Role of Confinement on Diffusion Barriers in Semiconductor Nanocrystals

Chan, Tzu-Liang; Zayak, Alexey T.; Dalpian, Gustavo M.; Chelikowsky, James R.

doi:10.1103/physrevlett.102.025901

Cited by 28 publications

(35 citation statements)

References 26 publications

(28 reference statements)

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“…This result suggests that solubility of dopants increase by reducing the semiconductor size, at least down to the investigated size (d ≈ 4 nm). This is in striking contrast to theoretical models predicting self-purification phenomena, 5,[37][38][39]49 and experiments far from equilibrium. 15,31,32,47,48 It is worth considering that all the calculations predicting the P solubility in Si NCs consider H-termination of the nanostructures, and they consequently suggest a decrease of the solubility with decreasing cluster size.…”

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confidence: 88%

“…Seminal work by Chelikowsky's group showed evidence of B and P segregation at the surface of H-terminated Si NCs and proposed the occurrence of a self-purification mechanism in NCs with d < 2 nm. 13,[37][38][39] Recently several authors have unambiguously demonstrated that this result cannot be transferred to O-terminated Si NCs: if the SiO 2 matrix is taken into account, incorporated P has a minimum of binding energy in the inner part or in the sub-interface region of the Si nanoclusters, suggesting the possibility to stably incorporate impurities within the Si NCs. However, a consensus on the effective binding energy values is still lacking with theoretical prediction ranging from 1 to 4 eV.…”

Section: Introductionmentioning

confidence: 99%

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Thermodynamic stability of high phosphorus concentration in silicon nanostructures

Perego¹,

Seguini²,

Arduca

et al. 2015

Nanoscale

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Doping of Si nanocrystals (NCs) has been the subject of a strong experimental and theoretical debate for more than a decade. A major difficulty in the understanding of dopant incorporation at the nanoscale is related to the fact that theoretical calculations usually refer to thermodynamic equilibrium conditions, whereas, from the experimental point of view, impurity incorporation is commonly performed during NC formation. This latter circumstance makes impossible to experimentally decouple equilibrium properties from kinetic effects. In this report, we approach the problem by introducing the dopants into the Si NCs, from a spatially separated dopant source. We induce a P diffusion flux to interact with the already-formed and stable Si NCs embedded in SiO 2 , maintaining the system very close to the thermodynamic equilibrium. Combining advanced material synthesis, multi-technique experimental quantification and simulations of diffusion profiles with a rate-equation model, we demonstrate that a high P concentration (above the P solid solubility in bulk Si) within Si NCs embedded in a SiO 2 matrix corresponds to an equilibrium property of the system. Trapping within the Si NCs embedded in a SiO 2 matrix is essentially diffusion limited with no additional energy barrier, whereas de-trapping is prevented by a binding energy of 0.9 eV, in excellent agreement with recent theoretical findings that highlighted the impact of different surface terminations (H-or O-terminated NCs) on the stability of the incorporated P atoms.

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confidence: 88%

Section: Introductionmentioning

confidence: 99%

Thermodynamic stability of high phosphorus concentration in silicon nanostructures

Perego¹,

Seguini²,

Arduca

et al. 2015

Nanoscale

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“…8,9 Real space configurations are not computationally biased and can form a complete set. 21 Furthermore partially periodic systems such as films or wires can also be solved with one or two dimensional periodicity. Crystalline systems can be solved with 3D periodicity, while localized systems can be solved naturally with no artificial periodicity introduced.…”

Section: Introductionmentioning

confidence: 99%

High order forces and nonlocal operators in a Kohn–Sham Hamiltonian

Bobbitt

Schofield

Lena

et al. 2015

Phys. Chem. Chem. Phys.

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Real space pseudopotentials have a number of advantages in solving for the electronic structure of materials. These advantages include ease of implementation, implementation on highly parallel systems, and great flexibility for describing partially periodic systems. One limitation of this approach, shared by other electronic structure methods, is the slow convergence of interatomic forces when compared to total energies. For real space methods, this requires a fine grid to converge a solution of the Kohn-Sham problem, which is accompanied by concurrent increase in memory and additional matrix-vector multiplications. Here we introduce a method to expedite the computation of interatomic forces by employing a high order integration technique. We demonstrate the usefulness of this technique by calculating accurate bond lengths and vibrational frequencies for molecules and nanocrystals without using fine real space grids.

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“…2(d), we found that the diffusion barrier decreases when starting from the T C site, but increases when starting from the T A , for instance, the diffusion barrier is lower for T C1 to T A1 sites than that for T A1 to T C2 sites. The Zn interstitial is more stable in the T A site than in the T C site, similar to the case of Zn interstitial in the II-VI semiconductors2829. After overcoming a large barrier crossing surface-to-inner region, it can be inferred that Zn interstitial can reach the interface.…”

Section: Resultsmentioning

confidence: 55%

Remote p-type Doping in GaSb/InAs Core-shell Nanowires

Feng

Tang

Zhang

et al. 2015

Sci Rep

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By performing first-principles calculation, we investigated the electronic properties of remotely p-type doping GaSb nanowire by a Zn-doped InAs shell. The results show that for bare zinc-blende (ZB) [111] GaSb/InAs core-shell nanowire the Zn p-type doped InAs shell donates free holes to the non-doped GaSb core nanowire without activation energy, significantly increasing the hole density and mobility of nanowire. For Zn doping in bare ZB [110] GaSb/InAs core-shell nanowire the hole states are compensated by surface states. We also studied the behaviors of remote p-type doing in two-dimensional (2D) GaSb/InAs heterogeneous slabs, and confirmed that the orientation of nanowire side facet is a key factor for achieving high efficient remote p-type doping.

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Role of Confinement on Diffusion Barriers in Semiconductor Nanocrystals

Cited by 28 publications

References 26 publications

Thermodynamic stability of high phosphorus concentration in silicon nanostructures

Thermodynamic stability of high phosphorus concentration in silicon nanostructures

High order forces and nonlocal operators in a Kohn–Sham Hamiltonian

Remote p-type Doping in GaSb/InAs Core-shell Nanowires

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