Hydrogen and Deuterium Incorporation in ZnO Films Grown by Atomic Layer Deposition

Sami Kinnunen,Timo Sajavaara,Kai Arstila,Manu Lahtinen

doi:10.3390/coatings11050542

Abstract

Zinc oxide (ZnO) thin films were grown by atomic layer deposition using diethylzinc (DEZ) and water. In addition to depositions with normal water, heavy water (2H2O) was used in order to study the reaction mechanisms and the hydrogen incorporation at different deposition temperatures from 30 to 200 ∘C. The total hydrogen concentration in the films was found to increase as the deposition temperature decreased. When the deposition temperature decreased close to room temperature, the main source of impurity in hydrogen changed from 1H to 2H. A sufficiently long purging time changed the main hydrogen isotope incorporated in the film back to 1H. A multiple short pulse scheme was used to study the transient steric hindrance. In addition, the effect of the storage of the samples in ambient conditions was studied. During the storage, the deuterium concentration decreased while the hydrogen concentration increased an equal amount, indicating that there was an isotope exchange reaction with ambient H2 and/or H2O.

Highlights

Atomic layer deposition (ALD) is a thin film deposition technique that is widely adopted in integrated circuits [1] and other modern devices such as in organic light emitting diodes (OLEDs) [2] and perovskite solar cells [3]
Doped Zinc oxide (ZnO) can be used as transparent conductive oxide (TCO) for optoelectronics [9] and ZnO can be deposited at near room temperature [6,10,11,12,13], making ALD a suitable deposition method for temperaturesensitive substrates such as polymers
Oxygen rich ZnO films deposited with ALD, especially at low deposition temperatures, have been reported previously [10,27,43,44,45]

Summary

Introduction

Atomic layer deposition (ALD) is a thin film deposition technique that is widely adopted in integrated circuits [1] and other modern devices such as in organic light emitting diodes (OLEDs) [2] and perovskite solar cells [3]. The electrical properties of ZnO can be tailored with doping, which makes it a versatile material for numerous applications [7]. The unique assets of ALD have attracted the attention of ALDgrown ZnO films for various applications. Doped ZnO can be used as transparent conductive oxide (TCO) for optoelectronics [9] and ZnO can be deposited at near room temperature [6,10,11,12,13], making ALD a suitable deposition method for temperaturesensitive substrates such as polymers. Spatial atomic layer deposition (SALD) has been harnessed for high throughput and large area depositions, making ALD more interesting for industrial use [6]. ALD ZnO has been studied for its reversible wettability [14,15], and it has been found to have antibacterial properties [16]

Methods

Results

Conclusion