Hetero-epitaxy of Γ-Al2O3 on Si by Pulsed Laser Deposition
1
Yuanxun Liao1, Santosh Shrestha1, Shujuan Huang1, Gavin Conibeer1, Stephen Bremner1
School of Photovoltaic and Renewable Energy Engineering, UNSW Australia, Sydney, Australia, 2052
Précis- The hetero-epitaxy of γ-Al2O3 on Si (111) substrates by pulsed laser deposition is achieved. A 13nm thick high
quality single crystal γ-Al2O3 has been identified with high resolution XRD, with γ-Al2O3 (222) // Si (111). High
resolution transmission electron microscopy (TEM) shows the atom arrangements of the epitaxial film agree well with
the cubic spinel structure of γ-Al2O3. This work shows PLD is an effective way to grow hetero-epitaxial γ-Al2O3 on Si
which could be used as virtue substrates for III-V materials and for diversified device purposes.
Γ-Al2O3 is an important crystal phase of Al2O3, which has been explored for diversified purposes such as virtual substrates
for III-V materials and Si, and electronic devices. Its importance relies on the fact that it is the first stable crystal phase of
Al2O3 which can be grown at relatively low temperatures. Besides, it has superior properties, such as high dielectric constant
(9.1), good film qualities, and stable thermal properties, comparing with similar materials like SiO2. Different ways to grow
epitaxial γ-Al2O3 film on Si have been tried, for example molecular beam epitaxy, metal-organic chemical vapour deposition,
e-beam evaporation, sputtering, and ion-beam deposition. Though PLD has been employed to grow amorphous or polycrystalline Al2O3 [1], the hetero-epitaxy of Al2O3 on Si by pulsed laser deposition (PLD) has not been reported. In this paper,
the hetero-epitaxy of γ-Al2O3 on Si (111) substrates by using PLD is achieved.
Fig 1 illustrates the single-crystal X-ray theta two-theta scan along substrate surface of Si (111) on a 13nm thick Al2O3 film
achieved by 200mJ 2Hz laser. Aside from the strong peaks of Si substrate: (111), (3/2 3/2 3/2) and (222), a small peak near 40°
coincides with the (222) reflection of the cubic gamma phase of Al2O3 [2]. The broadness of the peak is caused by the thin
thickness of the oxide films.
Correspondingly, as shown in Fig 2, epitaxial γ-Al2O3 layer of 58nm thickness have been achieved. To the author’s
knowledge, this is the thickest epitaxial γ-Al2O3 on Si reported with TEM so far, a strong support to the effectiveness of PLD
to grow γ-Al2O3 on Si.
Fig. 1. High resolution XRD along Si (111) surface of a
13nm thick γ-Al2O3 film.
Fig. 2. TEM of hetero-epitaxial γ-Al2O3 on Si of thickness
58nm.
[1]
[2]
R.Serna, M. J. de Castro, J. A.Chaos, C. N. Afonso, I. Vickridge, “The role of Er3+-Er3+ separation on the luminescence of Er-doped Al2O3 films
prepared by pulsed laser deposition”, Appl Phys Lett 75, (26), 4073-4075 (1999).
S. Y. Wu, M. Hong, A. R.Kortan, J.Kwo, J. P. Mannaerts, W. C. Lee, Y. L. Huang , “High-quality thin single-crystal gamma-Al2O3 films grown on Si
(111)”, Appl Phys Lett 87, (9) (2005).