Growth Mechanism and Structural Characterization of Nano-crystalline Diamond (NCD) and Micro-crystalline Diamond (MCD) Films Deposited on Silicon Substrates
12 Dec 2017-pp 511-515
TL;DR: In this paper, diamond thin films were deposited using hot filament chemical vapour deposition (HFCVD) technique on Si substrate, which is typically classified into nano-crystalline diamond (NCD; grain size 500 nm) based on their grain size.
Abstract: In this work, diamond thin films were deposited using hot filament chemical vapour deposition (HFCVD) technique on Si substrate. Diamond films are typically classified into nano-crystalline diamond (NCD; grain size 500 nm) based on their grain size. Process parameters such as the ratio of methane and hydrogen concentration (%CH4/H2) and chamber pressure were varied to grow MCD and NCD films. NCD and MCD films will be used as substrate to improve the performance of MEMS resonator. Structural characteristics and quality of the MCD and NCD films were confirmed using Raman spectroscopy and the surface features were imaged using high resolution scanning electron microscopy (HRSEM).
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TL;DR: The visible Raman spectra of poor quality chemical-vapor-deposited diamond is often used as the signature of nanocrystalline diamond as mentioned in this paper, which is not the case for sp-bonded diamond.
Abstract: The peak near 1150 cm 21 in the visible Raman spectra of poor quality chemical-vapor-deposited diamond is often used as the signature of nanocrystalline diamond. We argue that this peak should not be assigned to nanocrystalline diamond or other sp-bonded phases. Its wave number disperses with excitation energy, its intensity decreases with increasing excitation energy, and it is always accompanied by another peak near 1450 cm, which acts similarly. This behavior is that expected for sp-bonded configurations, with their smaller band gap. The peaks are assigned to transpolyacetylene segments at grain boundaries and surfaces.
1,115 citations
TL;DR: In this paper, the synthesis of nanocrystalline diamond films from carbon-containing noble gas plasmas is described, which is the result of new growth and nucleation mechanisms, which involve the insertion of C2, carbon dimer, into carbon-carbon and carbon-hydrogen bonds, resulting in hetereogeneous nucleation rates on the order 1010 cm−2 s−1.
Abstract: ▪ Abstract The synthesis of nanocrystalline diamond films from carbon-containing noble gas plasmas is described. The nanocrystallinity is the result of new growth and nucleation mechanisms, which involve the insertion of C2, carbon dimer, into carbon-carbon and carbon-hydrogen bonds, resulting in hetereogeneous nucleation rates on the order 1010 cm−2 s−1. Extensive characterization studies led to the conclusion that phase-pure diamond is produced with a microstructure consisting of randomly oriented 3–15-nm crystallites. By adjusting the noble gas/hydrogen ratio in the gas mixture, a continuous transition from micro- to nanocrystallinity is achieved. Up to 10% of the total carbon in the nanocrystalline films is located at 2 to 4 atom-wide grain boundaries. Because the grain boundary carbon is π-bonded, the mechanical, electrical, and optical properties of nanocrystalline diamond are profoundly altered. Nanocrystalline diamond films are unique new materials with applications in fields as diverse as tribolo...
858 citations
198 citations
TL;DR: In this article, a three-dimensional computer model was used to calculate the gas phase composition for the experimental conditions at all positions within the reactor, and the observed film morphology, growth rate, and across-sample uniformity can be rationalized using a model based on competition between H atoms, CH3 radicals, and other C1 radical species reacting with dangling bonds on the surface.
Abstract: Ar∕CH4∕H2 gas mixtures have been used to deposit microcrystalline diamond, nanocrystalline diamond, and ultrananocrystalline diamond films using hot filament chemical vapor deposition. A three-dimensional computer model was used to calculate the gas phase composition for the experimental conditions at all positions within the reactor. Using the experimental and calculated data, we show that the observed film morphology, growth rate, and across-sample uniformity can be rationalized using a model based on competition between H atoms, CH3 radicals, and other C1 radical species reacting with dangling bonds on the surface. Proposed formulas for growth rate and average crystal size are tested on both our own and published experimental data for Ar∕CH4∕H2 and conventional 1% CH4∕H2 mixtures, respectively.
122 citations
TL;DR: In this article, the fundamental and applied science performed to understand key aspects of UNCD and NCD films, including the nucleation and growth, tribomechanical properties, electronic properties, and applied studies on integration with piezoelectric materials and CMOS technology.
Abstract: There has been a tireless quest by the designers of micro- and nanoelectro mechanical systems (MEMS/NEMS) to find a suitable material alternative to conventional silicon. This is needed to develop robust, reliable, and long-endurance MEMS/NEMS with capabilities for working under demanding conditions, including harsh environments, high stresses, or with contacting and sliding surfaces. Diamond is one of the most promising candidates for this because of its superior physical, chemical, and tribomechanical properties. Ultrananocrystalline diamond (UNCD) and nanocrystalline diamond (NCD) thin films, the two most studied forms of diamond films in the last decade, have distinct growth processes and nanostructures but complementary properties. This article reviews the fundamental and applied science performed to understand key aspects of UNCD and NCD films, including the nucleation and growth, tribomechanical properties, electronic properties, and applied studies on integration with piezoelectric materials and CMOS technology. Several emerging diamond-based MEMS/NEMS applications, including high-frequency resonators, radio frequency MEMS and photonic switches, and the first commercial diamond MEMS product—monolithic diamond atomic force microscopy probes—are discussed.
119 citations