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. 2016 Jul 11:6:29444.
doi: 10.1038/srep29444.

Enhanced optoelectronic performances of vertically aligned hexagonal boron nitride nanowalls-nanocrystalline diamond heterostructures

Kamatchi Jothiramalingam Sankaran  1   2 , Duc Quang Hoang  1   2 , Srinivasu Kunuku  3 , Svetlana Korneychuk  4 , Stuart Turner  4 , Paulius Pobedinskas  1   2 , Sien Drijkoningen  1   2 , Marlies K Van Bael  1   2 , Jan D' Haen  1   2 , Johan Verbeeck  4 , Keh-Chyang Leou  3 , I-Nan Lin  5 , Ken Haenen  1   2
Affiliations

Enhanced optoelectronic performances of vertically aligned hexagonal boron nitride nanowalls-nanocrystalline diamond heterostructures

Kamatchi Jothiramalingam Sankaran et al. Sci Rep. .

Abstract

Field electron emission (FEE) properties of vertically aligned hexagonal boron nitride nanowalls (hBNNWs) grown on Si have been markedly enhanced through the use of nitrogen doped nanocrystalline diamond (nNCD) films as an interlayer. The FEE properties of hBNNWs-nNCD heterostructures show a low turn-on field of 15.2 V/μm, a high FEE current density of 1.48 mA/cm(2) and life-time up to a period of 248 min. These values are far superior to those for hBNNWs grown on Si substrates without the nNCD interlayer, which have a turn-on field of 46.6 V/μm with 0.21 mA/cm(2) FEE current density and life-time of 27 min. Cross-sectional TEM investigation reveals that the utilization of the diamond interlayer circumvented the formation of amorphous boron nitride prior to the growth of hexagonal boron nitride. Moreover, incorporation of carbon in hBNNWs improves the conductivity of hBNNWs. Such a unique combination of materials results in efficient electron transport crossing nNCD-to-hBNNWs interface and inside the hBNNWs that results in enhanced field emission of electrons. The prospective application of these materials is manifested by plasma illumination measurements with lower threshold voltage (370 V) and longer life-time, authorizing the role of hBNNWs-nNCD heterostructures in the enhancement of electron emission.

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Figures

Figure 1
Figure 1
The plane view SEM micrographs of (a) NCD films, (b) hBNNWs-NCD, (c) nNCD films and (d) hBNNWs-nNCD. (e) micro-Raman spectra for I. NCD films, II. hBNNWs-NCD, III. nNCD films and IV. hBNNWs-nNCD.
Figure 2
Figure 2. FTIR spectra for I. hBNNWs-Si, II. hBNNWs-NCD and III. hBNNWs-nNCD.
FTIR transmission spectra were undertaken vertically to the film surface in the range frequency of 400–4000 cm−1 with a resolution of 2.0 cm−1.
Figure 3
Figure 3
(a) The field electron emission properties (Je-E curves) and (b) the current density versus time curves of I. hBNNWs-Si, II. hBNNWs-NCD, III. hBNNWs-nNCD. The inset in “a” shows the corresponding Fowler-Nordheim plots. (c) The plasma current density versus applied voltage with the inset showing the plasma illumination stability, the life-time, of the microplasma cavities, which were fabricated using I. hBNNWs-Si, II. hBNNWs-NCD and III. hBNNWs-nNCD as cathode materials.
Figure 4
Figure 4. A cross-sectional HRTEM image with bright field cross-sectional TEM image as inset of hBNNWs-Si.
These micrographs show the presence of aBN and tBN sequentially prior to the growth of hBN phase when the hBNNWs were grown directly on Si substrates.
Figure 5
Figure 5
(a) Cross-sectional ADF-STEM image of the hBNNWs-NCD heterostructure. (b) High resolution ADF-STEM image of the NCD/hBN interface. The FT pattern from region A evidences the crystalline nature of the hBN, displaying the (002) reflection. The diamond particle is imaged along the [011] zone axis, as evidenced by the FT pattern taken from region B.
Figure 6
Figure 6
(a) ADF-STEM micrograph of the hBNNWs-NCD interface together with EELS elemental maps for carbon, boron and nitrogen taken from the region indicated by the white rectangle (b) Summed EELS core-loss spectra taken from the diamond and hBN regions in the maps in (a). A significant carbon incorporation into the hBN is evidenced by the carbon map (arrows) and the strong amorphous carbon peak in the EELS spectrum taken from the hBN region.
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