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Thickness-Dependent Relative Dielectric Constant of Organic Ultrathin Films
Caterina Summonte1, Francesco Borgatti2, Cristiano Albonetti2
1Consiglio Nazionale delle Ricerche - Istituto per la Microelettronica e Microsistemi (CNR-IMM), Via Gobetti 101, 40129, Bologna, Italy.
Summary
The dielectric constant of organic semiconductor films is crucial for device analysis. This study reveals its thickness-dependent behavior, highlighting a morphological influence on dielectric properties, especially near interfaces.
Area of Science:
- Materials Science
- Organic Electronics
- Surface Science
Background:
- The relative dielectric constant of organic semiconductor films is a fundamental parameter for analyzing organic electronic devices.
- This parameter is often assumed rather than measured, particularly for ultrathin films composed of discrete molecular layers.
Purpose of the Study:
- To investigate the relative dielectric constant of ultrathin organic semiconductor films.
- To understand the relationship between film morphology and dielectric properties.
Main Methods:
- Spectroscopy Ellipsometry
- Scanning Capacitance Microscopy
- Study of thin films made of N,N'-bis(n-octyl)-x:y,dicyanoperylene-3,4:9,10-bis(dicarboximide)
Main Results:
- The relative dielectric constant shows a non-monotonic trend with thickness, starting at 2.1 for a single molecular layer and saturating at 3.2 for thicker films.
- The dielectric constant reaches its bulk value around the third to fourth molecular layer, coinciding with a transition from 2D (Frank-Van der Merwe) to 3D (Volmer-Weber) growth.
- Molecular configuration changes from edge-on to a bent/distorted geometry as thickness increases.
Conclusions:
- The dielectric constant of organic films is morphologically dependent, particularly near the substrate interface.
- This dependence diminishes with increasing distance from the substrate.
- Accurate dielectric constant measurement is essential for interpreting organic electronic device performance.
Keywords:
Molecular layersMorphologyOrganic growthScanning capacitance microscopySpectroscopy ellipsometryUltrathin filmMore Related Videos
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