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Phase transition on the Si(001) clean surface prepared in UHV MBE chamber: a study by high-resolution STM and in situ RHEED.

Arapkina LV, Yuryev VA, Chizh KV, Shevlyuga VM, Storojevyh MS, Krylova LA - Nanoscale Res Lett (2011)

Bottom Line: A fraction of the surface area covered by the c(8 × 8) structure decreased, as the sample cooling rate was reduced.A model of the c(8 × 8) structure formation has been built on the basis of the STM data.Origin of the high-order structure on the Si(001) surface and its connection with the epinucleation phenomenon are discussed.PACS 68.35.B-·68.37.Ef·68.49.Jk·68.47.Fg.

View Article: PubMed Central - HTML - PubMed

Affiliation: A, M, Prokhorov General Physics Institute of RAS, 38 Vavilov Street, Moscow, 119991, Russia. arapkina@kapella.gpi.ru.

ABSTRACT
The Si(001) surface deoxidized by short annealing at T ~ 925°C in the ultrahigh vacuum molecuar beam epitaxy chamber has been in situ investigated using high-resolution scanning tunneling microscopy (STM)and redegreesected high-energy electron diffraction (RHEED. RHEED patterns corresponding to (2 × 1) and (4 × 4) structures were observed during sample treatment. The (4 × 4) reconstruction arose at T ≲ 600°C after annealing. The reconstruction was observed to be reversible: the (4 × 4) structure turned into the (2 × 1) one at T ≳ 600°C, the (4 × 4) structure appeared again at recurring cooling. The c(8 × 8) reconstruction was revealed by STM at room temperature on the same samples. A fraction of the surface area covered by the c(8 × 8) structure decreased, as the sample cooling rate was reduced. The (2 × 1) structure was observed on the surface free of the c(8 × 8) one. The c(8 × 8) structure has been evidenced to manifest itself as the (4 × 4) one in the RHEED patterns. A model of the c(8 × 8) structure formation has been built on the basis of the STM data. Origin of the high-order structure on the Si(001) surface and its connection with the epinucleation phenomenon are discussed.PACS 68.35.B-·68.37.Ef·68.49.Jk·68.47.Fg.

No MeSH data available.


The Si(001)-c(8 × 8) surface reciprocal lattice.
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Figure 10: The Si(001)-c(8 × 8) surface reciprocal lattice.

Mentions: Now we shall explain the observed discrepancy of results obtained by STM and RHEED within the proposed model. Figure 10 presents a sketch of the reciprocal lattice of c(8 ×8). The RHEED patterns obtained in the [110] azimuth correspond to the c(8 × 8) structure; the patterns observed in the [010] azimuth do not (Figure 4). The reason for this discrepancy may be understood from the filled-state STM image which corresponds to the electron density distribution of electrons paired in covalent bond of a Si-Si dimer. Figure 11 compares STM images of the same region on one terrace obtained in the empty-state (a) and filled-state (b) modes; insets show their Fourier transforms, the differences in which for the two STM modes are as follows: in the Fourier transform of the filled-state image, reflexes corresponding to the distance of 8a are absent in the [110] and [] directions, whereas the reflexes corresponding to 4a and 2a are present (it should be noticed that the image itself resembles that of the (4 × 4) reconstructed surface). If an empty-state image is not available, then it might be concluded that the (4 × 4) structure is arranged on the surface. An explanation of this observation is simple. Main contribution to the STM image is made by ad-dimers situated on the sides of the "rectangles", i.e., on tops of the underlying dimer rows. According to calculations made, e.g., in refs. [44,45], dimers located in such a way are closer to the STM tip and appear in the images to be brighter than those situated in the troughs. Hence, it may be concluded that the RHEED (4 × 4) pattern results from electron diffraction on the extreme dimers of the "rectangles" forming the c(8 × 8) surface structure.


Phase transition on the Si(001) clean surface prepared in UHV MBE chamber: a study by high-resolution STM and in situ RHEED.

Arapkina LV, Yuryev VA, Chizh KV, Shevlyuga VM, Storojevyh MS, Krylova LA - Nanoscale Res Lett (2011)

The Si(001)-c(8 × 8) surface reciprocal lattice.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211275&req=5

Figure 10: The Si(001)-c(8 × 8) surface reciprocal lattice.
Mentions: Now we shall explain the observed discrepancy of results obtained by STM and RHEED within the proposed model. Figure 10 presents a sketch of the reciprocal lattice of c(8 ×8). The RHEED patterns obtained in the [110] azimuth correspond to the c(8 × 8) structure; the patterns observed in the [010] azimuth do not (Figure 4). The reason for this discrepancy may be understood from the filled-state STM image which corresponds to the electron density distribution of electrons paired in covalent bond of a Si-Si dimer. Figure 11 compares STM images of the same region on one terrace obtained in the empty-state (a) and filled-state (b) modes; insets show their Fourier transforms, the differences in which for the two STM modes are as follows: in the Fourier transform of the filled-state image, reflexes corresponding to the distance of 8a are absent in the [110] and [] directions, whereas the reflexes corresponding to 4a and 2a are present (it should be noticed that the image itself resembles that of the (4 × 4) reconstructed surface). If an empty-state image is not available, then it might be concluded that the (4 × 4) structure is arranged on the surface. An explanation of this observation is simple. Main contribution to the STM image is made by ad-dimers situated on the sides of the "rectangles", i.e., on tops of the underlying dimer rows. According to calculations made, e.g., in refs. [44,45], dimers located in such a way are closer to the STM tip and appear in the images to be brighter than those situated in the troughs. Hence, it may be concluded that the RHEED (4 × 4) pattern results from electron diffraction on the extreme dimers of the "rectangles" forming the c(8 × 8) surface structure.

Bottom Line: A fraction of the surface area covered by the c(8 × 8) structure decreased, as the sample cooling rate was reduced.A model of the c(8 × 8) structure formation has been built on the basis of the STM data.Origin of the high-order structure on the Si(001) surface and its connection with the epinucleation phenomenon are discussed.PACS 68.35.B-·68.37.Ef·68.49.Jk·68.47.Fg.

View Article: PubMed Central - HTML - PubMed

Affiliation: A, M, Prokhorov General Physics Institute of RAS, 38 Vavilov Street, Moscow, 119991, Russia. arapkina@kapella.gpi.ru.

ABSTRACT
The Si(001) surface deoxidized by short annealing at T ~ 925°C in the ultrahigh vacuum molecuar beam epitaxy chamber has been in situ investigated using high-resolution scanning tunneling microscopy (STM)and redegreesected high-energy electron diffraction (RHEED. RHEED patterns corresponding to (2 × 1) and (4 × 4) structures were observed during sample treatment. The (4 × 4) reconstruction arose at T ≲ 600°C after annealing. The reconstruction was observed to be reversible: the (4 × 4) structure turned into the (2 × 1) one at T ≳ 600°C, the (4 × 4) structure appeared again at recurring cooling. The c(8 × 8) reconstruction was revealed by STM at room temperature on the same samples. A fraction of the surface area covered by the c(8 × 8) structure decreased, as the sample cooling rate was reduced. The (2 × 1) structure was observed on the surface free of the c(8 × 8) one. The c(8 × 8) structure has been evidenced to manifest itself as the (4 × 4) one in the RHEED patterns. A model of the c(8 × 8) structure formation has been built on the basis of the STM data. Origin of the high-order structure on the Si(001) surface and its connection with the epinucleation phenomenon are discussed.PACS 68.35.B-·68.37.Ef·68.49.Jk·68.47.Fg.

No MeSH data available.