier layer with a sidewall step coverage of greater than 30% and ample adhesion to dielectric layers. A copper interconnect barrier layer structure includes a thin titanium-nitride (TiN) (or tantalum nitride [TAN]) nucleation layer disposed directly on the dielectric substrate (e.g., a single or dual-damascene copper interconnect dielectric substrate). The copper interconnect barrier layer structure also includes a tungsten-­containing copper interconnect barrier layer (e.g., a W or WxN copper interconnect barrier layer) formed on the thin TiN (or TaN) nucleation layer using, for example, a CVD technique that employs a fluorine-free tungsten-containing gas (e.g., [W(CO)6]) or a WF6-based ALD technique.

Protective layers prior to alternating layer deposition

Abstract: Method and structures are provided for conformal lining of dual damascene structures in integrated circuits, and particularly of openings formed in porous materials. Trenches and contact vias are formed in insulating layers. The pores on the sidewalls of the trenches and vias are blocked, and then the structure is exposed to alternating chemistries to form monolayers of a desired lining material. In exemplary process flows chemical or physical vapor deposition (CVD or PVD) of a sealing layer blocks the pores due to imperfect conformality, and is followed by an atomic layer deposition (ALD), particularly alternately pulsed metal halide and ammonia gases injected into a constant carrier flow. An alternating process can also be arranged to function in CVD-mode within pores of the insulator, since the reactants do not easily purge from the pores between pulses. Self-terminated metal layers are thus reacted with nitrogen. Near perfect step coverage allows minimal thickness for a diffusion barrier function, thereby maximizing the volume of a subsequent filling metal for any given trench and via dimensions.

High-Speed Spatial Atomic-Layer Deposition of Aluminum Oxide Layers for Solar Cell Passivation

Abstract: In this Communication we show that with spatially separated ALD of Al2O3 growth rates of 1.2 nm s-1 can be achievd, showing excellent surface passivation (surface recombination velocities of <2 cm s-1). This implies a revolutionary breakthrough in industrial throughput ALD of Al2O3 passivation of silicon solar cells.

Water Splitting by Tungsten Oxide Prepared by Atomic Layer Deposition and Decorated with an Oxygen‐Evolving Catalyst

Abstract: When sunlight is used as direct energy input, water can be split into hydrogen and oxygen at conversion efficiencies similar to those of solar cells. This process offers a method for energy storage to address the problem that the sun does not shine continuously, and is a particularly appealing approach to solar-energy harvesting. Notwithstanding the intense research efforts, progress in this area is extremely slow. Efficient and inexpensive water splitting remains elusive. A key reason for the sluggish progress is the lack of suitable materials. The “ideal” material must absorb strongly in the visible range, be efficient in separating charges using the absorbed photons, and be effective in collecting and transporting charges for the chemical processes. Such a material has yet to be found. The difficulties in finding a suitable material stem from the competing nature of intrinsic material properties (e.g., optical depth, charge diffusion distance, and width of the depletion region, among others), which leaves limited opportunity for tunability. We recently demonstrated that heteronanostructures, a type of nanoscale material consisting of multiple components that complement each other, have a combination of properties which are not available in singlecomponent materials. For instance, we can add chargetransport components to oxide semiconductors to solve the issue of low conductivity that oxide semiconductors generally suffer. In a similar fashion, one can add an effective catalyst to address the challenge that oxygen evolution is complex and tends to be the rate-limiting step. These new materials will likely lead to significant improvement in solar watersplitting efficiencies. The success of a heteronanostructure design relies on the ability to produce high-quality components with interfaces of low defect density, and on the availability of various components. Here we show that crystalline WO3 can be synthesized by the atomic layer deposition (ALD) method in the true ALD regime. When coated with a novel Mn-based catalyst, the resulting WO3 survives soaking in H2O at pH 7 and produces oxygen by splitting H2O under illumination. We choose ALD to prepare WO3 because of the following advantages: 1) a high degree of control over the resulting materials; 2) excellent step coverage to yield conformal coatings; and 3) process versatility to tailor the composition of the deposit. WO3 was studied because it is one of the most researched compounds for water splitting. The widely available literature makes it easy to compare our results with existing reports and thus allows us to test the power of the heteronanostructure design. To avoid the production of corrosive byproducts during the ALD process and to ensure the reaction occurs in the true ALD regime, we used (tBuN)2(Me2N)2W as tungsten precursor and H2O as oxygen precursor, as described in the Experimental Section (see Supporting Information for more details). Our first goal was to verify that the growth indeed takes place in the ALD regime. The dependence of the growth rate on the precursor pulse times and on the substrate temperature unambiguously confirms this. In addition, the excellent linear dependence of the deposition thickness on the number of precursor pulses supports the ALD growth mechanism and shows the extent of control we can achieve (see Supporting Information). That a long H2O pulse time is necessary to initiate growth is a key finding of this work. Despite intentional strengthening of the oxidative conditions, as-grown WO3 exhibited a tinted color, indicating the existence of oxygen deficiencies, which was then corrected by an annealing step in O2 at 550 8C. The crystalline nature of the product is manifested in the highresolution (HR) TEM image in Figure 1a. We also synthesized WO3 on two-dimensional TiSi2 nanonets. [18,19] The uniformity and good coverage around the nanonet branches show that this deposition technique is suitable for the creation of heteronanostructures. Ready dissolution of WO3 in aqueous solutions with pH 4 is a significant challenge that impedes its widespread use. We sought to solve this problem by coating WO3 with an Mnbased catalyst. Derived from the Brudvig–Crabtree catalyst, this coating was prepared by thermally decomposing [(H2O)(terpy)Mn(O)2Mn(H2O)(terpy)](NO3)3 (terpy= 2,2’:6’,2’’terpyridine). Similar to the oxo-bridged dimanganese catalyst, the thermal decomposition product exhibits good [*] R. Liu, Y. Lin, S. W. Sheehan, Prof. Dr. D. Wang Department of Chemistry, Merkert Chemistry Center Boston College 2609 Beacon St., Chestnut Hill, MA 02467 (USA) Fax: (+1)617-552-2705 E-mail: dunwei.wang@bc.edu Homepage: http://www2.bc.edu/~dwang