Atomic and molecular layer deposition: off the beaten track

Abstract

Atomic layer deposition (ALD) is a gas-phase deposition technique that, by relying on self-terminating surface chemistry, enables the control of the amount of deposited material down to the atomic level. While mostly used in semiconductor technology for the deposition of ceramic oxides and nitrides on wafers, ALD lends itself to the deposition of a wealth of materials on virtually every substrate. In particular, ALD and its organic counterpart molecular layer deposition (MLD), have opened up attractive avenues for the synthesis of novel nanostructured materials. However, as most ALD processes were developed and optimized for semiconductor technology, these might not be optimal for applications in fields such as catalysis, energy storage, and health. For this reason, novel applications for ALD often require new surface chemistries, process conditions, and reactor types. As a result, recent developments in ALD technology have marked a considerable departure from the standard set by well-established ALD processes. The aim of this review is twofold: firstly, to capture the recent departure of ALD from its original development; and secondly, to pinpoint the unexplored paths through which ALD can advance further in terms of synthesis of novel materials. To that end, we provide a review of the recent developments of ALD and MLD of materials that are gaining increasing attention on various substrates, with particular emphasis on high-surface-area substrates. Furthermore, we present a critical review of the effects of the process conditions, namely, temperature, pressure, and time on ALD growth. Finally, we also give a brief overview of the recent advances in ALD reactors and energy-enhanced ALD processes.

Atomic/Molecular Layer Deposition of s‐Block Metal Carboxylate Coordination Network Thin Films

“…It is based on self‐limiting gas‐surface reactions of alternating gaseous precursors—a fact that enables the thin film uniformity and precise thickness control. Most importantly, by combining the ALD technique for inorganic materials with the currently strongly emerging molecular layer deposition (MLD) technique for organics, it is possible to deposit inorganic–organic materials in a well‐controlled layer‐by‐layer manner . Like ALD, the MLD technique is based on sequential and self‐limiting gas–surface reactions.…”

Low-temperature atomic layer deposition delivers more active and stable Pt-based catalysts

“…16,18 In brief, the system consists of a glass column (26 mm through an OAS Topzone ozone generator. The ozone-enriched air had an ozone content of about 1.5 wt%.…”

“…9,14,15 Atomic layer deposition (ALD) is a gas-phase and solventfree technique that is a promising route for the controlled deposition of NPs, subnanometer clusters, and even single atoms. 13,[16][17][18][19][20][21] Briefly, the advantage of ALD is that the deposition proceeds stepwise through cyclic self-terminating surface reactions, such that (1) each step can run to completion, even in hard-to-reach places in high-surface-area substrates, 14,16,19,20,22 (2) the amount deposited in each cycle of alternating reactions is tightly controlled, and (3) programming different precursors in sequences of cycles allow for more complex NPs such as bimetallic particles and core/shell and overcoated NPs. 17 In particular, when carried out in fluidized bed reactors (FBRs), ALD lends itself to the deposition of noble metals on bulk quantities of high-surface-area powders with hardly any loss of metal precursors.…”

Suppressing the Photocatalytic Activity of TiO2 Nanoparticles by Extremely Thin Al2O3 Films Grown by Gas-Phase Deposition at Ambient Conditions

“…Atomic layer deposition (ALD) is a gas-phase deposition technique that is carried out using alternating exposures of the substrate to chemical reactants, each having self-limiting surface reactions that enable the control of film thickness at the atomic level [20,21,22]. ALD has been developed for a few decades [23,24], and utilized in the deposition of a wealth of materials on virtually every substrate for applications in various fields such as microelectronics, catalysis, and energy conversion and storage [21,25,26].…”