Interfacial structure and defect analysis of nonpolar ZnO films grown on R-plane sapphire by molecular beam epitaxy

Abstract

The interfacial relationship and the microstructure of nonpolar (11−20) ZnO films epitaxially grown on (1−102) R-plane sapphire by molecular beam epitaxy are investigated by transmission electron microscopy. The already-reported epitaxial relationships [1−100]ZnO∥[11−20]sapphire and ⟨0001⟩ZnO∥[−1101]sapphire are confirmed, and we have determined the orientation of the Zn–O (cation-anion) bond along [0001]ZnO in the films as being uniquely defined with respect to a reference surface Al–O bond on the sapphire substrate. The microstructure of the films is dominated by the presence of I1 basal stacking faults [density=(1–2)×105cm−1] and related partial dislocations [density=(4–7)×1010cm−2]. It is shown that I1 basal stacking faults correspond to dissociated perfect dislocations, either c or a+c type.

Investigation of initial growth and very thin () ZnO films by cross-sectional and plan-view transmission electron microscopy

“…The densities of TDs and SFs in the 30 nm thick ZnO film were estimated to be $1.8 Â 10 10 cm À2 and $1.2 Â 10 5 cm À1 , respectively. These densities of structural defects in our ZnO film are very similar to those of the previously reported thick ZnO films grown on r-plane sapphire substrates by MBE methods [26,27].…”

Structural property of m-plane ZnO epitaxial film grown on LaAlO3 (112) substrate

“…4(a), a representative XTEM image taken near zone axis [0001] with g ¼ 1 2 1 0 reveals that most of TDs have characteristics near a-type and appear as wiggle-like lines in mplane ZnO film unlike most of dislocations in polar GaN and ZnO which are often observed as straight lines [16][17][18][19]. The most unenergetically favorable a + c-type TDs can be dissociated into BSFs with the displacement vector of a=6o 20234 through the equivalent relation of a=3/112 3S ¼ a=6/202 3S þa=6/022 3S [20]. Therefore, a+ c-type TDs are rarely observed in non-polar ZnO epitaxial film.…”

Acceptor Type Vacancy Complexes In As-Grown ZnO

“…More information about the growth process can be found in ref. [4] for the asgrown MBE film, ref. [5] for the O irradiated and Al doped MBE films and ref.…”