Optical and mechanical properties of nanolaminates of zirconium and hafnium oxides grown by atomic layer deposition

Abstract

Nanolaminates of ZrO2 and HfO2 were grown by atomic layer deposition, using metal halides and water as precursors, on silicon and fused quartz substrates at 300 °C. The crystalline phase composition, optical refraction, and mechanical performance of the multilayers were influenced by the relative contents of the constituent metal oxides. The crystal growth in as-deposited HfO2 dominantly led to the monoclinic phase, whereas ZrO2 was partially crystallized as its metastable and hard tetragonal polymorph. The hardness and elasticity of the nanolaminate structures could be modified by varying the amounts of either oxide contributing to the crystallographic order formed in the solid films. The refractive indexes depended on the nanolaminate structure.

Surface Modification of ZrO2 Nanoparticles with TEOS to Prepare Transparent ZrO2@SiO2-PDMS Nanocomposite Films with Adjustable Refractive Indices

“…This was because the volume fraction of the high-refractive-index ZrO 2 ( n = 2.16) decreased relatively and that of the low-refractive-index SiO 2 ( n = 1.46) increased with the increasing reaction time during the surface modification of NPs, considering the same NP weight content in aqueous solutions. The shell thicknesses of the SiO 2 layers of the ZrO 2 @SiO 2 NPs for each reaction time of 0, 3, 9, 18, 27, and 54 h were calculated as 0.0, 0.1, 0.7, 1.3, 2.1, and 4.2 nm, respectively (the red line in Figure 4 c) [ 34 , 46 , 47 , 48 , 49 ]. In particular, the calculated shell thickness of the ZrO 2 @SiO 2 NPs for the reaction time of 18 h (ZrO 2 @SiO 2 -18h) was consistent with that given by the TEM analysis, as described above ( Figure 2 b,e).…”

Mechanical and Magnetic Properties of Double Layered Nanostructures of Tin and Zirconium Oxides Grown by Atomic Layer Deposition

“…The substrate was characterized by the hardness similar to that of the softer oxide films, and the average elastic modulus remaining between those of the harder and softer oxide films (Figure 5). deposited earlier in a similar ALD process [23,24]. The 25 nm thick SnO2/Si film possessed noticeably higher hardness and stiffness than that based on the ZrO2.…”

“…The nanoindentation results are presented in Table 2 , where the geometric mean values for hardness and Young’s modulus are given for each film. Thereby, the 21 nm thick ZrO 2 /Si film possessed the hardness of 11.5 GPa and elastic modulus of 96 GPa, which are slightly lower values than those measured in approximately three times thicker films deposited earlier in a similar ALD process [ 23 , 24 ]. The 25 nm thick SnO 2 /Si film possessed noticeably higher hardness and stiffness than that based on the ZrO 2 .…”

Low-Temperature Dopant-Assisted Crystallization of HfO2 Thin Films

“…For thin films which are the subject of this proposal, crystallization usually proceeds by nucleation in the tetragonal phase due to the surface energy effect but the monoclinic phase takes over and appears the most dominant 5,6 . The most common approach to inducing crystallization is thermal treatment and there have been numerous examples in the literature for the types of films that are the subject of this work [7][8][9][10][11][12][13][14][15] . In most cases, such a process is not controlled, and thermodynamics tends to determine the abundance of the various phases present in the film.…”

“…Transition-metal oxides have been the subject of intense study due to their use in many technologies such as nanoelectronics, sensors, photocatalysis, and so forth., both in amorphous and crystalline forms. HfO 2 can be found in a variety of phases such as cubic, tetragonal, monoclinic, and, more recently, orthorhombic. − For thin films, which are the subject of this work, crystallization usually proceeds by nucleation in the tetragonal phase due to the surface energy effect but the monoclinic phase takes over and appears the most dominant. , The most common approach to inducing crystallization is thermal treatment and there have been numerous examples in the literature for the types of films that are the subject of this work. − In most cases, such a process is not controlled, and thermodynamics tend to determine the abundance of the various phases present in the film. Other approaches such as laser heating have been proposed to provide a more localized control of the process, but they have very low throughput. , There are instances where the as-deposited film is polycrystalline, for example, HfO 2 films prepared by reactive sputtering are monoclinic at temperatures around 150 °C .…”