Chemical vapor deposition of ZnO epitaxial films on sapphire

Abstract

A chemical vapor deposition system for the growth of epitaxial (112̄0) ZnO films on (011̄2) sapphire, employing the reaction of zinc vapor and carbon dioxide, was investigated. Growth rates as high as 30 μm/h at a substrate temperature of 700-750 °C were achieved. Films grown on substrates with thin presputtered layers exhibited smooth surfaces and improved crystal perfection as determined by SEM, reflection electron diffraction, and acoustic evaluation. Films had high resistivity which eventually degraded on exposure to atmosphere. Surface acoustic wave interdigital transducers were fabricated on lithium-diffused films, and the electromechanical coupling coefficient of 1.39% was measured for a film thickness to wavelength ratio of 0.13.

A comprehensive review of ZnO materials and devices

“…The growth of ZnO thin films has been studied for acoustical and optical devices because of their excellent piezoelectric properties and a tendency to grow with strong ͑0001͒ preferential orientation on various kinds of substrates, including glass, 149 sapphire, 150 and diamond. 151 The early reports dealt with deposition of ZnO utilizing growth techniques such as magnetron sputtering 151,152 and chemicalvapor deposition; [153][154][155] however, the films were mainly polycrystalline. Later attempts led to high-quality ZnO single-crystal films prepared by rf magnetron sputtering 156 and other growth techniques allowing a fine control over the deposition procedure, such as molecular-beam epitaxy ͑MBE͒, 157,158 pulsed-laser deposition ͑PLD͒, 159 metalorganic chemical-vapor deposition ͑MOCVD͒, 160 and hydride or halide vapor-phase epitaxy ͑HVPE͒.…”

“…One of the most popular growth techniques for early ZnO investigations was sputtering ͑dc sputtering, rf magnetron sputtering, and reactive sputtering͒. As compared to sol gel and chemical-vapor deposition, [153][154][155] the magnetron sputtering was a preferred method because of its low cost, simplicity, and low operating temperature. 188 ZnO films grow at a certain substrate temperature by sputtering from a high-purity ZnO target using a rf magnetron sputter system.…”

Preparation and properties of ZnO and devices

“…Early growth experiments with magnetron sputtering [39,41], and chemical vapor deposition (CVD) [42][43][44] led to polycrystalline films. Later attempts led to high quality ZnO single-crystal films prepared by RF magnetron sputtering [45] and methods such as molecular beam expitaxy (MBE) [46,47], pulsed laser deposition (PLD) [48], metal-organic CVD (MOCVD) [49], and hydride or halide vapor phase epitaxy (HVPE) [50,51].…”

ZnO thin films and light-emitting diodes

“…One of the most popular growth techniques for early ZnO investigations was sputtering (dc sputtering, rf magnetron sputtering and reactive sputtering). As compared with solgel and chemical vapour deposition [26][27][28], magnetron sputtering was a preferred method because of its low cost, simplicity and low operating temperature [29]. Figure 1 shows schematically the essential arrangements for rf sputtering with a capacitive, parallel-plate discharge.…”