Self‐diffusion in silicon – Change of a paradigm

Seeger, A.

doi:10.1002/pssb.201147002

Cited by 4 publications

(7 citation statements)

References 17 publications

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“…The activation energy of selfdiffusion is commonly larger (E d ∼ 4.8 eV) in clean silicon, but it can be reduced to ∼3 eV due to the presence of O 2 interstitials (in particular at the c-Si/SiO 2 interface). The injection of O 2 interstitials into Si is a well-known effect resulting from the thermal oxidation of Si [44].…”

Section: Resultsmentioning

confidence: 99%

The kinetics of dewetting ultra-thin Si layers from silicon dioxide

et al. 2012

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Section: Resultsmentioning

confidence: 99%

The kinetics of dewetting ultra-thin Si layers from silicon dioxide

et al. 2012

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“…A rough upper limit on the number of atoms in the defect is N < S self,I /s f , where s f is its formation entropy per atom and the inequality applies because S self,I includes both formation and migration entropy. Applying this to Seeger's 'liquid drop' model of an extended point defect [1], s f would be the entropy of fusion, 3.6 k/atom, resulting in a value of N < 8. This is too small to behave like a bulk liquid as confined liquids become solid-like [19], with much lower entropy and internal energy per atom.…”

Section: T (°C)mentioning

confidence: 99%

“…Similarly to the case of Si, where E λ = −0.5 eV [13] and E barrier < 0.05 eV [14], recent experiments in Ge in the temperature range T > 0.65 T m yield E λ in the range −0.8 eV [7] to −0.6 eV [8] with E barrier ≈ 0 eV [7][8][9]. Using equation (1) above this implies E self,I − E BI ≈ 1.2 to 1.6 eV, and since E BI ≈ 4.65 eV [6], we find E self,I ≈ 5.85 to 6.25 eV. This is nearly 2 eV higher than predicted from first principles [15], and more than 1 eV higher than E self,I in Si [16].…”

mentioning

confidence: 99%

Extended Point Defects in Crystalline Materials: Ge and Si

et al. 2013

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B diffusion measurements are used to probe the basic nature of self-interstitial 'point' defects in Ge. We find two distinct self-interstitial forms -a simple one with low entropy and a complex one with entropy ~30 k at the migration saddle point. The latter dominates diffusion at high temperature. We propose that its structure is similar to that of an amorphous pocket -we name it a morph. Computational modelling suggests that morphs exist in both self-interstitial and vacancy-like forms, and are crucial for diffusion and defect dynamics in Ge, Si and probably many other crystalline solids.A vast array of crystalline material properties arises from the behavior of atomic-scale 'point'defects, yet these defects are poorly understood. Knowledge of simple point defects -single atoms added interstitially to, or missing from, an otherwise undisturbed lattice -is well established from quantum theoretical calculations and low-temperature experiments, but diffusion experiments hint that more complex entities may be involved at high temperatures relevant to industrial processing [1][2][3][4][5]. This Letter provides the first definitive evidence for these elusive complex defects and presents a specific physical model for their structure and diffusion. 2 Recent interest in Ge-based nano-electronics has led to basic studies on diffusion [5][6][7][8][9] and implantation defects [10,11] in crystalline Ge. Most dopants in Ge are found to diffuse by vacancy mechanisms, with activation energies below that of vacancy-mediated self-diffusion (≈ 3.1 eV), but boron diffusion is an exception with an activation energy of ≈ 4.65 eV [6,12].Experiments [5,[7][8][9] show that boron diffuses via the reaction B + I  BI, where 'B' represents substitutional boron, 'I' the self interstitial, and 'BI' a mobile dopant-interstitial complex. The energetics involved is illustrated in Figure 1.The reduction in free energy on forming BI enables it to migrate a mean projected distance λ before dissociating to B and I. The mean number of jumps before dissociation depends on the energy difference between migration and dissociation of BI and the diffusional entropies of I and BI. In general,A is the impurity (here, boron), X the point defect driving AX diffusion (here, I), a the capture radius for the forward reaction, f AX the diffusion correlation factor (~1), E AX , S AX , E self,X , S self,X the activation energies and entropies of impurity diffusion and self-diffusion via the species AX and Fig. 1. Schematic of total energy versus configuration for the reaction mediating B diffusion in Ge. Also shown are energies inferred from previous experiments. E BI and E self,I are the respective energies of BI and I at their migration saddle points, relative to that of substitutional B. Under RED conditions (dashed curve) the fitted values of E λ shift 0.025 eV in the negative direction. This could be accounted for by a reduction of 0.05 eV in the migration energy of BI under H irradiation. T (°C)4To test this idea we have repeated the experiments...

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“…It has been established that oxidation enhanced diffusion of dopants in Si is tied to both point defects and crystallographic orientation. 44,45 If point defects play a role in Si diffusion in SiGe, 22,38,46 then it is likely that any oxidation enhanced diffusion of Si in SiGe due to point defects is also orientation dependent. By virtue of the dependence of the Ge condensation on the diffusivity of Si in SiGe, 26,27 any orientation dependence in the latter will have a direct consequence on the Ge content at the oxidation interface.…”

Section: Introductionmentioning

confidence: 99%

Nano-structuring in SiGe by oxidation induced anisotropic Ge self-organization

Long

Galeckas

Kuznetsov

et al. 2013

Journal of Applied Physics

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The present study examines the kinetics of dry thermal oxidation of (111), (110), and (100) silicon-germanium (SiGe) thin epitaxial films and the redistribution of Ge near the oxidation interface with the aim of facilitating construction of single and multi-layered nano-structures. By employing a series of multiple and single step oxidations, it is shown that the paramount parameter controlling the Ge content at the oxidation interface is the oxidation temperature. The oxidation temperature may be set such that the Ge content at the oxidation interface is increased, kept static, or decreased. The Ge content at the oxidation interface is modeled by considering the balance between Si diffusion in SiGe and the flux of Si into the oxide by formation of SiO 2. The diffusivity of Si in SiGe under oxidation is determined for the three principal crystal orientations by combining the proposed empirical model with data from X-ray diffraction and variable angle spectroscopic ellipsometry. The orientation dependence of the oxidation rate of SiGe was found to follow the order: ð111Þ > ð110Þ > ð100Þ. The role of crystal orientation, Ge content, and other factors in the oxidation kinetics of SiGe versus Si are analyzed and discussed in terms of relative oxidation rates. V

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Self‐diffusion in silicon – Change of a paradigm

Cited by 4 publications

References 17 publications

The kinetics of dewetting ultra-thin Si layers from silicon dioxide

The kinetics of dewetting ultra-thin Si layers from silicon dioxide

Extended Point Defects in Crystalline Materials: Ge and Si

Nano-structuring in SiGe by oxidation induced anisotropic Ge self-organization

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