The Effect of Boron Doping Level on The Morphology and Structure of Ultra/Nanocrystalline Diamond Films

Abstract

In this work, boron-doped nanocrystalline diamond (BDND) films are grown on silicon substrates by hot-filament (HF)CVD in Ar/H 2 /CH 4 gas mixtures. In this study, the transition from ultra-nanocrystalline to nanocrystalline diamond films is clearly shown by the addition of boron dopant to the growth of the gas mixture. The doping process consists of an additional H 2 line passing through a bubbler containing B 2 O 3 dissolved in methanol with various B/C ratios. Five sample sets are obtained with doping in the methanol bubbler solution of 2 000, 5 000, 10 000, 20 000, and 30 000 ppm for a 16 h growth time. The morphology, roughness, and structure of these films have markedly different properties. The cross-section of the films is characterized by scanning electron microscopy (SEM) showing the transition from ultra-nanocrystalline growth (renucleation process) to a columnar structure of nanocrystalline films. The acceptor density values, evaluated by Raman spectra and by Mott-Schottky plot analysis, vary from 10 20 to 10 21 B cm À3 as the doping level increases. The grain size and the relative intensity of the (111)/ (220) peaks are obtained from X-ray diffraction (XRD) patterns of the films. The diamond average grain size increases from 10 to 35 nm for films with 2 000 and 30 000 ppm B/C, respectively, in the methanol bubbler solution. The preferential orientation also changes, from (220) to (111), as the boron doping level increases.

Contactless Photoconductance Study on Undoped and Doped Nanocrystalline Diamond Films

“…The peaks observed at 1135 and 1475 cm –1 for undoped NCD and peaks 1150 and 1477 cm –1 for B-NCD (i.e., peaks i and iii in both cases) correspond to the C–H vibration modes, which also have been reported previously in these kind of films . The broad hump around 1550 cm –1 for undoped NCD (peak iv), 1600 cm –1 for B-NCD (peak iv) and 1550 cm –1 for P-NCD (peak i) are attributed to sp 2 -bonded carbon, which is predominantly expected to be present at the grain boundaries. , Finally, the peak observed at 1220 cm –1 for B-NCD film (peak v) can be ascribed to boron doping. , …”

“…30,31 Finally, the peak observed at 1220 cm −1 for B-NCD film (peak v) can be ascribed to boron doping. 32,33 To further characterize the surface of NCD films, we carried out XPS valence band measurements. Figure 4 are linked to H 1s orbitals, (ii) a peak around ∼12 eV that corresponds to the valence band derived from the 2s−2p hybridized levels of the diamond, (iii) a peak around ∼17 eV related to the 2s level of the diamond and (iv) a low-intensity peak around ∼25 eV, which is ascribed to the photoemission from O 2s.…”

Investigation of Boron Doped Nanocrystalline Diamond Films Grown on Porous Silicon Substrate under Different Doping Concentrations

“…This result is consistent with the conclusions obtained with the Raman spectra analysis. The difference in the films thickness may be related to the growth rate, which tends to decrease as the doping level increases, as also observed by Souza et al [22]. This occurs because boron affects the nucleus formation during the first step of growth.…”

“…Oxygen is known to lead to potential chemical reactions with species in the gas phase and to the consumption of some carbon and boron species, which usually reduces the diamond growth rate. Besides, as the oxygen concentration increases, the growth rate decreases because defective sites can be formed on graphitic carbon layers, which are potential nucleation sites [22]. Issaoui et al [23] have also reported that the addition of a small amount of oxygen (0.25%) with boron can drastically change the growth rates in the different crystallographic directions.…”

First adhesion measurements of conductive ultrananocrystalline diamond MEMS sidewalls

“…The conductivity of diamond is obtained via incorporation of nitrogen into the grain boundaries (N-UNCD) or substitutional doping with boron, that sits into the diamond crystal lattice (B-UNCD) [5], [6]. It has been reported by Sumant et al [7] that the work of adhesion between two undoped UNCD surfaces is (59.2 ± 2.0) mJ/m 2 and decreases to (10.2 ± 0.4) mJ/m 2 , if the diamond is previously treated with hydrogen plasma.…”