<i>Ab Initio</i>study of the mixed dimer formation in Ge growth on Si(100)

Ko, Young Jo; Park, Kang Ho; Ha, Jeong Sook; Yun, Wan Soo

doi:10.1103/physrevb.60.8158

Cited by 17 publications

(20 citation statements)

References 26 publications

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“…Our calculated barrier is slightly lower than that reported in Ref. 15 with a different xc functional and a less precise localization of the saddle point ͑E a = 1.4 versus 1.6 eV͒. As already noticed, this mechanism a͒ Present address: Department of Chemistry, Princeton University, Princeton, New Jersey 08544-1009. cannot contribute to intermixing at 330 K since its reaction rate is as low as ϳ 10 8 s −1 , as obtained from the Arrhenius relation = 0 exp͓−E a / ͑k B T͔͒, where 0 is set to the usual value of 10 THz.…”

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confidence: 42%

“…High-resolution photoemission data showed the formation of mixed SiGe dimers by depositing Ge on Si͑001͒ at 623 K, 13 while scanning tunneling microscopy measurements 14 revealed the formation of GeSi mixed dimers down to 330 K. Elementary processes leading to Si/ Ge intermixing have been theoretically investigated within density functional theory ͑DFT͒ as well. [15][16][17][18] An activation energy of 1.6 eV was calculated for a Si/ Ge exchange between the first and the second surface layer, 16 while exchanges between adatoms and surface atoms are predicted to have barriers of 1.6 eV ͓for Ge adatom on Si͑001͔͒ 15 or 1.5 eV ͓for Si adatom on Ge͑001͔͒. 16 Starting from a stable ad-dimer, intermixing with surface atoms would occur with calculated activation energies of 1.2 eV for a SiGe turning into a SiSi or 1.4 eV for the reverse mechanism.…”

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confidence: 99%

“…The overall activation energy E a is ϳ0.8 eV, i.e., almost half of the values reported so far in the literature for isolatedadatom exchanges. 15,16 By using the Arrhenius relation for T = 330 K, one finds an average exchange time of −1 = ex ϳ 0.1 s. Would a Ge adatom remain isolated for a time exceeding ex during deposition, then intermixing could take place; otherwise, dimers can form. To further address this issue, we follow the approach presented in Ref.…”

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First principles study of Ge∕Si exchange mechanisms at the Si(001) surface

Zipoli

Cereda

Ceriotti

et al. 2008

Applied Physics Letters

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Based on density functional theory calculations, we show that an isolated Ge adatom on Si͑001͒ triggers an exchange mechanism involving three atoms, which leads to the formation of a Si adatom and a mixed SiGe surface dimer. The activation energy calculated from first principles is sufficiently low ͑0.8 eV͒ to make such a process viable down to the lowest temperature ͑330 K͒ at which intermixing was reported. A second mechanism, with a higher barrier, is also proposed and shown to possibly contribute to the incorporation of Ge into deeper layers as experimentally observed at higher temperatures. © 2008 American Institute of Physics. ͓DOI: 10.1063/1.2926683͔ Deposition of Ge on Si leads to a wealth of interesting phenomena of great technological relevance. Both flat Gerich films and three-dimensional ͑3D͒ structures grown in the Stransky-Krastanow regime have been extensively studied and exploited for present and next-generation microelectronics devices.1,2 In these systems, Ge/ Si intermixing has been soon recognized as a key factor, since it affects the formation of sharp interfaces, 3 the release of strain behind the formation, stability, and evolution of 3D Ge islands, 4-10 and the reconstruction of wetting layers. 11,12Although Ge would tend to segregate at the surface due to its lower surface energy, entropy would lead to Si/ Ge intermixing also in a Ge capping layer on Si. To which extent thermodynamic equilibrium would be reached during heterostructures growth is still a matter of debate. High-resolution photoemission data showed the formation of mixed SiGe dimers by depositing Ge on Si͑001͒ at 623 K, 13 while scanning tunneling microscopy measurements 14 revealed the formation of GeSi mixed dimers down to 330 K. Elementary processes leading to Si/ Ge intermixing have been theoretically investigated within density functional theory ͑DFT͒ as well.15-18 An activation energy of 1.6 eV was calculated for a Si/ Ge exchange between the first and the second surface layer, 16 while exchanges between adatoms and surface atoms are predicted to have barriers of 1.6 eV ͓for Ge adatom on Si͑001͔͒ 15 or 1.5 eV ͓for Si adatom on Ge͑001͔͒. 16 Starting from a stable ad-dimer, intermixing with surface atoms would occur with calculated activation energies of 1.2 eV for a SiGe turning into a SiSi or 1.4 eV for the reverse mechanism. 18 Clearly, activation energies in the range of 1.4-1.6 eV ͑Ref. 19͒ are incompatible with intermixing at 330 K as reported in Ref. 14.In this letter, based on DFT calculations, we shall show that isolated Ge adatoms on Si͑001͒ are able to trigger exchange processes through a three-atom mechanism down to the lowest temperature ͑330 K͒ at which intermixing was observed.14 By combining our results with previously reported ones, we show that theory and experiments seem to be in good agreement for a wide set of observed phenomena. Spin unrestricted calculations were performed with gradient corrected exchange and correlation ͑xc͒ functional, 20 plane waves expansion of Kohn-Sham orbitals up to an ener...

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First principles study of Ge∕Si exchange mechanisms at the Si(001) surface

Zipoli

Cereda

Ceriotti

et al. 2008

Applied Physics Letters

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“…In this paper, we discuss how such simulations are performed, including elementary events such as deposition, as well as adatom and ad-dimer diffusion and taking into account the known anisotropy produced by the reconstruction of the Si (100) surface [4]. Importantly, studies [5][6][7] have also indicated that there is intermixing in the layers adjacent to the interface so that the Si-Ge interface. We have also included two inter-mixing mechanisms to account for this.…”

Section: Introductionmentioning

confidence: 99%

Kinetic Monte-Carlo simulations of germanium epitaxial growth on silicon

Akis

Ferry

2006

J Comput Electron

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We present Kinetic Lattice Monte Carlo (KLMC) simulations of Ge deposition onto a reconstructed Si (100) surface. In addition to the anisotropy brought on by surface reconstruction, we take into account the role of the exchange of Ge with Si atoms in the substrate and how it effects the interface between the materials. One method of controlling the resulting structures from the growth process is to use a pre-patterned substrate. We present results where the initial structure is a grid pattern. The KLMC simulations in this case yield Ge-Si stripes, that result largely from the anisotropy generated from the surface reconstruction.

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“…6,17,[21][22][23][24][25] It is now established experimentally and theoretically that Ge can mix with the surface dimers at room temperature, and that deep intermixing to the third and fourth atomic layers occurs at temperatures of 773 K and higher. Calculations also showed kinetic paths for Si/Ge exchange at the (105) surface.…”

Section: 4mentioning

confidence: 99%