Grain size tuning of nanocrystalline chemical vapor deposited diamond by continuous electrical bias growth: Experimental and theoretical study

Abstract

In this work, a detailed structural and spectroscopic study of nanocrystalline diamond (NCD) thin films grown by a continuous bias assisted CVD growth technique is reported. This technique allows the tuning of grain size and phase purity in the deposited material. The crystalline properties of the films are characterized by SEM, TEM, EELS, and Raman spectroscopy. A clear improvement of the crystalline structure of the nanograined diamond film is observed for low negative bias voltages, while high bias voltages lead to thin films consisting of diamond grains of only ∼10 nm nanometer in size, showing remarkable similarities with so‐called ultrananocrystalline diamond. These layers arecharacterized by an increasing amount of sp2‐bonded carbon content of the matrix in which the diamond grains are embedded. Classical molecular dynamics simulations support the observed experimental data, giving insight in the underlying mechanism for the observed increase in deposition rate with bias voltage. Furthermore, a high atomic concentration of hydrogen has been determined in these films. Finally, Raman scattering analyses confirm that the Raman line observed at ∼1150 cm−1 cannot be attributed to trans‐poly‐acetylene, which continues to be reported in literature, reassigning it to a deformation mode of CHx bonds in NCD.

Origin of graphitic filaments on improving the electron field emission properties of negative bias-enhanced grown ultrananocrystalline diamond films in CH4/Ar plasma

“…[21][22][23][24][25][26] The application of negative bias voltage in CH 4 / H 2 plasma attracts the positively charged species, such as H þ , CH 3 þ , CH þ and expels the electrons that markedly alter the plasma chemistry near the substrates. [21][22][23][24][25][26] Shigesato et al 48 found that negative biasing increased the concentration of atomic hydrogen in the CH 4 /H 2 plasma and proposed that this could cause preferential etching of sp 2 -bonded C. On the other hand, Robertson et al 49 proposed that ion subplantation due to applied negative bias causes deposition of nanocrystalline graphitic C, and that diamond nucleates where the graphitic planes are locally oriented perpendicular to the surface. Zhong et al 25 described that during negative bias in CH 4 /H 2 plasma, the diamond grains were formed easier than on graphitic phases, so the diamond grains grow rapidly covering the graphitic phases, minimizing the influence of the nucleation sites of the graphitic phases on the subsequent growth process of the diamond grains.…”

“…A few earlier reports [21][22][23][24][25] observed that the application of bias voltage in the CH 4 /H 2 plasma-based microwave plasma enhanced CVD (MPECVD) process not only facilitated the growth of diamond, but also efficiently reduced the size of the grains, resulting in diamond films with nanosized granular structure. In addition, Teng et al 26 reported the enhanced EFE behavior of bias-enhanced grown (BEG) nanocrystalline diamond (NCD) films using CH 4 CH 4 /H 2 plasma and the feasibility of bias enhanced growth of UNCD films using CH 4 /Ar plasma has not been reported yet.…”

Ferromagnetism appears in nitrogen implanted nanocrystalline diamond films

“…The MW PECVD diamond films are purer than the natural diamond ones, because the extrinsically impure elements will be excluded from the composition except some inevitable hydrogencarbon contaminations. To be different in the polycrystalline diamond films, the grain size in the NCD films is below 100 m μ [10][11][12]. It is expected that plenty of boundaries existing in the films influence the electronic and optical properties as well [13][14][15].…”

Boron Doped Ultrananocrystalline Diamond Films on Porous Silicon: Morphological, Structural and Electrochemical Characterizations

“…They used Raman spectroscopy with different wavelengths and discussed the TPA decomposition at temperature lower than that for the film growth. In conclusion, the peak at 1150 cm -1 was attributed to the deformation mode of the CH x bond 26 . The X-ray diffraction patterns of the BDUND/PS electrodes are presented in Figure 5.…”