Dissertation / PhD Thesis

PreJuSER-44172

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Electron Spin Resonance and Transient Photocurrent Measurements on Microcrystalline Silicon

Dylla, T. (Corresponding author)FZJ*

2004
Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag Jülich

Please use a persistent id in citations: http://hdl.handle.net/2128/530

Abstract: The electronic properties of microcrystalline silicon (μc-Si:H) films have been studied using electron spin resonance (ESR), transient photocurrent time-of-flight (TOF) techniques, and electrical conductivity measurements. Structural properties were determined by Raman spectroscopy. A wide range of structure compositions, from highly crystalline films with no discernable amorphous content, to predominantly amorphous films with no crystalline phase contributions, was investigated. Models and possible explanations concerning the nature and energetic distribution of electronic defects as a function of film composition are discussed. It is shown that the spin density N$_{S}$ in μc-Si:H films is linked strongly to the structure composition of the material. The highest N$_{S}$ is always found for material with the highest crystalline volume fraction. With increasing amorphous content, N$_{S}$ decreases, which is attributed to increasing hydrogen content and improved termination of dangling bonds. Moreover, the amorphous phase content, incorporated between the crystalline columns, appears to act as a passivation layer, leading to more effective termination of unsatisfied bonds at the column boundaries. Both reversible and irreversible changes in the ESR signal and dark conductivity due to atmospheric effects are found in μc-Si:H. These are closely connected to the structure composition, in particular the active surface area. The porous structure of highly crystalline material facilitates in-diffusion of atmospheric gases, which strongly affects the character and/or density of surface states. Two contributing processes have been identified, namely adsorption and oxidation. Both processes lead to an increase of N$_{S}$. In the case of adsorption the increase is identified as arising from changes of the db2 resonance (g=2.0052), while the intensity of the db1 resonance (g=2.0043) remains constant. With increasing amorphous content the magnitude of both adsorption and oxidation induced changes decreases, which may be linked to the greater compactness of such films. Measurements on n-type μc-Si:H films were used as a probe of the density of gap states, confirming that the spin density NS is related to the density of defects. The results confirm that for a wide range of structural compositions, the doping induced Fermi level shift in μc-Si:H is governed by compensation of defect states, [...]

Note: Record converted from VDB: 12.11.2012
Note: Freie Universität Berlin, Diss., 2004

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Contributing Institute(s):

1. Institut für Photovoltaik (IPV)

Research Program(s):

1. Photovoltaik (E02)

Appears in the scientific report 2004

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Database coverage:

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