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Dissertation
Deposition and characterization of diamond-like carbon, SiO₂, and their nanocomposite thin films by ion-assisted PECVD
Doctor of Philosophy (Ph.D.), Drexel University
1996
DOI:
https://doi.org/10.17918/00010131
Abstract
There has been much interest in depositing high quality thin films of diamond-like carbon (DLC) and silicon dioxide (SiO₂) at low temperatures for applications in wear-resistant coatings and microelectronics. In this work, the effects of reactor parameters on the structure, and properties of DLC, SiO₂, and their nanocomposite films are investigated. The films are deposited in a 13.56 MHz, rf power driven asymmetric reactor. In-situ impedance analysis is used to estimate the ion energy and flux at the substrate, while an on-line mass spectrometer (MS) and optical emission spectrometer (OES) are used to analyze plasma chemistry. The film structure is evaluated by a Raman spectrometer, a FTIR a Rutherford backscattering spectrometer (RBS), and an ellipsometer. In depositing DLC films, styrene (C₈H₈) is used as the source gas, while H₂ or Ar is used as the carrier gas. The impedance analysis shows that the ion energy flux (IEF) is linearly proportional to power/pressure ratio. The FTIR spectra of the deposited film indicate that CH₃* is likely to be the precursor for the DLC. The film structure reveals that the sp² carbon fraction, density, and refractive index of the film increase with increasing IEF, while the film's hydrogen content decreases. It appears that the IEF has a significant effect on the thermal stability and the optical band gap. For depositing SiO₂ films, tetraethylorthosilane (TEOS) is used as the source gas, while Ar and O₂ are used as carrier gases. The MS and OES results indicate that the decomposition of TEOS is enhanced as the power input is increased and that the role of O₂ is to oxidize the hydrocarbon molecules. It appears that high quality film close to thermal oxide can be obtained at relatively high IEF. It appears that the structure and properties of nanocomposite films are affected significantly by the gas flow rate ratio of the source gases. As the fraction of TEOS flow rate is increased, the refractive index, intrinsic stress, and graphitization decrease, while the transparency increases. The nanocomposite films show excellent adhesion on inorganic substrate, and thus relatively thick films (up to 5 [mu]m) can be deposited without delamination. Also, they exhibit comparable hardness to DLC films.
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Details
- Title
- Deposition and characterization of diamond-like carbon, SiO₂, and their nanocomposite thin films by ion-assisted PECVD
- Creators
- Junghwan Lee
- Contributors
- Young Hee Lee (Advisor) - Drexel University, Drexel University (1970-)
- Awarding Institution
- Drexel University
- Degree Awarded
- Doctor of Philosophy (Ph.D.)
- Publisher
- Drexel University; Philadelphia, Pennsylvania
- Number of pages
- xv, 209 pages
- Resource Type
- Dissertation
- Language
- English
- Academic Unit
- College of Engineering (1970-2026); Drexel University
- Other Identifier
- 991021889071404721