Morphology controlled synthesis of crystalline ZnO film by MOCVD: from hexagon to rhombus

Abstract

We grew crystalline ZnO films by non-catalyst metalorganic chemical vapor deposition. Through adjusting the mass flow rate of the diethylzinc source, the morphology of the crystalline ZnO film can be easily manipulated from hexagon to rhombus. The possible mechanism is the growth rate anisotropy, which is confirmed by FE-SEM, XRD, and TEM measurements.Crystal facet engineering has an important role in the performances of functional materials, such as heterogeneous catalysis, gas sensing, ion detection, molecule absorption, energy conversion and storage etc. 1 Zinc oxide (ZnO) with wide and direct band gap is probably the most investigated metal oxide due to its attractive and versatile properties for electronics, 2,3 optoelectronics, 4-6 chemical/biological sensing, 7 and renewable energy applications. 8 To improve the performance of ZnO, the facet engineering of crystalline ZnO films have attracted much attention in the past decades. However, the surface of crystalline ZnO films with nanostructures usually shows the hexagonal morphology due to the wurtzite crystal structure with preferential orientation along the c-axis [0001]. 9-14 Few researchers synthesized rhombus-shaped ZnO nanostructures except for Zhi. 15 Zhi achieved this goal based on aqueous electro-deposition using rhombus-shaped Zn(OH)F nanorods as precursors, and reported that the rhombus-shaped ZnO nanostructures shows remarkable hydrogen storage capacity. In this work, MOCVD was used to grow crystalline ZnO film with nanostructures. We know the MOCVD method can be easily extended to industry production. The surface morphologies were successfully controlled from hexagonal to rhombus shape. The growth mechanism is discussed in detail.ZnO thin films were deposited on sapphire, silicon and quartz substrates by MOCVD, respectively. The MOCVD was

A fluorine-mediated hydrothermal method to synthesize mesoporous rhombic ZnO nanorod arrays and their gas sensor application

“…[5][6][7] Pei et al have successfully realized the rhombus ZnO by metal-organic chemical vapor deposition (MOCVD). 8 However, these methods face problems of complicated operation procedures and severe operating conditions. Thus it is urgent to introduce a controllable method with low cost, process simplicity, environmental friendliness and high yield of products to synthesize the unique architecture of rhombic ZnO NR arrays.…”

EPD-deposited ZnO thin films: a review

“…Even though zinc oxide can have two other crystalline structures-zinc-blende and rocksalt-, the high polarity of the Zn-O bond accounts for the preferential formation of wurtzite rather than zinc-blende, which is metastable, or rocksalt, which can only be obtained at high pressures. In the wurtzite crystal structure, hexagonal-close-packed (hcp) M. VERDE [15], RF magnetron sputtering [16], spray pyrolysis [17], metal organic chemical vapor deposition (MOCVD) [18] or pulsed laser deposition (PLD) [19]. Nevertheless, these techniques present important drawbacks, such as the high energy consumption and sophisticated instrumentation required for the transformation of the Zn precursors to the gas state, which increase their cost and make them hardly scalable.…”

Microstructural and optical properties of high-quality ZnO epitaxially grown on a LiGaO2 substrate

“…2,3 These unique properties make ZnO a potential material for applications in electronics, optoelectronics, acoustics, and sensing. [1][2][3] Various growth techniques have been used to fabricate ZnO thin lms, such as molecular beam epitaxy (MBE), 4,5 metal-organic chemical vapor deposition (MOCVD), 6,7 chemical vapor deposition (CVD), 8,9 pulsed laser deposition (PLD), 10,11 atomic layer deposition (ALD), 12,13 sputtering, 14,15 and sol-gel. 16 Among them, CVD gains particularly concerns because it is a simple and economic technique that has been widely used in the semiconductor industry to produce thin lms.…”

“…The crystal quality of asgrown ZnO thin lms is superior to previously reported ZnO lms grown on (001) LiGaO 2 substrate [25][26][27] and comparable to that of ZnO thin lms grown by MBE, MOCVD, PLD and ALD. [4][5][6][7][10][11][12][13] The underlying growth mechanism towards the high-quality ZnO lms is also discussed in detail.…”