Chemical and structural study of electrically passivating Al2O3/Si interfaces prepared by atomic layer deposition
(Color online) High-resolution XPS spectra of the Si 2 p photoelectron peak (after background substraction) at blank Si substrates after HF dip, without further treatment (black, solid line) and after standard annealing step (blue, dashed line).
(Color online) Raw XPS spectra in the energy range of Si 2 p and Al 2 p, acquired at samples with 15 (black, solid line) and 30 (blue, dashed line) ALD cycles without subsequent annealing.
(Color online) Atomic ratio O/Al (black solid squares), the theoretical limit value expected for stoichiometric bulk Al2O3 (dashed horizontal line), and the relative Si signal (blue open circles) as functions of the ALD cycle number for as-grown (a), and annealed (b) Al2O3 samples. Two growth regimes are identified and separated by the vertical dashed line.
(Color online) Calculated atomic excess O fraction for both as-grown (squares) and annealed (triangles) samples as a function of the ALD cycle number [according to Eq. (1)]; the open symbols represent similar calculations for an in situ annealing experiment at an extra sample with 25 ALD cycles.
(Color online) Chemical shift of the Si 2p oxide peak with respect to the Si(0) 2p 3/2 peak as a function of the ALD cycle number for as-grown Al2O3 samples (solid symbols) and after annealing (open symbols), measured for different sample tilt angles; the chemical shift corresponds to the degree of O coordination of Si.
Fraction of SiO x peak area [after Eq. (3)] measured in situ as a function of the slowly increased temperature (constant rate of +0.5 °C/min) at a sample prepared with 25 ALD cycles on HF dipped Si substrate; smoothed data were calculated over 50 points by the Savitzky–Golay method.
(Color online) Model for the chemical structure near the Al2O3–Si interface: (1) before ALD, (2) during ALD cycling, and (3) after ALD and annealing step.
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