Atomic layer deposition (ALD) is a group of methods for the formation of nanofilms of materials, an atomic layer at a time using surface limited reactions.  The majority of those methods are based on use of the vacuum environment.  However there are methods such as sequential ionic layer adsorption reaction (SILAR) which uses the condensed phase, that is, aqueous solutions of precursor ions.  In addition, this group has been working on an electrochemical form of ALD for 25 years.   That work is referred to as electrochemical atomic layer deposition (E-ALD) or electrochemical atomic layer epitaxy (EC-ALE), and is based on using underpotential deposition (UPD) for surface limited reactions. The problem with using an electrochemical methodology for the formation of nanofilms is that many compatible with the conductive substrates normally used for E-ALD.  This has stimulated investigations into the growth of materials using an electroless form of ALD (EL-ALD).  The processes being explored are based on use of an adsorbed layer of a precursor, where the solution is then exchanged for a reducing agent, or vis versa.   This cycle is then repeated to desired thickness. One example is the use of an adsorbed (or absorbed) layer of hydrogen as the reducing agent (usually on Pd).  This is then used for surface limited redox replacement (SLRR) of the desired element.  Another example is the use of Sn²⁺ adsorption followed by Pd²⁺, which oxidizes the Sn²⁺ to Sn⁴⁺ and forms Pd on the surface. Studies are underway to build this into a cycle for EL-ALD.