Self-Texture in the Initial Stages of ZnO Film Growth

Abstract

X-ray absorption spectroscopy has been used to investigate the self-texture of ZnO films grown on Si(100) (lattice-mismatched substrate) by single-source chemical vapor deposition (SS-CVD) using Zn 4 O(acetate) 6 as precursor. For this system nonepitaxial growth of polycrystalline, c-axis oriented films can be controlled by addition of a water ambient during the deposition for a large variety of substrates. Angle dependent near edge X-ray absorption fine structure spectroscopy (NEXAFS) was used to study the orientation of the adsorbent molecules as a function of both water ambient used during the deposition and film thickness. The onset of self-structuring under optimum growth conditions (highest water pressure, P H 2 O ) 5 × 10 -4 mbar) is found to occur at film thicknesses on the order of 50 Å. The role of the water ambient during the film deposition is discussed using a kinetic model in which lattice stabilization due to filling of oxygen vacancies promotes the film crystallization. The model is used to explain the measured changes in the atomic environment of the oxygen atoms in the deposited ZnO films with variation in ambient water used. The interfacial restrictions in nonepitaxial CVD film growth are discussed. Our results indicate that in addition to structural restrictions due to lattice mismatch the chemical reactivity of the substrate material clearly must be considered.

Zno-based thin films synthesized by atmospheric pressure mist chemical vapor deposition

“…(2) did not exhibit any signs of crystallinity and were found to contain high levels (410 at%) of residual carbon contamination [25], and that films produced in the way of Eq. (3) were only nonstoichiometric ZnO 1Àx layers also with high levels of carbon contamination [38]. Therefore, H 2 O is very necessary in the synthesis process to obtain good-quality ZnO.…”

Chemical and structural characterization of thin films using electrons and photons

“…Films have been grown on a range of substrates and it has been found that the crystallographic quality is largely independent of the substrate (for more details, see Ref. 43). The ZnO films are of columnar structure and Fig.…”

“…Is there a transition layer? Figure 7 shows two O 1s NEXAFS measurements 43 for a c-axis-oriented ZnO film with a thickness of ¾150 nm. The measurement involved detection of the total electron yield and was performed for two orientations of the synchrotron polarization with respect to the sample surface.…”

“…(probably amorphous), which would explain why selftexturing appears to be independent of the structure of a (lattice-mismatch) substrate. 43 For clean lattice-match substrates, additional epitaxial forces have to be taken into account. The (111) surface of silicon has an almost perfect lattice match with cubic (111)-oriented ZnS.…”

Synthesis and Isomerisation Reactions of Tetranuclear and Octanuclear (Carbamato)zinc Complexes

“…However, ideal single-source behaviour was only observed with the (carbamato)zinc complex [Zn 4 (µ 4 -O)(O 2 CNEt 2 ) 6 ], [12] as the other precursors required additional oxygen sources to suppress the formation of high-carbon amorphous ZnO. [16] This singular behaviour of [Zn 4 (µ 4 -O)(O 2 CNEt 2 ) 6 ] may be due to the lability of the C-N bond of the diethylcarbamato ligand, [11] which may permit a facile decomposition pathway not available in the other complexes.…”