Photoluminescence properties and local structure of polymer-like a-C:H films

Journal Article · Sun Jan 30 04:00:00 EST 2000 · International Journal of Modern Physics B

DOI:https://doi.org/10.1142/S0217979200000273· OSTI ID:20023270

Godet, C; Heitz, T; Bouree, J E

In order to understand better the electronic properties of {pi}-bonded materials, some optical and photoluminescence properties of amorphous carbon films have been investigated as a function of film density (0.9 to 1.7 g.cm{sup {minus}3}). This study gives an overview of the radiative recombination properties in relation with local structure characterizations (in situ infrared ellipsometry and Raman spectroscopies) for a series of dual-plasma deposited polymer-like a-C:H films. Medium range topology has consequences in the hyperconjugation effects seen on infrared bands, as well as in optical and resonant Raman characteristics. Photoluminescence (PL) excitation spectroscopy reveals resonance features which are attributed to exciton-like electron-hole pairs in close Coulomb interaction. The PL efficiency shows a sharp quenching for densities above 1.3 g.cm{sup {minus}3} where a clear transition also occurs in the Raman fingerprint. In addition, quantitative analysis of IR ellipsometry and Elastic Recoil Detection give evidence of a strong decrease of both the effective dynamical charge e*(C-H) and the bandwidth of sp{sup 3} C-H vibrations; this is interpreted as being a result of the increase of local strains in the carbon skeleton, meaning that matrix distortions already appear at H content values as high as 46 H at.% due to film densification. An expected consequence is the mixing between {pi} and {sigma} molecular orbitals and the enhancement of the dissociation rate of confined electron-hole pairs. PL quenching would thus result from both a decrease of exciton confinement and an increase of the density of accessible nonradiative centers.

• Research Organization: Ecole Polytechnique, Palaiseau (FR)
• OSTI ID: 20023270
• Journal Information: International Journal of Modern Physics B, Journal Name: International Journal of Modern Physics B Journal Issue: 2-3 Vol. 14; ISSN IJPBEV; ISSN 0217-9792
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
AMORPHOUS STATE
CARBON
ELECTRICAL PROPERTIES
MICROSTRUCTURE
OPTICAL PROPERTIES
PHOTOLUMINESCENCE