Defect Studies in Thin-Film SiO<sub>2</sub> of a Metal-Oxide-Silicon Capacitor Using Drift-Assisted Positron Annihilation Lifetime Spectroscopy

Defect Studies in Thin-Film SiO<sub>2</sub> of a Metal-Oxide-Silicon Capacitor Using Drift-Assisted Positron Annihilation Lifetime Spectroscopy

This work investigates the impact of an internal electric field on the annihilation characteristics of positrons implanted in a <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>180</mn><m...

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Main Authors: Ricardo Helm, Werner Egger, Catherine Corbel, Peter Sperr, Maik Butterling, Andreas Wagner, Maciej Oskar Liedke, Johannes Mitteneder, Michael Mayerhofer, Kangho Lee, Georg S. Duesberg, Günther Dollinger, Marcel Dickmann
Format: Article
Language:English
Published: MDPI AG 2025-07-01
Series:Nanomaterials
Subjects:
drift-enhanced positron annihilation lifetime spectroscopy
thin-films
interface defects
positronium formation
positron drift
Online Access:https://www.mdpi.com/2079-4991/15/15/1142
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Summary:This work investigates the impact of an internal electric field on the annihilation characteristics of positrons implanted in a <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>180</mn><mo>(</mo><mn>10</mn><mo>)</mo><mspace width="3.33333pt"></mspace><mi>nm</mi></mrow></semantics></math></inline-formula> SiO<sub>2</sub> layer of a Metal-Oxide-Silicon (MOS) capacitor, using Positron Annihilation Lifetime Spectroscopy (PALS). By varying the gate voltage, electric fields up to <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>1.72</mn><mspace width="3.33333pt"></mspace><mrow><mi>MV</mi><mo>/</mo><mi>cm</mi></mrow></mrow></semantics></math></inline-formula> were applied. The measurements reveal a field-dependent suppression of positronium (Ps) formation by up to <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>64</mn><mo>%</mo></mrow></semantics></math></inline-formula>, leading to an enhancement of free positron annihilation. The increase in free positrons suggests that vacancy clusters are the dominant defect type in the oxide layer. Additionally, drift towards the SiO<sub>2</sub>/Si interface reveals not only larger void-like defects but also a distinct population of smaller traps that are less prominent when drifting to the Al/SiO<sub>2</sub> interface. In total, by combining positron drift with PALS, more detailed insights into the nature and spatial distribution of defects within the SiO<sub>2</sub> network and in particular near the SiO<sub>2</sub>/Si interface are obtained.
ISSN:2079-4991

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