Uniform ZnO epitaxial films formed at atmospheric pressure by high-speed rotation-type mist chemical vapor deposition

Abstract

Uniform ZnO epitaxial films were formed on 2-in.-diameter m-plane sapphire substrates by high-speed rotation-type mist chemical vapor deposition at atmospheric pressure, without using any vacuum equipment. The ZnO films were characterized by scanning electron microscopy, X-ray diffraction in θ–2θ and ϕ scanning modes, electron backscatter diffraction, and room-temperature photoluminescence measurements. Experimental results show that m-plane ZnO films were epitaxially grown on the m-plane sapphire substrates with high uniformity of not only thickness but also crystallinity and optical properties. These results will promote the progress of ZnO-based devices such as light-emitting diodes.

Improvement of m‐plane ZnO films formed on buffer layers on sapphire substrates by mist chemical vapor deposition

“…In contrast, uniform thickness was obtained at a rotation speed of 1000 rpm. Thickness variation was less than 2% from the average thickness over the 2‐inch substrate , which would satisfy an industrial requirement of a thin‐film formation system. In addition, uniform ZnO single‐crystal film was successfully formed over 2‐inch wafers as described below.…”

“…b, two peaks spaced by 180° were observed for both ZnO and sapphire, since the crystal lattices of m‐plane ZnO and m‐plane sapphire are both rectangular with two‐fold symmetry. The c ‐axes of ZnO and that of sapphire perpendicularly crossed each other on the sapphire substrate, namely ZnO [0001] || sapphire and ZnO || sapphire [0001]. In this φ scan measurement, the ZnO (10–11) and sapphire (11–20) planes were used as the monitoring planes, where Bragg conditions were set to be satisfied.…”

“…From these results of Figs. and , it was shown that the thickness and crystallographic properties were homogeneous across the substrate, and that the ZnO film was epitaxially grown on the sapphire substrate . In the direction lateral to the sapphire substrate, four small rectangular ZnO lattices are formed on one large sapphire rectangular lattice in the sapphire [0001] direction, indicating domain‐matching epitaxy , where the lattice mismatch in the ZnO [0001] direction is 9.7%, and that in the ZnO direction is 0.1%.…”

“…Therefore, it is important to create high‐speed rotation‐type systems also for mist‐CVD as a next‐generation low‐cost film‐formation method. We have developed high‐speed rotation‐type mist‐CVD, which provides uniform ZnO epitaxial films over 2‐inch sapphire substrates . At present, a technical barrier to realize ZnO‐based LEDs is to form p‐type ZnO.…”

Single crystalline SnO2 thin films grown on m ‐plane sapphire substrate by mist chemical vapor deposition

“…In order to obtain high crystallographic properties of SnO 2 , the growth of single crystalline SnO 2 require relatively expensive film formation methods such as metalorganic chemical vapour deposition (MOCVD) [10] or molecular beam epitaxy (MBE) [12,13], which needs vacuum equipment. One alternative approach is a mist chemical vapour deposition (mist-CVD), which can form various oxide semiconductors under atmospheric pressure with a simple and less expensive technique [9,[14][15][16][17][18][19]. Most of the previous studies targeted SnO 2 film grown on c-plane and r-plane sapphire substrate even under vacuum condition (MOCVD, MBE and so on) and only few studies have focused on the film grown on other planes of sapphire [10].…”