Nanostructure of hydrogenated amorphous silicon (a-Si:H) films studied by nuclear magnetic resonance

Furman, G. B.; Panich, A. M.; Xia, Yang

doi:10.1016/j.jmr.2023.107434

Cited by 3 publications

(10 citation statements)

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“…For gas or liquid entrapped in a nanopore with sizes less than 1 m the Hamiltonian of a spin system can be averaged over the random motion of molecules [14][15][16][17][18][19][20][21][22]. The averaged Hamiltonian describing the dipole-dipole (DD) interaction in the magnetic field 0 H along the zaxis ( 0 Hz ) is given by [27,28]:…”

Section: Echo Decay In a Single Nanoporementioning

confidence: 99%

“…In our previous works, we studied the relaxation processes in molecules that are entrapped in nano-sized cavities (nanopores) of the materials [14][15][16][17][18][19][20][21][22]. We have demonstrated that the parameters of nanostructures can be extracted from the angular dependence of the relaxation times T1, T1ρ, and T2.…”

Section: Introductionmentioning

confidence: 99%

“…We have demonstrated that the parameters of nanostructures can be extracted from the angular dependence of the relaxation times T1, T1ρ, and T2. To explain in detail the anisotropy of the relaxation times for liquid and gas entrapped in nanopores that have a characteristic size up to hundreds of nanometers, the model considered the restricted random motion of molecules at averaging the spin Hamiltonian [14][15][16][17][18][19][20][21][22].…”

Section: Introductionmentioning

confidence: 99%

“…It was shown [16][17][18][19][20][21][22] that the averaged Hamiltonian which describes the dipole-dipole interactions in the nanopores can be characterized by an effective coupling constant. Averaging the spatial part of the dipolar Hamiltonian, we developed the models which describe very nontrivial spin dynamics and allow us to obtain analytical expressions for the relaxation times T1, T1ρ, and T2.…”

Section: Introductionmentioning

confidence: 99%

“…Usually, a relaxation time is determined using one-or two-exponential functions for fitting experimental data [25,26]. It was shown [14][15][16][17][18][19][20][21][22] that the nanostructure of nanoporous materials can be analyzed using the angular dependence of the relaxation time obtained by a simple fitting of experimental data for a sample, that is put at different angles relative to an applied magnetic field. The fitting by one-or two-exponential functions is more problematic for nanoporous samples where the measured signal is formed by a superposition of signals from a set of nanopores with different orientations, volumes, etc.…”

Section: Introductionmentioning

confidence: 99%

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Мulticomponents of spin-spin relaxation, anisotropy of the echo decay, and nanoporous sample structure

Aptekarev

Furman

Panich

et al. 2023

Preprint

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We have experimentally and theoretically investigated multicomponent 1H nuclear magnetic resonance (NMR) echo decays in a-Si:H films containing anisotropic nanopores, in which randomly moving hydrogen molecules are entrapped. The experimental results are interpreted within the framework of the previously developed theory, in which a nanoporous material is represented as a set of nanopores containing liquid or gas, and the relaxation rate is determined by the dipole–dipole spin interaction, considering the restricted motion of molecules inside the pores. Previously, such characteristics of a nanostructure as the average volume of pores and their orientation distribution were determined from the angular dependences of the spin–spin and spin–lattice relaxation times. We propose a new approach to the analysis of the NMR signal, the main advantage of which is the possibility of obtaining nanostructure parameters from a single decay of the echo signal. In this case, there is no need to analyze the anisotropy of the relaxation time T2, the determination of which is a rather complicated problem in multicomponent decays. Despite multicomponent signals, the fitting parameter associated with the size and shape of nanopores is determined quite accurately. This made it possible to determine the size and shape of nanopores in a-Si:H films, herewith our estimates are in good agreement with the results obtained by other methods. The fitting of the decays also provides information about the nanostructure of the sample, such as the standard deviations of the angular distribution of pores and the polar and azimuthal angles of the average direction of the pore axes relative to the sample axis, with reasonable accuracy. The approach makes it possible to quantitatively determine the parameters of the non-spherical nanoporous structure from NMR data in a non-destructive manner.

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