Short Pulse Laser Production of Diamond Thin Films
The use of diamond thin films has the potential for major impact in many industrial and scientific applications. These include heat sinks for electronics, broadband optical sensors, windows, cutting tools, optical coatings, laser diodes, cold cathodes, and field emission displays. Attractive properties of natural diamond consist of physical hardness, high tensile yield strength, chemical inertness, low coefficient of friction, high thermal conductivity, and low electrical conductivity. Unfortunately, these properties are not completely realized in currently produced diamond thin films. Chemical vapor deposition, in its many forms, has been the most successful to this point in producing crystalline diamond films microns to millimeters in thickness which are made up of closely packed diamond crystals microns in physical dimension. However, high purity films are difficult to realize due to the use of hydrogen in the growth process which becomes included in the film matrix. These impurities are manifest in film physical properties which are inferior to those of pure crystalline diamond. In addition, the large density of grain boundaries due to the polycrystalline nature of the films reduce the films' diamond-like character. Finally, substrates must be heated to several hundred degrees Celsius which is not suitable for many materials. Pulsed laser deposition is attractive due to its ability to produce high purity films-limited only by the purity of the target. For diamond film production, high purity carbon can be ablated directly by lasers and deposited as thin films at ambient temperatures. However, lasers currently in use generally deliver long (>10 ns) pulses, and the generally explosive nature of laser ablation, in addition to the desired single-atom or single-ion carbon, liberates significant amounts of carbon clusters (C{sub n} where n=2-30) and macroscopic particles (> 1-10 pm) of carbon. These carbon particles interrupt the ordered deposition of crystalline diamond, forming undesirable grain boundaries and rough surfaces that are difficult to polish. In addition, PLD generated films tend to be ''amorphous'' or nanocrystalline with no observable long-range order, but still possessing physical properties which are diamond-like in some approximation. This has given rise to the term ''diamond-like carbon'' when referring to these PLD-produced, amorphous carbon films. Growth rates for PLD have been prohibitively slow until recently with the advent of high average power, high rep-rate lasers.
- Research Organization:
- Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
- Sponsoring Organization:
- USDOE Office of Defense Programs (DP) (US)
- DOE Contract Number:
- W-7405-Eng-48
- OSTI ID:
- 802091
- Report Number(s):
- UCRL-ID-130327; TRN: US200223%%725
- Resource Relation:
- Other Information: PBD: 20 Mar 1998
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
99 GENERAL AND MISCELLANEOUS//MATHEMATICS, COMPUTING, AND INFORMATION SCIENCE
AMBIENT TEMPERATURE
CHEMICAL VAPOR DEPOSITION
CUTTING TOOLS
DIAMONDS
ELECTRIC CONDUCTIVITY
FIELD EMISSION
GRAIN BOUNDARIES
HEAT SINKS
LASERS
PHYSICAL PROPERTIES
PRODUCTION
THERMAL CONDUCTIVITY
THIN FILMS
YIELD STRENGTH