Controlled Al-Doped Single-Crystalline 6H-SiC Nanowires

Abstract

We report for the first time the synthesis of Al-doped 6H-SiC nanowires with high yield and high quality. The nanowires were obtained by the catalyst-assisted pyrolysis of polymeric precursors with FeCl2 as the catalyst. The doping concentrations were controlled by tailoring the Al concentrations in the precursors. It was observed that the Al dopants caused red-shifts of the photoluminescence bands. The results suggest a simple technique to synthesize Al-doped SiC nanomaterials in a controlled manner. The obtained nanowires could be useful for making optical and electronic nanodevices.

SiC nanowires: material and devices

“…The authors have compared the spectrum with the corresponding one of bulk 6H-SiC and they have concluded that, the lattice parameters of the nanowires decrease without mentioning any quantitative result. The same conclusion has been obtained in [43], although the change in angle was of the order of 0.1º. This is attributed to a large incorporation of the big Al ions in substitutional sites of SiC resulting in a strained crystal and in a lattice constant change.…”

“…The diameters of the NWs thin ends are about 10-30 nm, while their thick ends range from tens of nanometers to more than 100 nm, depending on their lengths (maximum 1 μm). In a subsequent study, Gao et al [43] reported the synthesis of Al-doped 6H-SiC, [10 1 2 ]-oriented, nanowires 150-300 nm in diameter by catalyst-assisted (FeCl 2 ) pyrolysis of polymeric precursors. Wei et al [44] succeeded also to obtain 6H-SiC, [10 1 0 ]-oriented, NWs but with a lower diameter of 5-200 nm and a length of tens to hundreds of micrometers by using microwave heating of a xerogel containing Si and C precursors as well as nano-Al powders.…”

“…For the formation of 6H-SiC nanowires, the VLS [42,44] and the SLS [43] mechanisms have been proposed. However, only in one case [42], Fe alloy particles have been found on the tips of the NWs probably due to the fact that a purification process has been performed in the two other studies after the NW growth and prior to physical characterization.…”

“…Figure 4 shows typical SEM photos from the different categories of NW shapes. NWs are either straight mostly aligned towards one direction (figure 4a, [32]) or straight and interlaced between them (figure 4b, [43]) or straight and interlaced but with entanglement points (figure 4c, [46]) or curved/buckled interweaved between them (figure 4d, [35]). There is not an obvious correlation between growth mechanism and these categories.…”

“…Peaks attributed to the Si substrate and the stacking faults (sf) of SiC were also found in some cases as in Figure 6 although they are not present in the spectra reported in most studies. Additional peaks corresponding to other [32], [43], [46] and [35] respectively).…”