Ion Exchange in Ultrathin Films of Cu₂S and ZnS under Atomic Layer Deposition Conditions

Abstract

Atomic layer deposition allows for a wide variety of materials to be deposited in nearly ideal, conformal multilayers. We report a marked deviation from this behavior, in the form of ion exchange, in two metal sulfide systems when using standard precursors and typical growth conditions.

High‐resolution secondary ion mass spectrometry depth profiling of nanolayers

“…We apply here a gentle DB approach to better understand the chemistry and structure of ultra‐thin films produced by atomic layer deposition (ALD). The ALD technique is widely used for a layer‐by‐layer materials synthesis and has great application potential in many areas due to its ability to coat high‐aspect‐ratio substrates by conformal layered structures with precisely predefined compositional profiles . One such important application area is the functionalization of material surfaces for use in novel detectors and sensors.…”

“…The ALD technique is widely used for a layer-by-layer materials synthesis and has great application potential in many areas due to its ability to coat high-aspect-ratio substrates by conformal layered structures with precisely predefined compositional profiles. [22,23] One such important application area is the functionalization of material surfaces for use in novel detectors and sensors. Our effort here is a contribution to the Large Area Picosecond Photo-Detector collaboration, [24] which is focused on fast particle detectors with large areas functionalized by ALD.…”

In Situ Microgravimetric Study of Ion Exchanges in the Ternary Cu-In-S System Prepared by Atomic Layer Deposition

“…For Cu 2 S, even though the ALD synthesis of this material has been reported by several groups [24,[35][36][37], the detailed mechanisms is complex and, as far as we know, has never been investigated by QCM. The overall reaction may be:…”

“…A 10-50 nm thick Al 2 O 3 passivation film was deposited on the reaction walls, prior to each experiment, and on the quartz crystal. It mitigates the cation exchange mechanisms [24,29], so that only the reactions between the quartz surface and the precursor(s) pulsed are revealed. Each experiment is referred in the text by the names given in the Table 1.…”

“…The complexity of the ALD deposition process of CIS, as for sulfide multinary compounds in general, lies in the high propensity of the cation exchange mechanisms, the greater diffusion rates and the unintentional annealing of the labile sulfur [8,[21][22][23]. Besides a deep understanding and control of the chemical process, a rigorous cleaning of the various parts of the reactor must often also be carried out to obtain a homogeneous film [21,24]. To date, two teams have mastered these conditions and reported CIS homogenous deposition by employing quartz and small scale (5 × 5 cm 2 ) reactors [20,21,25].…”