Growth of Nanostructured Diamond Films on Glass Substrates by Low-Temperature Microwave Plasma-Enhanced Chemical Vapor Deposition for Applications in Nanotribology

Abstract

Low-temperature fabrication of superior nano-/microcrystalline diamond (NCD/MCD) films is a major thrust in diamond technology. The widely used seeding techniques applied on the substrate surface are usually harsh, lead to defect formation, and suffer from the lack of reproducibility in maintaining homogeneity and uniformity over nano-/microdimensions. Low-temperature growth of a significant diamond phase on purely untreated glass substrates is indeed a challenging task. Using CO2 as the supplementary gas-phase constituent included in the (CH4 + H2)-plasma and a specific shadow-mask assembly to generate the diffuse plasma environment above the growth zone, the present experiment succeeds in the spontaneous growth of nanocrystalline diamond (NCD), including microcrystalline diamond (MCD) of an average crystal size of ∼0.9–1.2 μm at ∼300 °C on glass substrates, without any seeding pretreatment. In the plasma, the shadow mask establishes a virtual remote plasma configuration in setting the diffuse plasma, protects the growth surface from a direct bombardment of energetic ions, generates negative self-bias on the substrate, and, importantly, promotes significant gas-phase nucleation dominant over typical solid-state nucleation. The incubation of diamond embryo clusters onto the untreated glass substrates under the shadow-mask structure and its growth evolution through the efficient transport of the preferential carbonaceous precursors proceed within the diffuse plasma. In the course of network modification under the diffuse plasma, atomic O remains instrumental for efficient etching of the a-C overlayer on a diamond embryo and atomic H, with its small physical dimension, conveniently penetrates within the diamond network and promotes crystallization via transferring its moderate chemical energy to the diamond lattice. The low-temperature-grown nanostructured diamond films are up-and-coming for applications in nanotribology.

Recent Progress of Nanodiamond Film in Controllable Fabrication and Field Emission Properties

“…Moreover, the microwave plasma (MW) CVD is widely used to synthesize ND films on various chemically dissimilar surface substrates owing to the relatively low growth temperature, which utilizes the microwave energy to heat and decompose the gas molecules in the cavity into reactive groups, then finally obtain a high-quality ND film [ 65 , 66 , 67 , 68 , 69 , 70 ]. For example, Cheng C.Y.…”

“…et al prepared the ND films and microdiamond films via a MW plasmas method in Figure 3 a. Additionally, it was suggested that the growth quality of ND film was restricted by the substrate surface pretreatment condition (scratching and seeding) rather than gas-phase condition [ 69 ]. Das D. et al successfully synthesized the ND films and even microdiamond films on glass substrates at the temperature of ∼300 °C using CO 2 /CH 4 /H 2 and provided a specific shadow-mask assembly to promote the nucleation of the diamond species and the diffusion growth of the nano-/micro diamond network on the untreated glass substrates, as shown in Figure 3 b [ 70 ]. The CO 2 was introduced as the supplementary gas to eliminate the amorphous carbon component in the synthesized nano-microdiamond.…”

“…The growth parameters using CVD with different energy source are summarized in Table 1 . It can be concluded that the obtained ND films from various CVD method are normally grown in a H 2 -rich, carbon-containing gas-lean mixture atmosphere under growth substrate temperature from 250 °C to 1200 °C [ 59 , 62 , 64 , 69 , 70 , 71 , 72 , 73 , 74 , 75 ]. Presumably the higher ratio of CH 4 in H 2 , the more non-diamond carbon incorporation quantity, and the smaller grain size of ND particle in ND film.…”

“…( a ) The SEM images of microdiamond film and ND films, and the corresponding variation of the samples as functions of substrate temperature and gas composition [ 69 ]. ( b ) Schematic diagram of the active plasma zone and the growth process of the low-temperature nano-/microcrystalline diamond growth [ 70 ]. ( c ) The formation evolution process and the CV scans of the ND film [ 71 ].…”

Application of Nano-Crystalline Diamond in Tribology

“…This research has provided new ideas for wear-resistant coatings on steel alloys. At the same time, NCD film was successfully synthesized by Das et al [ 105 ] on an untreated glass substrate through spontaneous growth at low temperatures (~300 °C), providing a new method for the preparation of NCD films for nano-tribological application. During the deposition, CO 2 was used as a supplemental gas phase in the (CH 4 + H 2 ) plasma.…”