Issue 31, 2023

Atomic layer deposition of CoF2, NiF2 and HoF3 thin films

Abstract

The present study describes atomic layer deposition (ALD) processes and characterization of CoF2, NiF2, and HoF3 thin films. For CoF2 deposition CoCl2(TMEDA) (TMEDA = N,N,N′,N′-tetramethylethylenediamine) and NH4F were used as precursors. CoF2 deposition was studied at 180–275 °C, resulting in a growth per cycle (GPC) of 0.7 to 1.2 Å. All the films consist of tetragonal CoF2 according to XRD. The impurity contents were measured with ToF-ERDA and less than 1 at% of N and Cl were detected in the films, indicating effective reactions. In addition, the F/Co ratio is close to 2 as measured by the same method. The saturation of the GPC with respect to precursor pulses and purges was verified at 250 °C. The common feature of ALD metal fluoride films – remarkable roughness – is encountered also in this process. However, the films became smoother as the deposition temperature was increased. CoF2 deposition was also demonstrated on graphite substrates. NiF2 deposition was studied at 210–250 °C by using Ni(thd)2 and TaF5 or a new fluoride source NbF5 as the precursors. Tetragonal NiF2 was obtained, but the oxygen and hydrogen contents in the films were remarkable, up to ∼11 at%, as measured by ToF-ERDA. This was observed also when the films were in situ capped with YF3. NbF5 was shown to be a potential fluoride precursor by combining it with Ho(thd)3 to deposit HoF3 films. Orthorhombic HoF3 was obtained at deposition temperatures of 200–275 °C. The films deposited at 235–275 °C are pure, and the Nb contents in films deposited at 250 and 275 °C are only 0.21 and 0.15 at%. The main impurity in both films is oxygen, but the contents are only 1.5 and 1.6 at%. The saturation of the GPC with respect to precursor pulses was verified at 250 °C. The GPC is ∼1 Å.

Graphical abstract: Atomic layer deposition of CoF2, NiF2 and HoF3 thin films

Article information

Article type
Paper
Submitted
04 Jun 2023
Accepted
18 Jul 2023
First published
24 Jul 2023
This article is Open Access
Creative Commons BY license

Dalton Trans., 2023,52, 10844-10854

Atomic layer deposition of CoF2, NiF2 and HoF3 thin films

E. Atosuo, M. Mäntymäki, L. Pesonen, K. Mizohata, T. Hatanpää, M. Leskelä and M. Ritala, Dalton Trans., 2023, 52, 10844 DOI: 10.1039/D3DT01717F

This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. You can use material from this article in other publications without requesting further permissions from the RSC, provided that the correct acknowledgement is given.

Read more about how to correctly acknowledge RSC content.

Social activity

Spotlight

Advertisements