Chemical-etch-assisted growth of epitaxial zinc oxide
ABSTRACT We use real-time spectroscopic polarimetric observations of growth and a chemical model derived therefrom, to develop a method of growing dense, two-dimensional zinc oxide epitaxially on sapphire by metalorganic chemical vapor deposition. Particulate zinc oxide formed in the gas phase is used to advantage as the deposition source. Our real-time data provide unequivocal evidence that: a seed layer is required; unwanted fractions of ZnO are deposited; but these fractions can be removed by cycling between brief periods of net deposition and etching. The transition between deposition and etching occurs with zinc precursor concentrations that only differ by 13%. These processes are understood by considering the chemistry involved. Comment: 9 pages, 5 figures
- Journal of Modern Optics - J MOD OPTIC. 01/1976; 23(10):841-842.
Article: Atomic processes in crystal growth[show abstract] [hide abstract]
ABSTRACT: The thermodynamic and kinetic processes which are involved in the early stages of crystal growth are discussed, with especial reference to vapor deposition of thin films. The atomic processes taking place during deposition are described in terms of rate and diffusion equations; the concept of “competitive capture” is outlined, where adatoms are forced to choose between competing sinks. The use of microscopy and surface physics techniques to study nucleation in films is emphasised. Examples of island (Volmer-Weber), layer (Frank-van der Merwe) and layer plus island (Stranski-Krastanov) growth in metal/insulator, metal/semi-conductor and semiconductor/semiconductor deposition systems are given.Surface Science 01/1994; · 1.84 Impact Factor
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ABSTRACT: Wurtzitic ZnO is a wide-bandgap (3.437 eV at 2 K) semiconductor which has many applications, such as piezoelectric transducers, varistors, phosphors, and transparent conducting films. Most of these applications require only polycrystalline material; however, recent successes in producing large-area single crystals have opened up the possibility of producing blue and UV light emitters, and high-temperature, high-power transistors. The main advantages of ZnO as a light emitter are its large exciton binding energy (60 meV), and the existence of well-developed bulk and epitaxial growth processes; for electronic applications, its attractiveness lies in having high breakdown strength and high saturation velocity. Optical UV lasing, at both low and high temperatures, has already been demonstrated, although efficient electrical lasing must await the further development of good, p-type material. ZnO is also much more resistant to radiation damage than are other common semiconductor materials, such as Si, GaAs, CdS, and even GaN; thus, it should be useful for space applications.Materials Science and Engineering: B. 01/2001;