Atomic layer deposition of ZnO: a review

Abstract

Due to the unique set of properties possessed by ZnO, thin films of ZnO have received more and more interest in the last 20 years as a potential material for applications such as thin-film transistors, light-emitting diodes and gas sensors. At the same time, the increasingly stringent requirements of the microelectronics industry, among other factors, have led to a dramatic increase in the use of atomic layer deposition (ALD) technique in various thin-film applications. During this time, the research on ALD-grown ZnO thin films has developed from relatively simple deposition studies to the fabrication of increasingly intricate nanostructures and an understanding of the factors affecting the fundamental properties of the films. In this review, we give an overview of the current state of ZnO ALD research including the applications that are being considered for ZnO thin films.

Forming-free resistive switching of tunable ZnO films grown by atomic layer deposition

“…This suggests that more O2 2− or VO defects are generated with longer O2 plasma times while the formation of both the stoichiometric Zn-O bond and the O-H bond are suppressed. Hall measurements revealed that all ZnO films deposited in this work were n-type, in correspondence with other reported works [12]. It is believed this n-type conductivity originates from the presence of the defects and impurities in the ZnO crystal.…”

“…0.90 to 0.94 was observed which corresponds well with other reported ZnO films deposited by ALD with plasma treatment [16]. In addition, all films exhibit relatively good stoichiometry compared to the ZnO films deposited from thermal ALD [12,16]. This is due to the fact that O2 plasma is much more reactive than H2O [12].…”

“…In addition, all films exhibit relatively good stoichiometry compared to the ZnO films deposited from thermal ALD [12,16]. This is due to the fact that O2 plasma is much more reactive than H2O [12]. In addition, the oxygen concentration increases monotonically with the increase of plasma exposure, indicating that longer O2 plasma times result in more complete oxidization.…”

“…ALD has been established as an excellent method in fabricating RS memory devices [12]. Comparing with the conventional thermal ALD, PE-ALD offers better process control which facilitates the modulation of the resultant film properties.…”

Iron-based inorganic–organic hybrid and superlattice thin films by ALD/MLD

“…The number of the small peaks was two less than the number of oxide layers (N-2, N=number of repetition cycles), as expected. 27 The N-2 trend was clearly seen in superlattice structures having 4-7 oxide layers but not anymore with 8. The XRR patterns are displayed in Fig.…”