SALD: Spatial Atomic Layer Deposition

Spatial atomic layer deposition (SALD) is an alternative to conventional ALD in which the precursors are continuously injected in different locations of the reactor, being separated by a flow of inert gas. As a result, SALD is up to orders of magnitude faster than conventional ALD, achieving deposition rates more typical of CVD. In addition, SALD can easily be performed at atmospheric pressure an even in the open air, i.e. without the need of a deposition chamber. At the same time, the unique assets of ALS, namely, the thickness control at the nanometer, the high conformality and the deposition of high quality materials at low temperatures (RT to 350 C),  are maintained.  At LMGP, we work with the close-proximity approach based on a manifold head, initially reported by D. Levy et al. from Kodak.  More info on the principle of SALD and a video of one of our systems can be found here. The SALD research is structured in three main lines:

1.- Design and optimization of the SALD reactors. The SALDs at LMG have been designed and fabricated in the lab. The systems have been conceived to be easily adapted to different types of samples, materials and reaction activation. At present, there are two systems operative, while a third one is currently being implemented. Computational Fluid Dynamic (CFD) simulations are used to guide our designs. As example of our developments, we have recently fabricated a compact atmospheric plasma head through a collaboration with the GREMI lab, allowing us to perform atmospheric-plasma-activated SALD.

2.- Fundamental studies. This line includes the characterization (including in situ) of the reaction mechanism and the study of the effect of open-air processing in the properties of the materials deposited. We also tackle the deposition of new materials and materials which have not beed deposited by SLAD before. These include oxides, metals and hybrid materials. For that, new precursors are explored thanks to different collaborations with synthetic chemistry groups.  The materials currently deposited at LMGP include: Al2O3, ZnO, ZnO:Al (AZO), TiO2, SiO2 and Cu2O. Our studies have allowed us to develop a new theoretical model for the conductivity of polycrystalline oxide semiconductive films.

3.- Application to devices. Through different collaboration inside and outside the LMGP, the films developed by the team are applied in functional materials and devices. In particular, we focus on the study of transparent conductive materials for different optoelectronic devices. Other devices include thin film transistors, sensors, MIM diodes, etc…